Large-scale energy backup system

Abstract

Energy backup systems and methods are provided, which combine an aluminum air sub-system having one or more replaceable aluminum air modules with multiple aluminum air cell stacks with a rechargeable buffer. The backup systems and methods provide electricity upon requirement from the rechargeable buffer, monitor the statuses of the rechargeable buffer and the aluminum air sub- system as well as the electricity consumption of the load which the system backups - and determine respectively the operation profile of the aluminum air sub-system to supply electricity to the load and to recharge the buffer when needed, optimizing the operational parameters with respect to the operation and configuration of the aluminum air sub-system and the buffer(s), from the system configurations and self-testing, through management of maintenance procedures and down to the configuration and operation of a large number of cell stacks.

Description

LARGE-SCALE ENERGY BACKUP SYSTEMBACKGROUND OF THE INVENTION1. TECHNICAL FIELD

[0001] The present invention relates to the field of energy backup systems, and more particularly, to backup systems combining aluminum air units with rechargeable buffer(s).2. DISCUSSION OF RELATED ART

[0002] Energy backup is a wide-spread need, from small scale systems like electric vehicles and isolated small devices, through various municipal and medium scale data centers up to large-scale facilities such as large server farms and production factories that may require energy backup in the scale of a city. Configuration and efficient operation, especially of large-scale energy backup systems, is thus highly challenging.SUMMARY OF THE INVENTION

[0003] The following is a simplified summary providing an initial understanding of the invention. The summary does not necessarily identify key elements nor limit the scope of the invention, but merely serves as an introduction to the following description.

[0004] One aspect of the present invention provides a large-scale energy backup system comprising: an aluminum air sub-system comprising a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells, wherein the aluminum air modules comprise replaceable stand-alone units, a rechargeable buffer, and a controller configured to: provide electricity upon requirement from the rechargeable buffer, monitor a status of the rechargeable buffer, monitor a status of the aluminum air sub-system, monitor an electricity consumption of a load which the system backups, determine an operation profile of the aluminum air sub-system to supply electricity to the load and recharge the buffer when needed, to optimize operational parameters of the aluminum air sub-system while providing the required electricity to the load, and operate the aluminum air sub-system within the optimized operational parameters of the operation profile.

[0005] One aspect of the present invention provides a backup system in which the aluminum air cell stacks are electrically connected in at least two parallel lines of serially connected stacks, andwherein electrolyte flow is delivered between groups of stacks of the at least two parallel lines that provide a same voltage.

[0006] One aspect of the present invention provides a backup system in which at least some of the aluminum air cells are configured to have a dynamically adaptable gap between a cell anode and one or two cell cathodes, which receives electrolyte during operation and is dynamically adapted to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode.

[0007] One aspect of the present invention provides a backup system in which the operation profile of the aluminum air sub-system comprises starting and stopping times of the aluminum air subsystem with respect to the monitored statuses of the rechargeable buffer and the aluminum air subsystem, and with respect to the monitored electricity consumption of the load.

[0008] One aspect of the present invention provides a backup system that includes a self-testing configuration, in which the controller is further configured to monitor the status of the aluminum air sub-system during periods in which the aluminum air sub-system does not operate, by receiving measurements from sub-system components and deriving the status therefrom.

[0009] One aspect of the present invention provides a backup system that includes an electrolyte management unit configured to optimize electrolyte use with respect to the operation profile of the aluminum air sub-system.

[0010] One aspect of the present invention provides a backup system that is services in a staggered replacement configuration of aluminum anodes and / or electrolyte that comprises operating the aluminum air modules to form a gradient in a utilization level thereof and replacing or servicing the modules one at a time, maintaining an overall power supply from the aluminum air sub-system. For example, the aluminum air modules may be configured to be replaced or serviced in a roundrobin (RR) scheduling, wherein each replacement comprises replacing the anodes of the cells in the stacks of the respective module and replacing the electrolyte circulating through the cells in the stacks of the respective module.

[0011] One aspect of the present invention provides a method of providing power backup to a large-scale facility, the method comprising: combining a high energy aluminum air sub-system and a fast rechargeable buffer to supply power to the large-scale facility during power interruptions, operating the buffer to bridge brief interruptions or brief power requirement surges from the large- scale facility, and during starting or stopping of the aluminum air sub-system, and optionally tooptimize the operation of the aluminum air sub-system, and operating the aluminum air sub-system to provide power for long durations of interrupted power.

[0012] One aspect of the present invention provides a method that comprises electrically connecting the aluminum air cell stacks are in at least two parallel lines of serially connected stacks, and delivering electrolyte flows between groups of stacks of the at least two parallel lines that provide a same voltage.

[0013] One aspect of the present invention provides a method that comprises configuring at least some of the aluminum air cells to have a dynamically adaptable gap between a cell anode and one or two cell cathodes thereof, which receives electrolyte during operation, and dynamically adapting the gap to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode.

[0014] One aspect of the present invention provides a method that comprises setting the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

[0015] One aspect of the present invention provides a method that comprises self-testing the aluminum air sub-system by monitoring the status thereof during periods in which the aluminum air sub-system does not operate, receiving measurements from sub-system components and deriving the status therefrom.

[0016] One aspect of the present invention provides a method that comprises managing and optimizing electrolyte use with respect to the operation profile of the aluminum air sub-system.

[0017] One aspect of the present invention provides a method that comprises operating the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof, and replacing or servicing the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

[0018] One aspect of the present invention provides a computer program product for providing power backup to a large-scale facility during power interruptions by a backup system combining a high energy aluminum air sub-system and a fast rechargeable buffer, the computer program product comprising a non-transitory computer readable storage medium having computer readable program embodied therewith, the computer readable program comprising computer readable program configured to operate the buffer to bridge brief interruptions or brief power requirement surgesfrom the large-scale facility, and during starting or stopping of the aluminum air sub-system, and optionally to optimize the operation of the aluminum air sub-system, and computer readable program configured to operate the aluminum air sub-system to provide power for long durations of interrupted power.

[0019] One aspect of the present invention provides a computer program product that includes computer readable program configured to set the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

[0020] One aspect of the present invention provides a computer program product that includes computer readable program configured to self-test the aluminum air sub-system by monitoring the status thereof during periods in which the aluminum air sub-system does not operate, receiving measurements from sub-system components and deriving the status therefrom.

[0021] One aspect of the present invention provides a computer program product that includes computer readable program configured to operate the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof and computer readable program configured to replace or service the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

[0022] These, additional, and / or other aspects and / or advantages of the present invention are set forth in the detailed description which follows, possibly inferable from the detailed description, and / or learnable by practice of the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout. In the accompanying drawings:

[0024] Figures 1A-1C are high-level schematic block diagrams and illustrations of a large-scale energy backup system, according to some embodiments of the invention.

[0025] Figures 2A and 2B are high-level schematic illustrations of aluminum air sub-system with aluminum air modules, according to some embodiments of the invention.

[0026] Figures 3A-3C illustrate schematically the management and optimization of power output from backup systems and from aluminum air sub-systems, utilizing power buffer for load demand, according to some embodiments of the invention.

[0027] Figure 4 is a high-level schematic block diagram illustrating various configurations of backup systems, according to some embodiments of the invention.

[0028] Figures 5A-5C are high-level schematic illustrations of aluminum air batteries, and their integration into, and operation in backup systems, according to some embodiments of the invention.

[0029] Figures 5D and 5E provide schematic illustrations of a mechanical arrangement for aluminum air cell stacks, according to some embodiments of the invention.

[0030] Figure 6 is a high-level schematic illustration of an energy backup system module, according to some embodiments of the invention.

[0031] Figures 7A, 7B and 8A-8F are high-level schematic illustrations of configurations for reducing or preventing shunt currents in energy backup system modules, according to some embodiments of the invention.

[0032] Figures 9A-9H provide schematic illustrations of configurations of aluminum air cells having unused anodes, according to some embodiments of the invention.

[0033] Figures 10A-10D provide schematic illustrations of configurations of aluminum air cells having consumed (corroded) anodes, according to some embodiments of the invention.

[0034] Figures 11A-11F provide high level schematic illustrations of configurations of aluminum air cells having one or two cathode(s), according to some embodiments of the invention.

[0035] Figures 12A-12C are high level schematic block diagrams of self-testing configurations of cell stacks, modules and sub-systems, according to some embodiments of the invention.

[0036] Figures 13A and 13B are high level schematic block diagram illustrations of electrolyte circulation schemes, according to some embodiments of the invention.

[0037] Figures 14A-14C are high level schematic examples for module reactions to changing load, temperature and voltage (respectively), which may be monitored and managed in relation to the batch-wise delivery of the electrolyte, according to some embodiments of the invention.

[0038] Figures 15A and 15B are high level schematic illustrations of staggered servicing configurations of modules and sub-modules, respectively, according to some embodiments of the invention.

[0039] Figure 15C is high level schematic illustration of staggered aluminum module replacement configurations, according to some embodiments of the invention.

[0040] Figure 15D is high level schematic illustration of staggered electrolyte replacement configurations, according to some embodiments of the invention.

[0041] Figure 16 provides a partial view of aluminum air sub-systems with stack and module replacement mechanisms, according to some embodiments of the invention.

[0042] Figures 17A and 17B illustrate schematically two stages of replacing consumed anodes with fresh anodes, according to some embodiments of the invention.

[0043] Figure 18 is a high-level flowchart illustrating methods of providing power backup to a large-scale facility, according to some embodiments of the invention.

[0044] Figure 19 is a high-level block diagram of exemplary controllers or any other control or management unit disclosed herein, which may be used with embodiments of the present invention.

[0045] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.DETAILED DESCRIPTION OF THE INVENTION

[0046] In the following description, various aspects of the present invention are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well-known features may have been omitted or simplified in order not to obscure the present invention. With specific reference to the drawings, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0047] Before at least one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments that may be practiced or carried out in various ways as well as to combinations of the disclosed embodiments. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

[0048] Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "processing", "computing", "calculating", "determining", “enhancing”, "deriving" or the like, refer to the action and / or processes of a computer or computing system, or similar electronic computing device, that manipulates and / or transforms data represented as physical, such as electronic, quantities within the computing system's registers and / or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.

[0049] Some embodiments of the present invention provide efficient and economical methods and mechanisms for combining and configuring operation of aluminum air units with rechargeable buffer(s) and thereby provide improvements to the technological field of energy backup systems. Energy backup systems and methods are provided, which combine an aluminum air sub-system having one or more replaceable aluminum air modules with multiple aluminum air cell stacks with a rechargeable buffer. The backup systems and methods provide electricity upon requirement from the rechargeable buffer, monitor the statuses of the rechargeable buffer and the aluminum air subsystem as well as the electricity consumption of the load which the system backups - and determine respectively the operation profile of the aluminum air sub-system to supply electricity to the load and to recharge the buffer when needed, optimizing the operational parameters with respect to the operation and configuration of the aluminum air sub-system and the buffer(s), from the system configurations and self-testing, through management of maintenance procedures and down to the configuration and operation of a large number of cell stacks.

[0050] Figures 1A-1C are high-level schematic block diagrams and illustrations of a large-scale energy backup system 100, according to some embodiments of the invention. Large-scale energy backup system 100 is configured to provide efficient and reliable electricity backup to large-scalefacilities (referred to herein as load 90), such as data centers or other large scale computation and / or communications-related facilities, large service facilities such as hospitals, and large-scale manufacturing facilities in various industries (e.g., processing raw materials such as wood, metal, petroleum, producing various types of chemicals or other mass products such as cement, textiles, etc.). In some embodiments, systems 100 in various configurations may be used as main energy source (rather as a backup system), especially with disclosed seamless and continuous servicing configurations that enable full utilization of the consumables and seamless servicing throughout long periods or continued operation.

[0051] Large-scale energy backup system 100 comprises an aluminum air sub-system 120 comprising a plurality of aluminum air modules 130 for generating electricity, each comprising a plurality (e.g., stacks 160) of aluminum air cells 165 (see, e.g., Figures 2A and 2B). As a nonlimiting example illustrated in Figure 1A, aluminum air sub-system 120 may comprise 52 aluminum air modules 130, each providing 75V and 200A to yield a power supply of 15kW, which may be delivered via 20kW DC / DC converters 115A and then through a DC / AC inverter 115 to load 90, with a rechargeable buffer 110 (denoted BESS) for providing additional power on demand, e.g., to bridge brief interruptions or brief power requirement surges, during starting or stopping of aluminum air sub-system 120, to optimize the operation of aluminum air sub-system 120 and so forth, as disclosed herein.

[0052] In various embodiments, backup system controller(s) 60 may be configured to monitor that states of power supply to load 90 and the states of elements in backup system 100 (e.g., rechargeable buffer 110, aluminum air sub-system 120 and components thereof), and adjust the operation profile of backup system 100 correspondingly, e.g., adjust operation profiles of rechargeable buffer 110 and aluminum air sub-system 120, adjust maintenance operations, especially of aluminum air sub-system 120 as disclsoed herein, etc.

[0053] It is noted that disclosed configurations of backup systems 100 with aluminum air subsystem 120 and rechargeable buffer 110 may be implemented at any scale - from small scales (e.g., including one of two stacks 160), through medium scales (e.g., including several or tens of stacks 160), and up to large scales (e.g., including many tens or hundreds of stacks 160).

[0054] The energy capacity of aluminum air backup system 120 is determined by the total amount of aluminum available (as anodes 167) inside of cells 165, and the total amount of electrolyte 157 enabling the electric generation reaction. In various embodiments, depending on the powerrequirements of large-scale facility 90 and configuration of aluminum air sub-system 120, the number of aluminum air modules 130 may vary (e.g., between 1-100 aluminum air modules 130, or intermediate values) and the power output of each aluminum air module 130 may vary (e.g., between l-50kW, or intermediate values).

[0055] The capacity and configuration of rechargeable buffer 110 may be determined during a planning stage of backup system 100 with respect to an expected power supply quality to load 90 - e.g., availability of power, expected profile of power interruptions, alternative power sources and backup options, etc. In some embodiments, the capacity and configuration of rechargeable buffer 110 may be adjusted in case the operational profile of load 90 and / or of backup system 100 suggest that operative improvements may be achieved through such changes (e.g., adding or reducing buffer capacity with respect to the actual interruption profile, or with respect to changes in the power supply to load 90).

[0056] Backup system 100 may be connected to load 90 delivering energy in DC (direct current) or delivering energy in AC (alternating current) after conversion through a DC / AC inverter 115. For example, aluminum air sub-system 120 may comprise multiple aluminum-air modules 130 that are connected in parallel to provide DC power, with buffer module 110 also connected in parallel to modules 130, and the delivered power may be converted to AC - providing maximal operation flexibility. In another example, multiple aluminum air modules 130 may be connected in series, and several serial branches may be connected in parallel, and in parallel to buffer 110 to provide the delivered power.

[0057] As illustrated schematically in Figure IB, large-scale energy backup system 100 may be operated in an AC backup configuration 100A with DC / AC inverter 115, e.g., providing 400- 470V AC in three phases over a 50 or 60Hz bus as a non-limiting example, and may be set up alongside other AC sources such as renewable energies 80A, grid 80B, power turbines 80C, etc.; and / or large-scale energy backup system 100 may be operated in a DC backup configuration 100B, e.g., in association with or interfacing to a UPS (uninterruptible power supply) system 95, e.g., providing 300-600VDC, in non-limiting examples. Figure 1C provides another schematic illustration of energy backup system 100, which may be configured to provide backup power to smaller loads 90 which regularly receive power from grid 80 via AC / DC inverter 117. In this configuration, backup system 100 may provide DC directly to load 90, with one or more control unit(s) 60 controlling the operation of aluminum air sub-system 120 (or unit(s), for smallersystems) and buffer battery(ies) 110 such as Li-ion batteries, as explained herein. Electrolyte management unit(s) 190 may be configured to manage electrolyte supply, removal and possibly reuse to and from aluminum air sub-system 120, as disclosed herein.

[0058] Figures 2A and 2B are high-level schematic illustrations of aluminum air sub-system 120 with aluminum air modules 130, according to some embodiments of the invention. Aluminum air modules 130 may comprise replaceable stand-alone units, such as stacks 160 of aluminum air cells 165, or sub-modules 140 thereof, as disclosed herein. Figures 2A and 2B illustrate schematically a part of aluminum air sub-system 120 with containerized aluminum air modules 130 supporting modular assembly and easy transport and replacement. In a non-limiting example, each containerized aluminum air module 130 may be configured to provide 800kW of power, with total energy content for a sub-module 140 with four containers of 38MWh (48h capacity). In various embodiments, containerized aluminum air module 130 may be configured to provide between 300 and 1500kW of power, or intermediate values, with total energy content per container between 5 and 30 MWh, or intermediate values. For example, large-scale energy backup system 100 may comprise 26 containerized aluminum air modules 130 in a non-limiting example, or between 1 and 50 (or intermediate values) containerized aluminum air modules 130 in various embodiments, and depending on the size of each containerized aluminum air modules 130. Various embodiments may include variable numbers of modules 130, variable numbers of sub-modules 140 per module 130, and variable numbers of stacks 160 per sub-module 140 or per module 130 - depending on the required power and energy outputs, and required operational durations - which influence on servicing configurations as disclosed herein and may require having larger capacity to accommodate periodic replacement of stacks 160, sub-modules 140 and / or modules 130 (see, e.g., Figures 15A-15D). In the following, modules 130 and sub-modules 140 may be referred to in an interchangeable manner, applicable depending on specific configuration and scale of aluminum- air sub-system 120.

[0059] In various embodiments, buffer 110 may comprise one or more rechargeable battery stacks and aluminum-air sub-system 120 may comprise single aluminum-air battery module 130 or multiple aluminum-air battery modules 130 and control and management units for the components and system 100 as a whole. Aluminum-air sub-system 120 may be modular, allowing adding or removing aluminum-air modules 130. Each aluminum-air module 130 typically includes multiple aluminum-air stacks 160 (possibly arranged into sub-modules 140 or branches), each includingmultiple aluminum- air cells 165. Cell stacks 160 in each aluminum- air module 130 may also be arranged modularly, in replaceable casings that holed the anodes, cathodes and flow paths for the electrolyte, in a mechanical structure that optimize all aspect of operation of cells 165 (see disclosed herein). Stacks 160 of cells 165 may be removed and replaced in a simple manner, by pulling each stack 160 out of module 130 and replacing it with a new stack 160, e.g., upon depletion of the aluminum anodes in cells 165 (see disclosed herein). Electrolyte for operating cells 165 may be circulated through cells 165, e.g., from and to a common electrolyte work tank 150 associated with module 130 and utilizing respective circulation elements such as pump(s), conduits, valves, etc. (denoted schematically by numeral 155 and with further details disclosed herein). Electrolyte work tanks 150 of modules 130 may be connected to electrolyte reservoir(s) 152 from which fresh electrolyte is supplied, and to which utilized electrolyte is delivered, e.g., for collecting and regeneration.

[0060] As illustrated schematically, each containerized aluminum air modules 130 may comprise operable multiple sub-modules 140, each comprising multiple stacks 160 of aluminum-air cells 165 (see further details herein) as well as supplies to cells 165 and operational management unit(s) disclosed herein, including: Electrolyte working tanks 150, electrolyte handling pipework and pumps 155, management unit(s) 59 for managing electrolyte, thermal management, air flow, aluminum anode reloading and / or cell replacement, etc. Management unit(s) 59 may be implemented as controller(s) 60, and are described in further detail herein. Containerized aluminum air modules 130 are configured to collect and provide power from sub-modules 140 (and submodules 140 are configured to collect and provide power from stacks 160 of aluminum-air cells 165). Be easily replaceable for service when needed (indicated schematically in a non-limiting manner as being transportable 130A by truck, see Figure 2B), and within energy backup system 100 - be associated with additional sub-systems that support the operation of aluminum air modules 130, such as electrolyte reservoirs 152 connected to working tanks 150 and cooling units 135 for thermal management. These sub-systems may be connected to corresponding sub-units within containerized aluminum air modules 130, such as electrolyte working tanks 150, electrolyte handling pipework and pumps 155 and management unit(s) 59.

[0061] Aluminum air sub-system 120 is typically characterized by its ability to provide large amounts of energy over extended periods, but may require some time to start and to stop and somemaintenance for handling used electrolyte and aluminum anodes - issues which are addressed herein in various disclosed embodiments.

[0062] Large-scale energy backup system 100 comprises rechargeable buffer 110, which may comprise various rechargeable energy sources such as lithium batteries. Rechargeable buffer 110 is typically characterized by its ability to provide energy without an initialization period, and by its simple starting, stopping and recharging procedures. Rechargeable buffer 110, e.g., lithium batteries, is typically limited in use by its lower energy content (per volume, weight and / or cost) compared to aluminum air batteries as well by a significant decline in available energy during wait (not-operating) periods (e.g., due to self-discharge in lithium batteries) - requiring a very large and typically not feasible extent of storage capacity to provide a single solution to extended electricity requirements of large-scale facilities.

[0063] Large-scale energy backup system 100 further comprises one or more control units, or controllers 60 configured to: provide electricity (to a load 90, such as a large-scale facility) upon requirement from rechargeable buffer 110, monitor a status of rechargeable buffer 110, monitor a status of aluminum air sub-system 120, monitor an electricity consumption of load 90 (e.g., historical consumption patterns, past electricity outage patterns, etc.) which system 100 backups, determine an operation profile of aluminum air sub-system 120 to supply electricity to load 90 and recharge buffer 110 when needed, to optimize operational parameters of aluminum air sub-system 120 while providing the required electricity to load 90, and operate aluminum air sub-system 120 within the optimized operational parameters of the operation profile.

[0064] In various embodiments, the operation profile of aluminum air sub-system 120 may comprise starting and stopping times of aluminum air sub-system 120 with respect to the monitored statuses of rechargeable buffer 110 and aluminum air sub-system 120, and with respect to the monitored electricity consumption of load 90. In various embodiments, backup system 100 may be configured to recharge buffer 110 during operation of aluminum air sub-system 120.

[0065] In various embodiments, controller(s) or control unit(s) 60 may be configured to determine the operation profile of aluminum air sub-system 120 to operate aluminum air sub-system 120 during long durations of power interruption to load 90, while operating only rechargeable buffer 110 during brief interruptions.

[0066] Figures 3A-3C illustrate schematically the management and optimization of power output from backup system 100 and from aluminum air sub-system 120, utilizing power buffer for loaddemand, according to some embodiments of the invention. Figure 3A illustrates schematically the difference between characteristic power momentary demand by load 90 (denoted “Demand”), which may fluctuate drastically throughout the operation time due to various reasons - changes in power requirements by load 90, changes in available power from intermittent power providers, such as renewable energy sources. It is noted that periods with over-supply of power may be present, that can be utilized by backup system 100, e.g., to recharge buffer 110 (denoted “Recharge”) irrespective of aluminum air sub-system 120. In contrast to fluctuating demand and supply, aluminum air sub-system 120 may be operated under regulated conditions (denoted “Base load”) to optimize its performance. Buffer 110 may be used to bridge the gaps between the optimal power provided by aluminum air sub-system 120 (by discharging the buffer, denoted “Discharge”) and the fluctuating demand and supply (with the former equal or larger than the average of the latter). Hence, buffer 110 may be configured to handle transient extremes of power demand and supply (“Discharge” to supply excessive demand and “Recharge” to receive excessive supply) without compromising the operational efficiency of aluminum air sub-system 120, support auxiliary demands for starting, stopping and / or maintaining aluminum air sub-system 120 and possibly interface with additional energy sources (e.g., renewables, electric vehicles etc.), as disclosed herein. It is noted that disclsoed embodiments are applicable at any scale of system 100, from small scales (e.g., a vehicle as load 90 with instantaneous power demands, e.g., for acceleration, and power supply, e.g., via regenerative braking) to medium and large scales (e.g., devices, machinery and facilities receiving fluctuating power from renewable source and / or from the grid, with possible power interruptions).

[0067] Figures 3B and 3C schematically illustrate the advantages of managing aluminum air subsystem 120 to operate at its optimal configuration (Figure 3C) with respect to unmanaged operation thereof (Figure 3B). As the electrochemical reactions are exothermic, the electrolyte temperature rises during operation of cells 165. However, in unmanaged systems the quick initial temperature rise reduces performance, and if allowed to rise uncontrolled results in a temperature runaway and a significant reduction in cell performance - illustrated schematically in Figure 3B as the reduction of voltage provided by the cell for a stable current. Managing electrolyte temperature may comprise cooling electrolyte 157 (e.g., through heat exchangers 135, 136, see, e.g., Figures 6, 7A, 8B, 8E, 12C, 16, etc.), e.g., following an initial heating (warm-up) stage. The temperature of the electrolyte may be managed to achieve a flat or more stable discharge curve, to maximizeenergy output, to maintain a desired working point characterized by maintaining a set (e.g., optimal) efficiency regardless of power, to increase electrolyte utilization and / or to adjust the voltage according to anode thickness (~5mV / mm, and see also the dynamic adjustment of the anode-cathode gap and the adjustment of electrolyte volumes disclosed herein) - in various embodiments. Disclosed management configurations of cells 165 and stacks 160 are adjusted accordingly. Figures 14A-14C provide further examples that demonstrate temperature management of cells 165 and cell stacks 165.

[0068] Energy backup system 100 may be configured to provide power for long durations of grid interruptions, integrating and operating aluminum air sub-system 120 (also termed AA - Aluminum Air sub-system) and rechargeable buffer 110 (also termed BESS - Battery Energy Storage System) to use their respective advantages and overcome their respective shortcomings. When power is required, it is initially taken from buffer 110. System 100 monitors the status of buffer 110 (e.g., SOC - state of charge, overall capacity, aging, and / or previous or historic charge / discharge curves, and so forth), the status of aluminum air sub-system 120 (e.g., capacity, internal temperature, performance history and / or aging, and so forth) and load 90 (e.g., actual load, load history, a load lookahead electricity pricing and / or pricing of consumables, and so forth) and decides when to start and stop aluminum air sub-system 120. Specifically, in various embodiments, the monitored status of rechargeable buffer 110 may comprise a SOC (state of charge), an overall capacity, aging and / or previous or historic charge / discharge curves. In various embodiments, the monitored status of aluminum air sub-system 120 may comprise a capacity, internal temperature, performance history and / or aging. In various embodiments, the monitored electricity consumption of load 90 may comprise an actual load, a load history, a load lookahead electricity pricing and / or pricing of consumables. System 100 may set aluminum air sub-system 120 to work at various power ratings according to all of the parameters mentioned above. Buffer 110 may be charged either from aluminum air sub-system 120 or from various energy sources 80 (e.g., renewable energies 80A, grid 80B, power turbines 80C, etc., see, e.g., Figure IB).

[0069] Advantageously, energy backup system 100 may be configured to provide the following characteristics and advantages. The available peak power is proportional to the power available from buffer 110 (higher power), rather than the power available from aluminum air sub-system 120, while the available energy is provided by aluminum air sub-system 120 (high energy capacity) rather than the energy available from buffer 110. Their combination allows provision of both highpower on demand and sufficient energy over a long duration of grid interruption. Moreover, the combination allows operating both components under ideal conditions, for example, aluminum air sub-system 120 may be operated under optimal conditions regardless of load 90 served by system 100, as buffer 110 allows variation in power delivered to load 90 while maintaining constant load on aluminum air sub-system 120 (for higher efficiency), and also enables providing the required demand by load 90 irrespective of variation in aluminum air power (e.g., during electrolyte cycles, electrolyte replacement and aluminum reloading). Additionally, upon starting backup system 100, buffer 110 supports load 90 as well as the power required for starting aluminum air sub-system 120 and provides online backup response of the overall system 100 (rather than waiting for aluminum air sub-system 120 to start). Using buffer 110 also optimizes operational cost by serving load 90 during short interruptions using stored grid energy before starting consuming aluminum. Specifically, in embodiments, aluminum air sub-system 120 may be configured to operate under optimal performance conditions, while rechargeable buffer 110 is operated to provide additional power if higher power is required by load 90 compared to the power provided by aluminum air sub-system 120 operated under optimal performance conditions, or be recharged from aluminum air sub-system 120 if lower power is required by load 90 compared to the power provided by aluminum air sub-system 120 operated under optimal performance conditions.

[0070] Figure 4 is a high-level schematic block diagram illustrating various configurations of backup system 100, according to some embodiments of the invention. In various embodiments, rechargeable buffer 110 may comprise a single buffer external to aluminum air sub-system 120, may comprise internal buffer(s) 112 as part of aluminum air sub-system 120, may comprise internal buffer(s) 114 as part of aluminum air modules 130 and / or may be associated with external power sources, such as renewable energy sources 80A or electrical vehicles, as disclosed herein.

[0071] In some embodiments, disclosed large-scale energy backup system 100 may be integrated with various renewable energy sources 80A have operation cycles that are determined by natural phenomena, e.g., photoelectric panels generate electricity when sunlight is available, and do not generate electricity when it’ s dark. In between, there may be partial power generation depending on the clouds, dust, or any other elements obscuring the sunlight. Electricity consumption in most places also has cycles, with most power consumed around mid-day, and the least power consumed during the night. Therefore, rechargeable electricity storage is used to store energy when the production exceeds the demand and to serve the demand when the production is not sufficient tofulfill the demand. When using a rechargeable battery for cycles of production and consumption, the effective capacity of the battery is significantly lower than its rated capacity - due to the effect of deep cycles of the lifetime of the battery. The deeper the cycles, the shorter the life of the battery.

[0072] In disclosed aluminum-air-based backup systems 100, which are a hybrid between using aluminum air batteries and using a rechargeable battery, buffer 110 may be enlarged such that it is used for periodic cycles of energy production and demand (e.g., a daily cycle if coupled with photovoltaic electric source). By unifying rechargeable buffer 110 of backup system 100 with the storage for the periodic cycles (e.g., of renewable energy sources 80A), it is possible to increase the lifetime of the rechargeable portion.

[0073] In a non-limiting example, for an overall capacity of 100% of the combined rechargeable battery (denoted schematically by numeral 110A as including part of renewable energy sources 80A), composed of 80% required for the periodic cycle, and 20% for buffer 110 of energy backup system 100. During normal operation, running the periodic 80% cycles implies shallower cycles of the complete 100% battery 110A, thus increasing its lifetime. When backup energy is required, and rechargeable battery 110A is used as buffer 110, if its state of charge is anywhere between 20% to 100%, the cycle that will be used is shallower than if the 20% buffer would be a standalone, thus again increasing the lifetime of the battery. Furthermore, when backup is required, if the state of charge of rechargeable battery 110A is higher than the 20% associated with backup system 100, the backup system 100 may choose to further serve load 90 from rechargeable battery 110A / 110 rather than starting aluminum air sub-system 120, thus saving on consumables for the operation of aluminum air sub-system 120.

[0074] Aluminum-air modules 130 may further comprise heat management elements 180 (see Figure 4) that regulate heat delivery to and from cells 165. Buffer modules 110 may be used at system level (e.g., buffer(s) 110 used in conjunction with aluminum-air sub-system 120 as a whole), at module level (e.g., buffer(s) 112 associated with one or more modules 130) and / or at sub-module level (e.g., buffer(s) 114 associated with one or more sub-modules 140, branches or stacks 160 within modules 130). External buffers (e.g., buffer(s) used in conjunction with renewable energy sources) may also be associated with and managed by backup system 100 as disclosed herein.

[0075] Figure 4 further illustrates schematically electrolyte management units 190 that manage fresh and used electrolyte and reservoirs 152, 192 (see further details disclosed herein), batterystack management units 260 that manage stack and cell replacements (see further details disclosed herein) and heat management units 180 that monitor and remove excessive heat (see further details disclosed herein) - any of which may be implemented and / or controlled by one or more controller 60, 60A. Backup system 100 may be arranged in a modular manner, with containers 130 including aluminum-air sub-systems 120 that have replaceable stacks 165 or anodes 167 within an infrastructure that includes large electrolyte reservoirs 152, 192 (to feed electrolyte working tanks 150, and received used electrolyte therefrom, respectively) and heat management units 180 supporting containers 130. For example, modules 180 may provide tens of kW (delivering hundreds of kWh) and be combined into sub-system 120 providing several MW. The multiple levels of modularity provide efficient maintenance and continuous power backup over long durations of power interruption.

[0076] Advantageously, the combination of buffer 110 and aluminum air sub-system 120 provides a solution to both supplying peak demands and fluctuations (using buffer 110), as well as providing long term stable energy (using aluminum air sub-system 120). The combination also allows saving consumables through sizing of the different parts of system 100. That is, the specifications (e.g., power and capacity) of the components may be determined based on power-loss statistics for load 90 - to encompass a specified percentage of briefer power-loss events, and with respect to a threshold discharging level defined for buffer module 110. For example, in case 80% of power interruptions are shorter than ten minutes, buffer module 110 may be operated for ten minutes before operating aluminum-air sub-system 120, leaving the latter for longer periods of operation during longer power interruption to utilize the greater energy supply available from aluminum-air sub-system 120, while sparing the operation of starting and stopping operation of aluminum-air sub-system 120 for brief power interruptions.

[0077] Figures 5A-5C are high-level schematic illustrations of aluminum air batteries, and their integration into, and operation in backup system 100, according to some embodiments of the invention. Figure 5A provides a high-level schematic illustration of aluminum air cell 165 comprising an air cathode 168, electrolyte 157 and an aluminum anode 167. Electrochemical reactions gradually consume aluminum from anode 167 and react with oxygen at catalytic sites on air cathode 168 to yield the battery voltage and provide power. Aluminum-air cells 165 are operated using air cathodes 168 to provide oxygen that oxidizes replaceable aluminum anodes 167 (e.g., aluminum plates) to yield power.

[0078] Figure 5B provides a high-level schematic illustration of the operation of stack 160 of aluminum air cells 165, e.g., within sub-module 140 or 130 or branch, which are configured together to provide a required level of voltage, a required level of power and / or an amount of available energy, and are managed with respect to various operational aspects such as thermal control via heat exchanger(s) 136 and provision of electrolyte 157 (e.g., KOH, NaOH, etc.) from electrolyte work tank 150. Aluminum-air cells 165 operate once fluid electrolyte (e.g., aqueous KOH solution) 157 is introduced between air cathodes 168 and aluminum anodes 167 to initiate and support the electrochemical reactions, in which aluminum is oxidized, aluminum anodes 167 are gradually corroded, and flowing electrolyte 157 removes oxidation products and heat from cells 165. Electrolyte 157 is circulated until it is saturated with oxides, with full utilization defined according to specific performance and operational considerations.

[0079] Figure 5C provides a more detailed high-level schematic illustration of control operations 170 involved in operating aluminum air cell stacks 160, according to some embodiments of the invention. Various control operations 170 may be implemented using one or more controller(s) 60 disclosed herein. Electrolyte flow of electrolyte 157 in electrolyte work tank 150 to and from cells 165 in stack 160 may be controlled according to the starting and stopping of the operation of aluminum air sub-system 120, and the used electrolyte may be treated, e.g., to remove aluminum precipitates (e.g., in an aluminum precipitator 188) and possibly re-used 187 and / or generated 186 and supplied back to electrolyte work tank 150, as disclosed further herein. In addition, hydrogen that may formed during the operation of aluminum air stacks 160 may be removed from the electrolyte and treated 184. Aluminum air cell stacks 160 may be managed with respect to their temperature (e.g., controlled by a heater 182, disclosed herein), a halting process 180 of aluminum air cells 165 may be controlled, and additional aspects such as prevention of shunt currents 200 and protection 210 of anodes 167 may also be managed, as disclosed herein.

[0080] Figures 5D and 5E provide schematic illustrations of a mechanical arrangement for aluminum air cell stacks 160, according to some embodiments of the invention. Aluminum air cells 165 may be arranged in a mechanical system that includes replaceable aluminum anodes 167 (e.g., aluminum plates, see Figure 5E, and also Figure 16), air cathodes 168, flow pathways for electrolyte and electric contacts (see, e.g., U.S. Patent No. 11,418,640, incorporated herein by reference in its entirety, for more structural details). Elements of single cells may be replaceable (indicated schematically by numeral 161), and / or whole stacks 160 of cells 165 may be replaceableas units (indicated schematically by numeral 162 denoting a handle that may be used to pull and replace whole stack 160, see also Figure 16), simplifying maintenance. Figure 5D further provides a photo of the back side of stack 160, that includes flow channels 163 for delivering electrolyte to cells 165 (e.g., via electrolyte delivery channels 215, see, e.g., Figures 9A-9H). Circulating electrolyte enables the electrochemical reaction of cells 165 that provide energy, and electrolyte circulation also removes heat from cells 165 as part of thermal management (e.g., by a thermal management unit 180 disclosed herein). During operation, aluminum anodes 167 are gradually corroded, and electrolyte 157 gradually gets saturated with aluminum oxides and requires periodic replacement (e.g., via aluminum precipitator 188).

[0081] Figure 6 is a high-level schematic illustration of energy backup system module 140, according to some embodiments of the invention. The small-scale illustration demonstrates the application of disclosed principles for operating system 100, which are scaled up, modified and elaborate in the design of disclosed large-scale energy backup system 100. Illustrated system module 140 comprises stacks 160 of cells 165 (as illustrated in Figure 5D), control system 60 and buffer battery 110, electrolyte work tank 150 as well as electrolyte reservoir 152 and peripheral components such as electrolyte handling pipework and pumps 155. Illustrated system module 140 further comprises cooling unit 135 (which may be positioned, e.g., underneath module 140) and halting module 180 (illustrated schematically) configured to control the halting process of stopping the operation of system module 140.

[0082] In various embodiments, smaller versions of disclosed energy backup system module 140 may be used in electric vehicles to supply the electric motor. Aluminum air (AA) sub-system 120 may be used to provide a weight-efficient energy source for providing the average power to the vehicle, while rechargeable buffer (BESS) 110 (e.g., a lithium-ion battery) may handle power fluctuations - provide momentary high-power requirements (e.g., upon strong acceleration or while driving uphill) and receiving superfluous power (e.g., when the vehicle is breaking or idle while AA 120 is operating), as well as supporting auxiliary modules in the vehicle if needed. Aluminum air (AA) sub-system 120 may be simply replaced when needed, and / or aluminum anodes 167 and / or electrolyte may be replaced simultaneously or after AA replacement, as disclosed herein. System 100 may be configured to monitor the status of buffer 110 (SOC - state of charge, overall capacity, aging, etc.), the status of aluminum air sub-system 120 (capacity, internal temperature, performance history) and load 90 (actual load, load history, load lookahead) and decides when tostart and stop aluminum air sub-system 120 - possibly operating AA 120 during long drives and sparing AA 120 during brief uses. Backup system 100 may set aluminum air sub-system 120 to work at various power ratings according to all of the parameters mentioned above. Buffer 110 may be charged either from aluminum air sub-system 120 or from vehicle 90 (e.g., via regenerative braking).

[0083] In various embodiments, aluminum-air modules 140 may be combined with rechargeable buffer(s) 110 to provide initial power - to form energy backup system 100 that delivers both immediate power and long-term energy for power interruptions. Illustrated examples range from aluminum-air modules 140 with two stacks 160 (e.g., Figure 6), through aluminum-air modules 140 with 2x2, 3x6, 3x10, or more stacks 160 (each stack 160 typically including 20-25 cells 165), e.g., 26 modules 140 per backup facility 100 or per container 130 in backup facility 100 (see Figures 1A, 2A and 2B) - to provide large scale power and energy backup requirements.

[0084] Figures 7A, 7B and 8A-8F are high-level schematic illustrations of configurations 200 for reducing or preventing shunt currents in energy backup system module 140, according to some embodiments of the invention. Electrolyte management unit(s) 190 may be configured to implement configurations 200 as disclosed herein. Similar configurations may be applied to larger modules 130. It is noted that disclosed configurations 200 for reducing or preventing shunt currents may be applied to backup systems 100 at medium scales (e.g., including several or tens of stacks 160) or large scales (e.g., including many tens or hundreds of stacks 160).

[0085] Figure 7A provides a schematic high-level illustration of system 100 with only two stacks 160A, 160B illustrated, for simplicity. Configuration 200 involves, in backup system 100 comprising multiple modules 140 each with multiple aluminum air cell stacks 160 - connecting at least some of stacks 160 (or cells 165 in each stack 160) in serial electric connection, while delivering electrolyte to these stacks 160 (or cells 165 in each stack 160) in parallel - to reduce the voltage gradient over the flowing electrolyte. It is noted that electric connection is illustrated schematically in thin and in broken lines, while electrolyte flows to and from stacks 160A, 160B are illustrated schematically in thick lines.

[0086] Figure 7A further illustrates additional electrical components, such as internal or external buffers 112, 110, DC-DC converter(s) and / or DC-AC inverters 111, 115 supplying the power to load 90. Figure 7A further illustrates additional electrolyte flow management components, such as electrolyte work tank 150 (which delivers electrolyte to cells 165), fresh electrolyte tank 152 (usedto supply fresh electrolyte when required), used electrolyte tank 192 (used to receive drained used electrolyte when required). Figure 7A further illustrates additional heat management components, such as heat exchanger(s) 136 in module 140 and radiator(s) 135 outside module 140. Figure 7A further illustrates additional circulation elements 155, including pipework for circulating electrolyte, pipework, sensors and pumps for circulating and monitoring electrolyte and / or cooling fluids, etc. Figure 7A further illustrates additional control components, such as module controller 60B, system controller 60A and electrolyte management unit(s) 190 associated therewith and managing parallel electrolyte flows 156.

[0087] Figure 7B is a high-level schematic illustration of module 140 with multiple stacks 160 (see also Figure 2A), in which parallel electrolyte flows 156 are illustrated in a highly schematic manner, as are circulation elements 155 for supporting, maintaining and handling the parallel electrolyte flows, as managed by electrolyte management unit(s) 190.

[0088] In some embodiments, each stack 160 may include multiple aluminum air cells 165 connected electrically in series while sharing a common flow of electrolyte. However, in such configurations, when the system is operating - liquid electrolyte is continuously circulated through the cells and may cause shunt currents (current losses over the liquid electrolyte, resulting in energy loss). That is, current may bleed through the liquid that serves as a medium between the cells that have potential differences (voltages) between them. For example, when 4 stacks of 20 cells are electrically connected in series, a potential difference between the first and the last cells of about 100V occurs. If the electrolyte flows to the cells through the same pipe, then a 100V potential may cause a shunt current to flow through the liquid. Furthermore, if more power is required, common practice design adds an additional string of 4 stacks connected electrically in parallel to the first string, supplying same voltage (e.g., 100V) with double the current thus supplying double wattage. The common practice, which is also the simplest practice, is to connect the electrolyte to flow serially through the additional string, so that the flows of electricity and of electrolyte are common in each string of stacks.

[0089] However, in contrast to prior art logic, disclosed configurations 200 deviate from the common practice scheme, and comprise parallel electrolyte flows 156 across stacks 160 that belong to multiple and different electrically serially connected strings of stacks 160 - to reduce or prevent shunt currents. While this configuration is more complex - relating all stacks 160 in all strings in a current-electrolyte flow matrix and thus requiring more complex electrolyte management andregulation 190 of electrolyte flow patterns -the advantages of reducing or eliminating shunt currents may in some embodiments sufficiently compensate for the added complexity.

[0090] For example, for aluminum air sub-system 120 with 12 stacks 160 of cells 165, where the electric configuration is in two electrically serially connected strings of six stacks 160 each, the electrolyte may be circulated in six circuits (instead of only one or two circuits in the prior art), each electrolyte circuit connecting respective stacks 160 in strings that have the same voltage. Each electrolyte flow serves stacks 160 that are under the same volage in the respective strings, and thus the voltage across each electrolyte flow is minimized. In some cases, pairs of stacks 160 under the same voltage but from different strings may share electrolyte circulation - yielding a smaller or no shunt current while reducing the complexity of the fluid connections among stacks 160.

[0091] In some embodiments, electrolyte flows through aluminum-air battery stacks 160 may be configured to limit a voltage drop over any of the electrolyte flows to be below a specified threshold (e.g., 0V, 5V, 10V, 20V or intermediate values). Keeping the voltage drop over the electrolyte flow smaller than the overall voltage of stacks (of the full string of serially connected stacks, which may reach, e.g., 50V, 72V, 100V or any other value depending on the number of cells and stacks serially connected) - reduces or prevents current leakage through the electrolyte, and thus reduces or avoids related energy losses to heat and risks for unwanted reactions.

[0092] Figures 8A-8C provide partial high-level schematic illustrations of shunt current management and prevention in system 100, according to some embodiments of the invention. Figure 8A provides a more elaborate example compared to Figure 7A, with configuration 200 comprising three pairs of stacks 160A, 160B - connected electrically in series in two parallel lines (stacks 160A - Al, A2, A3 - forming one string, stacks 160B - Bl, B2, B3 - forming another string)- with rising voltage values along each line as stacks 160 contribute additional voltage. In contrast to the serial electrical connections, electrolyte (hydraulic) flow connections 156 are parallel for each pair of stacks 165A, 165B that share a similar voltage (each pair of Al, Bl; A2, B2; A3, B3- in the illustrated non-limiting example), so that the voltage over the flow of electrolyte remains small (e.g., 12V over each of electrolyte (hydraulic) flows 156, compared to 36V over each string of stacks 160A or 160B). It is noted that electric connection is illustrated schematically in thin and in broken lines, while electrolyte flows to and from stacks 160A, 160B are illustrated schematically in thick lines. Clearly, system 100 may comprise a larger number of stack pairs, providing higher overall voltage while configuration 200 maintains low voltage over each electrolyte flow.Electrolyte management unit(s) 190 may be configured to monitor and manage electrolyte flows 156, e.g., with respect to electrolyte work, fresh and used tanks (150, 152, 192, respectively) and corresponding heat management (see Figure 7A).

[0093] For example, Figure 8B illustrates schematically a part of module 140 or 130 within a part of system 100, having electrolyte configuration 200 to prevent shunt current by connecting hydraulically each pair of stacks 160A, 160B in parallel (noted as “common electrolyte connection”), and orthogonally the other two pairs (each of stacks 160A and 160B) are connected electrically in series (noted as “serial electric connection”). It is emphasized that while Figure 8B only illustrates four stacks 160 to simplify the description of configuration 200 - systems 100 may be configured to have (in one or more of modules 140) - cells stacks 160 that are electrically connected in at least two parallel lines of serially connected stacks 160 (Al, A2, etc. for one line, Bl, B2, etc. for another line, and so forth), and electrolyte flow is delivered between groups of stacks 160 (Al, Bl, etc. for one group, A2, B2, etc. for another group, and so forth) of the parallel lines that provide a same voltage, or at least the voltage across each electrolyte flow does not exceed a value that starts to cause shunt currents through the electrolyte.

[0094] As in Figure 7A, Figure 8B too illustrates schematically optional internal buffers 112, additional electrolyte flow management components, such as electrolyte work tank 150 (which delivers electrolyte to cells 165), fresh electrolyte tank 152 (used to supply fresh electrolyte when required), used electrolyte tank 192 (used to receive drained used electrolyte when required). Figure 8B also illustrates additional heat management components, such as heat exchanger(s) 136 and radiator(s) 135 which may be part of module 140 or 130; additional circulation elements 155, including pipework for circulating electrolyte, pipework, sensors and pumps for circulating and monitoring electrolyte and / or cooling fluids, etc.; as well as additional control components, such as module controller 60B, system controller 60A and electrolyte management unit(s) 190 associated therewith and managing parallel electrolyte flows 156.

[0095] Figure 8C illustrates in a highly schematic manner a matrix of 18 cell stacks 160 arranged in configuration 200 in (i) three serially electrically-connected lines (stacks denoted schematically 160A, 160B, 160C for each of the three lines) along which the voltage contributions of the respective stacks accumulate and (ii) in six parallel hydraulic electrolyte flow circuits 156 (denoted by roman numerals I, II, III, IV, V and VI) used to circulate electrolyte through stacks 160 that have the same voltage levels (e.g., first group I of stacks 160A, 160B, 160C, second group II ofstacks 160A, 160B, 160C and so on, until the sixth group VI of stacks 160A, 160B, 160C). Clearly, the same principle may be used to configure 200 any number of cell stacks 160 in module 140 or 130. In various embodiments, the number of electrolyte flows 156 may be reduced to simplify infrastructure, for example to combine electrolyte flows 156 that have an overall voltage (potential difference) that does not cause shunt currents to flow through the electrolyte hydraulic lines (depending on the flow characteristics). Such options are noted schematically as the optional combinations (pairings) of flows if the voltage does not cause shunt currents indicated in Figure 8C. Electrolyte flows 156 may be insulated electrically, and circulation elements 155 such as pipework and associated components (e.g., pumps) and liquid management elements configured to support, maintain and handle each separate electrolyte flow are indicated in a highly schematic manner.

[0096] In various embodiments, shunt currents over the flow lines of electrolyte 157 may be prevented electrically by separating stacks 160 or groups of stacks 160 by, e.g., DC / DC converters 111 configured to have their output side completely isolated from the input side, not even sharing a ground connection - so that each increase of the voltage along the serially connected stacks 160 is isolated, or floating, with respect to the preceding and the consecutive increases. Such electrical prevention of shunt currents may be used instead or possibly in addition to the hydraulic prevention of shunt currents by separating electrolyte streams, as disclosed herein. Figures 8D-8G illustrate schematically such electrical configurations that parallel the ones illustrated in Figures 8A-8C, yet it is noted that elements from corresponding configurations may be combined, e.g., in different sections of aluminum air sub-system 120, and / or with respect to the same or to different stacks 160 or groups of stacks 160.

[0097] In some embodiments, each stack 160 may include multiple aluminum air cells 165 connected electrically in series yet separated by DC / DC converters 111 to limit the voltage across each part of the electrolyte flow, thus preventing the formation of shunt currents (current losses over the liquid electrolyte, resulting in energy loss). Due to the floating configuration of DC / DC converters 111 with respect to each other, no overall large voltage is applied on the complete stream of electrolyte, but sections of the stream (e.g., flowing through each of stacks 160) experience low voltages locally, which do not accumulate over the whole length of the flow and thus do not generate shunt currents, or merely very small shunt currents. In various embodiments, one or more of stacks 160 may be separated from other one or more stacks 160 by corresponding DC / DCconverters 111 in a floating configuration to limit a voltage on electrolyte flows 156 through the stack 160.

[0098] For example, when 4 stacks 160 of 20 cells 165 are electrically connected in series, a potential difference between the first and the last cells of about 100V may occur. Including DC / DC converters 111 between stacks 160 results in a potential difference of 25V between the first and the last cells of each module, but without summation of the voltage over all stacks 160. Such embodiments may be selected with respect to the tradeoff between: (i) accepting losses due to shunt currents, (ii) cost and complexity of operating multiple parallel electrolyte streams, and (ii) cost of including floating DC / DC converters between modules or groups of modules. Various embodiments of aluminum air sub-system 120 may comprise either solution or combinations thereof, with respect to the dimensions and numbers of the modules, their operational parameters and the overall design requirements from of aluminum air sub-system 120.

[0099] In another example, for aluminum air sub-system 120 with 12 stacks 160 of cells 165, where the electric configuration is in two electrically serially connected strings of six stacks 160 each, floating DC / DC converters 111 may be set between stacks 160 to reduce the voltage over each electrolyte flow stream to the stack voltage rather than to the accumulate voltage from all the stacks- yielding a smaller or no shunt current while avoiding the complexity of multiple parallel fluid connections among stacks 160.

[0100] In some embodiments, floating DC / DC converters 111 may be set between stacks 160 to limit a voltage drop over any part of the electrolyte flows (separated by floating DC / DC converters 111 on either side thereof) to be below a specified threshold (e.g., 0V, 5V, 10V, 20V or intermediate values). Keeping the voltage drop over the electrolyte flow smaller than the overall voltage of stacks (of the full string of serially connected stacks, which may reach, e.g., 50V, 72V, 100V or any other value depending on the number of cells and stacks serially connected) - reduces or prevents current leakage through the electrolyte, and thus reduces or avoids related energy losses to heat and risks for unwanted reactions.

[0101] Figures 8D-8G provide partial high-level schematic illustrations of shunt current management and prevention in system 100, according to some embodiments of the invention. Figure 8D illustrates embodiments with separate pairs of stacks 160A, 160B connected electronically in parallel and to DC / DC converter 111 (e.g., instead of hydraulic separation of electrolyte flows that is illustrated in Figure 8A), with DC / DC converters 111 connected in seriesto yield the floating connection configuration that maintains the voltage over the electrolyte flows small (section-wise). It is noted that Figure 8D illustrates configurations that are simpler hydraulically (simpler electrolyte flows 156 and management 190) and more complex electrically (requiring DC / DC converters 111 between stacks 160), compared to Figure 8A.

[0102] Similarly, Figure 8E illustrates embodiments with further details, that separate stacks 160 by DC / DC converters 111 instead of the hydraulic separation of electrolyte flows that is illustrated in Figure 8B. It is noted that Figure 8E illustrates configurations that are simpler hydraulically (simpler electrolyte flows 156 and management 190) and more complex electrically (requiring DC / DC converters 111 between stacks 160), compared to Figure 8B. In various embodiments, stacks 160A, 160B may be connected in parallel to respective DC / DC converter 111, or stacks 160A, 160B may be each connected to respective DC / DC converters 111, and DC / DC converters 111 may be connected in parallel to each other. DC / DC converters 111 connected to different pairs or groups of stacks 160 may be connected in series and / or parallel with respect to each other and to buffer 110.

[0103] Figures 8F and 8G illustrate schematically configurations that replace some of the additional electrolyte flow circuits provided in Figure 8C by DC / DC converters 111, to simplify the hydraulic configuration and reduce the hydraulic elements compared to configurations illustrated in Figure 8C. In some embodiments, all or some of the separate electrolyte flows 156 illustrated in Figure 8C may be replaced by DC / DC converters 111 set between stacks 160 or groups of stacks 160 - to reduce the overall voltage applied to each electrolyte flow - reducing or preventing shunt current from flowing through the electrolyte, generating heat and reducing the overall available power and energy. In various embodiments, any pair of stacks 160 may be separated by corresponding DC / DC converters 111, or only some of stacks 160 may be separated by corresponding DC / DC converters 111, depending on the voltage required to form shunt currents above a given threshold, with respect to performance analysis and requirements, and cost, complexity and maintenance considerations.

[0104] In non-limiting examples, Figure 8F illustrates a maximal voltage of 24V applied to electrolyte flows 156, while Figure 8G illustrates a maximal voltage of 150V applied to electrolyte flows 156.

[0105] For example, Figure 8F illustrates schematically pairs of strings of stacks 160 connected in series with respect to electrolyte flows 156, and connected electrically in parallel to respectiveDC / DC converters 111. DC / DC converters 111 are connected in series to accumulate the voltage provided (e.g., 3 times 24V to 72V, as a partial non-limiting example).

[0106] For example, Figure 8G illustrates schematically a large-scale high voltage configuration 200 of module 130 or 140, which delivers 80A at 900V, optionally through buffer 110. Strings of stacks 160 may be arranged to deliver 80A at 150V each, accumulating over DC / DC converters 111 so as to limit the maximal voltage falling over any electrolyte flow 156 through the respective string of stacks 160 to 150V (reducing or preventing shunt currents, compared to the overall 900V). In the illustrated configuration, some degree of hydraulic separation is provided by parallel electrolyte flows 156, complemented by electric separation of stack strings by DC / DC converters 111. In various embodiments, various such configurations 200 may be adjusted to specific requirement and limitations related to backup system 100. In some embodiments, electrolyte flows 156 may be delivered from an 8001 electrolyte reservoir 150, via pump(s) (e.g., at a throughput of 40m3 / h) as part of electrolyte circulation subunits 155, and via heat exchanger(s) 135 (e.g., 90kW). Clearly, the specific values may be modified according to the configuration and scale of the system.

[0107] Figures 9A-9H provide schematic illustrations of configurations of aluminum air cells 165 having unused anodes 167, according to some embodiments of the invention. Figure 9A is a perspective view of aluminum air cells 165 within frame 212, supporting paths 215 for delivering electrolyte into and out of cells 165 as disclosed herein. Figure 9A further illustrates anode contacts 217 to anode 167 (e.g., one or more aluminum studs) and cathode contacts 218 to cathode 168 (not illustrated in Figure 9A) for delivering energy and connecting between cells 165 as disclosed herein. Figure 9A further illustrates optional spacers 216 configured to maintain a minimal gap between anode 167 and cathode(s) 168 and seal 219 configured to prevent electrolyte leakage out of cell 165 and protect the edges of anode 167 from corrosion by preventing contact thereof with electrolyte 157 (not shown). Figure 9B is a schematic front view of aluminum air cells 165 within frame 212, showing cathode 168 with cathode contact 218 (e.g., a conductive tab) above anode 167 (indicated by an arrow to be below cathode 168). Figures 9A and 9B further illustrate a flexible element 220, such as a membrane, configured to mechanically support cathode 168 and enable movement of cathode 168 to dynamically adapt the width of the gap between cell anode 167 one or two cell cathodes 168 (on one or both sides of anode 167), as disclosed herein. The dynamically adaptable gap receives electrolyte 157 during operation (see Figures 11A and 11B) and is 1dynamically adapted to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode 167, as explained herein.

[0108] It is noted that disclosed configurations of aluminum air cells 165 may be applied to backup systems 100 at any scale - from small scales (e.g., including one of two stacks 160), through medium scales (e.g., including several or tens of stacks 160), and up to large scales (e.g., including many tens or hundreds of stacks 160).

[0109] The amount of energy in aluminum air cells 165 is determined by the usable amount of aluminum in anodes 167. For a certain form factor (length and width) of anode 167, cell capacity may be changed by changing the thickness of anode 167. The thicker the anode, the bigger the gap between anode 167 and cathode 168, which results from the gradual consumption of anode 167 by corrosion (electrochemical reactions) during the operation of cell 165. However, designing an increased gap to accommodate thicker anodes results in lowering the cell voltage and correspondingly lower power and lower energetic utilization. For example, anode thickness may be 20mm, theoretically providing two times the energy of 10mm anodes. However, as the anode is consumed, and the gap between the anode and the cathode is increased, and the practical amount of energy available for the load is reduced. In various embodiments, anodes 167 may have dimensions ranging between 100-700mm in length, 70-200mm in height and 7-30mm in thickness. In various embodiments, anodes 167 may have any intermediate value in any of the dimensions, and the cell structure may be designed to support corresponding anodes 167 as disclosed herein.

[0110] Figure 9C illustrates a schematic top view of a horizontal cross-section of aluminum air cells 165, indicating full thickness of anode 167 (e.g., 20mm), sealing of the anode edges by seal 219 around anode 167, and supports 216 that maintain a minimal gap (denoted schematically) between anode 167 and cathode 168. Figures 9D and 9E illustrate the horizontal cross-section in a perspective view, with and without cathode 168 (which hides supports, e.g. spacers 216) respectively. It is noted that in different embodiments of cells 165 - spacers 216 may be used or not, depending on the design details of cells 165.

[0111] Figures 9F-9H illustrates a longitudinal cross-section of aluminum air cells 165, in sideview (Figures 9F) and perspective views (Figures 9G and 9H) - without and with supports (spacers) 216, respectively. It is noted that either or both flexible element 220 (e.g., membrane) and supports 216 (spacers) may be used to manage the dynamically adaptable gap, e.g., by the former enabling controlled movement of cathode(s) 168 and the latter maintaining a minimal gap- preventing contact between anode 167 and cathode 168. In some embodiments only one of flexible element 220 (e.g., membrane) and supports 216 (spacers) may be used to manage the dynamically adaptable gap, e.g., by a mechanical configuration of flexible element 220 that maintains the minimal gap, or by application of passive force on cathode 168 against support 216 and configuring support 216 to be positioned against anode 167 even as it is consumed (corroded) by the electrochemical operation of cell 165.

[0112] In various embodiments, at least some, or all, of aluminum air cells 165 in stack(s) 160 may be configured to have a dynamically adaptable gap between cell anode 167 and one or two cell cathodes 168, which receives electrolyte 157 during operation and is dynamically adapted to maintain a specified anode-cathode gap during operation-related corrosion of respective cell anode 167.

[0113] For example, Figures 10A-10D provide schematic illustrations of configurations of aluminum air cells 165A having consumed (corroded) anodes 167A, according to some embodiments of the invention. In a non-limiting example, anodes 167A illustrated in Figures 10A- 10D may be thinner than corresponding anodes 167 in the same cell configuration 165, as illustrated in Figures 9A-9H, with the cell configuration managed to support continued efficient operation of cell 165A in spite of the reduction in anode thickness. For example, while anode 167 illustrated in Figures 9A-9H may be 20mm thick, anode 167A illustrated in Figures 10A-10D may be 10mm thick. It is noted that consumed anodes are denoted by numeral 167A, corresponding states of the cells are denoted by numeral 165A, the modified positions of the flexible element (e.g., membrane) and consequently the cathode(s) are denoted by numeral 220A and 168A, respectively. Seal 219 is configured to maintain protection of the edges of corroded anode 167A throughout the process of thickness reduction to prevent accelerated corrosion of the edges, as disclosed in U.S. Patents No. 11,418,640, incorporated herein by reference in their entirety.

[0114] Figures 10A and 10B provide perspective and side views of a longitudinal cross section of aluminum air cells 165A, respectively, while Figures 10C and 10D provide perspective and top views of a horizontal cross section of aluminum air cells 165A, respectively. Thus, Figures 10A, 10B, 10C, 10D correspond to Figures 9G, 9F, 9E, 9C, respectively. As noted herein, supports (spacers) 216 are optional in the disclosed cell configurations. Cathode contacts 218 are arranged to maintain contact to cathode(s) 168 throughout the movement of cathode(s) 168 (^168A) towardanode 167A during the consumption process of anode 167. The gap maintained between corroded anode 167A and moved cathode 168A is denoted schematically in Figure 10D.

[0115] Figures 11A-11F provide high level schematic illustrations of configurations of aluminum air cells 165 having one or two cathode(s) 168, according to some embodiments of the invention. Figure 11A illustrates in a highly schematic manner a string (line) of serially connected cells 165, each having two cathodes 168 and one intermediate anode 167, with the corresponding schematic electrical contacts. Cells 165 having two cathodes 168 per anode 167 are referred to herein as double-sided cells 165. Electrolyte 157 is delivered into the gaps between anode 167 and each cathode 168, e.g., to corresponding cells 165 in parallel strings as disclosed herein (see, e.g., Figures 7A, 7B and 8A-8C). It is noted that the serially connected cells 165 may embody cell stack 160, or cell stack 160 may comprise several lines of serially connected cells 165, as indicated schematically by the three dots. Figure 11B illustrates in a highly schematic manner a string (line) of serially connected cells 165, each having one cathode 168 and one anode 167, with the corresponding schematic electrical contacts. Cells 165 having one cathode 168 per anode 167 are referred to herein as single-sided cells 165. Electrolyte 157 is delivered into the gaps between anode 167 and cathode 168, e.g., to corresponding cells 165 in parallel strings as disclosed herein (see, e.g., Figures 7A, 7B and 8A-8C). It is noted that the serially connected cells 165 may embody cell stack 160, or cell stack 160 may comprise several lines of serially connected cells 165, as indicated schematically by the three dots. In some embodiments, stack 160, modules 140 or 130 and / or aluminum air sub-system 140 may comprise a combination of double-sided cells 165 and singlesided cells 165.

[0116] Figures 11C and 11D illustrate in a highly schematic manner the two states of having a fresh anode 167 and having a consumed (corroded) anode 167A in respective cells 165, 165A, in each of the double-sided configuration and the single-sided configuration of the cells, respectively. Both configurations illustrate the dynamic adaptation of the anode-cathode gap to enable full use of the energy in aluminum-air cell 165 during the gradual consumption of anode 167. For example, in cells having 20mm-thick anodes 167 with two air cathodes 168 - as illustrated, e.g., Figure 11C, one cathode 168 on either side of anode 167, effectively defining two electrochemical cells within one mechanical cell configuration - the anode-cathode gap may be dynamically adapted by up to 10mm on each side of anode 167 to maintain the specified anode-cathode gap for optimal cell operation and maximal energy delivery.

[0117] In certain embodiments, a similar dynamically adaptive gap may be implemented for thinner anodes 167 (e.g., 10mm anode 167 with cathode 168 facing only one of the anode’s sides, requiring up to 10mm adjustment of the gap), or for anodes having other thicknesses. Similar dynamical adjustment of the anode-cathode gap may be implemented in one-sided cells 165 as illustrated schematically, e.g., Figure 11D, e.g., by configuring flexible element 220, such as a membrane, to move (220B) cathode(s) 168 (^168A) towards anode 167 to maintain specified anode-cathode gap size, possibly with supports 216 (e.g., spacers) marinating a minimal gap size. It is noted that numerals 220A denote the flexible element in its adjusted position, while numerals 220B denote schematically the movement of flexible element 220 to accommodate the space being left by the consumed anode.

[0118] In various embodiments, the anode-cathode gap may be dynamically adapted during consumption of anode 167 to the extent required to maintain an optimal, or a reduced gap between anode 167 and one or two cathodes 168 against which anode 167 is operated. This extent would typically be the difference between the gap with a new anode 167 and the gap with a fully consumed anode 167A. As noted herein, one or more of aluminum air cells 165 may comprise mechanical barrier(s) 216 such as supports 216 configured to maintain a minimal gap between respective anode 167 and one or two cathodes 168.

[0119] Seals 219 configured to prevent electrolyte leakage out of cell 165 and protect the edges of fresh anode 167 and consumed anode 167 from corrosion by preventing contact thereof with electrolyte 157. It is noted that while illustrated seals 219 do not extend much or at all beyond the edges of fresh anodes 167 (see illustrated in some structural detail in Figures 9A-9H, and illustrated schematically on the left hand side of in Figures 11C and 11D), as anode is consumed 167A, the edges thereof recede and seals 219 extend beyond the edges of consumed anode 167A (see illustrated in some structural detail in Figures 10A-10D, and illustrated schematically on the right hand side of in Figures 11C and 11D and in Figures HE and HF), maintaining protection of the edges of the corroding anode 167A.

[0120] Various embodiments, illustrated schematically, may be implemented to reduce and maintain a minimal, or relatively small gap between anode 167 and cathode 168 (the gap is filled with electrolyte 157 during operation of cell 165). In particular, for initially thick anodes 167, disclosed embodiments provide partial or full compensation for the increasing size and volume of the gap as the anode corrodes. Keeping the gap small allows using less electrolyte 157 and increasesthe power output and capacity of cells 165. The various configurations may be implemented in two-sided cells (having two air cathodes for each intermediate aluminum anode) and / or in onesided cells (having one air cathode for each aluminum anode, which is backed by the cell frame).

[0121] The one or two cell cathodes 168 may be supported by corresponding one or two flexible elements 220, such as frame(s) or membrane(s) at the circumference of air cathode 168, configured to enable movements of the respective cathode 168 (^168A) towards anode 167A as the anode corrodes during operation - to reduce the gap between them. The gaps that are maintained throughout the movements are denoted schematically in Figures 11C and 11D. For example, in order to maintain a fixed gap between anode 167 and cathode 168 regardless of anode usage, air electrode (the cathode) 168 may be fixed to frame 212 through flexible membrane 220 (made, e.g., of PTFE, polytetrafluoroethylene) that allows the cathode to move back and forth to and from the anode (towards the anode as it thins due to corrosion, from the anode after it is replaced by a new, thicker anode). A mechanical barrier (e.g., spacers) may be set between the anode and the cathode to maintain a minimal gap between them throughout the process of consumption of the anode. The anode is fixed to the frame at its narrow circumference (edges) in a way that protects the edges from corrosion (e.g., using a flexible seal, e.g., an elastomer, or preventing the electrolyte from reaching the edges of the anode in any other way, e.g., coating, mechanical structure, etc., e.g., as taught in U.S. Patents Nos. 10,096,873 and 11,418,640, incorporated herein by reference in their entirety). The flexible connection of the cathode(s) may be implemented symmetrically and allow using two air electrodes on both sides of an aluminum anode, or may be implemented in cells with one cathode per anode.

[0122] Figures HE and HF illustrate in a highly schematic manner the two states of having a fresh anode 167 and having a consumed (corroded) anode 167A in respective cells 165, 165A, in each of the double-sided configuration and the single-sided configuration of the cells, respectively.

[0123] In various embodiments, cell structures may be configured to have membranes 220 that allow air cathodes 168 to move (^168A) towards aluminum-air anode 167 as anode 167A is being consumed, and re-establish an original distance (gap) between anode 167A and cathode(s) 168 after aluminum-air anode 167A is replaced with a fresh anode 167. Spacers 216 may be used to assure that cathode(s) 168 and anode 167 do not touch each other during movements 220B of cathode(s) 168 and possibly also movements 226 of anode 167 (see Figure HF for a non-limiting example) - the latter being an optional configuration to complement movements 220B of cathode(s)168, with (consumed) anode 167A being movable towards cathode 168 to dynamically adjust the gap-

[0124] The flexibility of membrane(s) 220, optional spacers 216 and optional anode movements 226 are configured to enable the dynamical adaptation of the relative positions of cathode(s) 168 with respect to anode 167 - maintaining the optimal or reduced gap therebetween (the gap is denoted schematically, and may be maintained with or without spacers 216, depending on the design details). It is noted that aluminum anode 167 typically includes an aluminum plate that is being gradually consumed through the electrochemical reactions and therefore gradually thins. Air cathodes 168 include porous oxygen-delivering structures with catalytic material that catalyzes the electrochemical reaction - which may be moved and supported at the appropriate gap distance due to their light weight, while maintaining their structural and functional integrity.

[0125] In various embodiments, various types of elements 225 may be used to move one or two cell cathodes 168 to dynamically adapt the gap to anode 167A and / or back to fresh anode 167 after replacement of consumed corroded anode 167A. Non-limiting examples for elements 225, denoted schematically be arrows on both or one side(s) of double or single sided cells 165 in Figures HE and HF respectively, include (i) one or more elastic passive element 225A (e.g., spring, foam), (ii) one or more threaded rod or screw 225B and / or (iii) one or more elements that apply internal and / or external pressure 225C. In various embodiments, elements 225 may be used in addition to flexible membrane(s) 220 or without flexible membrane(s) 220.

[0126] In some embodiments, cathode(s) 168 may be affixed in the respective proper position (depending on the thickness of anode 167) by various mechanisms, e.g., by pressing cathode 168 against the gap barriers (e.g., spacers 216) to maintain proper proximity to anode 167. The pressing may be implemented using any of: (i) elastic passive element(s) or device 225A (e.g., spring, foam) placed outside cell 165 and continuously pressing cathode 168 inward towards anode 167 - with gap barriers 216 ensuring minimal gap without short circuiting anode 167 and cathode 168; (ii) threaded rod(s) (or screws) 225B may be used to set the gap between anode 167 and cathode 168 - the gap may be set according to anode consumption and may be reset when fresh anode 167 is loaded into cell 165, without or with gap barriers 216 (which may be used as an additional safety measure to avoid short-circuiting anode 167 and cathode 168); (iii) Application of internal and / or external pressure 225C to press cathode 168 inward towards anode 167, e.g., using a pressure difference between atmospheric pressure outside cell 165 and lowered pressure inside cell 165,using a pressure in a balloon (not shown) that is attached to cathode 168 and pushes it towards anode 167, and / or using electrolyte hydraulic pressure against one or both electrodes to set the gap between anode 167 and cathode 168. Gap barriers 216 may be used to maintain the gap between anode 167 and cathode 168.

[0127] In single cathode configurations (single sided cells 165, e.g., as illustrated schematically in a non-limiting manner in Figure 11F), elements 225, denoted schematically be arrows on both or one side(s) of double or single sided cells 165 in Figures HE and HF respectively, include (i) one or more elastic passive element 225A (e.g., spring, foam), (ii) one or more threaded rod or screw 225B and / or (iii) one or more elements that apply internal and / or external pressure 225C. In various embodiments, elements 225 may be used in addition to flexible membrane(s) 220 or without flexible membrane(s) 220.

[0128] In single cathode configurations (single sided cells 165, e.g., as illustrated schematically in a non-limiting manner in Figure HF), elements 226 (indicated by the arrows) such as one or more elastic passive element 226A (e.g., spring, foam), (ii) one or more threaded rod or screw 226B and / or (iii) one or more elements that apply internal and / or external pressure 226C. In various embodiments, elements 226 may be used as only elements for adjusting the cathode-anode gap, or elements 226 may be used in addition to elements 225 and / or flexible membrane(s) 220.

[0129] In some embodiments, anode 167 may be framed and connected to cell 165 through a flexible frame (not shown, e.g., similar to membrane 220), and pressed towards cathode 168 during the operation. Any of the disclosed configurations for moving cathode 168 may be applied to anode 167. Anode 167 may also be sealed on its back side (not illustrated) such that it is not exposed to electrolyte 157 on its back side, and spontaneous corrosion is avoided. Sealing may be carried out by gluing a protective plate, applying liquid masking material, or pressing anode 167 towards a flexible surface (e.g., elements 226C). Protection of the back side of anode 167 may be carried out in addition (or possibly in place of) to using seal 219, which is configured to line the perimeter of cell frame 212 facing anode 167 with, e.g., elastic material that is pressed against the anode perimeter and prevents electrolyte 157 from reaching it. Furthermore, draining electrolyte 157 from cell 165 may be configured to drain electrolyte 157 from the sides of the gradually corroding anode 167A, to prevent electrochemical reactions on the anode edges.

[0130] In various small-scale embodiments disclosed herein, such as electric vehicle implementations, as aluminum anodes 167 of cells 165 of aluminum air cell stack 160 or module140 or 130 are consumed, the gap between the gradually corroding anode 167A and cathode(s) 168 may be adjusted as disclosed herein, to optimize electrolyte usage and cell power and efficiency. The system may set aluminum air stack 160 or module 140 or 130 to work at various power ratings according to all of the parameters mentioned above.

[0131] Figures 12A-12C are high level schematic block diagrams of self-testing configurations 230 of cell stacks 160, modules 140 and sub-system 120, according to some embodiments of the invention. For example, one or more controller(s) 60 may be configured to monitor the status of aluminum air sub-system 120 during periods in which aluminum air sub-system 120 does not operate, by receiving measurements from sub-system components and deriving the status therefrom. It is noted that disclosed self-testing configurations 230 may be applied to backup systems 100 at any scale - from small scales (e.g., including one of two stacks 160), through medium scales (e.g., including several or tens of stacks 160), and up to large scales (e.g., including many tens or hundreds of stacks 160).

[0132] During standby mode 255, electrolyte 157 is kept outside of cells 165 and thus no chemical reaction occurs and there is no electricity generation. Aluminum air sub-system 120 may be in standby mode for long periods of time. Disclosed embodiments enable to monitor cell stacks 160, modules 140 and / or sub-system 120 and verify that the respective part and / or whole subsystem 120 is in proper operation condition during standby 255 and that it would operate properly when started - but without actually operating cell stacks 160, modules 140 and / or sub-system 120. Specifically, disclosed embodiments monitor and ensure the operability of cell stacks 160, modules 140 and / or sub-system 120 without generating energy, in order to avoid consuming consumables (e.g., aluminum anodes 167, electrolyte 157 etc.) and to avoid reducing system energy capacity. In case a malfunctioning component is detected, it may be repaired or replaced without causing system failure upon operation. Therefore, disclosed self-testing methodology and systems 230 increase the reliability of energy backup systems 100 and prevent malfunction upon or during operation of energy backup systems 100.

[0133] Self-testing may be carried out with respect to most or all elements that may malfunction, as long as testing them does not require full operation of respective cell stacks 160, modules 140 and / or sub-system 120. For example, system controller(s) 60 (or an external controller) may be configured to perform a series of self-tests that measure the behavior of the various devices in cell stacks 160, modules 140 and / or sub-system 120 - directly and / or indirectly. Integration of the self-testing results may be implemented in various manners, such as centrally and locally, or remotely, using various types of displays and alerts.

[0134] Figures 12A-12C illustrate embodiments of self-testing configurations 230 from various aspects, which may be combined with each other in part or fully. Figure 12A provides a high-level schematic block diagram of self-testing configurations 230 that include self-tests 232 of electrochemical cells 165, self-tests 234 of electrolyte and washing liquid circulation subunits 155 (e.g., utilizing respective circulation elements such as pump(s), conduits, valves, liquid level sensors, temperature sensors, pressure sensors, air flow sensors, liquid flow sensors, H2 sensors (see, e.g., Figure 5C) etc., see further details in Figures 12B and 12C), self-tests 236 of thermal management subunits 180 (e.g., tests of pumps, valves, sensors, heaters and mechanical devices such as fans and blowers, see further details in Figure 12C), self-tests 238 of electric / electronics subunits 240 and components thereof, as well as self-tests 242 of communications elements 245 in system 100. Any of self-tests 232, 234, 236, 238, 242 involving washing liquid rather than electrolyte, may be handled locally and / or communicated to system controller 60 or sub-units thereof at different system levels, e.g., by wire or wireless (represented schematically by communication link 99).

[0135] Figure 12B provides a more detailed high-level schematic block diagram of self-testing configurations 230 that include cell tests 232 of cells 165 or cell groups (e.g., cell stacks 160 or parts thereof) during various modes to monitor their state and alert if any deterioration or malfunction starts to develop. Passive self-testing during other operations (as described herein) yields indications derived from various operational aspects of the cells.

[0136] For example, during washing mode 250, in which respective stack 160, module 140 or 130 and / or sub-system 120, via respective controller(s) 60 - may be configured to fill cells 165 with washing liquid and measure the voltage of stacks 160 or cells 165 to ensure that they are in the expected range - as self-tests 252 (with washing liquid rather than electrolyte). The washing liquid does not consume anode 167 (as it does not initiate electrochemical reactions, unlike the electrolyte, as disclosed in WIPO Application No. PCT / IL2024 / 050104, incorporated herein by reference in its entirety) and thus does not reduce the system’s energy capacity while verifying system readiness. Self-tests 252 enable to check the operational voltages that cells 165 may provide upon operation - without actually operating cells 165 - avoiding consumption of anodes 167, utilization of electrolyte 157 and possible changes that may occur during brief but frequent fulloperation of cells 165, contrary to the design of cells 165 that is intended for prolonged but rare operation periods. Additionally, electrolyte and washing liquid circulation subunits 155 may be self-tested 234 during self-testing 252 in washing mode 250, e.g., to detect leakage, pumping and draining efficiency, liquid quality and electrolyte residues, etc. Examples for washing liquid include various liquids configured to remove electrolyte residues and prevent further reactions of the aluminum anode (see non-limiting examples in WIPO Publications Nos. 2015151108, 2018109767 and WIPO Application No. PCT / IL2024 / 050104 incorporated herein by reference in their entirety).

[0137] In another example, during standby mode 255, respective stack 160, module 140 or 130 and / or sub-system 120, via respective controller(s) 60 - may be configured to monitor the voltage(s) of cells 165 (denoted self-testing 256 of standby mode 255A) to ensure that the voltage(s) are within the expected range(s). For example, the voltage of cells 165 should drop as electrolyte 157 is drained out of cells 165. Deviation from the expected voltage drop or changes in its characteristics may be taken to indicate a possible issue. The voltages of cells 165 and / or stacks 160 measured in self-test 256 of standby 255A may also be used as indications for presence of electrolyte 157 and / or washing liquid (from washing mode 250) in cells 165, and help detect problems in electrolyte and washing liquid circulation subunits 155 such as possible leakages, pump failures, etc. (see Figure 12C for further details). For example, self-tests 258 of standby mode 255B may be configured to detect electrically liquids in cells 165 during standby mode 255.

[0138] In case aluminum air stacks 160 are connected in parallel to another source of voltage (e.g., to buffer battery 110 as disclosed herein), the voltage of stacks 160 may be forced by the voltage of the other source, and mask the internal voltage of cells 165. In such case, self-testing configuration 230 may include additional voltage sensor(s) 241 configured to perform independent measurements of internal voltages, e.g., between the negative pole of aluminum air system 120 and one or more arbitrary cell(s) 165 inside stacks 160 of cells 165. Additional sensor(s) 241 may be configured to allow small current(s) pass through sensor(s) 241. In operation mode of aluminum air cells 165, with electrolyte in them, the currents through sensor(s) 241 are negligible. In standby mode 255 however, without electrolyte 157 in cells 165, the low current shorts cells 165 between the negative pole and sensor(s) 241, so that their voltage reading drops to nearly zero. The accumulated voltage of the rest of cells 165 then equals to the voltage of the other voltage source(e.g., buffer 110). This voltage distribution serves as an indication for cells 165 being dry, and for the proper operation of the draining mechanism thus proper standby mode.

[0139] Additionally, self-tests 238 may be carried out for various components in electric and / or electronics subunits 240, and self-tests 242 may be carried out for various components in communications subunits 245, such as communication tests between all sub-units of system controller 60 and other components (see also Figure 12A).

[0140] Figure 12C provides further examples for components in stacks 160, modules 140 and / or sub-system 120 and associated subunits that may be self-tested during standby mode 255 or washing mode 250 during idle period in which cells 165 are not operated. In the non-limiting illustration, stacks 160 are illustrated as part of module 140 or 130. The following are non-limiting examples for various self-tests that may be performed on system components, without operating cells 165 (indicated schematically by triangles pointing to respective components).

[0141] Self-testing configurations 230 may include self-tests 232 of cell and stack components, e.g., self-tests 232A, 232B of and / or by stack or cell temperature sensors, self-tests 232C of pump pressures and self-tests 232D of valves - all indicated schematically to represent multiple components associated with stacks 160. Self-testing configurations 230 may include self-tests 234 of circulation elements and components 155, e.g., self-tests 232A, 232C, 234D, 234E, 234G of various inlets and outlets, e.g., to electrolyte work tank 150, fresh electrolyte tank 152, drain tank 192 for used electrolyte, as well as corresponding circulation elements of washing liquids (not shown); self-tests 234D of and / or by temperature sensors (and self-tests 236D of pump pressures), and self-tests 234B, 234F of valves - all indicated schematically to represent multiple components associated with circulation elements and components 155 (including electrolyte pumps, wash liquid pumps, coolant pumps, etc. - without filling the cells / stack with electrolyte). Self-testing configurations 230 may include self-tests 236 of heat management elements 180, such as self-tests 234E of heater(s) 182 associated, e.g., with electrolyte work tank 150, self-tests 236C of heater exchanger(s) 136, self-tests 236G of cooling unit(s) / radiator(s) 135, self-tests 236D, 236E of pumps, self-tests 236A, 236F of and / or by temperature sensors, self-tests 236B of F / M (flow metering) elements and so forth. Any of self-tests 232, 234, 236 may be handled locally and / or by communicated to system controller 60 or sub-units 60A, 60B, 60C (indicated schematically) thereof at different system levels, e.g., by wire or wireless (represented schematically by communication link 99).

[0142] For example, system configurations 230 may include closing a valve leading from work tank 150 to stacks 160 and then operating the respective pump. System configurations 230 may measure the hydraulic pressure (232C) between the pump and the valve which may be used to indicate the pump’s operation. System configurations 230 may measure the power consumed by the pump as an indication of a correct operation signal and pump operation, compared to normal power consumption of the pump. In this manner, some, most or all pumps in the system may be tested without actually circulating electrolyte. In some embodiments, valves may be installed for the self-tests (e.g., 232D, 234B, 234F), to enable testing specific pumps.

[0143] In another example, system configurations 230 may include testing mechanical devices such as cooling fans, air blowers, air fans (for circulating coolant, air, removing heat), etc., e.g., of heat management elements 180 (self-tests indicated schematically by numeral 236), or of other sub-units, e.g., mechanical latches, conveyors, element replacement sub-units, etc. System configurations 230 may include operating the mechanical devices and measuring their power consumption to ensure these are within the expected range (but without fully operating cells 165, stacks 160, modules 140 and sub-system 120 to generate electrochemical reactions). For example, for testing air blowers and air flow meters, system configurations 230 may include operating the blower(s) and measuring the airflow therefrom - to ensure the reading is within expected range; for testing heating elements system configurations 230 may include turning the heater(s) on and measuring e.g., the power consumption and / or the temperature of the heated liquid - verifying that the heating elements can provide the required temperature changes - all without fully operating cells 165, stacks 160, modules 140 and sub-system 120 to generate electrochemical reactions.

[0144] In addition, system configurations 230 may further include self-testing and monitoring at any given time how much energy is available in cells 165, stacks 160, modules 140 and / or subsystem 120 in order to better estimate the availability of the respective elements.

[0145] During operation, with electrolyte 157 being pumped into cells 165 and stacks 160- activating the electrochemical reactions, providing electricity while consuming aluminum anodes 167 - system controller(s) 60 may be configured to continuously measure current flow and aggregate the total charge (e.g., in ampere-hour) consumed from aluminum anodes 167 and calculate the total available capacity of cells 165, stacks 160, modules 140 and / or sub-system 120.

[0146] Self-testing configurations 230 may be also partially or fully conducted during operation of cells 165, in addition to their performance during standby mode and / or washing mode 250.

[0147] As disclosed herein, aluminum-air cells 165 operate once fluid electrolyte 157 (e.g., aqueous KOH solution) is introduced between air cathodes 168 and aluminum anodes 167 to initiate and support the electrochemical reactions, in which aluminum is oxidized, aluminum anodes 167 are gradually corroded (consumed), and the flowing electrolyte 157 removes oxidation products and heat from cell 165. Electrolyte 157 for operating cells 165 may be circulated through cells 165, e.g., from and to a common electrolyte work tank 150 associated with stack 160 or module 140 or 130 and respective circulation elements such as pump(s), conduits, valves, etc. (see, e.g., Figures 2A, 2B, 4, 7A, 7B, 12C). Electrolyte work tanks 150 of modules 140 may be connected to electrolyte reservoir(s) 152 from which fresh electrolyte is supplied, and to electrolyte reservoir(s) 192, to which utilized electrolyte is delivered, e.g., for collecting and regeneration. Electrolyte 157 is circulated until it is saturated with oxides, with full utilization defined according to specific performance and operational considerations.

[0148] In various embodiments, electrolyte management unit 190 may be configured to optimize electrolyte use with respect to the operation profile of aluminum air sub-system 120. Electrolyte may be supplied to groups of cells 165 (e.g., stacks 160) in batches that are circulated through a work tank until they are exhausted or the operation is halted; or in an amount that is circulated until it is exhausted or the operation is halted. Partly-used electrolyte may be used to further generate power (after the load requirements are satisfied) to recharge buffer 110, or may be discarded and possibly recycled. Electrolyte management unit 190 may be further configured to manage the temperature of electrolyte 157 used in cells 165 and stacks 160 to optimize a power output of stacks 160.

[0149] It is noted that disclosed configurations of backup systems 100 to optimize electrolyte use may be implemented at any scale - from small scales (e.g., including one of two stacks 160), through medium scales (e.g., including several or tens of stacks 160), and up to large scales (e.g., including many tens or hundreds of stacks 160).

[0150] Electrolyte 157 may be supplied from electrolyte reservoir(s) 152, typically into smaller work tanks 150 that serve one or more aluminum-air module 140 or 130. From respective work tank 150, electrolyte 157 is circulated through stacks 160 of cells 165 during operation, introduced to cells 165 during starting and drained from cells 165 during stopping of the cell operation (simultaneously for all cells 165 in stack 160, and all stacks 160 connected to the same electrolyte circulation loop). As during operation electrolyte 157 gradually degrades (accumulating aluminumoxides, reducing supplied power) and the required electrolyte volume gradually increases (as aluminum anodes 167 corrode and leave a larger gap between them and cathodes 168, except for embodiments involving the adjustment of the gap, as explained e.g., in Figures 9A-11F and in the related disclosure) - continuous management of electrolyte is carried out. Moreover, in some embodiments, electrolyte temperature and / or flow rate may be controlled and adjusted with respect to electrolyte utilization degree and / or with respect to anode thickness, e.g., to maintain a flat discharge curve (see Figure 3C), maintain a specified working point, maintain even consumption of the anode surface and / or operate cells 165 at optimized efficiency.

[0151] Figures 13A and 13B are high level schematic block diagram illustrations of electrolyte circulation schemes, according to some embodiments of the invention. In various configurations, electrolyte 157 may be supplied to stacks 160 of cells 165 from work tank(s) 150 continuously or in batches 270, and partly utilized batches (upon stopping of cell operation) may be stored and reused, or replaced with fresh electrolyte, as described herein. In various embodiments, (i) discrete batches 270 of electrolyte 157 may be circulated consecutively, possibly (but not necessarily) fully utilizing each batch before using the next batch (e.g., Figure 13A), (ii) an amount of electrolyte 157 may be circulated and its volume may be adjusted gradually as anodes 267 corrode and increase the available volume for electrolyte 157 in cells 165 (e.g., Figure 13B, with adjustment), and / or (iii) the complete amount of electrolyte 157 allotted for module 140 or 130, or a group of cells 165 may be circulated until it is fully or partly utilized, or disposed of (e.g., Figure 13B, without adjustment). In any of these cases, electrolyte 157 is continuously circulated through cells 165 during their operation to assure proper proceeding of the electrochemical reactions and removal of heat and oxidation products from cells 165.

[0152] As a non-limiting example of electrolyte use, various embodiments employ 4.5 liter electrolyte per stack 160 having cells 165 with fresh anodes 167, and use 9 liter electrolyte per stack 160 having cells 165A with fully depleted (consumed, corroded) anodes 167A (see e.g., Figures 10A-10B, but without the disclosed mechanisms for adjusting the gap between cathode(s) 168 and used anode(s) 167A, or only with partial adjustment that reduces the required increase in the volume of the electrolyte). For operation, in a non-limiting example, a required electrolyte flow rate may be 17.5+2.5 1 / min per stack 160, requiring partial replacement of used electrolyte with fresh electrolyte - in various embodiments as disclosed herein. It is emphasized that these numericalexamples are merely demonstrative, and the values may change with respect to many parameters, such as number of cells 165 per stack 160, configuration of cells 165, etc.

[0153] Figure 13A illustrates schematically batch-based management of electrolyte 157 (e.g., by electrolyte management unit 190), in which, when operating, discrete batches 270 of electrolyte 157 may be circulated between stacks 160 or groups of cells 165 (in aluminum air modules 130 or 140, depending on scale) and work tank 150. Upon saturation of batch (270^270A), the used electrolyte 270A is pumped out to used electrolyte tank 192A, and new batch 270 of fresh electrolyte 157 is pumped from fresh tank 152A to work tank 150, as illustrated schematically. If the operation of aluminum air system 120 (or of one or more aluminum-air module 130 or 140) is stopped before electrolyte 157 (of the batch in use) is fully utilized, the partly-used batch of electrolyte 157 may be drained from stacks 160 or groups of cells 165, and may be stored in work tank 150 as a partly used electrolyte batch until the next operation of aluminum air system 120 (or of one or more aluminum-air module 130 or 140). Work tank 150 may have heater 182 associated therewith, which may comprise an electric heater and / or an auxiliary heater that utilizes heat from other sources) - to maintain electrolyte 157 at a desired elevated temperature to keep it at the same working point as it was when stopping - as managed by heat management unit 180. Heat management unit 180 may be configured to adjust the temperature of the electrolyte with respect to various parameters such as level of usage of the electrolyte, degree of anode consumption, operational parameters of the cells, operation parameters of the stacks, modules and aluminum system, as well as expected operational patterns with respect to power requirements therefrom, etc. and in a way that optimizes various parameters such as required power levels and operation efficiency of the cells, electrolyte use, frequency of maintenance and electrolyte replacement, electrolyte re-use possibilities, etc. Consecutive use of discrete electrolyte batches 270 may enable good control of electrolyte use as well as thorough use of electrolyte amounts prior to replacing electrolyte, in view of the possibly variable use pattern of electrolyte in the cells.

[0154] In various embodiments, batch use of electrolyte allows “topping off’ the amount of electrolyte used in the cells. For example, at any given time, used electrolyte tank 192A may be drained (e.g., into a larger used electrolyte tank 192 serving multiple modules 130 or 140) and fresh electrolyte tank 152A may be filled (e.g., from a larger used electrolyte tank 152 serving multiple modules 130 or 140). Independent handling of fresh electrolyte tank 152A and used electrolyte tank 192A for each stack(s) 160 or groups of cells 165 - enables to maintain electricity generationfrom aluminum air modules 130 or 140 with continued circulation of electrolyte between stacks 160 of cells 165 and work tank 150 - while fresh electrolyte tank 152A and / or used electrolyte tank 192A are being replaced (see also disclosed herein configurations of aluminum air sub-system 120 with staggered replacement of electrolyte). Such configurations also enable supply of fresh electrolyte without mixing fresh and used electrolyte.

[0155] In some embodiments however, a single work tank 150 may be used (without modulespecific fresh electrolyte tank 152A and / or used electrolyte tank 192A), simplifying the system at the expense of wasting electrolyte that is not fully utilized. Optionally, in single work tank 150 configurations, electrolyte 157 may be fully utilized by providing power from aluminum-air module(s) 130 or 140 to a different consumer, such as rechargeable buffer 110 after the end of grid interruption - to derive a maximal amount of power per amount of (fully used) electrolyte.

[0156] Using small electrolyte batches 270, in combination with rechargeable buffer 110 disclosed herein, may enable in some embodiments to use buffer 110 to compensate for the low power periods that are due to increasing electrolyte utilization levels (providing less power than fresh / partially utilized electrolyte). Also, thermal management of the electrolyte (by unit 180), involving, e.g., heat dissipation and initial heating of electrolyte 157 (optionally with respect to the level of electrolyte utilization) may be carried out with respect to the circulated electrolyte batches. For example, work tanks 150 and / or small batches 270 may be pre-heated (see schematic indications in dotted lines in Figure 13A), possibly from rechargeable buffer 110 before starting of aluminum air sub-system 120, and / or by using heat from an external source(s) 80 (see, e.g., Figure IB), and / or using stored heat from a previous operation of same or other aluminum-air module(s) 130 or 140) - to provide higher power upon operation. Specifically, as the desired electrolyte temperature depends on the level of saturation of the aluminum-oxides in electrolyte 157 (electrolyte utilization), partially-used electrolytes may be stored in work tank 150 at elevated temperatures proportional to the level of saturation between runs (see, e.g., Figures 14A-14C).

[0157] In certain embodiments, aluminum air sub-system 120 may be operated with an adaptive batch size. The size of batch 270 may be adjusted with respect to the available cell volume, which is related to the thickness of anode 167 and may be monitored independently and / or as indicated by monitored electrolyte volumes removed from the respective cells. The adaptive batch size may be adjusted with respect to the amount of electrolyte that is required to maintain proper circulation through cells 165, as the free volume in cells 165 changes through the consumption of aluminumanodes 167 in the cells (see e.g., Figures 10A-10B, but without the disclosed mechanisms for adjusting the gap between cathode(s) 168 and used anode(s) 167A, or only with partial adjustment that reduces the required increase in the volume of the electrolyte) - a fresh cell 165 has a full amount of aluminum in it (minimal free volume for electrolyte), while a depleted cell 165A has nearly no aluminum in it (maximal free volume for electrolyte). An adaptive batch size uses the (minimal) volume of electrolyte that is required for proper circulation at any given time, e.g., by determining the batch size as the amount of electrolyte that fills the cells at any given state. This can be implemented either by measuring the batch size and matching it with the status of the aluminum in anodes 167 of cells 165, or by a mechanical design that limits the amount of electrolyte in work tank 150 according to the available volume in cells 165, e.g. using a float (not shown) in work tank 165 that makes sure that there is a minimal amount of liquid in tank 165 at any given time. Monitoring and managing batch sizes throughout cells 165, stacks 160 and modules 130, 140 provides high resolution management means that leads to better overall utilization of the electrolyte.

[0158] Referring to Figure 13B, in certain embodiments, aluminum air sub-system 120 may be operated without work tank 150, but instead with electrolyte management unit 190 configured to manage and deliver adaptive volumes of electrolyte 157 to cells 165, e.g., via an electrolyte circulation unit 158 associated with cells 165 and stacks 160 in modules 130 or 140. Aluminum- air modules 130 and / or 140 may include fresh electrolyte tank 152A and used electrolyte tank 192A, but no work tank 150. When starting, electrolyte 157 may be taken from fresh tank 152A, optionally heated by heater 182, pumped into cells 165 by electrolyte circulation unit 158 (including pipework and pumps, not shown, see, e.g., Figure 12C for the components in a different configuration that does include a work tank) and circulated in a closed loop back to cells 165. Once the electrolyte circulation loop is closed, electrolyte management unit 190 or a corresponding controller thereof may be configured to conclude that a minimal batch size of electrolyte 157, which fills all cells 165, has been taken from fresh electrolyte tank 152A, and it is circulated through cells 165 and electrolyte management unit 190 may be further configured to halt further delivery of more electrolyte 157 from fresh tank 152A. This, through closing of the electrolyte circulation loop, the initial required amount of electrolyte for cycling may be determined. During operation, water from electrolyte 157 are gradually consumed or evaporate, and the volume of cycled electrolyte decreases. Electrolyte management unit 190 (e.g., via controller(s) thereof) may be configured todetect the decrease in cycling electrolyte volume and compensate for the decreasing electrolyte volume by adding electrolyte from fresh electrolyte tank 152A (e.g., using a float valve, not shown). When aluminum-air modules 130 and / or 140 (or whole aluminum-air sub-system 120) is stopped, electrolyte 157 may be drained into used electrolyte tank 192A, regardless of the level of saturation (usage) of the electrolyte. This configuration ensures adaptive amount of electrolyte 157 at any given moment. In combination with rechargeable buffer 110, if load 90 on aluminum- air sub-system 120 drops before the amount of electrolyte 157 is fully exhausted, aluminum air module 130 and / or 140 may be configured to continue and generate energy to be stored in rechargeable buffer 110 until electrolyte 157 is fully utilized (or buffer 110 is full) and only then drain electrolyte 157 to used electrolyte tank 152A.

[0159] In some embodiments, used electrolyte from system’s used electrolyte tank 192 may be recycled to yield fresh electrolyte, delivered to system’s fresh electrolyte tank 152, possibly following a recycling period. Various embodiments comprise removing aluminum hydrates (e.g., by precipitation) to regenerate fresh electrolyte (e.g., KOH at a specified concentration), which may be especially beneficial at large scale systems 100 as disclosed herein. Disclosed electrolyte management configurations enable monitoring the degree of electrolyte usage throughout cells 165 and stacks 160 in modules 130, 140 in relation to the system’s power performance as disclosed herein, and configure electrolyte recycling parameters and timing in relation thereto, as well as in relation to the availability of external power sources 80 and requirement from load 90 - for example, recycle electrolyte 157 at low energy costs, at a volume related to the level of required power from aluminum air sub-system 120, and see staggered replacement configuration disclosed herein.

[0160] Figures 14A-14C are high level schematic examples for module reactions to changing load, temperature and voltage (respectively), which may be monitored and managed in relation to the batch-wise delivery of the electrolyte, according to some embodiments of the invention. The denoted values provide non-limiting examples for simulated scenarios and system reactions thereto. Figures 14A-14C elaborate on various embodiments of managing cell and stack operation (compared, e.g., with Figure 3C illustrating schematically temperature management). Figure 14A provides non-limiting examples for current management 280, Figure 14B provides non-limiting examples for electrolyte temperature management 282, and Figure 14C provides non-limiting examples for voltage management 284. Clearly all these and additional operational aspects may be managed in relation to each other to optimize overall system performance. Controller(s) 60 may beconfigured to dynamically adjust management of various aspects of the operation of cells 165 and stacks 160 in modules 140, 130 as disclosed herein, e.g., with respect to electric parameters (e.g., current, voltage, power, energy), electrolyte parameters (e.g., temperature, volume, batch volume, level of usage), status of the system (e.g., standby or operation, in relation to the operational profile), maintenance operations (e.g., replacement of electrolyte and / or anodes), and so forth.

[0161] For example, Figure 14A illustrates schematically different scenarios 280 for constant and dynamic load 90 (see, e.g., Figures 1A-1C). Non-limiting examples for scenarios 280 include a constant relatively low load 280A (e.g., 55A), a constant relatively high load 280B (e.g., 100A), cyclic load changes 280C fluctuating gradually between low and high loads (e.g., cycles between 55A and 100A), intermittent high loads 280D (usually low load, e.g., 55A, occasionally or periodically relatively short periods, or steps, of high loads, e.g., 100A), regularly step-wise oscillating load 280E (relatively frequent fluctuations between low and high loads, e.g., 55A and 100A) and intermittent high loads with interruption of operation 280F (similar to scenario 280D, and then interrupted).

[0162] In various embodiments, control unit(s) 60 of disclosed backup system 100 may be configured to adjust the operation of buffer 110 and aluminum air sub-system 120, including the internal operation of electrolyte management unit 190 and heat management unit 190 according to detected or expected load profiles. Non-limiting examples for active thermal responses 282 to scenarios 280 are illustrated in Figure 14B, including the load profile scenarios and the average of electrolyte temperature entering and exiting a non-limiting example of stack 160 that includes ten cells 165. Non-limiting examples for simulated voltage responses 284 to scenarios 280 are illustrated in Figure 14C, including the load profile scenarios and the average of voltage provided by a non-limiting example of stack 160 that includes ten cells 165. Clearly, modifications of stack design can be followed by adjustment of the monitoring units and their operation.

[0163] In the non-limiting examples, as illustrated in Figure 14B, active thermal response 282A to constant relatively low load scenario 280A includes a gradual rise in electrolyte temperature, which starts to accelerate above 50°C after ca. two operation hours; active thermal response 282B to constant relatively high load scenario 280B includes a much stronger rise in electrolyte temperature that quickly reaches a maximal temperature of ca. 85°C after about an hour of operation; active thermal response 282C to cyclic load changes scenario 280C includes a correspondingly cyclically fluctuating thermal response with a gradual increase in the respecttemperature values with added cycles; active thermal response 282D to intermittent high loads scenario 280D includes peaking temperatures that correspond to the occasional brief high load, over a gradual increase in temperatures; active thermal response 282E to regularly step-wise oscillating scenario 280E includes corresponding, gradually ascending fluctuating temperatures that correspond to the high load steps; and active thermal response 282F to intermittent high loads with interruption of operation scenario 280F is similar to active thermal response 282D to intermittent high loads scenario 280D.

[0164] Figure 14C illustrates the simulated voltage responses 284 to the respective load scenarios 280, taking into account the respective active thermal response 282. In the non-limiting examples, voltage response 284A to constant relatively low load scenario 280A includes a steady voltage supply (of around 13V in the non-limiting illustrated example); voltage response 284B to constant relatively high load scenario 280B includes a less stable voltage supply, which deteriorates (decreases) after 1.5 hours probably due to depletion of anodes 167 and / or exhaustion of electrolyte 157; voltage response 284C to cyclic load changes scenario 280C includes a fluctuating voltage around 13V (in the non-limiting illustrated example); voltage response 284D to intermittent high loads scenario 280D includes a strongly fluctuating voltage as the levels of load 90 change; voltage response 284E to regularly step-wise oscillating scenario 280E includes even stronger voltage fluctuations at load level changes; and voltage response 284F to intermittent high loads with interruption of operation scenario 280F is similar to voltage response 284D to intermittent high loads scenario 280D.

[0165] As disclosed herein, the energy capacity of aluminum air backup system 120 is determined by the total amount of aluminum available (as anodes 167) inside of cells 165, and the total amount of electrolyte 157 enabling the electric generation reaction.

[0166] For optimal utilization of the electrolyte, intermediate working tank 150 of electrolyte 157 may be used to exhaust each used amount of electrolyte 157 before draining and replacing used electrolyte 157A by fresh electrolyte 157. The size of working tank 150 may be designed for it to provide electrolyte 157 for a predetermined time before the electrolyte gets saturated and replaced. In case the electrolyte replacement happens during power generation (e.g., during grid outage), buffer battery 110 may be used to provide the power while aluminum air backup subsystem 120 drains the used electrolyte, refills fresh electrolyte into working tank 150 and restarts the aluminum power generation.

[0167] Aluminum-air sub-system 120 may comprise a single aluminum-air battery module 130 or 140, or multiple aluminum-air battery modules 130 or 140, and control and management units for the components and the system as a whole (indicated schematically as control units 60 and management units 59 such as electrolyte management unit(s) 190 and thermal management unit(s) 180 that includes controllers 60 - see, e.g., Figures 1A-2B). Aluminum-air sub-system 120 may be modular, allowing adding or removing aluminum-air modules 130 or 140. Each aluminum-air module 130 or 140 typically includes multiple aluminum-air stacks 160, each including multiple aluminum-air cells 165. As illustrated schematically, cell stacks 160 in each aluminum-air module 130 or 140 are also arranged modularly, in replaceable casings that holed anodes 167, cathodes 168 and flow paths for electrolyte 157, in a mechanical structure that optimize all aspects of operation of cells 165. Stacks 160 of cells 165 may be removed and replaced in a simple manner, by pulling each stack 160 out of module 130 or 140 and replacing it with a new stack 160, e.g., upon depletion of aluminum anodes 167 in cells 165. Electrolyte 157 for operating cells 165 may be circulated through cells 165, e.g., from and to a common electrolyte work tank 150 associated with module 130 or 140 and respective circulation elements such as pump(s), conduits, valves, etc. (see, e.g., Figures 2A, 2B, 4, 7A, 7B, 12C). Electrolyte work tanks 150 of modules 130 or 140 may be connected to electrolyte reservoir(s) 152, 192 from which fresh electrolyte 157 is supplied, and to which utilized electrolyte is delivered, e.g., for collecting and regeneration, respectively. Aluminum-air modules 130 or 140 may further comprise heat management elements that regulate heat delivery to and from cells 165 (see, e.g., Figure 5C and 7A).

[0168] For systems that can be designed to have multiple aluminum modules 130 or 140 with multiple working tanks 150, disclosed embodiments include staggered electrolyte replacement configurations 290 illustrated schematically in Figure 15D, and / or staggered aluminum module replacement configurations 295 (e.g., of aluminum anodes 167, cells 165 and / or whole cell stacks 160) illustrated schematically in Figure 15C - which may be implemented to support long duration grid outages. Staggered replacement of electrolyte (290) and / or aluminum modules (295) may be implemented by applying a round-robin (RR) scheduling (illustrated schematically in Figures 15A and 15B), configured to assign time slices to each replaceable element (e.g., one or more electrolyte working tanks 150, and / or their content - 290; and / or one or more cells 165 or stacks 160, and / or their respective depleted aluminum anodes 167A - 295; respectively) - in equal portions and handled in circular order - to maintain continuous operation of aluminum-air sub-system 120 as awhole, as long as the consumable materials (electrolyte 157 and / or aluminum anodes 167) are available and the replacement units operate.

[0169] In some embodiments, the staggered replacement configuration of aluminum anodes 167 and / or electrolyte 157 may include operating aluminum air modules 130 to form a gradient in a utilization level thereof and replacing or servicing modules 130 one (or more) at a time, maintaining an overall power supply from aluminum air sub-system 120.

[0170] Buffer battery or module 110 can serve load 90 during electrolyte replacement and / or during anode replacement if needed, either to bridge stopping periods of aluminum-air sub-system 120 or to provide additional power when parts of aluminum-air sub-system 120 are being serviced (e.g., replaced). In some embodiments, buffer 110 may be configured to provide additional power during each period of replacing or servicing modules 130 (for example, but not necessarily one at a time), and to be recharged by aluminum air sub-system 120 following the replacing or servicing of modules 130.

[0171] Figures 15A and 15B are high level schematic illustrations of staggered servicing configurations 290 and / or 295 of modules 130 and sub-modules 140, respectively, according to some embodiments of the invention. Figure 15C is high level schematic illustration of staggered aluminum module replacement configurations 295, according to some embodiments of the invention. Figure 15D is high level schematic illustration of staggered electrolyte replacement configurations 290, according to some embodiments of the invention.

[0172] In systems 120 that include multiple aluminum air modules 130 and rechargeable buffer 110, when operating under load 90, and when aluminum is depleted or nearly depleted in some or all of modules 130 - aluminum module servicing for replacing aluminum anodes 167 may be carried out in staggered manner 295 (one module at a time), as illustrated schematically in Figure 15C. Similarly, when electrolyte 157 is fully used (e.g., saturated with aluminum hydroxides, or operating below a minimal efficiency threshold) or nearly fully used in some or all of modules 130 - aluminum module servicing for replacing electrolyte 157 may be carried out in staggered manner 290 (one module at a time), as illustrated schematically in Figure 15D - during operation of aluminum-air system 120 under load 90 (possibly supported by buffer 110 if needed).

[0173] It is noted that each module 130 may typically be serviced as a single unit (including all respective stacks 160 that operate under one electrolyte circulation loop), so that when electrolyte circulation is stopped, all electrolyte 157 is drained from all stacks 160 in respective module 130,and all stacks 160 in module 130 are available to replacement - so that the electrolyte loop of a module forms the smallest serviceable unit in system 120 - as illustrated schematically in Figures 2A and 2B. Hence, modules 130 may be configured in a way that aluminum and electrolyte amounts per module 130 are depleted approximately together, so that servicing modules 130 enables effective staggered replacement of both aluminum and electrolyte in each module 130, implementing staggered aluminum module replacement configurations 295 and staggered electrolyte replacement configurations 290 - simultaneously, e.g., as illustrated schematically in Figures 15A and 15B.

[0174] For example, as illustrated schematically in Figure 15A - (i) a first module 130 may be shut down such that there is no electrolyte circulation in it - the rest of modules 130 may support load 90 and rechargeable buffer 110 may compensates for the power of the shut module if such compensation is required; and (ii) once stacks 160 or anodes 167 of first module 130 are replaced (see, e.g., Figure 5D for replaceable stack 160, replaceable as unit 162, and Figure 5E for replaceable anodes 167, which may in some embodiments be interconnected over multiple cells 165) - first module 130 is turned on, and next module 130 may be serviced (shut down and aluminum reload) and so on - as indicated schematically by the arrow in Figure 15A - until all modules 130 are reloaded with aluminum and / or electrolyte. In some embodiments - staggered aluminum replacement 295 (in any order of modules 130) may be carried out in parallel to staggered electrolyte replacement 290, e.g., in the respective working tank 150 of respective module 130.

[0175] Similar servicing configurations may be implemented at lower levels and smaller subunits of aluminum-air sub-system 120, e.g., depending on the scale of aluminum-air system 120, staggered servicing of module 140 and / or possibly even stacks 160 (in small scale systems, see, e.g., Figure 6 in which module 140 may include more than the two illustrated stacks 160, e.g., small-scale modules for electrical vehicles disclosed herein).

[0176] For example, as illustrated schematically in Figure 15B - (i) a first module 140 may be shut down such that there is no electrolyte circulation in it - the rest of modules 140 may support load 90 and rechargeable buffer 110 may compensates for the power of the shut module if such compensation is required; and (ii) once stacks 160 or anodes 167 of first module 140 are replaced (see, e.g., Figure 5D for replaceable stack 160, replaceable as unit 162, and Figure 5E for replaceable anodes 167, which may in some embodiments be interconnected over multiple cells165) - first module 140 is turned on, and next module 140 may be serviced (shut down and aluminum reload) and so on - as indicated schematically by the arrow in Figure 15A - until all modules 140 are reloaded with aluminum and / or electrolyte. In some embodiments - staggered aluminum replacement 295 (in any order of modules 130) may be carried out in parallel to staggered electrolyte replacement 290, e.g., in the respective working tank 150 of respective module 140.

[0177] After the first time staggered servicing configurations 290 and / or 295 of modules 130 and / or sub-modules 140 are used, the amount of electrolyte and / or aluminum in each modules 130 or 140 (out of modules 130 in system 120 or sub-modules 140 in module 130, respectively) is different according to its position / time in the replacement order. Thus, each module 130 or 140 can utilize the reloaded electrolyte and / or aluminum completely before the next replacement - ensuring full utilization of the consumables and seamless servicing throughout long periods of operation (possibly many hours or days).

[0178] Figure 15C is high level schematic illustration of staggered aluminum module replacement configurations 295, according to some embodiments of the invention. In cases of aluminum replacement / reload, staggered operation of at least some of aluminum-air modules 130 prevents a large drop in overall delivered energy during aluminum replacement and supports delivery of constant power during extended operation. It is noted that while Figure 15C illustrates staggered replacement 295 of modules 130, it is non-limiting and similar configurations 295 are applicable to sub-modules 140 (within module 130) or even stacks 160 (within module 140, in case of smaller aluminum air systems 120 such as for electric vehicle or small-scale applications).

[0179] Aluminum-air modules 130 may be managed to retain a gradient of deliverable energy (indicated schematically) between modules 130 - that allows reloading of modules 130 one by one in a given time per module 130 (indicted schematically as replacement of depleted module 130A and consecutively replacement of depleted module 130B), while maintaining a total available energy from backup facility 100 (and / or from aluminum air system 120) above a specified threshold. The state of individual modules 130 is indicated schematically as a percentage of usable energy 292 (hatched) and a percentage of module depletion 294). The gradient is illustrated schematically with modules 130A-D operated to a different extent (e.g., in a staggered manner, illustrated schematically by the different extent of the hatched area indicating remaining usable energy 292), so that each is used to a different degree. Additional modules (e.g., 130E) may bekept initially unused until required. As aluminum-air system 120 is used to deliver energy, modules 130 may be used equally to provide energy until first module 130A is depleted (second row from the top) and is replaced. During replacement (third row from the top) other modules 130B-E keep delivering energy, and additional module(s) (e.g., 130F) are operated to deliver energy instead of the modules (e.g., 130B) that are being serviced. The gradient of deliverable energy along modules 130, achieved through the initially staggered operation, is configured to allow time for aluminum replacement before the next module is depleted. After the depleted module is reloaded with new aluminum (fourth row from the top, module 130F may represent module 130A after servicing and reloading of anodes 167), the operation is continued until the next module is to be serviced. In certain embodiments, buffer module 110 may be used to provide additional energy during the replacement of one or more of modules 130, and recharged after respective module 130 is replaced.

[0180] Figure 15D is high level schematic illustration of staggered electrolyte replacement configurations 290, according to some embodiments of the invention. In cases of electrolyte replacement or refilling, staggered operation of at least some of aluminum-air modules 130 prevents a large drop in overall delivered energy during electrolyte replacement and supports delivery of constant power during extended operation. It is noted that while Figure 15D illustrates staggered replacement 290 of modules 130, it is non-limiting and similar configurations 290 are applicable to sub-modules 140 (within module 130) or even stacks 160 (within module 140, in case of smaller aluminum air systems 120 such as for electric vehicle or small-scale applications). It is further noted that while Figure 15D illustrates schematically electrolyte replacement in work tanks 150 of respective modules 130, similar staggered electrolyte replacement configurations 290 may be implemented in configurations of modules 130 without electrolyte work tanks (see, e.g., Figure 13B) - with respect to circulation units 158 and respective fresh and used electrolyte tanks 152, 192, respectively.

[0181] Aluminum-air modules 130 may be managed to retain a gradient of deliverable energy (indicated schematically) between modules 130 - that allows reloading of modules 130 (or re-filling electrolyte work tanks 150 thereof) one by one in a given time per module 130 - indicted schematically as replacement of utilized electrolyte tank 150A (of respective module 130A) and consecutively replacement of utilized electrolyte tank 150B (of respective module 130B) - while maintaining a total available energy from backup facility 100 (and / or from aluminum air system 120) above a specified threshold. The state of individual modules 130 is indicated schematicallyas a percentage of usable energy through fresh electrolyte 292 and a percentage of electrolyte depletion 294 (as generalized measure for electrolyte freshness versus electrolyte contamination and loss of efficiency, respectively). The gradient is illustrated schematically with tanks 150A-D operated to a different extent (e.g., in a staggered manner, illustrated schematically by the different usage percentages 294), so that each is used to a different degree. Additional tanks 150E (or possibly additional module in case of full module replacement together with aluminum anode replacement 292) may be kept initially unused until required. As aluminum-air system 120 is used to deliver energy, tanks 150 in modules 130 may be used equally to provide energy until electrolyte in first work tank 150A is fully used (second row from the top) and is replaced or refilled with fresh electrolyte. During replacement (third row from the top) other modules 130B-E (having corresponding tanks 150B-E) keep delivering energy, until tank 150A (in module 130A) is re-filled or replaced. The gradient of deliverable energy along modules 130, achieved through the initially staggered operation, is configured to allow time for electrolyte replacement before the work tank of the next module is depleted. After the used electrolyte tank is refilled with fresh electrolyte (fourth row from the top, illustrating refilled tank 150A of module 130A), the operation is continued until the next module is to be serviced. In certain embodiments, buffer module 110 may be used to provide additional energy during the replacement of one or more of modules 130 and / or refilling electrolyte into work tank 150 thereof, and recharged after respective module 130 is replaced and / or electrolyte is refilled into work tank 150 thereof.

[0182] In cases of electrolyte replacement 290, a staggered operation of at least some of modules 130 prevents a large drop in overall delivered energy during electrolyte replacement and supports delivery of constant power over extended operation. Electrolyte working tanks 150 may be managed to retain a gradient of utilization levels with respect to the level of electrolyte saturation by aluminum oxides - that allows replacing the electrolyte in work tanks 150 one by one in a given time per work tank 150, while maintaining a total available energy from backup facility 100 (and / or aluminum air sub-system 120) above a specified threshold. This principle of staggered operation 290 is similar to the one 295 presented for anodes 167 in aluminum-air modules 130. The gradient in electrolyte levels of utilization is illustrated schematically with work tanks 150 operated to a different extent (e.g., in a staggered manner), so that each is used to a different degree (the level of electrolyte utilization per work tank 150 is illustrated schematically by a vertical line and a schematically indicated percentage of utilization). Additional work tanks 150 (or modules 130, asin aluminum staggered replacement configuration 195 illustrated schematically in Figure 15C) may be kept initially unused until required. As aluminum-air modules 130 are used to deliver energy, work tanks 150 may be used equally in modules 130 to provide electrolyte 157 until the first electrolyte work tank is fully used (second row from the top) and is replaced. During electrolyte service (third row from the top) the other work tanks are used to provide electrolyte to their respective modules to keep delivering energy to the load, and an additional module is operated to deliver energy instead of the module that is being serviced. The gradient in the level of utilization between work tanks, achieved through the initially staggered operation, is configured to allow time for replacement or refilling before the next work tank should be serviced. After the depleted / saturated work tank is replaced or refilled (fourth row from the top), operation is continued until the next work tank is to be replaced or refilled. It is noted that servicing the module with respect to electrolyte replacement may be carried out by replacing the electrolyte in the tank or by replacing the tank itself with another tank with fresh electrolyte.

[0183] Figure 16 provides a partial view of aluminum air sub-system 120 with stack and module replacement mechanisms, according to some embodiments of the invention. Figure 16 illustrates schematically a few modules 130 with associated fresh electrolyte supplies 152 and heat management units 135 (illustrated schematically, in partly exploded view and partly section view) not necessarily on operating condition. Stack and module replacement mechanisms include a vertical stack conveyer 296 for replacing stacks 160 in raised modules 130, a stack replacement mechanism 298 for removing and replacing stacks 160 from modules 130, as well as an enlarged view of individual stacks 160 being extracted from module 130 (see also Figure 5D) and electrolyte work tanks 150 in modules 130 which may also be replaced or reviled using similar or different replacement mechanism(s). In non-limiting examples, vertical stack conveyer 296 and stack replacement mechanism 298 (illustrated in two parts) may be configured to remove empty stacks 160 from system modules 130, and, depending on storage type (stack replacement as in Figure 5D or aluminum anode replacement as in Figure 5E) - replace empty stacks 160 with full stacks 160 or reload stacks 160 with fresh aluminum anodes 167 (e.g., combined 166 as illustrated schematically in Figure 5E). The replacement mechanisms may be configured to operate on-the- fly during system operation, as disclosed herein. In a non-limiting example, each module 130 may comprise four sub-modules 140 configured to deliver 800kW to a total of 112MWh each, andreplacement mechanisms may be configured to include aluminum anodes 167 or full stacks 160 that include additional 112MWh for replacement when needed.

[0184] Alternatively or complementarity, e.g., as indicated in the enlarged section, replacement mechanisms (not shown) may comprise standard automatic-warehouse replacement systems adapted to replace individual stack 160, with stack interface (e.g., configuration of the flow channels 163, attachment of cells 165, etc., see e.g., Figure 5D) configured to support quick replacement. For example, Figures 17A and 17B illustrate schematically two stages of replacing consumed anodes 167A (not shown) with fresh anodes 167, according to some embodiments of the invention. In a first stage 299A (Figures 17A), stack 160 may be extracted within module 130, and in a second stage 299B (Figures 17B), a set of fresh anodes 166 (see e.g., Figure 5E) may be introduced into cells 165 in stack 160. Electrolyte circulation elements 156 are stopped during the replacement process, at least for handled stack 160. Electrolyte tanks 150 may be refilled during operation, or replaced during halts in operation.

[0185] Figure 18 is a high-level flowchart illustrating a method 300 of providing power backup to a large-scale facility (stage 305), according to some embodiments of the invention. The method stages may be carried out with respect to system, units and modules disclosed herein, which may optionally be configured to implement method 300. Method 300 may be at least partially implemented by at least one computer processor, e.g., in controller(s) 60, 59 or any control or management unit disclosed herein. Certain embodiments comprise computer program products comprising a computer readable storage medium having computer readable program embodied therewith and configured to carry out the relevant stages of method 300. Method 300 may comprise the following stages, irrespective of their order.

[0186] Method 300 may comprise combining a high energy aluminum air sub-system and a fast rechargeable buffer to supply power to the large-scale facility during power interruptions (stage 310), operating the buffer to bridge brief interruptions or brief power requirement surges from the large-scale facility, and during starting or stopping of the aluminum air sub-system (stage 320), and optionally to optimize the operation of the aluminum air sub-system (stage 325), and operating the aluminum air sub-system to provide power for long durations of interrupted power (stage 330).

[0187] In various embodiments, method 300 may further comprise providing electricity upon requirement from the rechargeable buffer (stage 340), monitoring a status of the rechargeable buffer (stage 342), monitoring a status of the aluminum air sub-system (stage 344), monitoring anelectricity consumption of the large-scale facility as load (stage 346), determining an operation profile of the aluminum air sub-system to supply electricity to the large-scale facility and recharge the buffer when needed, to optimize operational parameters of the aluminum air sub-system while providing the required electricity to the large-scale facility (stage 348), and operating the aluminum air sub-system within the optimized operational parameters of the operation profile (stage 350).

[0188] In non-limiting examples, the monitored status of the rechargeable buffer may comprise a SOC (state of charge), an overall capacity, aging and / or previous or historic charge / discharge curves, the monitored status of the aluminum air sub-system may comprise a capacity, internal temperature, performance history and / or aging, and the monitored electricity consumption of the load may comprise an actual load, a load history, a load lookahead, electricity pricing and / or pricing of consumables.

[0189] In some embodiments, method 300 comprises configuring the aluminum air sub-system to include a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells (stage 360), and configuring the aluminum air modules to include replaceable stand-alone units (stage 365).

[0190] Various embodiments of method 300 further comprise electrically connecting the aluminum air cell stacks in at least two parallel lines of serially connected stacks (stage 370), and delivering electrolyte flows between groups of stacks of the at least two parallel lines that provide a same voltage (stage 375). For example, each parallel line of serially connected stacks may comprise at least two stacks and method 300 may comprise delivering at least two separate electrolyte flows. Method 300 may further comprise electrically isolating the electrolyte flows from each other (stage 376), and supporting, maintaining and handling each separate electrolyte flow (stage 377).

[0191] In some embodiments, method 300 further comprises separating at least some of the aluminum air cell stacks by corresponding DC / DC converters in a floating configuration to limit a voltage on electrolyte flows through the stacks (stage 378), in place or in addition to the separation into electrolyte flows that are under partial voltage.

[0192] Various embodiments of method 300 further comprise configuring at least some of the aluminum air cells to have a dynamically adaptable gap between a cell anode and one or two cell cathodes thereof, which receives electrolyte during operation (stage 380), and dynamicallyadapting the gap to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode (stage 385).

[0193] In some embodiments, method 300 further comprises configuring all the aluminum air cells to have the dynamically adaptable gap between the respective anode and one or two cathodes (stage 390).

[0194] In some embodiments, method 300 may further comprise supporting the one or two cell cathodes by corresponding one or two flexible elements configured to move the respective cathode towards the anode as the anode corrodes during operation (stage 400).

[0195] In some embodiments, method 300 may comprise moving the one or two cell cathodes to dynamically adapt the gap to the anode by one or more elastic passive element, at least one threaded rod or screw, and / or by internal and / or external pressure (stage 405).

[0196] In some embodiments, method 300 may comprise using a mechanical barrier to maintain a minimal gap between the respective anode and one or two cathodes (stage 410).

[0197] In various embodiments, method 300 may comprise configuring at least some of the aluminum air cells to be single-sided - each comprising one anode and one cathode (stage 420). In some embodiments, method 300 may further comprise configuring the cell anode to be movable towards the cathode to dynamically adjust the gap (stage 422).

[0198] In various embodiments, method 300 may comprise configuring at least some of the aluminum air cells to be double-sided - each comprising one anode and two cathodes (stage 425).

[0199] Various embodiments of method 300 further comprise setting the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load (stage 430).

[0200] In some embodiments, method 300 may comprise determining a capacity and a configuration of the rechargeable buffer with respect to an expected power supply quality to the load (stage 440) and further comprise configuring the controller to operate the aluminum air subsystem during long durations of power interruption and operate only the rechargeable buffer during brief interruptions (stage 442). In some embodiments, method 300 may comprise determining the operation profile of the aluminum air sub-system to operate the aluminum air sub-system during long durations of power interruption to the load, while operating only the rechargeable buffer during brief interruptions (stage 445).

[0201] In some embodiments, method 300 further comprises operating the aluminum air subsystem under optimal performance conditions (stage 450), operating the rechargeable buffer to provide additional power if higher power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions (stage 452), and operating the rechargeable buffer to be recharged from the aluminum air subsystem if lower power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions (stage 454).

[0202] In some embodiments, method 300 may further comprise recharging the buffer during operation of the aluminum air sub-system (stage 460). In some embodiments, method 300 may further comprise operating the buffer in association with at least one external rechargeable battery that serves external renewable power sources (stage 462).

[0203] Various embodiments of method 300 further comprise self-testing the aluminum air subsystem (stage 470) by monitoring the status thereof during periods in which the aluminum air subsystem does not operate (stage 472), receiving measurements from sub-system components (stage 474) and deriving the status therefrom (stage 476). Non-limiting examples for components of the aluminum air sub-system that may be self-tested include inlets and outlets, temperature sensors, pressure sensors, heat management elements, electric and electronic components, mechanical components and / or communication components, as disclosed herein. In various embodiments, selftesting the aluminum air sub-system may be carried out by monitoring the status of the components during a standby mode thereof and / or during a washing mode thereof, wherein the measurements are of components taking part in washing the cells from electrolyte residues after an operation period.

[0204] Various embodiments of method 300 further comprise managing and optimizing electrolyte use with respect to the operation profile of the aluminum air sub-system (stage 480).

[0205] In some embodiments, method 300 may comprise delivering electrolyte to the stacks batch-wise, circulating each delivered batch of electrolyte through an electrolyte work tank until the batch is exhausted or the operation is halted (stage 490). In some embodiments, method 300 may comprise draining partly-used batches from the electrolyte work tank once operation is halted (stage 492), and replacing the drained batch by a new batch of electrolyte (stage 494). In some embodiments, method 300 may comprise using partly-used batches to further operate the respective stack to produce power until the electrolyte batch is exhausted (stage 500), providing power to theload and / or recharging the buffer (stage 502), and consecutively, draining the exhausted batch from the electrolyte work tank and replacing the drained batch by a new batch of electrolyte (stage 504). In some embodiments, method 300 may comprise adjusting a volume of the batch with respect to an available electrolyte volume in the cells (stage 510), optionally by adjusting a level of the electrolyte batch circulating through the electrolyte work tank (stage 512).

[0206] In some embodiments, method 300 may comprise circulating the electrolyte through the stacks continuously during operation and draining the electrolyte from the cells upon halting the operation (stage 520). In some embodiments, method 300 may comprise using partly used electrolyte to further operate the respective stacks to produce power until the electrolyte is exhausted (stage 522), providing power to the load and / or recharging the buffer (stage 524), and consecutively draining the exhausted electrolyte from the stacks and replacing the drained electrolyte by new electrolyte for consecutive operation (stage 526). In some embodiments, method 300 may further comprise adjusting a volume of the circulating amount of electrolyte with respect to an available electrolyte volume in the cells (stage 528).

[0207] In some embodiments, method 300 may comprise managing the temperature of the electrolyte used in the stacks to optimize a power output of the stacks (stage 530).

[0208] Various embodiments of method 300 further comprise operating the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof (stage 540), and replacing or servicing the modules one at a time, maintaining an overall power supply from the aluminum air sub-system (stage 542). In some embodiments, method 300 may comprise replacing or servicing the aluminum air modules in a round-robin (RR) scheduling (stage 550), wherein each replacement comprises replacing the anodes of the cells in the stacks of the respective module (stage 552), and / or replacing the electrolyte circulating through the cells in the stacks of the respective module (stage 554).

[0209] In some embodiments, method 300 may comprise refilling electrolyte in one or more work tank associated with the respective serviced module (stage 560).

[0210] In some embodiments, method 300 may comprise replacing consumed anodes with fresh anodes in the cells of the respective serviced module (stage 570).

[0211] In some embodiments, method 300 may further comprise providing additional power from the buffer during each of the replacing or servicing the modules one at a time (stage 580), andrecharging the buffer by the aluminum air sub-system following the replacing or servicing (stage 582).

[0212] Figure 19 is a high-level block diagram of exemplary controllers 60, 59 or any other control or management unit disclosed herein, which may be used with embodiments of the present invention. Controller(s) 60, 59 may include one or more controller or processor 63 that may be or include, for example, one or more central processing unit processor(s) (CPU), one or more Graphics Processing Unit(s) (GPU or general-purpose GPU - GPGPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a microprocessor, a chip, a microchip, an integrated circuit (IC), or any other suitable multi-purpose or specific processor, controller or computational device, an operating system 61, a memory 62, a storage 65, input devices 66 and output devices 67.

[0213] Operating system 61 may be or may include any code segment designed and / or configured to perform tasks involving coordination, scheduling, arbitration, supervising, controlling, or otherwise managing operation of controller(s) 60, 59, for example, scheduling execution of programs. Memory 62 may be or may include, for example, a Random- Access Memory (RAM), a read only memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM (SD-RAM), a double data rate (DDR) memory chip, a Flash memory, a volatile memory, a nonvolatile memory, a cache memory, a buffer, a short-term memory unit, a long-term memory unit, or other suitable memory units or storage units. Memory 62 may be or may include a plurality of possibly different memory units. Memory 62 may store for example, instructions to carry out a method (e.g., code 64), and / or data such as user responses, interruptions, etc.

[0214] Executable code 64 may be any executable code, e.g., an application, a program, a process, task or script. Executable code 64 may be executed by controller 63 possibly under control of operating system 61. For example, executable code 64 may when executed cause the production or compilation of computer code, or application execution such as VR execution or inference, according to embodiments of the present invention. Executable code 64 may be code produced by methods described herein. For the various modules and functions described herein, one or more computing devices and / or components of controller(s) 60, 59 may be used. Devices that include components similar or different to those included in controller(s) 60, 59 may be used and may be connected to a network and used as a system. One or more processor(s) 63 may be configured to carry out embodiments of the present invention by for example executing software or code.

[0215] Storage 65 may be or may include, for example, a hard disk drive, a floppy disk drive, a Compact Disk (CD) drive, a CD-Recordable (CD-R) drive, a universal serial bus (USB) device or other suitable removable and / or fixed storage unit. Data such as instructions, code, VR model data, parameters, etc. may be stored in a storage 65 and may be loaded from storage 65 into a memory 62 where it may be processed by controller 63. In some embodiments, some of the components shown in Figure 19 may be omitted.

[0216] Input devices 66 may be or may include for example a mouse, a keyboard, a touch screen or pad or any suitable input device. It will be recognized that any suitable number of input devices may be operatively connected to controller(s) 60, 59 as shown by block 66. Output devices 67 may include one or more displays, speakers and / or any other suitable output devices. It will be recognized that any suitable number of output devices may be operatively connected to controller(s) 60, 59 as shown by block 67. Any applicable input / output (I / O) devices may be connected to controller(s) 60, 59, for example, a wired or wireless network interface card (NIC), a modem, printer or facsimile machine, a universal serial bus (USB) device or external hard drive may be included in input devices 66 and / or output devices 67.

[0217] Embodiments of the invention may include one or more article(s) (e.g., memory 62 or storage 65) such as a computer or processor non-transitory readable medium, or a computer or processor non-transitory storage medium, such as for example a memory as disclosed herein, a disk drive, or a USB flash memory, encoding, including or storing instructions, e.g., computerexecutable instructions, which, when executed by a processor or controller, carry out methods disclosed herein.

[0218] In any of the disclosed embodiments, respective controllers may be configured to operate various computer program products for providing power backup to the large-scale facility during power interruptions by the backup system combining the high energy aluminum air sub-system and the fast rechargeable buffer. The computer program product may comprise a non-transitory computer readable storage medium having computer readable program embodied therewith. The computer readable program comprises computer readable program configured to operate the buffer to bridge brief interruptions or brief power requirement surges from the large-scale facility, and during starting or stopping of the aluminum air sub-system, and optionally to optimize the operation of the aluminum air sub-system, and computer readable program configured to operate the aluminum air sub-system to provide power for long durations of interrupted power.

[0219] In various embodiments, the computer readable program may further comprise computer readable program configured to provide electricity upon requirement from the rechargeable buffer, computer readable program configured to monitor a status of the rechargeable buffer, computer readable program configured to monitor a status of the aluminum air sub-system, computer readable program configured to monitor an electricity consumption of the large-scale facility, computer readable program configured to determine an operation profile of the aluminum air subsystem to supply electricity to the large-scale facility and recharge the buffer when needed, to optimize operational parameters of the aluminum air sub-system while providing the required electricity to the large-scale facility, and computer readable program configured to operate the aluminum air sub-system within the optimized operational parameters of the operation profile.

[0220] In various embodiments, the computer readable program may further comprise computer readable program configured to set the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

[0221] In various embodiments, the computer readable program may further comprise computer readable program configured to determine the operation profile of the aluminum air sub-system to operate the aluminum air sub-system during long durations of power interruption to the load, while operating only the rechargeable buffer during brief interruptions.

[0222] In various embodiments, the computer readable program may further comprise computer readable program configured to operate the aluminum air sub-system under optimal performance conditions, computer readable program configured to operate the rechargeable buffer to provide additional power if higher power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions, and computer readable program configured to operate the rechargeable buffer to be recharged from the aluminum air sub-system if lower power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions.

[0223] In various embodiments, the computer readable program may further comprise computer readable program configured to operate the buffer in association with at least one external rechargeable battery that serves external renewable power sources.

[0224] In various embodiments, the computer readable program may further comprise computer readable program configured to self-test the aluminum air sub-system by monitoring the status thereof during periods in which the aluminum air sub-system does not operate, receiving measurements from sub-system components and deriving the status therefrom.

[0225] In various embodiments, the computer readable program may further comprise computer readable program configured to monitoring the statuses during a standby mode of the aluminum air sub-system.

[0226] In various embodiments, the computer readable program may further comprise computer readable program configured to monitor the statuses during a washing mode of the aluminum air sub-system, wherein the measurements are of components taking part in washing the cells from electrolyte residues after an operation period thereof.

[0227] In various disclosed embodiments, the aluminum air sub-system comprises a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells, and the aluminum air modules comprise replaceable stand-alone units. The computer readable program may further comprise computer readable program configured to operate the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof, and computer readable program configured to replace or service the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

[0228] In various embodiments, the computer readable program may further comprise computer readable program configured to replace or servicing the aluminum air modules in a round-robin (RR) scheduling, wherein each replacement comprises replacing the anodes of the cells in the stacks of the respective module, and / or replacing the electrolyte circulating through the cells in the stacks of the respective module.

[0229] In various embodiments, the computer readable program may further comprise computer readable program configured to provide additional power from the buffer during each of the replacing or servicing the modules one at a time, and computer readable program configured to recharge the buffer by the aluminum air sub- system following the replacing or servicing.

[0230] Elements from Figures 1A-19 may be combined in any operable combination, and the illustration of certain elements in certain figures and not in others merely serves an explanatory purpose and is non-limiting. For example, in non-limiting examples, energy backup system 100 may be associated with large-scale, mod-scale or small-scale facility, loads or any powerconsuming systems, and may include any of the disclosed aspects, by itself or in combination with other disclosed aspects. For example, electrolyte management embodiments configured to prevent shunt currents (limiting the potential differences along electrolyte flow paths) and to manage delivered electrolyte amounts batch-wise and / or adaptively may be combined with each other and / or with management embodiments of the cell configuration, such as dynamically adapting the anode-cathode gap. Moreover, managing backup systems 100 may combine multiple disclosed aspects, such as self-testing of various components in backup system 100 without operating it, staggered replacement of aluminum modules and / or electrolyte, etc. The overall configuration and operation of backup systems 100 may also take into account any of the disclosed aspects, adjusting and optimizing configuration and operation schemes according to specific use cases, including any of the disclosed aspects and embodiments

[0231] Aspects of the present invention are described above with reference to flowchart illustrations and / or portion diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each portion of the flowchart illustrations and / or portion diagrams, and combinations of portions in the flowchart illustrations and / or portion diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or portion diagram or portions thereof.

[0232] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or portion diagram or portions thereof.

[0233] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or otherprogrammable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or portion diagram or portions thereof.

[0234] The aforementioned flowchart and diagrams illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each portion in the flowchart or portion diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the portion may occur out of the order noted in the figures. For example, two portions shown in succession may, in fact, be executed substantially concurrently, or the portions may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each portion of the portion diagrams and / or flowchart illustration, and combinations of portions in the portion diagrams and / or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0235] In the above description, an embodiment is an example or implementation of the invention. The various appearances of "one embodiment”, "an embodiment", "certain embodiments" or "some embodiments" do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. Certain embodiments of the invention may include features from different embodiments disclosed above, and certain embodiments may incorporate elements from other embodiments disclosed above. The disclosure of elements of the invention in the context of a specific embodiment is not to be taken as limiting their use in the specific embodiment alone. Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in certain embodiments other than the ones outlined in the description above.

[0236] The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined. While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.

Claims

CLAIMSWhat is claimed is:

1. A large-scale energy backup system comprising: an aluminum air sub-system comprising a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells, wherein the aluminum air modules comprise replaceable stand-alone units, a rechargeable buffer, and a controller configured to: provide electricity upon requirement from the rechargeable buffer, monitor a status of the rechargeable buffer, monitor a status of the aluminum air sub-system, monitor an electricity consumption of a load which the system backups, determine an operation profile of the aluminum air sub-system to supply electricity to the load and recharge the buffer when needed, to optimize operational parameters of the aluminum air sub-system while providing the required electricity to the load, and operate the aluminum air sub-system within the optimized operational parameters of the operation profile.

2. The large-scale energy backup system of claim 1, wherein the aluminum air cell stacks are electrically connected in at least two parallel lines of serially connected stacks, and wherein electrolyte flow is delivered between groups of stacks of the at least two parallel lines that provide a same voltage.

3. The large-scale energy backup system of claim 2, wherein each parallel line of serially connected stacks comprises at least two stacks.

4. The large-scale energy backup system of claim 2 or 3, comprising at least two separate electrolyte flows.

5. The large-scale energy backup system of any one of claim 2-4, wherein the electrolyte flows are electrically isolated from each other.

6. The large-scale energy backup system of any one of claim 2-5, further comprises pipework and circulation elements configured to support, maintain and handle each separate electrolyte flow.

7. The large-scale energy backup system of any one of claims 1-6, wherein at least some of the aluminum air cell stacks are separated by corresponding DC / DC converters in a floating configuration to limit a voltage on electrolyte flows through the stacks.

8. The large-scale energy backup system of any one of claims 1-7, wherein at least some of the aluminum air cells are configured to have a dynamically adaptable gap between a cell anode and one or two cell cathodes, which receives electrolyte during operation and is dynamically adapted to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode.

9. The large-scale energy backup system of claim 8, wherein all the aluminum air cells are configured to have the dynamically adaptable gap between the respective anode and one or two cathodes.

10. The large-scale energy backup system of claim 8 or 9, wherein the one or two cell cathodes are supported by corresponding one or two flexible elements configured to move the respective cathode towards the anode as the anode corrodes during operation.

11. The large-scale energy backup system of any one of claims 8-10, wherein the one or two cell cathodes are moved to dynamically adapt the gap to the anode by an elastic passive element.

12. The large-scale energy backup system of any one of claims 8-11, wherein the one or two cell cathodes are moved to dynamically adapt the gap to the anode by at least one threaded rod or screw.

13. The large-scale energy backup system of any one of claims 8-12, wherein the one or two cell cathodes are moved to dynamically adapt the gap to the anode by internal and / or external pressure.

14. The large-scale energy backup system of any one of claims 8-13, wherein the at least some of the aluminum air cells comprise a mechanical barrier configured to maintain a minimal gap between the respective anode and one or two cathodes.

15. The large-scale energy backup system of any one of claims 8-14, wherein the at least some of the aluminum air cells are single-sided - each comprising one anode and one cathode.

16. The large-scale energy backup system of claim 15, wherein the cell anode is movable towards the cathode to dynamically adjust the gap.

17. The large-scale energy backup system of any one of claims 8-16, wherein the at least some of the aluminum air cells are double-sided - each comprising one anode and two cathodes.

18. The large-scale energy backup system of any one of claims 1-17, wherein the operation profile of the aluminum air sub-system comprises starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

19. The large-scale energy backup system of claim 18, wherein a capacity and a configuration of the rechargeable buffer are determined with respect to an expected power supply quality to the load.

20. The large-scale energy backup system of claim 18 or 19, wherein the controller is configured to determine the operation profile of the aluminum air sub-system to operate the aluminum air sub-system during long durations of power interruption to the load, while operating only the rechargeable buffer during brief interruptions.

21. The large-scale energy backup system of claim 20, wherein the controller is configured to operate the aluminum air sub-system during long durations of power interruption and operate only the rechargeable buffer during brief interruptions.

22. The large-scale energy backup system of any one of claims 18-21, wherein the aluminum air sub-system is configured to operate under optimal performance conditions, while the rechargeable buffer is operated to provide additional power if higher power is required by the load compared to the power provided by the aluminum air sub-system operated under optimal performance conditions, or be recharged from the aluminum air sub-system if lower power is required by the load compared to the power provided by the aluminum air subsystem operated under optimal performance conditions.

23. The large-scale energy backup system of any one of claims 18-22, wherein the monitored status of the rechargeable buffer comprises at least one of: a SOC (state of charge), an overall capacity, aging and / or previous or historic charge / discharge curves.

24. The large-scale energy backup system of any one of claims 18-23, wherein the monitored status of the aluminum air sub-system comprises at least one of: a capacity, internal temperature, performance history and / or aging.

25. The large-scale energy backup system of any one of claims 18-24, wherein the monitored electricity consumption of the load comprises at least one of: an actual load, a load history, a load lookahead, electricity pricing and / or pricing of consumables.

26. The large-scale energy backup system of any one of claims 18-25, further configured to recharge the buffer during operation of the aluminum air sub-system.

27. The large-scale energy backup system of any one of claims 18-26, further configured to operate the buffer in association with at least one external rechargeable battery that serves external renewable power sources.

28. The large-scale energy backup system of any one of claims 1-27, further comprising a selftesting configuration, in which the controller is further configured to monitor the status of the aluminum air sub-system during periods in which the aluminum air sub-system does not operate, by receiving measurements from sub-system components and deriving the status therefrom.

29. The large-scale energy backup system of claim 28, wherein the sub-system components comprise at least one of: inlets and outlets, temperature sensors, pressure sensors, heat management elements, electric and electronic components, mechanical components, and communication components.

30. The large-scale energy backup system of claim 28 or 29, wherein the status is monitored during a standby mode of the aluminum air sub-system.

31. The large-scale energy backup system of any one of claims 28-30, wherein the status is monitored during a washing mode of the aluminum air sub-system, wherein the measurements are of components taking part in washing the cells from electrolyte residues after an operation period thereof.

32. The large-scale energy backup system of any one of claims 1-31, further comprising electrolyte management unit configured to optimize electrolyte use with respect to the operation profile of the aluminum air sub-system.

33. The large-scale energy backup system of claim 32, wherein the electrolyte management unit is configured to deliver electrolyte to the stacks batch-wise, circulating each delivered batch of electrolyte through an electrolyte work tank until the batch is exhausted or the operation is halted.

34. The large-scale energy backup system of claim 33, wherein partly used batches are drained from the electrolyte work tank once operation is halted, and replaced by a new batch of electrolyte.

35. The large-scale energy backup system of claim 33 or 34, wherein partly used batches are used to further operate the respective stack until the electrolyte batch is exhausted, providing power to the load and / or to recharge the buffer, and wherein consecutively the exhausted batch is drained from the electrolyte work tank and replaced by a new batch of electrolyte.

36. The large-scale energy backup system of any one of claims 33-35, wherein the electrolyte management unit is further configured to adjust a volume of the batch with respect to an available electrolyte volume in the cells, optionally by adjusting a level of the electrolyte batch circulating through the electrolyte work tank.

37. The large-scale energy backup system of claim 32, wherein the electrolyte management unit is configured to circulate electrolyte through the stacks continuously during operation and drain the electrolyte from the cells upon halting the operation.

38. The large-scale energy backup system of claim 37, wherein partly used electrolyte is used to further operate the respective stacks until the electrolyte is exhausted, providing power to the load and / or to recharge the buffer, and wherein consecutively the exhausted electrolyte is drained from the stacks and replaced by a new electrolyte for consecutive operation.

39. The large-scale energy backup system of claim 37 or 38, wherein the electrolyte management unit is further configured to adjust a volume of the circulating amount of electrolyte with respect to an available electrolyte volume in the cells.

40. The large-scale energy backup system of any one of claims 32-39, wherein the electrolyte management unit is further configured to manage the temperature of the electrolyte used in the stacks to optimize a power output of the stacks.

41. The large-scale energy backup system of claim any one of claims 1-40, further comprising a staggered replacement configuration of aluminum anodes and / or electrolyte that comprises operating the aluminum air modules to form a gradient in a utilization level thereof and replacing or servicing the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

42. The large-scale energy backup system of claim 41, wherein the aluminum air modules are configured to be replaced or serviced in a round-robin (RR) scheduling, wherein each replacement comprises replacing the anodes of the cells in the stacks of the respective module and replacing the electrolyte circulating through the cells in the stacks of the respective module.

43. The large-scale energy backup system of claim 41 or 42, comprising a staggered electrolyte replacement configuration that comprises refilling electrolyte in one or more work tank associated with the respective serviced module.

44. The large-scale energy backup system of any one of claims 41-43, comprising a staggered aluminum anode replacement configuration that comprises replacing consumed anodes with fresh anodes in the cells of the respective serviced module.

45. The large-scale energy backup system of any one of claims 41-44, wherein the buffer is configured to provide additional power during each of the replacing or servicing the modules one at a time, and to be recharged by the aluminum air sub-system following the replacing or servicing.

46. A method of providing power backup to a large-scale facility, the method comprising: combining a high energy aluminum air sub-system and a fast rechargeable buffer to supply power to the large-scale facility during power interruptions, operating the buffer to bridge brief interruptions or brief power requirement surges from the large-scale facility, and during starting or stopping of the aluminum air subsystem, and optionally to optimize the operation of the aluminum air sub-system, and operating the aluminum air sub-system to provide power for long durations of interrupted power.

47. The method of claim 46, further comprising: providing electricity upon requirement from the rechargeable buffer, monitoring a status of the rechargeable buffer, monitoring a status of the aluminum air sub-system, monitoring an electricity consumption of the large-scale facility, determining an operation profile of the aluminum air sub-system to supply electricity to the large-scale facility and recharge the buffer when needed, to optimize operationalparameters of the aluminum air sub-system while providing the required electricity to the large-scale facility, and operating the aluminum air sub-system within the optimized operational parameters of the operation profile.

48. The method of claim 47, further comprising: configuring the aluminum air sub-system to comprise a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells, and configuring the aluminum air modules to comprise replaceable stand-alone units.

49. The method of claim 48, further comprising: electrically connecting the aluminum air cell stacks in at least two parallel lines of serially connected stacks, and delivering electrolyte flows between groups of stacks of the at least two parallel lines that provide a same voltage.

50. The method of claim 49, wherein each parallel line of serially connected stacks comprises at least two stacks and the method comprises delivering at least two separate electrolyte flows.

51. The method of claim 49 or 50, further comprising electrically isolating the electrolyte flows from each other.

52. The method of any one of claims 49-51, further comprising supporting, maintaining and handling each separate electrolyte flow.

53. The method of any one of claims 49-52, further comprising separating at least some of the aluminum air cell stacks by corresponding DC / DC converters in a floating configuration to limit a voltage on electrolyte flows through the stacks.

54. The method of any one of claims 48-53, further comprising: configuring at least some of the aluminum air cells to have a dynamically adaptable gap between a cell anode and one or two cell cathodes thereof, which receives electrolyte during operation, and dynamically adapting the gap to maintain a specified anode-cathode gap during operation-related corrosion of the respective cell anode.

55. The method of claim 54, further comprising configuring all the aluminum air cells to have the dynamically adaptable gap between the respective anode and one or two cathodes.

56. The method of claim 54 or 55, further comprising supporting the one or two cell cathodes by corresponding one or two flexible elements configured to move the respective cathode towards the anode as the anode corrodes during operation.

57. The method of any one of claims 54-56, further comprising moving the one or two cell cathodes to dynamically adapt the gap to the anode by at least one of: one or more elastic passive element, at least one threaded rod or screw, internal and / or external pressure.

58. The method of any one of claims 54-57, further comprising using a mechanical barrier to maintain a minimal gap between the respective anode and one or two cathodes.

59. The method of any one of claims 54-58, further comprising configuring the at least some of the aluminum air cells to be single-sided - each comprising one anode and one cathode.

60. The method of claim 59, further comprising configuring the cell anode to be movable towards the cathode to dynamically adjust the gap.

61. The method of any one of claims 54-58, further comprising configuring the at least some of the aluminum air cells to be double-sided - each comprising one anode and two cathodes.

62. The method of any one of claims 47-61, further comprising setting the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air sub-system with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

63. The method of claim 62, further comprising determining a capacity and a configuration of the rechargeable buffer with respect to an expected power supply quality to the load.

64. The method of claim 62 or 63, further comprising determining the operation profile of the aluminum air sub-system to operate the aluminum air sub-system during long durations of power interruption to the load, while operating only the rechargeable buffer during brief interruptions.

65. The method of any one of claims 62-64, further comprising configuring the controller to operate the aluminum air sub-system during long durations of power interruption and operate only the rechargeable buffer during brief interruptions.

66. The method of any one of claims 62-65, further comprising:operating the aluminum air sub-system under optimal performance conditions, operating the rechargeable buffer to provide additional power if higher power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions, and operating the rechargeable buffer to be recharged from the aluminum air sub-system if lower power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions.

67. The method of any one of claims 62-66, wherein the monitored status of the rechargeable buffer comprises at least one of: a SOC (state of charge), an overall capacity, aging and / or previous or historic charge / discharge curves, wherein the monitored status of the aluminum air sub-system comprises at least one of: a capacity, internal temperature, performance history and / or aging, and wherein the monitored electricity consumption of the load comprises at least one of: an actual load, a load history, a load lookahead electricity pricing and / or pricing of consumables.

68. The method of any one of claims 62-67, further comprising recharging the buffer during operation of the aluminum air sub-system.

69. The method of any one of claims 62-68, further comprising operating the buffer in association with at least one external rechargeable battery that serves external renewable power sources.

70. The method of any one of claims 47-69, further comprising self-testing the aluminum air sub-system by monitoring the status thereof during periods in which the aluminum air subsystem does not operate, receiving measurements from sub-system components and deriving the status therefrom.

71. The method of claim 70, wherein the sub-system components comprise at least one of: inlets and outlets, temperature sensors, pressure sensors, heat management elements, electric and electronic components, mechanical components, and communication components.

72. The method of claim 70 or 71, further comprising monitoring the statuses during a standby mode of the aluminum air sub-system.

73. The method of any one of claims 70-72, further comprising monitoring the statuses during a washing mode of the aluminum air sub-system, wherein the measurements are ofcomponents taking part in washing the cells from electrolyte residues after an operation period thereof.

74. The method of any one of claims 48-73, further comprising managing and optimizing electrolyte use with respect to the operation profile of the aluminum air sub-system.

75. The method of claim 74, further comprising delivering electrolyte to the stacks batch-wise, circulating each delivered batch of electrolyte through an electrolyte work tank until the batch is exhausted or the operation is halted.

76. The method of claim 75, further comprising draining partly used batches from the electrolyte work tank once operation is halted, and replacing the drained batch by a new batch of electrolyte.

77. The method of claim 74 or 75, further comprising: using partly used batches to further operate the respective stack to produce power until the electrolyte batch is exhausted, providing power to the load and / or recharging the buffer, and consecutively, draining the exhausted batch from the electrolyte work tank and replacing the drained batch by a new batch of electrolyte.

78. The method of any one of claims 75-77, further comprising adjusting a volume of the batch with respect to an available electrolyte volume in the cells, optionally by adjusting a level of the electrolyte batch circulating through the electrolyte work tank.

79. The method of any one of claims 74-78, further comprising circulating the electrolyte through the stacks continuously during operation and draining the electrolyte from the cells upon halting the operation.

80. The method of claim 79, further comprising: using partly used electrolyte to further operate the respective stacks to produce power until the electrolyte is exhausted, providing power to the load and / or recharging the buffer, and consecutively draining the exhausted electrolyte from the stacks and replacing the drained electrolyte by new electrolyte for consecutive operation.

81. The method of claim 79 or 80, further comprising adjusting a volume of the circulating amount of electrolyte with respect to an available electrolyte volume in the cells.

82. The method of any one of claims 74-81, further comprising managing the temperature of the electrolyte used in the stacks to optimize a power output of the stacks.

83. The method of any one of claims 48-82, further comprising: operating the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof, and replacing or servicing the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

84. The method of claim 83, further comprising replacing or servicing the aluminum air modules in a round-robin (RR) scheduling, wherein each replacement comprises: replacing the anodes of the cells in the stacks of the respective module, and replacing the electrolyte circulating through the cells in the stacks of the respective module.

85. The method of claim 83 or 84, further comprising refilling electrolyte in one or more work tank associated with the respective serviced module.

86. The method of any one of claims 83-85, further comprising replacing consumed anodes with fresh anodes in the cells of the respective serviced module.

87. The method of any one of claims 83-86, further comprising: providing additional power from the buffer during each of the replacing or servicing the modules one at a time, and recharging the buffer by the aluminum air sub-system following the replacing or servicing.

88. A computer program product for providing power backup to a large-scale facility during power interruptions by a backup system combining a high energy aluminum air sub-system and a fast rechargeable buffer, the computer program product comprising a non-transitory computer readable storage medium having computer readable program embodied therewith, the computer readable program comprising: computer readable program configured to operate the buffer to bridge brief interruptions or brief power requirement surges from the large-scale facility, and during starting or stopping of the aluminum air sub-system, and optionally to optimize the operation of the aluminum air sub-system, andcomputer readable program configured to operate the aluminum air sub-system to provide power for long durations of interrupted power.

89. The computer program product of claim 88, wherein the computer readable program further comprises: computer readable program configured to provide electricity upon requirement from the rechargeable buffer, computer readable program configured to monitor a status of the rechargeable buffer, computer readable program configured to monitor a status of the aluminum air subsystem, computer readable program configured to monitor an electricity consumption of the large-scale facility, computer readable program configured to determine an operation profile of the aluminum air sub-system to supply electricity to the large-scale facility and recharge the buffer when needed, to optimize operational parameters of the aluminum air sub-system while providing the required electricity to the large-scale facility, and computer readable program configured to operate the aluminum air sub-system within the optimized operational parameters of the operation profile.

90. The computer program product of claim 89, wherein the computer readable program further comprises computer readable program configured to set the operation profile of the aluminum air sub-system to comprise starting and stopping times of the aluminum air subsystem with respect to the monitored statuses of the rechargeable buffer and the aluminum air sub-system, and with respect to the monitored electricity consumption of the load.

91. The computer program product of claim 90, wherein the computer readable program further comprises computer readable program configured to determine the operation profile of the aluminum air sub-system to operate the aluminum air sub-system during long durations of power interruption to the load, while operating only the rechargeable buffer during brief interruptions.

92. The computer program product of claim 90 or 91, wherein the computer readable program further comprises: computer readable program configured to operate the aluminum air sub-system under optimal performance conditions,computer readable program configured to operate the rechargeable buffer to provide additional power if higher power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions, and computer readable program configured to operate the rechargeable buffer to be recharged from the aluminum air sub-system if lower power is required by the large-scale facility compared to the power provided by the aluminum air sub-system operated under optimal performance conditions.

93. The computer program product of any one of claims 90-92, wherein the computer readable program further comprises computer readable program configured to operate the buffer in association with at least one external rechargeable battery that serves external renewable power sources.

94. The computer program product of any one of claims 89-93, wherein the computer readable program further comprises computer readable program configured to self-test the aluminum air sub-system by monitoring the status thereof during periods in which the aluminum air sub-system does not operate, receiving measurements from sub-system components and deriving the status therefrom.

95. The computer program product of claim 94, wherein the computer readable program further comprises computer readable program configured to monitoring the statuses during a standby mode of the aluminum air sub-system.

96. The computer program product of claim 94 or 95, wherein the computer readable program further comprises computer readable program configured to monitor the statuses during a washing mode of the aluminum air sub-system, wherein the measurements are of components taking part in washing the cells from electrolyte residues after an operation period thereof.

97. The computer program product of any one of claims 89-96, wherein the aluminum air subsystem comprises a plurality of aluminum air modules, each comprising a plurality of aluminum air cell stacks having aluminum air cells, and the aluminum air modules comprise replaceable stand-alone units; and wherein the computer readable program further comprises:computer readable program configured to operate the aluminum air modules in a staggered manner to form a gradient in a utilization level thereof, and computer readable program configured to replace or service the modules one at a time, maintaining an overall power supply from the aluminum air sub-system.

98. The computer program product of claim 97, wherein the computer readable program further comprises computer readable program configured to replace or servicing the aluminum air modules in a round-robin (RR) scheduling, wherein each replacement comprises replacing the anodes of the cells in the stacks of the respective module, and / or replacing the electrolyte circulating through the cells in the stacks of the respective module.

99. The computer program product of claim 97 or 98, wherein the computer readable program further comprises: computer readable program configured to provide additional power from the buffer during each of the replacing or servicing the modules one at a time, and computer readable program configured to recharge the buffer by the aluminum air subsystem following the replacing or servicing.

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