Fuel gas energy storage system

Abstract

The energy storage system has a first gravity-based energy storage subsystem having at least one weight movable between a first upper position and a second lower position defining a vertical displacement, and a second energy storage subsystem comprising a container for storing pressurized fuel gas, and has electrical input / output connections with an external power system, and at least one of a fuel gas inlet for supplying fuel gas from an external fuel gas source or network to the energy storage system and a fuel gas outlet for supplying fuel gas from the energy storage system to an external fuel gas user or network, and / or has at least one of a gas-to-power converter for converting energy from the fuel gas to electrical energy for storage in the first energy storage subsystem or for export to the external power system via the electrical output connection, and a power-to-gas converter for converting electrical energy to fuel gas for storage in the second energy storage subsystem or for export to the external fuel gas user or network via the fuel gas outlet, and a control system configured to control coordinated or complementary operation of the first and second energy storage subsystems according to requirements of the external power system and / or the external fuel gas network or user. The defined system allows for energy storage (charging) and discharging of systems linked to external power systems, such as power grids, and can use gravity-based storage devices to store energy and augment energy storage capacity while taking advantage of their rapid response times and fast charge / discharge rates.

Description

[Technical field]

[0001] The present invention relates generally to the field of energy storage, and in particular to systems, devices and methods for storing energy, such as from an electric power system or gas network, and supplying electricity or fuel gas. [Background technology]

[0002] The transition to low- and zero-carbon energy systems and increased reliance on renewable energy will result in greater variability between the timing of available supply and demand for energy compared to existing fossil fuel-based systems. As a result, energy storage, especially energy from renewable sources, may play an increasingly important role.

[0003] The transition to low- and zero-carbon systems includes a shift to low-carbon electricity, on which considerable progress has been made so far, but also heating and transport, which remain ongoing challenges.

[0004] The transition to low carbon solutions for heating is being driven through electricity-assisted heating (air-source and ground source heat pumps), potential future green gases (such as biogas and green hydrogen), and district heating schemes (from low carbon sources).

[0005] Ground transportation, for example, is transitioning to low-carbon systems including electric vehicles, hydrogen-electric vehicles, as well as hydrogen-powered trains (on non-electrified lines).

[0006] Gravity-based energy storage systems are increasingly being recognised as a reliable and efficient method of energy storage and grid balancing. Large-scale pumped hydro is well known, but more recent innovations in lifting weights (including in shafts or holes in the ground), particularly weight and cable systems, are not only improving the efficiency of energy storage, but also providing the benefit of energy capacity to meet the needs and improved response times of regional and national grids.

[0007] For example, GB 2509437 describes an energy storage system which has a weight suspended from a cable inside a shaft and which generates electrical energy as the weight is lowered down the shaft into the earth, and consumes and stores electrical energy as the weight is lifted through the shaft.

[0008] To be economically advantageous and provide high quality power receipt from or supply to an external power system, the energy storage system advantageously provides rapid response (i.e., short response time and the ability to adjust output to meet demand), large energy capacity, and continuous input and output across its full capacity.

[0009] The present inventors have identified improvements to energy storage systems that address shortcomings of energy storage systems and improve upon existing technology. Summary of the Invention

[0010] Improved energy storage systems are needed to provide higher capacity and higher quality energy storage via cable and weight gravity based systems. Energy storage for electricity, heat and transportation also needs to be addressed.

[0011] It is an object of the present invention to provide an energy storage system that allows for improved energy storage capacity using a gravity-based energy storage system while providing long term energy storage or supply.

[0012] It is an object of the present invention to provide an energy storage system for multiple purposes such as power supply, heating, and power supply for transportation.

[0013] According to a first aspect of the present invention, there is provided an energy storage system, comprising: a first energy storage subsystem comprising a gravity-based energy storage system including at least one weight movable between a first upper position and a second lower position, the first upper position and the second lower position defining a vertical displacement of the or each weight; a second energy storage subsystem comprising a vessel for storing pressurized fuel gas; an electrical input connection and an electrical output connection to an external power system; a fuel gas inlet for supplying fuel gas to the energy storage system from an external fuel gas source or network; a fuel gas outlet for supplying fuel gas from the energy storage system to an external fuel gas user or network; At least one of and / or a gas-to-power converter for converting energy from the fuel gas to electrical energy for storage in the first energy storage subsystem or for export to an external power system via an electrical output connection; a power to gas converter for converting electrical energy into fuel gas for storage in a second energy storage subsystem or for export to an external fuel gas user or network via a fuel gas outlet; At least one of the following: the energy storage system further comprising a control system for controlling coordinated or complementary operation of the first and second energy storage subsystems according to requirements of an external power system and / or an external fuel gas network or a user; An energy storage system is provided.

[0014] In a second aspect of the present invention, there is provided an energy storage system comprising: a first energy storage subsystem comprising: a gravity-based energy storage system comprising at least one weight movable between a first upper position and a second lower position through a volume (e.g., defined by a shaft formed in the earth), the first upper position and the second lower position defining a vertical displacement of the or each weight; a second energy storage subsystem comprising a pressurized fuel gas storage vessel, the vessel defining a fuel gas storage volume surrounding a volume defined by the first energy storage subsystem; An energy storage system is provided, comprising:

[0015] In a third aspect of the present invention, there is provided an energy storage system comprising: a first energy storage subsystem comprising a gravity-based energy storage system including at least one weight movable between a first upper position and a second lower position through a shaft (or other vertical passageway) formed in the earth, the first upper position and the second lower position defining a vertical displacement of the or each weight; a thermal energy capture and / or storage subsystem comprising a heat capture element disposed within or around the shaft of the first energy storage subsystem for capturing thermal energy from within or around the shaft; An energy storage system is provided, comprising:

[0016] In a fourth aspect of the present invention, a method for the storage and supply of energy to and from an external energy system is provided, the method comprising: providing an energy storage system as defined above; operating a control system to control the storage of electric energy from an external power source or network as potential energy by lifting a weight in a first storage subsystem or as chemical energy by conversion of electric energy into fuel gas by a power-to-gas converter; controlling the storage of energy from fuel gas from an external fuel gas supplier or network as compressed fuel gas by supplying the fuel gas to a second energy storage subsystem or by storing the fuel gas as potential energy by conversion of the supplied fuel gas into electric energy using a gas-to-power converter, storing the resulting fuel gas in the second energy storage subsystem; storing the energy as potential energy by lifting a weight in the first storage subsystem according to the energy storage requirements of the external gas and power network or supplier and depending on the fuel gas and electric energy storage capacities of the first and second energy storage subsystems and predefined or predicted fuel gas and electric energy output requirements.

[0017] Advantages of the Invention The energy storage system and method of the present invention allows for energy storage (charging) and discharging linked to an external power system, such as a power grid, and can use gravity-based storage devices to store energy and augment energy storage capacity while taking advantage of their rapid response times and fast charge / discharge rates. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 illustrates the process flow and interrelationships between subsystems of an energy storage system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an energy storage system according to another embodiment of the present invention. [Diagram 3]FIG. 13 is a schematic cross-sectional view of an energy storage system according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The invention according to a first aspect is an energy storage system comprising a first energy storage subsystem, a second energy storage subsystem, and optionally a thermal energy storage subsystem and a further energy storage subsystem.

[0020] The first energy storage subsystem comprises a gravity-based energy storage system comprising at least one weight movable between a first upper position and a second lower position, the first upper position and the second lower position defining a vertical displacement of the or each weight.

[0021] The second energy storage subsystem includes a vessel for storing pressurized fuel gas.

[0022] The system is provided with at least one of electrical input and output connections to an external power system, a fuel gas inlet for supplying fuel gas from an external fuel gas source or network to the energy storage system and a fuel gas outlet for supplying fuel gas from the energy storage system to an external fuel gas user or network, and / or at least one of a gas-to-power converter for converting energy from the fuel gas to electrical energy for storage in a first energy storage subsystem or export to the external power system via the electrical output connection, and a power-to-gas converter for converting electrical energy to fuel gas for storage in a second energy storage subsystem or export to an external fuel gas user or network via the fuel gas outlet.

[0023] The energy storage system further comprises a control system for controlling coordinated or complementary operation of the first and second energy storage subsystems according to requirements of an external power system and / or an external fuel gas network or a user.

[0024] The first energy storage subsystem preferably comprises a passageway or shaft, preferably a vertical passageway or shaft, through which the at least one weight is movable between a first upper position and a second lower position. The container of the second energy storage subsystem preferably comprises the passageway or shaft of the first energy storage subsystem. The passageway or shaft is preferably formed in the earth and may be, for example, an adaptation of an existing mine shaft or a newly excavated custom shaft.

[0025] Preferably, the gravity-based energy storage subsystem comprises a winch and cable arrangement with at least one winch located at or associated with the shaft opening at the top of the shaft, whereby a cable can be wound and unwound by the winch to raise and lower the weight, and the winch and cable arrangement is located within the vessel. The cable may be of any suitable shape, such as a steel cable or synthetic cable, but preferably (particularly when used with storage vessels for fuel gases such as hydrogen) is a synthetic material or rope that is not subject to embrittlement in the presence of hydrogen.

[0026] Preferably, the vessel comprises a cap or dome located and sealed above the shaft. The shaft may be lined, preferably comprising a lining or lining coating that is resistant to embrittlement or corrosion by hydrogen as the fuel gas.

[0027] The winch and cable arrangement may be driven by any suitable means: even when located within a fuel gas storage vessel, the winch and cable arrangement may be driven by a tightly sealed electric motor, or preferably a hydraulic or pneumatic drive system, bearing in mind the need to avoid sparks that could cause ignition of the fuel gas if air is leaking into the enclosure or vessel.

[0028] Preferably, the winch and cable arrangement is hydraulically driven by the hydraulic drive system when the first energy storage subsystem is receiving or charging power and hydraulically drives a hydraulic generator when the first energy storage subsystem is releasing or discharging power. The hydraulic drive system may be configured to have a motor or generator located outside the vessel of the second energy storage subsystem, and hydraulic drive supply and return pipes connect the motor or generator with a corresponding hydraulic motor / pump in the vessel adjacent the winch for operating the winch and cable arrangement. The hydraulic drive supply and return pipes preferably pass through openings formed in the vessel wall, and a seal is formed in the vessel wall around the pipes to prevent leakage of pressurized gas from the interior of the vessel to the surrounding atmosphere.

[0029] Preferably, the system further comprises a heat capture and / or storage subsystem configured to capture thermal energy from material in and / or around the vessel of the second energy storage subsystem, for example via one or more heat exchange elements or members. Optionally, the heat capture and / or storage subsystem comprises a heat pump device located at some distance from the shaft or vessel of the first or second energy storage subsystem and which may be connected to the heat capture means or heat exchange members by supply and return pipes for transporting a heat carrying fluid.

[0030] Optionally, the heat capture and / or storage subsystem is configured to provide heating and / or cooling to the fuel gas storage subsystem vessel via the heat exchange element to maintain the temperature of the fuel gas storage vessel within predefined operating limits.

[0031] The fuel gas may be hydrogen, methane or other commercially useful gases such as propane or natural gas which can be easily compressed and stored. Preferably, the fuel gas is hydrogen. The fuel gas, particularly hydrogen, may be stored in the vessel at any suitable pressure, such as a pressure of up to 300 bar, preferably up to 100 bar, for example up to about 85 bar. In any case, it is preferred that the pressure in the vessel at full capacity is at least 30 bar.

[0032] In one embodiment, the first energy storage subsystem comprises a multiple weight gravity-based energy storage device comprising a shaft (or other vertical passage) and a plurality of weights configured to be raised and lowered through the shaft by a transport (e.g., winch and cable arrangement). In one such embodiment, a plurality of weights (e.g., two) are provided side-by-side and follow non-overlapping paths under the control of respective winch arrangements. In this embodiment, the winches may remain connected to the respective weights via cables. In another such embodiment, two or more weights may overlap or have the same path and may be stored in a storage location at the top and / or bottom of the shaft according to this embodiment. For example, a capped volume at the top of the shaft / vessel may include a weight storage area. Such a system according to this latter embodiment may be characterized by having a primary energy capacity with a discontinuity in power flow capability.

[0033] In this embodiment, there is preferably a third energy storage subsystem configured to operate cooperatively and / or complementary with the first energy storage subsystem to provide one or more of the following to the energy storage system: i) continuous input or output power during a charge or discharge cycle over at least two energy events of the first energy storage subsystem, the energy events being separated by a discontinuity in the output from the first energy storage subsystem; ii) Enhanced or faster system start-up response, which enables the system to reach predetermined or desired power input and output levels by responding to the requirements of the external power system using both the primary and secondary energy storage devices simultaneously. iii) Enhanced system discharge termination capability, which allows the system to quickly terminate discharge to an external power system without generating a power output surge that exceeds the desired system power output and is intended for temporary energy storage in a secondary energy storage device. iv) Power surge input / output capability, which allows the system to input / output power at power levels that exceed the power rating of the energy storage system or primary power storage device for short periods of time.

[0034] In such a system, the system may have a system power rating that is the maximum power that can be input or output to the external power system over the range of the system's energy capacity. The third energy storage subsystem preferably has a tertiary power rating at least equal to the system power rating and a tertiary energy capacity at least equal to the maximum energy gap resulting from the discontinuous nature of the power input and output of the first energy storage subsystem when the system power input and output are constant at the system power rating. Preferably, the tertiary energy capacity is up to 10 times the maximum energy gap, preferably up to 5 times the maximum energy gap, more preferably up to 2 times the maximum energy gap, and optionally up to 1.8 or 1.5 times the maximum energy gap. Preferably, the primary power rating is greater than the tertiary power rating.

[0035] The third energy storage subsystem is preferably selected from a battery, a capacitor or supercapacitor, a compressed air energy storage system, a flywheel, or a second gravity-based energy storage system.

[0036] The system of the present invention preferably has a fuel gas outlet for supplying fuel gas from the second energy storage subsystem to the gas network pipeline.

[0037] Optionally, the system comprises a vehicle charging and / or refueling station comprising an eV charging station and / or a fuel gas vehicle refueling station, the vehicle charging station and / or the refueling station being supplied from the energy storage system via a vehicle charging station electrical supply connection and / or a refueling fuel gas outlet connection.

[0038] In one embodiment, in another aspect, the energy storage system comprises a first energy storage subsystem and a second energy storage subsystem. The first energy storage subsystem comprises a gravity-based energy storage system comprising at least one weight movable between a first upper position and a second lower position through a volume (e.g., defined by a preferably vertical passageway or shaft typically formed in the earth), the first upper position and the second lower position defining a vertical displacement of the or each weight. The second energy storage subsystem comprises a pressurized fuel gas storage vessel, the vessel defining a fuel gas storage volume surrounding the volume defined by the first energy storage subsystem. The fuel gas may be any suitable fuel gas, such as methane, natural gas, or other fuel gas, but is preferably hydrogen. The fuel gas may be stored in the vessel at a suitable pressure, as described above.

[0039] In the embodiment of the invention described herein comprising a first energy storage subsystem comprising a gravity-based energy storage system and a second energy storage subsystem comprising a vessel for storing pressurized fuel gas such as hydrogen, it is preferred that the first and second energy storage subsystems occupy a shared volume, preferably a volume within the vessel that accommodates at least the volume required for raising and lowering the weight of the first energy storage subsystem. Preferably, the first energy storage subsystem comprises a winch (ideally hydraulically driven) and cable for raising and lowering the weight through the vertical path volume, and preferably the winch, cable and weight and the vertical path volume are within the vessel of the second energy storage subsystem. Preferably, the vessel defining the vertical passage of the first energy storage subsystem and the fuel gas storage volume of the second energy storage subsystem is arranged to be at least partially underground, for example formed by lining a shaft in the earth. The vessel may comprise a cap, for example a dome, formed on the lined shaft (for example a cylindrical shaft), for example on the rim or other upper rim flange of the shaft. Optionally, the entire shaft, preferably the entire vessel, is arranged underground. Providing the vessel of the fuel gas storage subsystem (second energy storage subsystem) as a shared volume with the shaft of the first energy storage subsystem is particularly beneficial due to the cost savings from the use of the same infrastructure (i.e. a shaft buried in the ground) and the impact on the leveling costs of the storage, in addition to the mass benefits in the ground if in close contact with the pressure vessel, in addition to the structural integrity of the vessel, e.g. to its resistance to rupture. Thus, the amount of material or lining material (e.g. steel) required to form the vessel can be significantly reduced while still achieving the amount required to achieve adequate structural integrity, which can lead to cost savings. Furthermore, in view of the risk of fire and explosion when storing pressurized fuel gas, providing the vessel partly or entirely underground in this way can help contain fires and explosions and minimize damage to surrounding property (personnel).

[0040] In a further aspect of another preferred embodiment of the present invention, the energy storage system comprises a first energy storage subsystem and a thermal energy capture and / or storage subsystem. According to this embodiment / aspect, the first energy storage subsystem may comprise a gravity-based energy storage system comprising at least one weight movable between a first upper position and a second lower position, preferably through a shaft (or other preferably vertical passage) formed in the earth, the first upper position and the second lower position defining a vertical displacement of the or each weight. The thermal energy capture and / or storage subsystem preferably comprises a heat capture element disposed within or around the shaft of the first energy storage subsystem for capturing thermal energy from within or around the shaft.

[0041] Further provided is a method for the storage and supply of energy to and from an external energy system, the method comprising: providing an energy storage system as defined above; operating a control system to control the storage of electric energy from an external power source or network as potential energy by lifting a weight in a first storage subsystem or as chemical energy by conversion of electric energy into fuel gas by a power-to-gas converter; controlling the storage of energy from fuel gas from an external fuel gas supplier or network as compressed fuel gas by supplying the fuel gas to a second energy storage subsystem or by storing the fuel gas supplied by conversion of the fuel gas into electric energy using a gas-to-power converter as potential energy, storing the resulting fuel gas in the second energy storage subsystem; storing energy as potential energy by lifting a weight in the first storage subsystem according to the energy storage requirements of the external gas and power network or supplier and depending on the fuel gas and electric energy storage capacities of the first and second energy storage subsystems and predefined or predicted fuel gas and electric energy output requirements.

[0042] In each of the above aspects, the energy storage system preferably comprises a control system for controlling the coordinated or complementary operation of the first and second energy storage subsystems, the optional thermal energy recovery and / or storage system, and the optional further energy storage subsystems according to the requirements of an external power system and / or an external fuel gas network or a user. This includes any conversion of forms of energy between two or more subsystems to ensure that a desired or predicted service is available (e.g., providing power for rapid delivery or providing capacity to receive electrical energy for storage). Preferably, the control system, including control software typically operating on the cup, is configured to minimize the number of energy conversions, particularly between the subsystems, while maintaining the desired service, taking into account the relative capacity of the available storage.

[0043] The invention will now be described in more detail, without limitation, with reference to the accompanying drawings, in which:

[0044] 1, an energy storage system 1 according to an embodiment of the invention comprises a multi-weight gravitational energy storage subsystem 3 and a compressed hydrogen (as the preferred fuel gas) storage subsystem 5. The system optionally further comprises a thermal energy capture and storage subsystem 7.

[0045] Electric power can be supplied to the energy storage system via an external power grid input connection 9, through which the gravitational energy storage subsystem 3 as the first energy storage subsystem can be powered. The gravity-based energy storage subsystem 3 comprises a winch device 11 configured to raise and lower a weight 13 through a vertical passage or shaft (not shown) via a cable (not shown), which can be a composite cable depending on whether it is a storage / charging event or a discharging event in the gravitational energy storage subsystem 3. The winch device 11 is driven by a motor / generator device 15 using the stored electrical energy to lift the weight 13, which acts as a generator to generate electrical energy to supply to the external grid via a system power output connection 17 during a discharging event, for example to meet the requirements of the external grid. If the winch and weight device is located within the vessel of the second energy storage subsystem and thus in a fuel gas atmosphere, it is preferable to seal the electrical components or preferably be outside the pressure vessel containing the fuel gas. According to this embodiment, the power unit for the winch is preferably hydraulically driven from outside the pressurized enclosure by an externally located electro-hydraulic pump / motor when surrounded by a fuel gas environment.

[0046] A second energy storage subsystem is provided by a fuel gas storage subsystem 5, which is preferably a hydrogen storage subsystem 5. The hydrogen storage subsystem 5 is for storing compressed hydrogen gas in a storage volume defined by a vessel (not shown), which preferably includes the volume of a vertical passage or shaft through which weights 13 in the gravity-based energy storage subsystem 3 rise and fall. One advantage of this single volume is the sharing of infrastructure, in addition to the advantage of more efficient heat capture.

[0047] Hydrogen for storage in the hydrogen storage subsystem 5 can be supplied from many sources for energy storage purposes. For example, power from the grid can be split for energy storage to both the gravity-based energy storage subsystem 3 and the hydrogen storage subsystem 5 by diverting a portion of the excess power from the grid via a branch power inlet 19 to a pre-electrolyzer 21 to produce hydrogen, which can be supplied to the hydrogen energy storage subsystem 5, typically through a compressor to pressurize the hydrogen to a desired or maximum desired pressure for storage in the hydrogen storage subsystem 5. The desired or maximum pressure can be any suitable pressure, for example up to 800 bar, or up to 400 bar, but preferably up to 200 bar, optionally up to 100 bar, for example about 85 bar. Higher pressures allow more hydrogen to be stored, but this is energy intensive and requires additional infrastructure to implement. With this configuration, the hydrogen storage subsystem 5 can act as a supplementary system to the gravity-based energy storage subsystem 3, having the effect of potentially increasing the power and capacity of the system 1. It also serves to allow for the storage of much larger amounts of energy than the energy capacity of the gravity-based energy storage subsystem 3. Thus, electrical energy from the grid can be stored as potential energy in the gravity-based energy storage subsystem 3 and as chemical energy in the form of an energy carrier such as fuel gas or hydrogen in the hydrogen storage subsystem 5.

[0048] Optionally, hydrogen (as fuel gas) may also be supplied to the system 1 from a hydrogen source via a hydrogen system inlet connection 23 for storage for future use. The inlet connection 23 may be supplied from any suitable hydrogen source, such as a hydrogen network pipeline (not shown), a hydrogen supply pipeline (not shown) (e.g., from a remote renewable hydrogen production facility) or by tanker. The supplied hydrogen typically passes through a compressor to pressurize the hydrogen gas in a vessel of the hydrogen energy storage subsystem 5 to any suitable pressure, such as up to 250 bar, for example, about 85 bar, or other level for storage. Optionally, the hydrogen supplied to the system 1 may be immediately supplied via a branch hydrogen inlet 25 to a standby fuel cell 27 (or other power generating device, such as an engine) to generate electrical energy, which may then be supplied to the motor 15 powering the winch 11, which is stored as potential energy in the gravity-based energy storage subsystem 3. Alternative fuel gases, such as natural gas and methane, or hydrocarbons such as propane and butane, may be used in the fuel gas storage subsystem.

[0049] The energy stored in the gravity-based energy storage subsystem 3 as potential energy can be converted to chemical energy stored in the hydrogen storage subsystem by supplying power from the gravity-based energy storage subsystem to an intermediate electrolyzer / compressor 29, which supplies the generated pressurized hydrogen gas to a reservoir in the hydrogen storage subsystem 5. Thus, when the gravity energy storage subsystem 3 is near maximum capacity (i.e., most of the weights in the system are lifted), but more rapidly responsive electrical energy storage capacity is required or predicted, some of the energy stored in the gravity-based energy storage subsystem can be converted to hydrogen (or rather used to generate hydrogen) and stored in the hydrogen storage subsystem 5. Optionally, the energy stored in the hydrogen storage subsystem 5 as chemical energy can be converted to potential energy stored in the gravity-based energy storage subsystem by supplying hydrogen from the hydrogen storage subsystem 5 to an intermediate expander / fuel cell 31. Thus, when the Gravity Energy Storage Subsystem 3 is significantly discharged (i.e., the weight is significantly lowered) and / or when a power demand is anticipated, the system 1 can be configured to increase the available energy from the Gravity-Based Energy Storage Subsystem 3 with rapid response and rapid discharge. The ability to move energy from one form of energy storage to another within the system 1 allows for substantial flexibility. Such flexibility allows energy to be stored either as potential energy in the Gravity-Based Energy Storage Subsystem 3 or as chemical energy in the form of hydrogen in the Hydrogen Storage Subsystem 5, and optionally rebalance the energy storage levels between the two subsystems, according to available capacity, anticipated capacity requirements, and power demands.A control system (not shown) may be configured to control the energy storage devices between the two systems to facilitate prioritization to meet storage demands (which may be rapid storage requirements in terms of both response time and speed of storage), the amount of energy storage required, the predicted output demands (the nature, rate and amount of energy output), and the efficiency of energy storage (whereby energy exchange between forms of storage must be minimized).

[0050] In general, the system 1 is provided with a system gas output connector 33 that supplies hydrogen to an output hydrogen demand, such as a hydrogen gas network or a gas network into which hydrogen may be injected at a predefined percentage (e.g., natural gas / methane). This network may be a local network or to a tanker for transportation or other hydrogen gas uses (e.g., as a feedstock). The system gas output connector 33 is supplied from a vessel outlet 35 via an expander 37.

[0051] In one embodiment, system 1 may house or supply a vehicle charging / refueling station 39 for charging electric or hybrid electric vehicles and / or refueling hydrogen or hybrid hydrogen vehicles (e.g., cars, trucks, buses, or trains). Accordingly, optionally, system 1 may include a charging station power outlet connection 41 and / or a refueling hydrogen outlet 43.

[0052] Optionally, a gas-to-power converter and / or a power-to-gas converter (not shown) may be provided downstream of each of the first and second energy storage subsystems to supply power to a corresponding power outlet 17, 41 from the hydrogen storage subsystem or to supply a hydrogen outlet 33, 43 from the gravity-based energy storage subsystem 3.

[0053] A thermal energy capture and storage subsystem 7 (thermal energy system) is preferably integrated into system 1. Thermal energy system 7 may typically comprise a thermal energy storage 45, such as a water tank (or other thermal energy carrier liquid tank) or phase change material, that may store energy collected from the reserve fuel cell 27 and electrolyzer 21, intermediate electrolyzer / compressor 29 and intermediate fuel cell and expander 31, and from the motor 15 and winch 11, via a thermal energy collection loop or circuit 47, typically via a circulating fluid. A geothermal source heat loop / heat exchanger 49 may typically be located around the vertical passage or shaft of the gravity-based energy storage subsystem 3 to collect geothermal source heat from surrounding materials, and / or may be located inside or associated with the storage vessel of the hydrogen storage subsystem 5 to collect heat from within the hydrogen storage vessel. By collecting heat from the operating motors and components and from the vertical passage / shaft and / or hydrogen storage vessel for use elsewhere, the effective efficiency of the storage of energy in system 1 is increased. The thermal energy stored in the thermal energy storage 45 can be used in any suitable way, for example by exporting it via the heat demand circuit 51. This may be to a district heating scheme, to nearby industrial (low grade) heat users, or even to a thermal power converter (such as a thermoelectric generator) for feeding back into the power supply to the motor 15.

[0054] In FIG. 2, which shows a cross-sectional view of the energy storage system 1 of the preferred embodiment, the hydrogen energy storage subsystem surrounds the vertical passageway or shaft 53 of the gravity-based energy storage subsystem. The hydrogen storage subsystem consists of a storage vessel 55 including a shaft 53 having a lining 57 made of steel (or concrete lining or other material), optionally with a coating to protect the steel lining from embrittlement by hydrogen gas, and a dome 59 disposed at the top of the shaft 53 to complete the vessel 55. The lining 55 extends around the top of the shaft 53 to its interface with the dome 59. Hydrogen can be pumped in and out of the vessel 55 via a valve 61 disposed within the dome 59, which is connected by a pressurized supply pipe 63 to a compressor / expander 65 and to the hydrogen system inlet connection 23 and the system hydrogen output connection 33.

[0055] The gravity-based energy storage subsystem includes a number of weights 13 (two shown here) that can be hoisted from a lowered position to an upper position to store energy and lowered from an upper position to a lower position to release energy. A winch 67 is provided with a synthetic cable 69 (hydrogen embrittlement resistant material) that is connected to the side of the weights 13 via a linkage 71. The winch 67 is hydraulically driven by (and hydraulically drives) a hydraulic motor / generator 73 that is located outside the storage vessel 55 and connected to the winch 13 by a hydraulic cable 75 that passes through a sealed opening 77 in the dome 59. The hydraulic motor / generator 73 is connected to a grid input / output connection 79.

[0056] Behind or within the lining 57 is a heat exchange element 81 of a cooperating thermal energy collection circuit 83, preferably in thermally conductive communication with the lining. The heat exchange element 81 can be used to collect geothermal heat from the materials surrounding the shaft and any heat from within the shaft 53. It can also be used to regulate the thermal changes within the shaft 53 to increase the storage efficiency of the hydrogen. Optionally, the thermal energy collection circuit 83 can also be connected to the hydraulic motor / generator 73 and the compressor / expander 65 to capture lost heat. By capturing and using the heat generated by components such as the motor / generator 73 and the compressor / expander 65, the overall efficiency of the energy storage of the system 1 can be improved, and can even be further improved by utilizing the geothermal energy accessible through the shaft wall via a geothermal heat collector. Optionally, the collected thermal energy can be stored and used by local heat users, or converted to electrical energy and provided as input to the hydraulic motor 73.

[0057] The potential energy stored by the lifted weight 71 can be converted to chemical energy by using the output from generator 73 when the weight is lowered to power an electrolyzer (not shown) to produce hydrogen gas which is fed to compressor 65 and stored as compressed hydrogen at a pressure of, for example, 85 bar, thereby significantly increasing the energy storage capacity of system 1 while maintaining its rapid response and fast charge / discharge capabilities (associated with gravity-based energy storage subsystems) and, optionally, maintaining the round-trip storage efficiency of the gravity-based energy storage subsystem when charge / discharge cycle requirements are within its capacity. The reverse conversion can also be facilitated.

[0058] A hydrogen energy storage subsystem significantly expands the energy storage capacity of the system. For example, using a 500 meter deep hole or shaft with a diameter of 6 meters and a single weight of 1,000 tons, a gravity-based energy storage subsystem has an energy storage capacity of about 1.2 MWh. If the same space were filled with 50 bar hydrogen, its heating value would be about 1,800 MWh, producing at least 500 times more electrical energy than one descent of the weight, even considering a generator with only 30% efficiency. In other words, storing hydrogen in pressurized form would increase the capacity to raise the weight about 500 times, thereby increasing the storage capacity of the system by about 500 times (assuming that all the gas can be used, but of course the pressure will drop to some minimum allowable level before it is all used).

[0059] The system provides a combined storage system with rapid response that can store much more electrical energy (converted from gas) than any other storage system that can be deployed on a decentralized basis and provide grid stability.

[0060] System 1 is therefore controlled by a controller that manages the balance of energy storage between the subsystems in the most efficient and / or effective manner (depending on priorities at a particular time), providing a flexible energy storage solution for both gas and electric energy, with improved efficiency through effective thermal collection and storage / use.

[0061] 3 illustrates an alternative embodiment of the energy storage system 1 in which a vertical passageway or shaft 53 in the earth 93 is provided for a multiple weighted gravity energy storage subsystem 3, the shaft volume being defined by a vessel 55 having a dome / cap 59 sealing the top and provided in the earth 93 for containing a fuel gas such as hydrogen as part of a fuel gas storage subsystem. The shafts 53 and vessels 55 of the multiple weighted gravity storage subsystem 3 occupy or define the same volume, leading to shared infrastructure and improved cost and land efficiencies.

[0062] A multi-weight gravitational energy storage system 3 according to one embodiment comprises a first winch device 11 arranged on a platform 95 in the shaft 53 and having a first weight 13 suspended therefrom via a first composite cable 69, and a second winch device 87 arranged above the platform 95 and having a second weight 89 suspended therefrom via a second composite cable 91. The winches 11, 87 are operated by a hydraulic motor / pump (not shown) in the vessel 55 and are driven by hydraulic fluid supplied from a hydraulic motor / generator 73 via a hydraulic pipe 75 extending through a sealed service link 85 via a sealed opening. The hydraulic motor / generator is supplied with power from the external power grid via an inlet / outlet 79. In use, when there is excess energy in the power grid, power is supplied via the inlet / outlet 79 to the hydraulic motor 73 which pumps fluid through the hydraulic pipe 75 to drive the winch motor so that one or the other or both of the winches 11, 87 raise the weights 13, 89. When it is desired to export energy to the external grid, the weight 13, 89 can be lowered and the winch 11, 87 pumps hydraulic oil through the hydraulic oil pipe 75 to the hydraulic generator 73 via a sealed service linkage 85, generating electrical energy that is exported via the power input / output connector 79. The raising and lowering of the weight 13, 89 is controlled by a controller (not shown), for example according to the requirements of the external grid.

[0063] Hydrogen (or other fuel gas in some embodiments) may be stored in a vessel 55 in which a winch and weight device is placed at any suitable pressure (e.g. up to 800 bar, but preferably up to 400 bar, more preferably up to 100 bar, e.g. up to about 85 bar). Hydrogen may optionally be supplied from an external hydrogen source via hydrogen input / output connection 23 and, after storage, may optionally be exported to an external hydrogen user via input / output connection 23, such as by injection into a natural gas network or a local hydrogen network or a hydrogen refueling station. Hydrogen supplied from an external hydrogen network may pass through a compressor / expander 65, then be supplied via a hydrogen inlet pipe passing through a sealed service link 85 and stored in the vessel 55.

[0064] When the potential energy stored in the weights 13, 89 is at or near its maximum value, or when the controller or control software predicts or anticipates a significant demand for power storage, the system 1 can convert the form of the stored energy from potential energy to chemical energy (in the form of hydrogen) by lowering the weights 13, 89 in the shaft / vessel 53, 55 to generate electrical energy in the generator 73 in the manner described above, which is fed to the electrolyzer 29 to form hydrogen gas (from water), which can then be compressed via the compressor 65 and returned to the same vessel 55 for storage. Similarly, if a need for electrical energy is anticipated, and more specifically, if a need for rapid power supply to the external grid (e.g., black start) is anticipated when the weight 13, 85 is near the bottom of the shaft 53, hydrogen from the container 55 can be supplied to the fuel cell 31 via a gas supply pipe via a sealed service linkage 85 and expander 65 to operate the hydraulic motor 73 to power the winch 11, 87 and lift the weight 13, 89 in the shaft to provide electrical energy that is stored as easily deployable potential energy.

[0065] To further increase the efficiency and flexibility of system 1, a thermal energy storage subsystem is provided around the shaft 53 to collect geothermal source heat from the ground 93 outside the shaft / vessel 53, 55, and comprises heat exchange elements that collect heat from the interior of the vessel 55 (e.g. as a result of pressure changes). This heat can be exported via a thermal energy collection circuit 83 to thermal energy storage (not shown) or for external use (e.g. a district heating scheme). Thus, a flexible and efficient energy storage system can be provided within a single shaft that supplies heat, fuel and power according to the needs of external systems.

[0066] The present invention has been described with reference to preferred embodiments, but those skilled in the art will appreciate that variations and modifications can be made without departing from the scope of the invention.

Claims

1. 1. An energy storage system comprising: a first energy storage subsystem comprising: a gravity-based energy storage system comprising at least one weight movable between a first upper position and a second lower position, the first upper position and the second lower position defining a vertical displacement of the or each weight; a second energy storage subsystem comprising a vessel for storing pressurized fuel gas; an electrical input connection and an electrical output connection to an external power system; a fuel gas inlet for supplying fuel gas to the energy storage system from an external fuel gas source or network; a fuel gas outlet for supplying fuel gas from the energy storage system to an external fuel gas user or network; and, a gas-to-power converter for converting energy from the fuel gas into electrical energy for storage in the first energy storage subsystem or for export to an external power system via the electrical output connection; a power to gas converter for converting electrical energy into fuel gas for storage in the second energy storage subsystem or for export to an external fuel gas user or network via a fuel gas outlet; The energy storage system further comprises a control system for controlling coordinated or complementary operation of the first and second energy storage subsystems in accordance with requirements of the external power system and / or an external fuel gas network or a user.

2. 2. The energy storage system of claim 1, wherein the first energy storage subsystem comprises a vertical passage or shaft through which the at least one weight is movable between the first upper position and a second lower position, and the container of the second energy storage subsystem comprises the shaft of the first energy storage subsystem.

3. The energy storage system of claim 2 , wherein the shaft is formed in the earth.

4. 4. The energy storage system of claim 2 or claim 3, wherein the first energy storage subsystem comprises a winch and cable arrangement comprising at least one winch positioned at or associated with a shaft opening at the top of the shaft, whereby a cable can be wound and unwound by the winch to raise and lower the weight, and wherein the winch and cable arrangement is disposed within the vessel, the vessel comprising a cap or dome positioned and sealed at the top of the shaft.

5. 5. The energy storage system of claim 4, wherein the winch and cable arrangement is hydraulically driven by a hydraulic drive means when the first energy storage subsystem is receiving or charging power and hydraulically drives a hydraulic generator when the first energy storage subsystem is releasing or discharging power, the hydraulic drive means and hydraulic generator are located outside the vessel of the second energy storage subsystem, hydraulic drive supply and return pipes connecting the hydraulic drive means and hydraulic generator with the winch and cable arrangement pass through openings formed in a wall of the vessel, and seals are formed in the vessel wall around the pipes to prevent leakage of pressurized gas from the interior of the vessel to the surrounding atmosphere.

6. 6. The energy storage system of claim 1, further comprising a heat capture and / or storage subsystem configured to capture thermal energy from material within and / or surrounding the container of the second energy storage subsystem.

7. 7. The energy storage system of claim 6, wherein the heat capture and / or storage subsystem comprises a heat pump device.

8. 8. The energy storage system of claim 6 or claim 7, wherein the heat capture and / or storage subsystem is configured to provide heating and / or cooling to the fuel gas storage subsystem vessel via a heat exchange element to maintain a temperature of the fuel gas storage vessel within predefined operating limits.

9. 9. The energy storage system of any one of claims 1 to 8, wherein the fuel gas is hydrogen, or methane, or other commercially available gases such as propane or natural gas that can be easily compressed and stored.

10. 10. The energy storage system of claim 9, wherein the fuel gas is hydrogen.

11. 11. The energy storage system of claim 9 or claim 10, wherein the hydrogen or other fuel gas is stored in the vessel at a pressure of 300 bar or less.

12. the first energy storage subsystem comprises a multiple weight gravity-based energy storage device comprising a shaft (or other vertical passageway) and a plurality of weights configured to be raised and lowered through the shaft by a transport (e.g., a winch and cable arrangement) and stored in a storage location at a top and / or bottom of the shaft, the first energy storage subsystem having a primary energy capacity and characterized by a discontinuity in power flow capability; The energy storage system includes: i) a continuous input or output power during a charge or discharge cycle of the first energy storage subsystem over at least two energy events, the energy events being separated by a discontinuity in the output from the first energy storage subsystem; and ii) an enhanced or faster system start-up response, whereby the system can reach a predefined or desired power input / output level by responding to requirements of an external power system using both the primary energy storage device and the secondary energy storage device simultaneously; and iii) an enhanced system discharge termination capability, whereby the system can quickly terminate discharge to an external power system without generating a power output surge that exceeds a desired system power output, the power output surge being intended for temporary energy storage in the secondary energy storage device; iv) a power surge input / output capability whereby the system can input or output power at power levels that exceed the power rating of the energy storage system or the primary power storage device for a short period of time; An energy storage system according to any one of claims 1 to 11.

13. 13. The energy storage system of claim 12, wherein the third energy storage subsystem is selected from a battery, a capacitor or supercapacitor, a compressed air energy storage system, a flywheel, or a second gravity based energy storage system.

14. 14. The energy storage system of any one of claims 1 to 13, comprising a fuel gas outlet for supplying fuel gas from the second energy storage subsystem to a gas network pipeline.

15. 15. An energy storage system according to any one of claims 1 to 14, comprising a vehicle charging and / or refuelling station comprising an eV charging station and / or a fuel gas vehicle refuelling station, said vehicle charging station and / or refuelling station being supplied from the energy storage system via a vehicle charging station electrical supply connection and / or a refuelling fuel gas outlet connection.

16. 1. An energy storage system comprising: a first energy storage subsystem comprising: a gravity-based energy storage system comprising at least one weight movable through a volume (e.g., defined by a shaft formed in the earth) between a first upper position and a second lower position, the first upper position and the second lower position defining a vertical displacement of the or each weight; a second energy storage subsystem comprising a pressurized fuel gas storage vessel defining a fuel gas storage volume surrounding the volume defined by the first energy storage subsystem.

17. 1. An energy storage system comprising: a first energy storage subsystem comprising: at least one weight movable between a first upper position and a second lower position through a shaft (or other vertical passageway) formed in the earth, the first upper position and the second lower position defining a vertical displacement of the or each weight; a thermal energy capture and / or storage subsystem comprising a heat capture element disposed within or around the shaft of the first energy storage subsystem to capture thermal energy from within or around the shaft.

18. 20. A method for the storage and supply of energy to and from an external energy system, comprising: providing an energy storage system as claimed in claim 1; operating the control system to control the storage of the electric energy from an external power source or network as potential energy by lifting a weight in a first storage subsystem or as chemical energy by conversion of electric energy to fuel gas by the power to gas conversion device; controlling the storage of energy from fuel gas from an external fuel gas supplier or network as compressed fuel gas by supplying the fuel gas to the second energy storage device or by storing the fuel gas supplied by conversion of the fuel gas to electric energy using a gas to power conversion device as potential energy by storing the resulting fuel gas in the second energy storage subsystem; and storing the energy as potential energy by lifting a weight in the first storage subsystem according to energy storage requirements of an external gas and power network or supplier and depending on the fuel gas and electric energy storage capacities of the first and second energy storage subsystems and the predefined or predicted fuel gas and electric energy output requirements.

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