Energy production system that combines a fuel cell and a rechargeable battery, and procedures that implement said system

Abstract

The present invention relates to a system (1) for low-power energy generation comprising a fuel cell (71) fed by a gas network (2) and a rechargeable energy storage system (72). The present invention also relates to a method of energy generation and a method of energy management implementing said energy generation system.

Description

[0001] The present invention falls within the field of energy recovery systems (generally referred to as " Energy Harvesting Systems » (in English) to supply electrical power to electronic systems.

[0002] More specifically, the present invention relates to an energy production system comprising a fuel cell. The present invention also relates to an energy production method and an energy management method implementing such a device.

[0003] Electronic systems, particularly measurement systems (or sensors), found in industrial settings, are becoming increasingly energy-intensive and are communicating more and more frequently via radio frequency systems. In this context, the energy autonomy of these electronic systems is a growing concern. Currently, they are powered either by the mains electricity grid or by electrochemical cells (redox reactions). These power solutions are costly, have limited energy levels, and present technical deployment challenges.

[0004] The goal today is to give electronic systems the ability to operate for years without human intervention. The installed products all aim to move towards the same "ready-to-install" philosophy (known in English as " Install and Forget "), the equivalent of "ready to shoot" (in English " Plug and Play") multimedia peripherals. These systems must, from the moment of installation, be integrated into their environment, both in terms of communication and power supply.

[0005] The challenge for electronic systems, in addition to their main functions (sensor, actuator), is to minimize the costs associated with their power supply by finding energy present in their environment.

[0006] However, the environment of electronic systems is not always energy-rich, and this limitation of the energy source limits their functionality.

[0007] Currently, there are three solutions for powering an electronic system: mains power supply when it is materially and financially feasible to run a cable to the system to be powered; redox fuel cell power supply; power supply by an energy recovery system ( Energy Harvesting » (in English) which recovers energy present in the environment. This energy source can be radiative, thermal, mechanical, or chemical. To increase the time interval between two maintenance periods, a solution using batteries recharged by energy recovered from the ambient environment via a transducer can be considered.

[0008] In the case of a mains-powered electronic system, this solution has the following disadvantages: Physical drawback: a system placed in a hard-to-reach location cannot be powered by cables. Financial drawback: the cost of such a power supply becomes prohibitive when the system is located far from the electrical grid.

[0009] Powering electronic systems with batteries also has drawbacks, in particular: The system's lifespan, without maintenance, depends on the battery life, which is linked to the battery technology, their capacity (based on the electronic system's power consumption), their size (which limits installation in spaces), and their weight. The cost of maintenance, which requires multiple battery replacements during the electronic system's lifespan, is also a factor.

[0010] The energy recovery solution of the type "Energy Harvesting" Radiative, mechanical, and thermal energies also present disadvantages, and in particular: The available energy is dependent on the environment; the energy present in the environment is not always sufficient, the amount of energy may be limited in terms of maximum power; the assessment and prediction of available energy can sometimes be complex.

[0011] Gas transmission networks, through the gas they carry, represent an unlimited energy source for sensors installed on these networks. Fuel cell solutions operating on natural gas exist. For example, US 2011 / 0300457 describes a fuel cell system comprising at least one fuel cell unit for generating electrical power and at least one component, upstream and / or downstream of said fuel cell unit in the anode flow path, said component preventing, as a reoxidation barrier, the reoxidation of parts of the anode sections or of the anode sections as a whole in the event of the ingress of an oxidizing gas. US 5,332,630, meanwhile, describes a power system for supplying an electric motor in an electric vehicle that includes a rechargeable battery connected to the motor to drive the motor and a fuel cell assembly connected to the battery to recharge the battery.However, they are poorly suited to powering small electronic systems and mostly operate at high temperatures and have limited operating lifespans. The difficulty here lies in three points: difficulty of having a fuel cell that runs on natural gas with all of these components, lifespan of fuel cells, especially solid oxide fuel cells (commonly referred to by the acronym SOFC for the English expression " Solid Oxide Fuel Cell " which is not currently technically sufficient to operate continuously on a gas network, operating problems of SOFC type fuel cells related to the presence of sulfur elements in natural gas.

[0012] Of the three aforementioned solutions for powering an electronic system, the third energy recovery solution is of the type "Energy Harvesting"is currently the most attractive option for powering electronic systems, both in terms of logistics and cost. The limitation of radiative, mechanical, and thermal energy remains the energy available in the environment.

[0013] In the context of powering an electronic system located on a natural gas network, the energy source available in the environment of the pipelines, present in abundance and without limitation, remains natural gas.

[0014] However, exploiting it is problematic, because fuel cells have a limited lifespan and require high-temperature reforming systems that are often complicated to operate at low temperatures without a third-party energy input (electrical connection).

[0015] To overcome the aforementioned defects and drawbacks, the applicant has developed an energy production system combining a fuel cell and a rechargeable battery, in which the fuel cell can operate on gas from a standard gas network and be supplied with oxygen from the air. Such a device allows for the continuous power supply to an energy consumer, such as an electronic system like a measuring (sensor) system, a radio communication system, an actuator, or a mechanical, audible, or visual alarm system.

[0016] For the purposes of this application, continuous supply of an energy consumer means a supply of the energy consumer without any possible interruption or break in supply, and not a continuous supply with a current.

[0017] For the purposes of this application, the term "gas network" means a gas distribution network, but also internal gas networks within civil or industrial facilities, the gas transport network, gas storage facilities, liquefied natural gas (LNG) supply systems and oil and gas extraction platforms.

[0018] The combination of a fuel cell and an electrical energy storage device is known from the prior art.

[0019] Thus, international patent application WO 2007 / 142169 describes, in particular, a fuel cell comprising a capacitor for storing electrical energy, and the method for using said fuel cell. However, this patent describes the use of the stored electrical energy for the fuel cell itself and not for powering another component, as is the case in the present invention. Furthermore, WO 2007 / 142169 does not describe the sizing of the fuel cell / battery combination and its operation in relation to this sizing.

[0020] The present invention therefore relates to an energy production system according to claim 3.

[0021] The energy production system according to the invention is an ambient energy recovery solution, as it avoids the need for an energy reserve and therefore limits maintenance or recharging operations. Consequently, there is no gas storage involved in the energy production system according to the invention.

[0022] Furthermore, while the energy production system according to the invention is capable of continuously supplying an energy consumer, the fuel cell in this system does not operate continuously, but intermittently, that is, only to recharge the electrical storage system (generally a battery). The frequency of this recharging can range from a few hours to once a year, depending on the power consumption of the electronic system being powered. The energy reserve is therefore sized so that its desired discharge level is reached at the end of this period. Indeed, a fuel cell has a limited lifespan due to two phenomena: the number of on / off cycles, the operating time

[0023] In contrast, a fuel cell does not have a calendar lifespan. This means that a fuel cell can, in theory, never have been used for 10 years and still have the same number of on / off cycles and the same number of operating hours as if it were brand new.

[0024] The lifespan of a fuel cell can range from 1,000 to 100,000 hours for the most efficient models, but typically, the lifespan of a fuel cell is around 5,000 hours. Since there are 8,760 hours in a year, a fuel cell with a lifespan of 5,000 hours cannot operate continuously for more than one year.

[0025] With the energy production system according to the invention, combining a SOFC fuel cell with an electrical energy storage system such as a battery, it is possible to store the energy produced without having to supply energy continuously.

[0026] Furthermore, a fuel cell used alone has a reaction time that is far too long (typically several seconds) compared to the current peaks required to power a sensor. Combining the fuel cell with an electrical energy storage system (such as a battery) in the energy production system according to the invention allows for a buffer between the amount of energy demanded by the sensor and the energy deliverable by the fuel cell.

[0027] In the energy production system according to the invention, the fuel cell is a solid oxide fuel cell (SOFC), which can operate with various types of hydrocarbons as well as hydrogen. It includes a reforming system to convert hydrocarbons into hydrogen.

[0028] The gas supplying the energy production unit can be natural gas, liquefied natural gas, evaporation gas from LNG, town gas, biogas, biomethane, synthetic methane or hydrogen.

[0029] For the purposes of this application, biogas means a gas produced by the methanation of biomass or second generation biogas.

[0030] The bypass connecting the fuel cell to the intake duct can be controlled by an actuator or by permeation. This bypass system allows the oxidizer to be recovered from the duct.

[0031] Advantageously, the SOFC solid oxide fuel cell of the power generation system according to the invention can be thermally insulated by a thermal insulation system and can include a heating system (the rise and maintenance of temperature being done by electronic or chemical heating (combustion to heat said fuel cell).

[0032] For this purpose, the solid oxide fuel cell preferably has a tubular or microtubular structure, which consists of a tubular-shaped system. This format is more resistant to the thermal expansion of materials and associated mechanical stresses, and therefore prevents accelerated aging linked to these thermal expansion phenomena. However, other architectures are not excluded from the present invention.

[0033] Advantageously, the electrical energy storage system management device can be an electronic device for managing the energy supply of the fuel cell.

[0034] Advantageously, the energy production system according to the invention may include at the inlet of the gas intake duct and upstream of the fuel cell a passive desulfurization filter to remove sulfur molecules present in the gas, which are harmful to the operation of the fuel cell.

[0035] Advantageously, the energy production system according to the invention may further include a system for the evacuation or treatment of the effluents produced by the fuel cell (CO2, H2O and O2). An effluent evacuation system prevents discharges of effluents that could be dangerous to a third party or to the gas network.

[0036] The present invention also relates to a method according to claim 1.

[0037] Advantageously, in the energy management process, the management module can start the fuel cell when the electrical energy storage system is discharged to a threshold between 60 and 99% of the storage capacity, and preferably between 70 and 90% of the storage capacity for a supply period of between 5 and 20 years.

[0038] This description also relates to an energy production process implementing an energy production system intended to be connected to a gas network, said energy production system comprising: a gas inlet duct from said network into said power generation system, an effluent discharge duct, a power generation unit comprising a solid oxide fuel cell (SOFC), which is supplied with gas via a bypass connected to said inlet duct, and supplied with oxygen via an air inlet duct, a rechargeable electrical energy storage system associated with said fuel cell, a management module comprising a fuel cell management device and an electrical storage system management device to control its charge, said process being characterized in that the fuel cell continuously supplies an energy consumer consuming on average between 1mW and 1W

[0039] In the energy production process, the energy storage system can also be used to ignite the fuel cell and reignite it as needed.

[0040] Preferably, in the energy production process, the fuel cell can continuously supply an energy consumer consuming on average between 1mW and 100mW of energy. Below 1mW, the solution of supplying the energy production system according to the invention is no longer economically competitive, and above 100mW, the technical constraints become too significant.

[0041] Whether for the energy management process according to the invention or the energy production process, the fuel cell may advantageously include a thermal insulation system and a heating system to heat said fuel cell.

[0042] For this reason, the solid oxide fuel cell will preferably have a tubular or microtubular structure, which consists of a tubular shape. This format is more resistant to the thermal expansion of materials and associated mechanical stresses, and therefore helps to avoid accelerated aging linked to these thermal expansion phenomena.

[0043] Advantageously, the electronic management device can trigger the start-up of the fuel cell when the capacity of the electrical energy storage system is discharged to a threshold between 60 and 99% of the storage capacity, and preferably between 70 and 90% of the storage capacity, for a supply period of between 5 and 20 years.

[0044] Advantageously, the storage device will be sized to optimize the supply duration according to the performance criteria of the fuel cell technology and the electricity storage system. The minimum sizing follows the equations below: That is D the calendar life of the battery at a power P operating function d the desired power supply duration of the consumption point C min the minimum battery capacity P The continuous power required. N PaC: the number of fuel cell cycles. N stock: the number of storage system cycles. N min = min N PaC N stock The cycle life of the fuel cell is greater than the cycle life of the storage system; otherwise, α (in %) is the trigger threshold depending on the battery technology. E is the total energy that can be produced by the fuel cell: (1) E pile = D * P fct (2) E pile > d * P (3) C min = α * E pile / N min The factor α is related to the electrical storage technology used and must take into account: Whether for the energy management process according to the invention or the energy production process, the electronic device for managing the electrical energy storage system can further manage the fluid supply to the fuel cell and the electrical energy supply to the electrical consumer (for example, a sensor), as follows: The electronic management device triggers the start-up of the fuel cell when the capacity of the electrical energy storage system is discharged to a predetermined threshold, for a supply period of between 5 and 20 years.

[0045] Advantageously, the electronic management device can trigger the start-up of the battery to the self-discharge of the electrical storage; Electrical storage capacity as a function of operating temperature; Calendar lifetime of electrical storage; Decline in electrical storage capacity as a function of time; Ability of electrical storage to provide current peaks for power demands. Depending on the storage types, α can be between 1.5 and 3.

[0046] Whether for the energy management process according to the invention or the energy production process, the energy production system may further include upstream of the fuel cell a passive desulfurization filter to eliminate sulfur molecules present in the gas.

[0047] Whether for the energy management process according to the invention or the energy production process, the energy production system may further include a system for evacuating or a system for treating the effluents produced by the fuel cell.

[0048] Whether for the energy management process according to the invention or the energy production process, the gas can be natural gas, liquefied natural gas, evaporation gas from LNG, town gas, biogas, biomethane, synthetic methane or hydrogen.

[0049] Other advantages and features of the present invention will become apparent from the following description, given by way of non-limiting example and with reference to the accompanying figures: ∘ the figure 1 represents a general schematic diagram of the energy production system according to the invention; ∘ the figures 2a and 2b represent respectively a cross-sectional view ( figure 2a ) and a side view ( figure 2b ) of a first example of the realization of a tubular structure fuel cell; ∘ the figures 2c and 2d represent respectively a side view ( figure 2c ) and a cross-sectional view ( figure 2d) of a second example of a tubular fuel cell design; ∘ the figure 3 represents a schematic cross-sectional view of an energy production system according to a second embodiment of the invention, in which the solid fuel cell has a microtubular structure; ∘ the figure 4 represents a schematic perspective view of an array of microtubes in the fuel cell of the figure 4 .

[0050] The identical elements represented on the figures 1 to 4 are identified by identical numerical references.

[0051] On the figure 1 A general schematic diagram of the energy production system 1 according to the invention, which is connected to a standard gas network 2, is shown. figure 1This shows that gas from network 2 is introduced, via a gas inlet duct 4 connected to the gas network 2, into the power generation system 1. The inlet duct 4 is connected to a branch 41 which supplies gas, within the power generation system 1, to a solid oxide fuel cell 71 (SOFC). The SOFC is also supplied with oxygen via an air inlet duct. The effluents produced by the fuel cell (CO2, H2O, and O2) are removed from the power generation system via an effluent discharge duct 5. The operation of the fuel cell 71 is managed by a control device 91 of a control module 9.Within the energy production system 1, the fuel cell 71 is associated, in an energy production unit 7, with a rechargeable electrical energy storage system 72, which is managed by a specific management device 92, also part of the management module 9. This management device 92 allows the charging of the electrical storage system 72 to be controlled. The . figure 1 also shows that a thermal insulation system 14 is placed around the fuel cell 71, on which 14 is arranged an electrical resistance 11.

[0052] The tubular structure of the fuel cell is shown in more detail on the figures 2a to 2d . THE figures 2a and 2b represent respectively a cross-sectional view ( figure 2a ) and a side view ( figure 2b) of a first example of the realization of this tubular structure, which consists of a thick support tube of electrolyte 7111 (in particular ceramic), coated on the outside with an outer layer of cathode 7110 and on the inside with a thin layer of anode 7112. The figures 2c and 2d represent respectively a side view ( figure 2c ) and a cross-sectional view ( figure 2d ) of a second example of an embodiment of this tubular structure, which consists of a thick anode support tube 7112, successively coated from the tube with a layer of electrolyte 7111, then with an outer layer of cathode 7110. The figure 3 represents a schematic cross-sectional view of an energy production system 1 according to a second embodiment of the invention, in which the solid fuel cell 71 comprises a microtubular structure, which consists of rows of microtubes 712, separated from each other by separators 713, as illustrated in the figure 4 . There figure 3 also shows that a thermal insulation system 14 is placed around the fuel cell 71, on which 14 is arranged an electrical resistance 11.

[0053] The following examples illustrate the invention without, however, limiting its scope. EXAMPLES EXAMPLE 1: Power supply for an energy-autonomous gas monitoring system (pressure, flow rate, temperature).

[0054] The system according to the invention is used to power a system of an industrial programmable logic controller for gas monitoring, generally designated by the acronym RTU (for the English " Remote Terminal Unit”), which transmits measurement information via wire or radio waves. The system is powered by the 220V mains supply and, when this is not possible, batteries are used.

[0055] When battery power is chosen, data transmission is carried out by radio frequency wave and energy autonomy depends on the use of the RTU as well as the capacity of the batteries.

[0056] In the context of a RTU (Remote Transmission Unit) installed at a pressure reduction station, the target autonomy is 2 years and the average consumption is 20 mW. According to the invention, a fuel cell power solution offers an acquisition cost twice that of an RTU, but an operating cost four times lower. The return on investment is estimated at 4 years based on these assumptions, which are pessimistic. For example, an electrical consumer consuming an average of 20 mW, with a minimum N value of 250 and an alpha factor of 1.5, requires an 18 Wh battery, assuming it is recharged every 15 days and has a lifespan of 10 years.

[0057] This example shows that using a system according to the invention allows for gains from an economic point of view. EXAMPLE 2: Example of sizing an energy production system according to the invention.

[0058] For the sizing of an energy production system according to the invention, the chosen use case attempts to be as representative as possible of the requirements that may be encountered in terms of consumption and sensor lifespan: The fuel cell has a service life of 5000 hours, the sensor, powered via a battery, consumes an average of 10 mA at 3.3 V, i.e. a power of 33 mW.

[0059] The period between two maintenance phases is 10, 15 or 20 years.

[0060] Table 1 below presents the approach used to size a fuel cell to meet the energy requirements of the use case described in this example. The left-hand column lists the questions, in order, that must be answered, while the right-hand column presents three different ways to answer these questions for three different maintenance-free periods (10, 15, and 20 years).

[0061] According to this table, a fuel cell with an operating life of 5,000 hours and a power of 2 W can, over 20 years (operating 250 h / year), power a system (= recharge a battery powering the sensor) which consumes on average 10 mA at 3.3 V. Table 1 Power supply voltage 10 mA on average, or 87.6 hours per year 10 mA on average, or 87.6 hours per year 10 mA on average, or 87.6 hours per year Sensor power consumption 3,3 V 3,3 V 3,3 V Energy needed over a year 289 Wh / year 289 Wh / year 289 Wh / year Period between two maintenance phases 10 years 15 years 20 years Fuel cell lifespan in operating hours 5000 hours 5000 hours 5000 hours Number of operating hours per year to reconcile the lifespan of the fuel cell and the interval between two maintenance phases 500 hours / year 333 hours / year 250 hours / year Power that the fuel cell must supply during its operating phases 0,6 W 0,9 W 1,2 W Total return (taking into account the different returns of the transfer. 64 % 64 % 64 % Actual power that the fuel cell must deliver during its operating phases at 50% of its power 1,8 W 2,8 W 3,6 W Minimum battery capacity 18 Wh 27 Wh 36 Wh

Claims

1. Energy management method using an energy production system (1) intended for connection to a gas network (2), said gas being natural gas, liquefied natural gas, LNG evaporation gas, town gas, biogas, biomethane, synthetic methane or hydrogen, said energy production system (1) comprising - a gas intake duct (4) from said network (2) into said energy production system (1), - an effluent discharge pipe (5), - an energy production unit (7) comprising a solid oxide fuel cell (71) SOFC, which is ∘ supplied with gas via a bypass (41) connected to said intake duct (4), and ∘ supplied with oxygen by an air intake duct (8), - a rechargeable electrical energy storage system (72) associated with said fuel cell (71), said energy production system continuously supplying an energy consumer consuming on average between 1 mW and 100 mW of power, - a management module (9) comprising a management device (91) for said fuel cell (71) and an electronics management device (92) for said electrical storage system (72) to control charging thereof, said method being characterized in that the management module (9) starts the fuel cell (71) when the electrical energy storage system (72), having an energy between 0.1 Wh and 100 Wh, is discharged up to a predetermined threshold, and in that the fuel cell (71) operates intermittently, only to recharge the rechargeable electrical storage system (72).

2. Method according to claim 1, wherein the management module (9) starts the fuel cell (71) when the electrical energy storage system (72) is discharged up to a threshold of between 60 and 99% of the storage capacity, for a supply period of between 5 and 20 years.

3. Energy production system (1) intended for connection to a gas network (2), said gas being natural gas, liquefied natural gas, LNG evaporation gas, town gas, biogas, biomethane, synthetic methane or hydrogen, said energy production system (1) comprising: - a gas intake duct (4) from said network (2) into said energy production system (1), - an effluent discharge pipe (5), - an energy production unit (7) comprising a solid oxide fuel cell (71) SOFC, which is ∘ supplied with gas via a bypass (41) connected to said intake duct (4), and ∘ supplied with oxygen by an air intake duct (8), - a rechargeable electrical energy storage system (72) associated with said fuel cell (71), said energy production system continuously supplying an energy consumer consuming on average between 1 mW and 100 mW of power, - a management module (9) comprising a management device (91) for said fuel cell (71) and an electronics management device (92) for said electrical storage system (72) to control charging thereof, said system being characterized in that the management module (9) is configured to start the fuel cell (71) when the electrical energy storage system (72), having an energy between 0.1 Wh and 100 Wh, is discharged up to a predetermined threshold and such that the fuel cell (71) operates intermittently, only to recharge the rechargeable electrical storage system (72).

4. System according to claim 3, wherein the fuel cell (71) comprises a thermal insulation system (14) and a heating system (11) for heating said fuel cell (71).

5. System according to claim 4, wherein the fuel cell (71) comprises a tubular (711) or microtubular (712) structure.

6. System according to any of claims 3 to 5, wherein said electronics management device (92) of said electrical energy storage system (72) is further configured to manage the supply of fluid to the fuel cell (71) and the supply of electrical energy to the energy consumer as follows: said electronics management device (92) triggers the start-up of the fuel cell (71) when the capacity of the electrical energy storage system is discharged up to a predetermined threshold, for a supply period of between 5 and 20 years.

7. System according to claim 6, wherein said electronics management device (92) is configured to trigger the start-up of the fuel cell (71) when the capacity of the electrical energy storage system is discharged up to a threshold of between 60 and 99% of the storage capacity, for a supply period of between 5 and 20 years.

8. System according to any of claims 3 to 7, wherein the energy production system (1) further comprises, upstream of the fuel cell (71), a passive desulfurization filter (10) for removing sulfur molecules present in the gas.

9. System according to any of claims 3 to 8, wherein the energy production system (1) further comprises a system for discharging or a system for treating effluent produced by the fuel cell.

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