Improvement of a method and system for autonomous stationary electricity production using an organic chemical fuel

Abstract

Improvement of a method for producing electricity in a stationary, self-contained situation, using a chemical fuel obtained from organic sources, including the steps for: supplying chemical fuel from a fuel tank (3), distributing said chemical fuel to a plurality of energy conversion modules, each comprising a reforming unit and a high-temperature fuel cell unit, in each energy conversion module: reforming (30) the chemical fuel to produce syngas, injecting (31) said syngas into a high-temperature fuel cell unit to produce electrical energy, processing (32) said electrical energy produced by said energy conversion modules to generate a rated electrical power suitable for the voltage and current required for one or more consumers,storage (33 in a storage unit (6a) part of the electrical energy not used by the consumer (8,) manage said energy conversion modules so that one or more of said energy conversion modules are put into idle mode, depending on the required efficiency level, while others are kept in operational mode and / or used to heat said energy conversion module in idle mode. See Figure 3,

Description

Title of the invention: Improvement of a method and a system for producing electricity in an autonomous stationary situation using a chemical fuel of organic source Field of invention

[0001] The invention generally relates to a method for producing electrical energy intended to be used by local systems such as charging station operators or other consumers of equivalent power levels. It also relates to an autonomous electricity production system implementing said method, state of the art

[0002] A fuel cell system may refer to a configuration of one or more fuel cells configured to produce electrical power. Individual fuel cells, such as solid oxide fuel cells, may be arranged to form fuel cells. A fuel cell may refer to a plurality of individual fuel cells that are electrically connected in series. The number of individual fuel cells that comprise a given fuel cell system may depend on the amount of electrical power that the given fuel cell system is intended to generate. A fuel cell system may also include any other individual fuel cell configuration, as disclosed in EP2258017B1.

[0003] The current-voltage characteristics of fuel cells depend, for example, on the composition of the reactants, the mass flow rate, the temperature, and the pressure. The electrochemical reactions in the fuel cell react quickly to fluctuations in the fuel cell load. However, the response capability of the reactant input system is usually much slower, meaning response times of seconds or even minutes. When trying to achieve more efficiency from the fuel cells than the dominant input of reactants allows, this leads to a weakening of the fuel cell voltages, and even irreversible damage to the fuel cells is possible.In addition, load changes cause rapid temperature changes in the fuel cell, which, especially in high-temperature fuel cells, causes harmful thermomechanical stress, resulting in a significant reduction in fuel cell performance and lifetime. Thus, fuel cell systems must be designed so that the load on each fuel cell is kept as constant as possible and that a . possible change of load is attempted to be as controllable as possible, as indicated in EP 2377226B1.

[0004] Fuel cell systems typically operate on gaseous fuel sources such as hydrogen, ammonia, natural gas, or biogas. These fuel sources require gas compression for storage or complex piping infrastructure for gas delivery. with an added risk of leakage and greenhouse effect. Other systems using liquid fuel sources are very dangerous to humans such as methanol which can cause blindness by ingesting as little as 10ml.

[0005] The problem to be solved is to maintain the high temperature fuel cell, such as a solid oxide fuel cell (SOFC) at temperature regardless of the climatic situation and the output power, and to avoid any shutdown of the modules which would induce complexities in deactivating and restarting the FC modules. Definitions

[0006] • Energy conversion module: A module comprising a reforming unit, a fuel cell module and a “Balance of Plant” (BOP), intended to produce electrical energy and thermal energy from fuel. • Fuel cell module: A module comprising fuel cells. • Fuel cell: A stack of elementary fuel cells. • Fuel cell generator: A fuel cell system intended to generate electrical energy for external loads. • Module Off: An energy conversion module for which the fuel supply is interrupted and / or fuel conversion is inactive. • Minimum power level: Minimum power level required to maintain low activity for the energy conversion module (e.g. 20% of nominal power) Thermal equilibrium is no longer satisfied below this minimum power level. • Module operating mode: An energy conversion module is in operating mode when said module generates both electrical energy (for example from 25% to 100% of the nominal power) and exhaust gases at nominal temperature, with thermal equilibrium. • Module Idle Mode: A power conversion module is in idle mode when the module is generating only a residual level of electrical power compared to the nominal power. In idle mode, a power conversion module is out of thermal equilibrium and will require power from other modules, at low temperatures.

[0007]

[0008]

[0009]

[0010]

[0011] • Fuel Cell Generator Inactive Mode: Mode of an FC generator set in which no electrical energy is supplied by the generator set to an external load. Summary of the invention According to the invention, a method is provided for producing electrical energy in a stand-alone stationary situation using a chemical fuel obtained from an organic source, including steps for: - supply chemical fuel from a fuel tank, - distributing said chemical fuel to a plurality of modules of energy conversion each comprising a pre-forming unit and a high-temperature fuel cell unit, in each energy conversion module: - reform chemical fuel to produce synthesis gas, - injecting said synthesis gas into a high-temperature fuel cell to produce electrical energy, - process said electrical energy produced by said energy conversion modules, in order to generate a nominal electrical power adapted to the voltage and current required for one or more consumers, - store in a storage unit part of the electrical energy not used by the consumer, - managing said energy conversion modules so that one or more of said energy conversion modules are put into inactive mode depending on the required output level, while others are kept in operating mode and / or used to heat said energy conversion module in inactive mode. The energy conversion management step can advantageously include: - a step for processing data on instantaneous power demands, - a step for determining a certain number of energy conversion modules necessary to adjust the power demands, - a step to put into inactive mode those energy conversion modules which are not needed, - a step for maintaining said energy conversion modules in inactive mode at a predetermined temperature. The step of maintaining the energy conversion modules in idle mode at a predetermined temperature can be achieved by transferring the heat generated by the active energy conversion modules. The step to keep the energy conversion modules in idle mode at a predetermined temperature can be achieved by generating heat from electrical energy derived from active energy conversion modules or minimum power energy conversion modules.

[0012] The method according to the invention may further include a step for controlling the output power of one or more energy conversion modules among the plurality of energy conversion modules, depending on the instantaneous required electrical energy, and a step for processing the data in order to anticipate the power demands on the basis of recorded or external data. The chemical fuel may comprise ethanol.

[0013] According to another aspect of the invention, there is provided a system for producing electrical energy in a stand-alone stationary situation using a chemical fuel obtained from an organic source, including: - means for storing a chemical fuel, - means for distributing said chemical fuel to a plurality of energy conversion modules, each of these modules comprising: - means of reforming chemical fuel to produce synthesis gas, - means for supplying synthesis gas to a plurality of high-temperature fuel cell units, to produce electrical energy, - means for processing the electrical energy supplied by said plurality of energy conversion modules, to generate a nominal electrical power adapted to the voltage and current required for a consumer, - means for storing part of the electrical energy that is not used by the consumer, - means for managing said plurality of energy conversion modules, called management means comprising: - (i) means for putting some of these modules into inactive mode energy conversion, depending on the required level of efficiency and - (ii) means for adjusting the output power of the active energy conversion modules so as to be operational and / or used to heat said module in inactive mode.

[0014] The fuel cell management means may comprise programmed processing means for: - process data on instantaneous power demands, - determine a number of energy conversion modules corresponding to the energy needs, - control said idle mode adjustment means and said battery power adjustment means.

[0015] The system may also include communication means for centralizing operational data necessary to maintain the fuel cell generator system operational.

[0016] In an advantageous configuration of the system according to the invention, in which each energy conversion module further comprises an exhaust outlet and an air inlet, the energy production system according to the invention further comprises: - first means for selecting a connection of the exhaust outlet of one or more of these energy conversion modules to an inlet of a heat exchanger intended to produce heated air from ambient air, - second means for selecting a connection of the air inlet of one or more of these energy conversion modules to an outlet of said heat exchanger,

[0017] said first and second selection means being controlled by said management of the energy conversion modules to maintain one or more of these energy conversions in idle mode by transferring thermal energy from one or more working modules.

[0018] The claimed solution lies in a variation of the SOFC power combined with the use of one SOFC to maintain the other SOFCs in a thermal state. The power is produced by a fuel cell system. The power is delivered in direct current or alternating current. The fuel consumed by the fuel cell system is ethanol.

[0019] The invention provides sufficient energy storage allowing autonomous operation without the need to be connected to an energy infrastructure or pipeline. The storage of this fuel is done safely using a non-toxic organic fuel source which is liquid under ambient storage conditions.

[0020] Energy efficiency is achieved by a fuel cell device to produce electrical energy. The fuel cell is based on SOFC technology that operates at high temperature. By adapting the fuel flow in real time and controlling the temperature of the fuel cell system, the electrical power varies according to demand.

[0021] A battery pack provides temporary energy storage that can instantly provide power during transition phases of the fuel cell system, to ensure even faster response time of the fuel cell generator system.

[0022] Energy is stored in the form of a non-toxic liquid fuel source which provides electrical energy through an electrochemical reaction. Ethanol is preferably used as a liquid fuel source. Ethanol is abundantly available and is an organic molecule. Description of FIGURES

[0023] - [Fig.l] illustrates the architecture of an embodiment of an FC system for producing electrical energy according to the invention, - [Fig.2] comprises an embodiment of a module management unit of energy conversion implemented in a system according to the invention, - [Fig.3] presents the main stages of a method for producing electrical energy according to the invention, - [Fig.4] shows an example of heat transfer from a module of active energy conversion to idle mode energy conversion modules in an energy production system according to the invention, - [Fig.5] is a flowchart of an embodiment of the method for producing electrical energy according to the invention, - [Fig.6] is a schematic view of a mode of operation in an FC system for producing electrical energy according to the invention, - [Fig.7] is a schematic view of an inactive mode in the FC system of production of electrical energy of [Fig.6], and - [Fig.8] illustrates a specific embodiment of an FC system for producing electrical energy using selectors. Detailed description

[0024] With reference to [Fig.l], an autonomous system 1 for producing electrical energy according to the invention comprises a tank 3 for storing a chemical fuel obtained from an organic source such as ethanol, three energy conversion modules 2.1,2.2,2.3 for converting the chemical fuel energy supplied by the tank 3 by means of pipes 91,92,93 into electrical energy supplied to a connection unit 8 by electrical connections 121,122,123, the connection 8 being provided for supplying said electrical energy to an external variable load 8 and to an energy storage unit such as an electrochemical battery 6.

[0025] Each conversion module 2.1,2.2,2.3 comprises a reforming unit 41,42,43 supplying the synthesis gas to high temperature fuel cells 21,22,23 through synthesis gas pipes 101,102,103 and a voltage converter 51,52,53 connected to the electrical output of the fuel cells 21,22,23. Gas recycling loops 111,112,113 are provided for supplying surplus synthesis gas from the fuel cells 21,22,23 to the pre-forming units 41,42,43.

[0026] The autonomous electrical energy production system 1 further comprises a energy conversion module management unit 7 provided for communicating with a remote data center 14 and with the fuel storage tank 3, the energy conversion modules 2.1,2,2,2,3 and the voltage converters 51,52,53, respectively via the link buses 110,130,140.

[0027] This management unit 7 can be global, functioning as a supervision unit common to all the modules, or divided within each module, in a master-slave configuration.

[0028] The modules must be interchangeable and repairable without having to shut down the entire energy production system, with the aim of continuity of service thanks to a modular architecture.

[0029] The fuel cell management unit 7 comprises, with reference to [Fig. 2], a unit 101 for managing the energy conversion modules, which is connected to a data processing unit 70 via a connection bus 104 and to a control unit 75 provided for implementing real-time optimization (RTO) and controlling a fuel-input control unit 71 via a connection bus 102 and a unit 72 for driving and controlling the energy conversion modules via a connection bus 103. The data processing unit is provided for communicating with external equipment via a connection bus 100.

[0030] The control units 71,72 are connected via the respective buses 110,120, for connection respectively to the storage tank 3 and to the energy conversion modules 2.1,2,2,2,3, while the data processing unit 70 is connected via the link bus 140 to the voltage converters 51,52,53.

[0031] With reference to Figures 3 and 4, a method for producing electrical energy in a stand-alone stationary situation using a chemical fuel obtained from an organic source comprises a step 30 for reforming the chemical fuel supplied from a fuel tank 3 to produce synthesis gas, a step 31 for injecting said synthesis gas into the SOFC fuel cell unit at high temperature to produce electrical energy, said fuel cell unit comprising a plurality of cells, a step 41 for recycling the excess synthesis gas from the fuel cell into the reformer, a step 32 for processing said electrical energy to generate a nominal electrical power adapted to the voltage and current required for the consumer, a step 33 for storing in a storage unit a portion of the electrical energy not used by the consumer, and a step 34 for energy management.the conversion modules such that some of these energy conversion modules are set to inactive mode, depending on the required output level, while others are kept in operational mode and / or used to heat said energy conversion modules in inactive mode.

[0032] Step 34 of managing the fuel cell comprises a step of processing data on the instantaneous power demands, a step of determining a certain number of energy conversion modules corresponding to the adjustment of the power demands, a step of adjusting in idle mode the unused energy conversion modules to a minimum power level and a step for maintaining said FC cells in inactive mode at a predetermined temperature.

[0033] The step of maintaining the energy conversion modules in idle mode at a predetermined temperature is carried out by transferring heat generated by the active FC cells and / or generating heat from electrical energy derived from the active FC cells.

[0034] The method according to the invention may further include a step for controlling the output power of one or more FC cells of the plurality of FC cells, depending on the instantaneous required electrical energy or the demand of the customer 40, and a step 42 for processing the data in order to anticipate the power demands on the basis of recorded or external data.

[0035] With reference to [Fig.4], assuming that the power conversion module management unit 7 has determined that the absence of customer demand should require keeping the power conversion modules 2.2 and 2.3 in inactive mode, the power conversion module 2.1 is kept switched-on and thus active. A portion of the heat H1.2, H1.3 generated in the active power conversion module 2.1 is transferred via heat exchangers to the inactive power conversion modules 2.2 and 2.3 in order to maintain said modules at a predetermined temperature. As soon as a customer demand is detected and processed by the FC battery management unit 7, the power conversion modules 2.2 and 2.3 are again activated in operating mode to provide power to the customer load 8.

[0036] In an exemplary embodiment of the method for producing electrical energy according to the invention, illustrated by [Fig. 5], this method comprises a step I of the initial start-up procedure followed by a step II for obtaining information on the current state (active or inactive mode) of the energy conversion modules, and a step III for deciding whether the overall energy system 1 must be switched off or not, depending on whether the system shutdown conditions are met or not (step VIII). If these conditions are met, a step VI of the final shutdown procedure is launched. If this is not the case, a step IV for validating or not an inactive mode request is implemented depending on the results of a step IX for the inactive mode selection conditions.

[0037] For example, step IX is performed in the background in the data processing unit 70 to determine whether at least one of the stopping conditions or another module energy conversion is met. These conditions are for example: - an electricity consumption demand is lower than a predetermined percentage x% compared to a nominal consumption value, - the voltage level of the batteries 6 is lower than a predetermined percentage y% compared to a nominal value of the battery voltage, - a major failure of the main fuel cell has been detected.

[0038] If the output of step IV results in an inactive mode activation, an inactive mode procedure is initiated (step VII) in which, for example, module 2.1 is controlled as operating while modules 2.2 and 2.3 are controlled as inactive. Otherwise, this results in all energy conversion modules being controlled as active at a level based on customer demand.

[0039] With reference to figures 6 and 7, an energy production system according to the invention comprises n energy conversion modules 2.1,2.2,... ,2.n having a nominal power of 50 kW, each module being included in a hotbox 210,220,... 2n0 and each having an electrical power 216,226,... ,2n6 connected to a battery 6.

[0040] Each module 2.1,2.2,... 2.na has an inlet [Ethanol+H20] 213,223,... 2n3, an air outlet 212,222,... 2n2, and an exhaust outlet 211,221,.... ,2nl, and is provided with the electric heater 214,224,.... ,2n4 connected to the battery 6 via the wires 215,225,.... ,2n5.

[0041] The exhaust outlets 211 221,... The 2nl of each energy conversion module are connected by valves 410 to a common heat exchanger 412 which is provided to heat the ambient air 411 and supply heated air to other energy conversion modules. The heat exchanger 412 also has a container exhaust outlet.

[0042] Note that in Figures 6 and 7, only one valve is shown for readability, and that each other energy conversion module can play the role of module 2.1.

[0043] As illustrated in [Fig.6], all the energy conversion modules 2.1,2,... ,2.n are in operating mode, in response to a need for energy to be supplied to the load. The effective power level 217a of each module is illustrated with reference to the maximum power 217,227,2n7.

[0044] In this operating mode configuration, the electric heaters 214 224,... ,2n4 are not activated, since the heat balance is obtained in each energy conversion module. In addition, the levels of heated air provided by the heat exchanger 412 in the energy conversion modules are very low.

[0045] With reference to [Fig.7], which corresponds to a “night” situation where the vehicle chargers do not need energy, only the first energy conversion module 2.1 is in operating mode while the other energy conversion modules 2.2,...,2.n are set to an inactive mode in which they do not do not contribute to generating electrical energy. In idle mode, the heat delivered with the exhaust gases produced by the active module 2.1 is exchanged by means of the heat exchanger 412 to heat the ambient air 411 and inject this heated air 222,... ,2n2 into the idle mode energy conversion modules 2.2,... ,2n.

[0046] The power level 217a provided by the working module 2.1 is medium to low depending on the heat requirements of the other inactive modules 2.2,... 2.n, while the power levels of these inactive modules are very low close to zero. The electric heaters are used to obtain precise adjustment of the required temperatures in the energy conversion modules at idle.

[0047] In this “night” configuration, the levels of heated air 222,...,2n2 injected into the energy conversion modules at idle are high.

[0048] It is important to note that all energy conversion modules in an FC energy production system according to the invention can be assigned the task of producing heat to the inactive modules and are therefore interchangeable.

[0049] This interchangeability can be implemented using the configuration illustrated in [Fig.8]. Each energy conversion module 2.1, 2.2, ... 2.na has its exhaust outlet 211,221,2nl connected by a pipe to a first selector device 415 whose outlet is connected to the heat exchanger 412 by the valve 410, and its air inlet 212,222,... ,2n2 connected by a pipe to a second selector device 416 whose inlet is connected to the outlet of the heat exchanger 412.

[0050] This configuration implementing two selection devices allows a wide range of combinations between the working modules and the inactive modules.

[0051] By way of non-limiting example, an electrical energy production system according to the invention can manage a nominal electrical power of the order of [10; 1000] kW.

[0052] For example, an energy production system according to the invention may comprise six energy conversion modules each having a nominal power of 50 kW.

[0053] An SOFC energy conversion module may for example be designed to heat another SOFC energy convention module with a nominal power ratio in the range [25%; 100%]. For example, the fuel consumption of an energy production system according to the invention may be in the range [0.1; 10] liters / minute. The ethanol tank may for example be in the range [1,000; 50,000] liters.

[0054] Of course, this invention is not limited to the embodiments described above and many other embodiments can be designed without departing from the scope of the invention.

Claims

Claims

1. Method for producing electricity in a stand-alone stationary situation, using a chemical fuel obtained from organic sources, comprising steps for: - supply chemical fuel from a fuel tank (3), - distributing said chemical fuel to a plurality of energy conversion modules each comprising a pre-forming unit and a high-temperature fuel cell unit, in each energy conversion module: - reform (30) chemical fuel to produce synthesis gas, - injecting (31) said synthesis gas into a high-temperature fuel cell unit (2.1,2.2,2.3) to produce electrical energy, - processing (32) said electrical energy produced by said energy conversion modules, in order to generate a nominal electrical power adapted to the voltage and current required for one or more consumers (8), - store (33) in a storage unit (6) part of the electrical energy not used by the consumer (8) - managing said energy conversion modules (2.1,2.2,2.3) so that one or more of said energy conversion modules are set to reach an inactive mode corresponding to a predetermined low energy level, depending on the required efficiency level while other module(s) are kept in operation and / or used to heat said energy conversion module in idle mode.

2. The method of claim 1, wherein the step of managing the energy conversion (34) comprises: - a step to process data on instantaneous power demands, - a step for determining a number of energy conversion modules required to adjust the power demands, - a step for putting those energy conversion modules that are not required into inactive mode, - a step for maintaining said energy conversion modules in idle mode at a predetermined temperature.

3. The method of claim 2, wherein the step of maintaining the idle mode energy conversion modules (23,24) at a predetermined temperature is achieved by transferring heat generated by the active energy conversion modules (25).

4. The method of claim 2, wherein the step of maintaining the energy conversion modules in inactive mode at a predetermined temperature is achieved by generating heat from electrical energy derived from the active energy conversion module.

5. A method according to any preceding claim, further comprising a step for controlling the output power of one or more energy conversion modules from the plurality of energy conversion modules, depending on the instantaneous required electrical energy.

6. A method according to any preceding claim, further comprising a step (42) for processing the data to anticipate power demands based on recorded or external data.

7. A method according to any preceding claim, wherein the chemical fuel comprises ethanol.

8. System (1) for producing electricity in a stand-alone stationary situation using a chemical fuel obtained from organic sources, comprising: - means (3) for storing a chemical fuel (9), - means for distributing said chemical fuel to a plurality of energy conversion modules, each of these modules comprising: - means (4) for reforming the chemical fuel (9) to produce synthesis gas, - a plurality of high-temperature fuel cell units temperature from syngas, to produce electrical energy, - means (5) for processing the electrical energy supplied by said plurality of energy conversion modules, to generate a nominal electrical power adapted to the voltage and current required for a consumer (8), - means for storing a part of the electrical energy which is not used by the consumer (8), - means (7) for managing said plurality of energy conversion modules (2.1,2.2,2.3), called management means (7) comprising: - (i) means for putting certain (23,24) of these energy conversion modules to rest, depending on the required level of efficiency and - (ii) means for adjusting the output power of the active energy conversion modules so as to be active and / or used to heat said energy conversion module(s) in idle mode.

9. System according to the preceding claim, in which at least one of the energy conversion modules comprises a voltage converter.

10. System according to one of the two preceding claims, in which the fuel cell management means (7) comprise processing means programmed to: - process the data on the instantaneous power demands, - determine a certain number of energy conversion modules to match the power demands, - control said idle mode adjustment means and said power adjustment means.

11. System (1) of one of the three preceding claims, wherein at least one of the energy conversion modules comprises at least one SOFC fuel cell unit (21,22,23) and a reformer (4) for converting the chemical fuel into synthesis gas.

12. System (1) according to any one of the four preceding claims- preceding, further comprising communication means (14) for centralizing the operating data necessary for maintaining the operation of the electrical energy generator system (1).

13. A system according to any one of claims 8 to 12, wherein each energy conversion module further comprises an exhaust outlet and an air inlet, further comprising: - first means for selecting a connection of the exhaust outlet of one or more of these energy conversion modules to an inlet of a heat exchanger intended to produce heated air from ambient air, - second means for selecting a connection of the air inlet of one or more of these energy conversion modules to an outlet of said heat exchanger, said first and second selection means being controlled by said management of the energy conversion modules to maintain one or more of these energy conversions in idle mode by transferring thermal energy from one or more working modules.

14. A system according to any one of claims 8 to 13, wherein the fuel comprises ethanol.

Images