Electricity production process using a fuel cell

Abstract

The invention relates to a method for producing electricity (6) employing a fuel cell (1), in which the fuel (3) is produced by means of a thermal dissociation process applied to at least one of the products (7) of the cell (1), using heat (17, 19, 21) produced by at least one heat pump (13) electrically powered (14) by the cell (1). (Fig. 1)

Description

Title of the invention: Method for producing electricity using a fuel cell

[0001] The present invention relates to a method for producing electricity using a non-galvanic fuel cell, and an installation for implementing this method.

[0002] As is known per se, a non-galvanic fuel cell - referred to simply as fuel cell in the following - makes it possible to produce electricity by the oxidation of the fuel supplied to it.

[0003] In the particular case of a hydrogen fuel cell for example, the cell comprises an anode and a cathode separated by an electrolyte; the hydrogen arrives at the anode, the oxygen at the cathode, and the oxidation reaction of the hydrogen by the oxygen generates electric current, water and heat.

[0004] WO2023001779 teaches how, advantageously, one can produce a part of the fuel of a fuel cell by means of a thermal dissociation process using the heat produced by the cell.

[0005] The present invention aims to provide a method of this type making it possible to produce all of the fuel for the fuel cell.

[0006] This object of the invention is achieved with a method for producing electricity using a fuel cell, in which the fuel is produced by means of a thermal dissociation method applied to at least one of the products of the cell, using heat produced by at least one heat pump electrically powered by the cell.

[0007] The cumulative use of the heat produced by the heat pump can generate a sufficient quantity of fuel, and thus make the process autonomous in fuel consumption.

[0008] According to other optional characteristics of the method according to the invention, taken alone or in combination:

[0009] - the heat produced by the fuel cell is further used to put into operation implements the said thermal dissociation process: the use of this additional heat makes it possible to increase the quantity of fuel produced;

[0010] - the heat produced by one or more elements of the device is also used to provide so-called cogeneration heat to users of the process;

[0011] - said dissociation process comprises a succession of chemical reactions in- dothermic;

[0012] - said dissociation process comprises at least one electrolysis step and uses part of the electricity from said battery to power this electrolysis reaction;

[0013] - part of the heat produced by said heat pump and / or by said battery for directly producing electricity while lowering the temperature of the heat to a level required by one of the chemical reactions;

[0014] - hydrogen is used as fuel, and it is applied to the water produced by the fuel cell the following series of iodine / sulfur cycle reactions to dissociate water: 2 H2SO4^ 2 SO2 + 2 H2O + O2 HI I2 + H2 I2 + SO2 + 2 H2O 2 HI +H2SO4

[0015] - the reaction HI —> I2 + H2 is carried out with a proton exchange membrane cell operating between 50°C and 100°C, for example 80°C.

[0016] The present invention also relates to an installation for implementing the aforementioned method, comprising a fuel cell, at least one heat pump, and at least one unit for producing said fuel thermally connected to said heat pump, capable of receiving said product from the cell and dissociating it to produce said fuel.

[0017] Preferably, said fuel production unit is further thermally connected to said fuel cell.

[0018] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate:

[0019] [Fig-1]: an electricity production installation implementing a first embodiment of the method according to the invention;

[0020] [Fig.2]: an electricity production installation implementing a second embodiment of the method according to the invention.

[0021] For clarity, identical or similar elements are identified by identical or similar reference signs throughout the figures.

[0022] In the following, the invention will be illustrated with a cell in which the fuel is hydrogen, but it must be clearly understood that the precepts of the invention can be applied to other types of fuel cells.

[0023] Referring to the first embodiment illustrated in [Fig.l], a hydrogen cell is shown, in which the fuel is hydrogen 3, oxidized by oxygen 5 within an electrolytic system, as mentioned in the preamble to the present description.

[0024] This oxidation reaction allows the circulation of electrons between the anode and the cathode of the electrolytic system, and thus the production of electricity 6.

[0025] This oxidation reaction also has the effect of producing water 7 and release a significant amount of heat 9, typically reaching a temperature of around 830°C.

[0026] As taught by WO2023001779, the heat 9 released by the hydrogen fuel cell can be recovered to produce hydrogen in a series of reactors 11 using a cascade of endothermic chemical reactions, such as the reactions of the iodine / sulfur cycle mentioned above, or reactions of the bromine / sulfur cycle, or reactions of the chlorine / sulfur cycle, or reactions using an alkali metal hydride, or reactions using iron III chloride and iron II chloride, or even vanadium chloride and vanadium tetrachloride.

[0027] In the context of the present invention, at least one heat pump 13 is provided, powered by part of the electricity 14 produced by the hydrogen cell 1.

[0028] This heat pump 13 is used to raise the temperature of a cold source 15 (typically of the order of 20°C but can also be hotter, for example 80°C) such as for example ambient air, water from a river, from the sea or from a geothermal installation, to the different temperatures 17, 19, 21 which are needed to implement the endothermic reactions for producing hydrogen in the reactors.

[0029] The term "heat pump" used in the context of the present invention may designate a plurality of heat pumps and / or a heat pump comprising a plurality of cascade cycles whose compressible gases work at temperatures below their critical temperatures and above their boiling temperatures.

[0030] For example, gaseous mercury, water vapor, and chlorine can be used as heat pump gases.

[0031] For example, when the iodine / sulfur cycle is used to produce hydrogen, heat transfer fluids at respective temperatures of 830°C, 650°C and 120°C can be circulated between the heat pump 13 and the various reactors 11, making it possible to implement the following three endothermic reactions of dissociation of the water 7 supplied by the fuel cell 1:

[0032] 2 H2SO4^ 2 SO2 + 2 H2O + O2 HI I2 + H2 I2 + SO2 + 2 H2O 2 HI +H2SO4

[0033] By recovering the heat 17, 19, 21 generated by the heat pump 13, sufficient energy is provided to generate the quantity of hydrogen 3 necessary for the autonomous operation of the hydrogen cell 1, that is to say for operation not requiring the external supply of fuel.

[0034] By also recovering the heat 9 generated by the hydrogen cell 1, to generate of hydrogen 3, we can reduce the share of electricity taken from the production of the fuel cell for the thermochemical production of hydrogen.

[0035] In certain cases it may be necessary to use the heat 9 released by the cell 1 so that the quantity of hydrogen produced by the thermochemical reactions is sufficient for the operation of the cell.

[0036] In the second embodiment illustrated in [Fig.2], the water dissociation reactions comprise on the one hand endothermic chemical reactions, and on the other hand at least one electrolysis reaction.

[0037] More particularly, a five-step cycle using copper and chlorine may be used, as described in the article "Energy analyses of heat exchangers in the copper-chlorine thermochemical cycle to enhance thermal effectiveness and cycle ef-ficiency", published in the "International Journal of Low-Carbon Technologies, Volume 6, Issue 3, September 2011

[0038] The five steps E1 to E5 of this cycle are as follows: [Tables 1] Steps Energy source Reaction temperature Reactions El heat 400°C 2CuC12(s) + H2O(g) -> CuO-CuCl2(s) + 2HCl(g) E2 heat 500°C CuO-CuCl2(s) -> 2CuCl(l) + l / 2O2(g) E3 electricity 25-80°C 4CuCl(s) + H2O -> 2CuCl2(aq) + 2Cu(s) E4 heat >100°C CuCl2(aq) -> CuCl2(s) E5 heat 430-475°C 2Cu(s) + 2HCl(g) -> 2CuCl(l) + H2(g)

[0039] The reaction of step E3 is electrolytic in nature, and therefore requires an input of electricity.

[0040] Advantageously, this contribution is taken 23 from the electricity produced by the hydrogen cell 1.

[0041] With regard to the endothermic chemical reactions of steps E1, E2, E4 and E5, the necessary reaction temperatures 19, 24, 17, 21 of 400°C, 500°C, 120°C and 430°C respectively, are provided by heat transfer fluids circulating between the heat pump 13 and the hydrogen production reactors 11 3 in which these different reactions take place.

[0042] Advantageously, a heat engine (not shown) can be used to lower the temperature released by the hydrogen fuel cell from 830°C to 500°C in order to implement in particular the aforementioned step E2, this heat engine to provide an additional source of electricity production.

[0043] According to a variant of this second embodiment, the aforementioned iodine / sulfur cycle can be used to produce hydrogen, but the HI —> I2 + H2 step can be carried out using a proton exchange membrane cell operating between 50°C and 100°C, for example at 80°C.

[0044] Such a membrane cell can operate by taking part of the electricity produced by the hydrogen cell 1.

[0045] Such a membrane cell comprises a catalyst at its electrodes, such as platinum or cerium gadolinium oxide (CGO) Ceo.9Gdo.1O1.95 developed in particular by the company Cres Power Ltd.

[0046] As will be understood in light of the above, the method and the electricity production installation according to the invention make it possible to operate a fuel cell autonomously, that is to say without an external supply of fuel.

[0047] This autonomy is obtained by accumulating the quantities of heat produced by the fuel cell itself, and by at least one additional heat pump: these quantities of heat, making it possible to implement endothermic chemical reaction cycles, possibly associated with an electricity supply making it possible to implement electrolytic reactions, provide sufficient energy to produce the fuel for the fuel cell without external input.

[0048] Naturally, the invention is described in the above by way of example. It is understood that those skilled in the art are able to carry out different variant embodiments of the invention without departing from the scope of the invention.

[0049] Thus, in particular, the invention covers a method and an installation in which the heat enabling the reactions to be carried out in the fuel production unit 11 could only come from the heat pump 13 - and therefore not come from the fuel cell 1.

Claims

Claims

1. Method for producing electricity (6) using a fuel cell (1), in which the fuel (3) is produced by means of a thermal dissociation method applied to at least one of the products (7) of the cell (1), using heat (17, 19, 21; 24) produced by at least one heat pump (13) electrically powered (14) by the cell (1).

2. A method according to claim 1, wherein the heat (9) produced by the fuel cell (1) is further used to carry out said thermal dissociation method.

3. Method according to one of claims 1 or 2, in which said dissociation method comprises a succession of endothermic chemical reactions.

4. A method according to any one of the preceding claims, wherein said dissociation method comprises at least one electrolysis step, and a portion (23) of the electricity from said cell (1) is used to power this electrolysis reaction.

5. Method according to any one of the preceding claims, in which part of the heat produced by said heat pump and / or by said battery is recovered to directly produce electricity.

6. A method according to any one of the preceding claims, wherein hydrogen (3) is used as fuel, and the following series of iodine / sulfur cycle reactions are applied to the water (7) produced by the fuel cell (1) to dissociate the water: 2 H2SO4^ 2 SO2 + 2 H2O + O2 HI I2 + H2 I2 + SO2 + 2 H2O 2 HI +H2SO4

7. A method according to claim 6, wherein the reaction HI —> I2 + H2 is carried out with a proton exchange membrane cell operating between 50°C and 100°C, for example at 80°C.

8. Installation for implementing a method according to any one of the preceding claims, comprising a fuel cell (1), at least one heat pump (13), and at least one unit (11) for producing said fuel (3) thermally connected to said heat pump (13), capable of receiving said product (7) from the cell (1) and dissociating it to produce said fuel (3).

9. Installation according to claim 8 for implementing a method according to claim 2, wherein said fuel (3) production unit (11) is further thermally connected to said fuel cell (1).

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