System for the production of hydrogen or synthesis gas

Abstract

System (1) for the production of hydrogen or synthesis gas, comprising a high-temperature electrolyzer system (3), a compression heat pump system (5) comprising at least one compression heat pump (13), wherein the compression heat pump system (5) generates water vapor (B) for the high-temperature electrolyzer system (3), and a photovoltaic system (7) comprising a plurality of photovoltaic cells (9), comprising a cooling system for the photovoltaic cells (9), wherein during irradiation of the photovoltaic cells (9) with solar radiation the cooling system cools the photovoltaic cells (9) by means of a cooling medium, wherein the cooling medium heated by the cooling of the photovoltaic cells (9) provides thermal energy for the at least one compression heat pump (13), and the photovoltaic system (7) provides electrical energy for the compression heat pump system (5) and / or the high-temperature electrolyzer system (3).

Description

[0001] The present invention relates to a system for producing hydrogen or synthesis gas by high-temperature electrolysis.

[0002] Currently, there is a high industrial demand for hydrogen as a basis for alternative fuels and various chemical processes. Hydrogen production is comparatively energy-intensive, so various approaches are being pursued to make hydrogen production as efficient and environmentally friendly as possible.

[0003] There is also an industrial need for so-called synthesis gas, which is a gas mixture containing carbon monoxide and hydrogen.

[0004] Hydrogen can be produced, for example, using an electrically powered water splitting electrolyzer. For environmentally friendly hydrogen production, the use of renewable electricity is advisable. High-temperature electrolyzers achieve the highest electrical efficiencies, but these require a supply of superheated steam. High-temperature electrolyzers can also be used to produce synthesis gas from steam and carbon dioxide.

[0005] However, for the environmentally friendly operation of high-temperature electrolyzers, it is necessary not only to provide electrical energy from renewable energy sources, but there is also a high demand for heat.

[0006] The above description is part of the applicant's general knowledge, but does not necessarily refer to a specific published prior art.

[0007] The object of the present invention is to provide a system for the production of hydrogen or synthesis gas that is as environmentally friendly as possible and requires as little equipment as possible.

[0008] The system according to the invention is defined by the features of claim 1.

[0009] The system according to the invention for producing hydrogen or synthesis gas comprises a high-temperature electrolyzer system, a compression heat pump system with at least one compression heat pump, and a photovoltaic system with a plurality of photovoltaic cells. The compression heat pump system generates steam for the high-temperature electrolyzer system. The photovoltaic system includes a cooling system for the photovoltaic cells, wherein, during irradiation of the photovoltaic cells with solar radiation, the cooling system cools the photovoltaic cells by means of a cooling medium. The cooling medium, heated by the cooling of the photovoltaic cells, provides thermal energy for the at least one compression heat pump, and the photovoltaic system provides electrical energy for the compression heat pump system and / or the high-temperature electrolyzer system.

[0010] The system according to the invention thus provides that, in addition to electrical energy, so-called low-temperature heat is also supplied by cooling the photovoltaic cells. This low-temperature heat can be raised to a higher temperature level via the at least one compression heat pump of the compression heat pump system, from which steam can be generated for the high-temperature electrolyzer system. The electrical energy generated by the photovoltaic system can be used to operate the at least one compression heat pump of the compression heat pump system and / or the high-temperature electrolyzer system. By using the photovoltaic system, electrical energy is thus produced in an environmentally friendly manner, and thermal energy is also provided, which can be further utilized via the compression heat pump system.Since both electrical and thermal energy are provided by the same system, the technical complexity of the equipment is kept comparatively low. Preferably, the photovoltaic system includes a solar radiation concentration system, which concentrates solar radiation onto the photovoltaic cells of the photovoltaic system. The system according to the invention can thus provide a concentrating photovoltaic system that, on the one hand, has a high efficiency in generating electricity and, on the other hand, provides a relatively large amount of waste heat that can advantageously be used via the compression heat pump system. In principle, it is also possible to provide additional thermal energy via further solar thermal energy sources, which is then used by the compression heat pump system.

[0011] Within the scope of the invention, compression heat pumps are understood to be compression heat pumps with a closed or open circuit, which can be operated with various working fluids. Thus, within the scope of the invention, the compression heat pump system can comprise a classic compression heat pump with a closed circuit or a mechanical vapor compressor with an open circuit. In the variant with a mechanical vapor compressor as the compression heat pump, waste heat in the form of water vapor must be supplied to it. For example, it can be provided that the cooling medium of the cooling system for the photovoltaic cells is water, which is supplied to the mechanical vapor compressor in vapor form for compression.

[0012] Preferably, the high-temperature electrolyzer system comprises a solid oxide electrolyzer. For example, the solid oxide electrolyzer can be composed of a plurality of solid oxide electrolyzer cells, which may, for instance, have a ceramic electrolyte made of zirconium dioxide stabilized with yttrium oxide. The high-temperature electrolyzer system can also include electrolyzer cells with proton-conducting ceramic electrolytes based on perovskite oxides.

[0013] Such an electrolyzer system has proven to be particularly advantageous and efficient.

[0014] In the system according to the invention, some or all components can in principle also be supplied with electrical energy by other energy sources, for example by the public electricity grid, separate photovoltaic systems or other power plants.

[0015] Preferably, the solar radiation concentrator system includes a line-focusing concentrator consisting of multiple mirror facets. This can concentrate the solar radiation, for example, up to a hundredfold and reflect it onto the photovoltaic cells. Of course, it is also possible for the solar radiation concentrator system to include other concentrators, such as point-focusing dish concentrators, tower concentrators, or lens-based concentrators.

[0016] The photovoltaic cells can be multilayer solar cells, preferably with layers of gallium indium phosphide, (indium) gallium arsenide, and germanium. Such multilayer solar cells exhibit a particularly high efficiency because they can utilize different wavelength ranges of solar radiation.

[0017] The compression heat pump system can include an evaporator, with the at least one compression heat pump providing thermal energy to the evaporator. The evaporator can, for example, be an evaporator heat exchanger, in which a heat transfer medium from the compression heat pump system is circulated within the evaporator heat exchanger.

[0018] In the system according to the invention, the cooling medium of the photovoltaic system's cooling system can be used as the working medium for the at least one compression heat pump of the compression heat pump system. However, it is also possible, in principle, for the heated cooling medium to heat the working medium of the compression heat pump via a further heat exchanger.

[0019] In the event that the cooling medium of the photovoltaic system's cooling system and the working medium of the compression heat pump are water or water vapor, a mechanical vapor compressor (MVR) can be used as a compression heat pump.

[0020] This reduces the complexity of the equipment, as the evaporator can be omitted. In this embodiment, the water or steam flows from the cooling system of the photovoltaic system via the heat pump into the further sections of the system according to the invention for the production of hydrogen or synthesis gas, for example directly into the high-temperature electrolyzer system or directly into a steam superheater described below.

[0021] Preferably, the system according to the invention includes a steam superheater for superheating the steam generated or processed by the compression heat pump system. By superheating the steam, steam at a particularly high temperature level can be supplied to the high-temperature electrolyzer system.

[0022] The steam superheater can include an electric superheater, with the photovoltaic system preferably providing electrical energy for the steam superheater.

[0023] Additionally, the steam, or in the case of synthesis gas production, the steam-carbon dioxide mixture, can be mixed with hydrogen in the steam superheater. This prevents oxidation of the catalyst at the cathode in the solid oxide electrolyzer. The addition of hydrogen in the steam superheater also superheats the hydrogen, ensuring that a gas mixture with a uniform temperature enters the solid oxide electrolyzer.

[0024] Additionally or alternatively, the steam superheater can also be provided with a heat exchanger, wherein a product stream from the high-temperature electrolyzer system can be directed into the heat exchanger to provide thermal energy. In other words, the product generated in the high-temperature electrolyzer system, for example, the synthesis gas or the hydrogen or a hydrogen-steam mixture, can be passed through the heat exchanger so that heat recovery can occur, as the hot product provides heat for steam superheating. In an embodiment in which the steam superheater has an electric superheater and a heat exchanger, the heat exchanger can be located upstream of the electric superheater.

[0025] Preferably, the system according to the invention includes a condenser in which the vapor contained in the product stream, which was not converted in the high-temperature electrolyzer system, is condensed. The enthalpy of condensation can thus be partially utilized, for example in the compression heat pump system or for preheating gases used in the system. The condensed water can, for example, be fed to the compression heat pump system for evaporation.

[0026] The system according to the invention can also include a gas preheater for preheating a gas, for example air, for the high-temperature electrolyzer system.

[0027] For efficient operation, high-temperature electrolyzer systems often require a gas flow consisting of a hot gas used as a purge gas, such as hot air, or an inert gas, such as nitrogen, to prevent oxidation on the anode side. A gas preheater can provide this hot gas flow. The gas preheater can, for example, be electric, with a photovoltaic system supplying the electrical energy for the gas preheater.

[0028] The gas preheater can be operated additionally or alternatively, at least partially, with thermal energy provided by the compression heat pump system.

[0029] Additionally or alternatively, the gas preheater can also include a gas heat exchanger, whereby an exhaust gas stream from the high-temperature electrolyzer system can be directed into the gas heat exchanger to provide thermal energy. During operation of the high-temperature electrolyzer system, an oxygen-air mixture or oxygen-gas mixture is produced, which has a comparatively high temperature. Therefore, heat recovery can occur via the gas heat exchanger by preheating the gas or air supplied to the high-temperature electrolyzer system with the exhaust gas stream.

[0030] In the system according to the invention, it can therefore be provided that the photovoltaic system provides, on the one hand, electrical energy for the operation of the compression heat pump system, the high-temperature electrolyzer system, the steam superheater and the gas preheater, and on the other hand, thermal energy for the compression heat pump system.

[0031] In principle, the operation of the system according to the invention depends on solar radiation. Therefore, the electrically operated systems can also be supplied with electricity from the power grid, thus enabling continuous operation.

[0032] The compression heat pump can, of course, also be supplied with thermal energy by low-temperature heat obtained from other sources.

[0033] When the system is not operating due to a lack of solar radiation, for example at night, it is often necessary to maintain the high-temperature electrolyzer system at a specific temperature level. This can be achieved using inert gases at a suitable temperature. These inert gases can be heated, for example, by an additional heat storage unit or an additional heat source. Heating the inert gases using electricity from the power grid is also possible. Alternatively, the high-temperature electrolyzer system can be directly maintained at a specific temperature level using an electric heating system.

[0034] The system according to the invention thus enables very environmentally friendly operation, while keeping the equipment requirements to a minimum. Hydrogen or synthesis gas can therefore be produced relatively cheaply and in an environmentally friendly manner using the system according to the invention.

[0035] Ideally, all the electrical energy required for the system, as well as the thermal energy required for the operation of the compression heat pump system, is obtained through solar radiation.

[0036] The invention will be explained in more detail below with reference to the following figure.

[0037] The single figure schematically shows a principle sketch of the system 1 according to the invention for the production of hydrogen or synthesis gas. The system 1 according to the invention comprises a high-temperature electrolyzer system 3, a compression heat pump system 5, and a photovoltaic system 7.

[0038] The photovoltaic system 7 comprises a multitude of photovoltaic cells 9 onto which solar radiation is concentrated by means of a solar radiation concentration system 11, as indicated by the arrow. The photovoltaic cells 9 are cooled by a cooling system (not shown), for example, on the back side, by circulating a cooling medium along the back side of the photovoltaic cells 9.

[0039] The cooling medium heated by the photovoltaic cells 9 is fed to the compression heat pump system 5.

[0040] The compression heat pump system 5 comprises at least one compression heat pump 13, which uses the heated cooling medium as the working medium. In the compression heat pump 13, the thermal energy provided by the heated cooling medium (indicated by the arrow with "Q") is raised to a higher temperature level, and this thermal energy is then supplied to an evaporator 15 (also indicated by the arrow with "Q").

[0041] The compression heat pump 13 is also operated with electrical energy from the photovoltaic system 7 (shown by the arrow with “W”).

[0042] Water A is added to the evaporator 15 and evaporated using the energy provided by the compression heat pump 13. The resulting steam B is then fed to a steam superheater 17 of the system 1 according to the invention. The steam superheater 17 can consist of several sections. For example, the steam superheater 17 can include an electric superheater 19, which is operated by electrical energy from the photovoltaic system 7. Furthermore, the steam B can also be mixed with hydrogen C in the steam superheater 17. The superheated hydrogen-steam mixture E is then fed to the high-temperature electrolyzer system 3, and hydrogen is produced.

[0043] The steam superheater 17 can further comprise a heat exchanger 21, wherein thermal energy for the heat exchanger 21 is supplied by a product stream D of the high-temperature electrolyzer system 3 in order to recover the residual heat contained therein. The product stream D can, for example, be a hydrogen-water vapor mixture.

[0044] Furthermore, system 1 according to the invention comprises a condenser 22 in which the vapor contained in the product stream J, which was not converted in the high-temperature electrolyzer system 3, is condensed. The enthalpy of condensation is partially utilized in the compression heat pump 13. The condensed water A' is fed to the evaporator 15.

[0045] A hot air stream H may be necessary for the operation of the high-temperature electrolyzer system 3. Therefore, the system 1 according to the invention additionally includes a gas preheater 23, which heats an air stream F. The gas preheater 23 can include an electric gas preheater 25, wherein the photovoltaic system 7 provides electrical energy for the electric gas preheater 25. The gas preheater 23 can further include a gas heat exchanger 27, which further heats the air (hot air stream H), wherein the gas heat exchanger 27 is operated by an exhaust gas stream G of the high-temperature electrolyzer system 3.

[0046] The exhaust gas stream G of the high-temperature electrolyzer system 3 can, for example, be an oxygen-air mixture.

[0047] The product J, cooled by the heat exchanger 21 and in the illustrated embodiment a hydrogen-water vapor mixture, is fed to the condenser 22 as described above. Hydrogen is obtained as the final product K.

[0048] To ensure that the high-temperature electrolyzer system 3 remains at a desired temperature during periods of low solar radiation, for example at night, an additional heat source 29 can also be provided, which heats an inert gas.

[0049] In the schematic representation of the principle according to the invention, the electrical supply is shown by corresponding arrows with a “W”, whereas the provision of heat energy is shown by an arrow with “Q”.

[0050] The system 1 according to the invention for the production of hydrogen or synthesis gas offers a particularly environmentally friendly method of producing hydrogen or synthesis gas, while simultaneously requiring comparatively little equipment. This is achieved by using a concentrating photovoltaic system 7, which on the one hand provides electrical energy and on the other hand the thermal energy required for the operation of the compression heat pump system 5. Reference symbol list 1 system 3 High-temperature electrolyzer system 5 Compression heat pump system 7 Photovoltaic system 9 photovoltaic cells 11 Solar radiation concentrator system 13 Compression heat pump 15 evaporators 17 steam superheaters 19 electric superheaters 21 heat exchangers 22 Capacitor 23 gas preheaters 25 electric gas preheaters 27 gas heat exchangers 29 additional heat sources A water A' condensed water B Water vapor C Hydrogen The product E superheated steam F Air Exhaust gas H hot air J cooled product K final product

Claims

[1] System (1) for the production of hydrogen or synthesis gas, with a high-temperature electrolyzer system (3), with a compression heat pump system (5) with at least one compression heat pump (13), wherein the compression heat pump system (5) generates water vapor (B) for the high temperature electrolyzer system (3) and with a photovoltaic system (7) with a plurality of photovoltaic cells (9), with a cooling system for the photovoltaic cells (9), wherein during irradiation of the photovoltaic cells (9) with solar radiation the cooling system cools the photovoltaic cells (9) by means of a cooling medium, wherein the cooling medium heated by the cooling of the photovoltaic cells (9) provides thermal energy for the at least one compression heat pump (13) and the photovoltaic system (7) provides electrical energy for the compression heat pump system (5) and / or the high temperature electrolyzer system (3). [2] System according to claim 1, characterized by , that the high-temperature electrolyzer system (3) has a solid oxide electrolyzer. [3] System according to claim 1 or 2, characterized by , that the photovoltaic system (7) has a solar radiation concentrator system (11) wherein the solar radiation concentration system (11) concentrates solar radiation onto the photovoltaic cells (9) of the photovoltaic system (7). [4] System according to claim 3, characterized by , that the solar radiation concentrator system (11) has a line-focusing concentrator consisting of several mirror facets. [5] System according to any one of claims 1 to 4, characterized by , that the photovoltaic cells (9) are multilayer solar cells, preferably with layers of gallium indium phosphide, (indium) gallium arsenide and germanium. [6] System according to any one of claims 1 to 5, characterized by, that the compression heat pump system (5) has an evaporator (15), wherein the at least one compression heat pump (13) provides thermal energy for the evaporator (15). [7] System according to any one of claims 1 to 5, characterized by , that the cooling medium of the cooling system of the photovoltaic system (7) is water or water vapor and the at least one compression heat pump (13) is designed as a mechanical vapor compressor, wherein the cooling medium of the cooling system of the photovoltaic system (7) can be supplied to the mechanical vapor compressor as a working medium in vapor form. [8] System according to claim 6 or 7, characterized by , a steam superheater (17) for superheating water vapor (B) generated or processed by the compression heat pump system (5). [9] System according to claim 7 or 8, characterized by, that the steam superheater (17) has an electric superheater (19), wherein the photovoltaic system (7) provides electrical energy for the steam superheater (17). [10] System according to claim 8 or 9, characterized by , that in the steam superheater (17) the water vapor (B) can be reacted with hydrogen (C). [11] System according to any one of claims 8 to 10, characterized by , that the steam superheater (17) has a heat exchanger (21) wherein a product stream (D) of the high temperature electrolyzer system (3) is conductable into the heat exchanger (21) to provide thermal energy. [12] System according to any one of claims 1 to 11, characterized bya condenser (22) in which the steam contained in a product stream (D) of the high-temperature electrolyzer system (3) or in a product (J) cooled by the heat exchanger (21) can be condensed, wherein preferably water (A') condensed in the condenser (22) can be supplied to the compression heat pump system for evaporation. [13] System according to any one of claims 1 to 12, characterized by a gas preheater (23) for preheating a gas for the high-temperature electrolyzer system (3). [14] System according to claim 13, characterized by , that the gas preheater (23) has an electric gas preheater (25), wherein the photovoltaic system (7) provides electrical energy for the gas preheater (23). [15] System according to claim 13 or 14, characterized by , that the gas preheater (23) can be operated at least partially with thermal energy from the compression heat pump system (5). [16] System according to any one of claims 13 to 15, characterized by , that the gas preheater (23) has a gas heat exchanger (27) wherein an exhaust gas stream (G) of the high temperature electrolyzer system (3) is conductable into the gas heat exchanger (27) to provide thermal energy.

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