HYDROGEN PRODUCTION SYSTEM AND METHOD FOR PRODUCING HYDROGEN IN A HYDROGEN PRODUCTION SYSTEM

Abstract

Provided is a hydrogen production system including a thermal energy storage having a housing, a storage chamber with heat storage material inside the storage chamber and a fluid inlet port fluidically connected to the storage chamber and a fluid outlet port fluidically connected to the storage chamber, and at least one high temperature electrolyser for producing hydrogen, whereby the at least one high temperature electrolyser is thermally connected to the heat storage material of the storage chamber of the thermal energy storage. Several modes of operation are defined. A method for producing hydrogen in the hydrogen production system is also provided.

Claims

1. A hydrogen production system comprising a thermal energy storage having a housing, a storage chamber with heat storage material inside the storage chamber and a fluid inlet port fluidically connected to the storage chamber and a fluid outlet port fluidically connected to the storage chamber, and at least one high temperature electrolyser for producing hydrogen, wherein the at least one high temperature electrolyser is thermally connected to the heat storage material of the storage chamber of the thermal energy storage, wherein the fluid inlet port and/or the fluid outlet port of the thermal energy storage are thermally connected to an electric heater, and wherein a control unit is coupled to the hydrogen production system, wherein the control unit is configured to operate the hydrogen production system in a first mode, in which electrical energy is supplied to the electric heater, wherein it is converted to thermal energy, wherein the thermal energy is transferred to the high temperature electrolyser, in which hydrogen is produced, a second mode, in which electrical energy is supplied to the electric heater, wherein it is converted to thermal energy, wherein the thermal energy is transferred to the thermal energy storage, in which it is stored, a third mode, in which no electrical energy is supplied to the electric heater but thermal energy from the thermal energy storage is transferred to the high temperature electrolyser, in which hydrogen is produced, and a fourth mode, in which neither electrical energy is supplied to the electric heater nor thermal energy is transferred to the thermal energy storage.

2. The hydrogen production system according to claim 1, wherein, the thermal energy storage is a sensible heat storage, a latent heat storage or a thermo-chemical heat storage.

3. The hydrogen production system according to claim 1, wherein the heat storage material comprises sand and/or stones.

4. The hydrogen production system according to claim 1, wherein the heat storage material forms a tunnel system of heat exchange channels within the storage chamber.

5. The hydrogen production system according to claim 1, wherein the electric heater is electrically connected to a renewable energy source.

6. The hydrogen production system according to claim 1, wherein the control unit is further configured to operate the hydrogen production system so that: (a) in the first and/or the second mode, charging mode working fluid is heated in a charging mode, so that a heated charging mode working fluid is obtained, and the heated charging mode working fluid is transported to the fluid inlet port of the thermal energy storage, wherein thermal energy from the heated charging mode working fluid is transferred to the heat storage material of the storage chamber, so that stored thermal energy is stored in the heat storage material, (b) in the third and/or fourth mode, discharging mode working fluid of a discharging mode is transported to the fluid inlet port of the thermal energy storage, wherein the stored thermal energy from the heat storage material of the storage chamber is transferred to the discharging mode working fluid, so that a heated discharging mode working fluid is obtained, which exits the fluid outlet port of the thermal energy storage and the heat from the heated discharging mode working fluid is thermally transferred to the at least one high temperature electrolyser, wherein hydrogen is produced in the at least one high temperature electrolyser by using the heat from the heated discharging mode working fluid.

7. The hydrogen production system according to claim 1, wherein, the at least one high temperature electrolyser is thermally connected to the heat storage material of the storage chamber of the thermal energy storage by means of a heat exchanger.

8. The hydrogen production system according to claim 1, wherein, at least two high temperature electrolysers of the at least one high temperature electrolyser are fluidically connected in series to each other.

9. The hydrogen production system according to claim 1, wherein, a turbine is connected to the at least one high temperature electrolyser, wherein the turbine is connected to a generator.

10. The hydrogen production system according to claim 9, wherein the turbine and the at least one high temperature electrolyser fluidically connected in parallel to each other.

11. The hydrogen production system according to claim 1, wherein, the at least one high temperature electrolyser is connected via at least one hydrogen line to a hydrogen storage, a polymer electrolyte membrane fuel cell, a solid oxide fuel cell, a combustion chamber, an ammonia synthesis device, a methanation device and/or a hydrogen infrastructure.

12. The hydrogen production system according to claim 11, wherein, the combustion chamber is connected to a turbine, wherein the turbine is connected to a generator and the turbine is thermally connected to the fluid inlet port.

13. A method for producing hydrogen in the hydrogen production system according to claim 1, wherein the method comprises the steps of: (a) heating a charging mode working fluid in a charging mode, so that a heated charging mode working fluid is obtained, (b) transporting the heated charging mode working fluid to the fluid inlet port of the thermal energy storage, wherein thermal energy from the heated charging mode working fluid is transferred to the heat storage material of the storage chamber so that stored thermal energy is stored in the heat storage material, (c) transporting discharging mode working fluid of a discharging mode to the fluid inlet port of the thermal energy storage, wherein the stored thermal energy from the heat storage material of the storage chamber is transferred to the discharging mode working fluid, so that a heated discharging mode working fluid is obtained, which exits the fluid outlet port of the thermal energy storage and the heat from the heated discharging mode working fluid is thermally transferred to the at least one high temperature electrolyser, (d) producing hydrogen in the at least one high temperature electrolyser by using the heat from the heated discharging mode working fluid.

14. The method for producing hydrogen in the hydrogen production system according to claim 13, wherein, the heat from the heated discharging mode working fluid is transferred to the at least one high temperature electrolyser when a capacity of thermal energy of the storage chamber is at a defined threshold or production of hydrogen is demanded.

15. The method for producing hydrogen in the hydrogen production system according to claim 13, wherein, the at least one thermal energy storage is connected to a renewable energy source and heat from the heated discharging mode working fluid is transferred to the at least one high temperature electrolyser so that a constant hydrogen production level of the at least one high temperature electrolyser is maintained.

Description

BRIEF DESCRIPTION

[0043] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0044] FIG. 1 shows a sectional cut through a thermal energy storage as can be used in a hydrogen production system according to embodiments;

[0045] FIG. 2 shows a circuit diagram of a hydrogen production system according to a first embodiment; and

[0046] FIG. 3 shows a circuit diagram of a hydrogen production system according to a second embodiment.

DETAILED DESCRIPTION

[0047] Same objects in FIGS. 1 to 3 are denominated with the same reference number. If there is more than one object of the same kind in one of the figures, the objects are numbered in ascending order with the ascending number of the object being separated from its reference number by a dot. The specific dimensions of features and parts in the figures are exemplary and may be enlarged for ease of reference only.

[0048] FIG. 1 shows a sectional cut through a thermal energy storage 10 as can be used in a hydrogen production system 1 (see FIGS. 2 and 3) according to embodiments of the invention. The thermal energy storage 10 comprises a housing 11, in which a storage chamber 12 filled with heat storage material 13 is located. Working fluid may enter a fluid inlet port 14 of the housing 11 in the direction indicated by an arrow. The fluid inlet port 14 is connected to a diffusor section 15. The fluid inlet port 14 and the diffusor section 15 are formed by the housing 11. Further, the working fluid may exit the housing 11 in the direction indicated by a further arrow through a fluid outlet port 16. The fluid outlet port 16 is connected to a nozzle section 17. The fluid outlet port 16 and the nozzle section 17 are formed by the housing 11.

[0049] FIG. 2 shows a circuit diagram of a hydrogen production system 1 according to a first embodiment of the invention.

[0050] The thermal energy storage 10 of the hydrogen production system 1 is thermally connected by means of a heat exchanger 50.1 to a steam cycle B.1, B.2 of a high temperature electrolyser 20.1. In particular, an air cycle A.1 passing the thermal energy storage 10 is connected to the heat exchanger 50.1. In this particular case, the air cycle A.1 is at atmosphere pressure of 1 bar. The air cycle A.1 may be alternatively any other fluid cycle having a working fluid. Cold air flowing in the air cycle A.1 by means of a fan 40.1 flows to an electric heater 30.1 thermally connected to the thermal energy storage 10. The fan 40.1 may alternatively or additionally be a compressor. In particular, a flow channel of the air cycle A.1 is connected to the electric heater 30.1. The electric heater 30.1 may be supplied with renewable electrical energy from a wind turbine (not shown), for example, and heat up the air in the air cycle A.1. From the electric heater 30.1, the heated working fluid is released at a temperature in the range of 500° C. to 1500° C., in particular 600° C. to 1000° C. and more particularly 700° C. to 900° C. into the fluid inlet port 14. Thereby, the heat storage material 13 of the thermal energy storage 10 is charged with thermal energy in a charging mode. Cold air is released from the fluid outlet port 16 of the thermal energy storage 10 into the air cycle A.1 and the air streams back to the fan 40.1. From there, the charging mode is continued with heating the thermal energy storage 10 until a certain threshold of thermal capacity is reached or energy supply from renewable sources stops, for example.

[0051] Then, in a discharge mode, the electric heater 30.1 is turned off and cold discharge mode working fluid, in this case cold air, streams through the thermal energy storage 10, in particular the heated heat storage material 13. Stored heat from the heat storage material 13 is transferred to the cold air, so that the air is heated. As a heated discharge mode working fluid, the air leaves the fluid outlet port 16. Optionally, the fluid outlet port 16 is thermally connected to a further electric heater 30.2. By means of the further electric heater 30.2, the air can be further heated up to even achieve higher temperatures of the air, e.g. in the range of 600° C. to 1500° C., in particular 700° C. to 900° C., before exchanging its heat with the steam cycle B.1, B.2, in particular water vapor steam cycle, of the high temperature electrolyser 20.1. The further electric heater 30.2 may be supplied with electrical energy from a renewable source as well.

[0052] At the heat exchanger 50.1, the heat from the heated air is transferred to the steam cycle B.1, B.2 by means of the heat exchanger 50.1. Steam, in particular water vapor, in a steam line B.1 of the steam cycle B.1 is streamed by a fan or compressor 40.2 within the steam cycle B.1, B.2 to the heat exchanger 50.1. The steam is heated by means of the heat of the heated air that is transferred through the heat exchanger 50.1 and streamed through steam line B.2 to the high temperature electrolyser 20.1 in order to produce hydrogen D.1. Therefore, also electricity C.1 is supplied to the high temperature electrolyser 20.1, which may be from a renewable source. The high temperature electrolyser 20.1 may be a solid oxide electrolyser cell. The temperature of the air after passing the heat exchanger 50.1 may be in the range of 300° C. to 1500° C., in particular 500° C. to 900° C., for example.

[0053] Further, there is another steam cycle B.3, B.4 to which the air cycle A.1 is connected by means of a further heat exchanger 50.2. This steam cycle B.3, B.4 may be provided instead of the steam cycle B.1, B.2 and heat exchanger 50.1 or additionally. In the steam cycle B.3, B.4 the steam line is indicated by B.3 and the steam line by B.4, whereby a pump 60 is arranged within the steam line B.4. In the steam line B.4, water is condensed and transported by means of the pump 60. A further electrical heater 30.3 may be arranged in the steam line B.3 as shown. In the steam cycle B.3, B.4, two further high temperature electrolysers 20.2, 20.3 are connected to each other in a series connection, whereby the overall efficiency is increased. Parallel to each of the high temperature electrolysers 20.2, 20.3, a turbine 70.1, 70.2 connected to a generator 71.1, 71.2 is connected. The circuitry comprises multiple valves for switching operation between the high temperature electrolysers 20.2, 20.3 and the turbines 70.1, 70.2. By means of the turbines 70.1, 70.2 and generators 71.1, 71.2, a residual heat of the steam coming from the high temperature electrolysers 20.2, 20.3 may be facilitated to even further increase the overall efficiency of the hydrogen production system by producing electricity C.4, C.5 by means of the turbines 70.1, 70.2 and generators 71.1, 71.2. Also, it can be switched between a production of hydrogen D.2, D.3 by means of the high temperature electrolysers 20.2, 20.3 and a production of electricity C.4, C.5 if preferred. As shown, a further electrical heater 30.4 is arranged in a line of the turbine 70.1 for reheating. Also, as shown, a further heat exchanger 50.3 or condenser for example with cooling tower, is arranged in the steam line B.4.

[0054] A bypass air line A.2 is connected to the air cycle A.1 bypassing the thermal energy storage 10. The bypass air line A.2 comprises a valve. When the valve is switched on, the air in the air cycle A.1 can bypass the thermal energy storage 10. When the valve is switched off, the air in the air cycle A.1 flows through the thermal energy storage 10. Thereby, the thermal energy from the heated air can be provided at either of the high temperature electrolysers 20.1, 20.2, 20.3 without passing the thermal energy storage 10. This operation may be in particular provided and useful when the thermal energy storage 10 is out of order due to service or modification work or in the first mode of operation of the hydrogen production system 1, for example.

[0055] FIG. 3 shows a circuit diagram of a hydrogen production system 1 according to a second embodiment of the invention. Here, the air cycle A.1 of the thermal energy storage 10 is connected to three heat exchangers 50.1, 50.2, 50.3 arranged in a flow direction of the air after the thermal energy storage 10 and the high temperature electrolyser 20. These heat exchangers 50.1, 50.2, 50.3 may be connected to another steam cycle, a process steam cycle and a district heating cycle, for example.

[0056] The produced hydrogen flows through a hydrogen line D to a hydrogen storage 80. Therefrom, it may be distributed to a polymer electrolyte membrane fuel cell 81 to produce electricity C.2, to a solid oxide fuel cell 82 to produce electricity C.3, to an ammonia synthesis device 83 to produce ammonia F and nitrogen E and a methanation device to produce methane G. A methanation line G of the methanation device 84 is also connected to a combustion chamber 72.2, which is connected to a turbine 70.2 and a generator 71.2 in order to produce electricity C.5 by means of the produced methane G. Also, the hydrogen line D coming from the hydrogen storage 80 is connected to a combustion chamber 72.1, which is connected to a turbine 70.1 and a generator 71.1 to produce electricity C.4 by means of the produced hydrogen D. In this case, both turbines 70.1, 70.2 are connected by steam line B.1 to a further heat exchanger 50.4 to form a combined cycle power plant, but alternatively only one of the turbines 70.1, 70.2 may be provided and/or connected thereto. The heat exchanger 50.4 is connected by means of a further steam cycle B.2 to a heat exchanger 50.5 arranged in the air cycle A.1 in the direction of air flow before the thermal energy storage 10. Thereby, residual heat from the heat exchanger 50.4 of the combined cycle power plant may be used to preheat the air in the air cycle A.1 before it enters the thermal energy storage 10 to increase the overall efficiency even further. Thus, in an embodiment it is preferred that energy from the hydrogen is provided as residual heat to preheat the working fluid, in this case air, entering the thermal energy storage 10.

[0057] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0058] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.