Solid oxide electrolysis system for seawater evaporation recycling based on waste heat driving

Abstract

The invention discloses a waste heat driven solid oxide electrolysis system for seawater evaporation recycling, and relates to the technical field of water electrolysis and seawater desalination, the waste heat driven solid oxide electrolysis system comprises a seawater evaporation device, a steam compressor, a solid oxide electrolytic tank and a steam turbine, the steam compressor is connected with the solid oxide electrolytic tank, a tail gas outlet of the solid oxide electrolytic tank is connected with a tail gas inlet of the steam turbine, and a tail gas outlet of the steam turbine is connected with the seawater evaporation device; and the power output end of the steam turbine is electrically connected with the power input ends of the steam compressor and the solid oxide electrolytic tank respectively. Seawater evaporation is achieved through waste heat brought by tail gas generated in the water electrolysis process, subsequently generated water vapor serves as main input in the water electrolysis reaction, the requirement for fresh water is finally avoided, and meanwhile output electricity is generated through the steam turbine to provide power for a user or the whole device.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis and seawater desalination, and specifically to a solid oxide electrolysis system for the recovery and utilization of seawater evaporation driven by waste heat. Background Art

[0002] Facing the challenges of global energy demand and climate change, the over-reliance on traditional fossil fuels has led to serious environmental problems, including greenhouse gas emissions, air pollution, and irreversible ecological damage. The exacerbation of these problems has prompted the global community to seek cleaner and more sustainable energy solutions. Against this background, hydrogen energy, as an ideal energy carrier, has become an important research direction for global energy transformation and climate change response. The research and development of hydrogen energy not only helps to reduce the dependence on fossil energy, promote the wider application of renewable energy, but also provides clean energy alternatives for multiple fields such as electricity, transportation, and industry, thus providing technical support for achieving low-carbon economy and sustainable development goals.

[0003] Hydrogen energy stores and transmits energy in the form of the chemical potential of hydrogen. Since hydrogen only produces water when burned in air, it does not produce greenhouse gases and other harmful substances and can be considered a clean energy source. In addition, hydrogen has a high calorific value of combustion (up to 120 MJ / kg), which is three times that of gasoline, so it can provide energy efficiently. Hydrogen energy involves three main links, namely hydrogen production, hydrogen storage, and hydrogen utilization. Hydrogen is generally used for fuel cell power generation and can also be used in hydrogen combustion engines.

[0004] However, since hydrogen does not exist in nature, among the above three links, the major challenge lies in hydrogen production. The most common current hydrogen production scheme is the steam reforming method, whose principle is mainly based on the chemical reaction of hydrocarbons and water vapor at high temperatures, which results in the emission of greenhouse effect gases such as carbon dioxide, so it cannot be considered a clean energy technology.

[0005] On the other hand, hydrogen can also be produced by combining water electrolysis with renewable energy. There are usually various water electrolysis technologies such as proton exchange membrane water electrolysis (PEM), alkaline electrolytic cell (AKC), and solid oxide electrolytic cell (SOEC). Among them, the operating temperature of SOEC is usually as high as 650 to 850 °C, and the enthalpy value of high-temperature water vapor is relatively high, so that the electrolysis voltage of SOEC can be as low as 1.3 V, while the electrolysis voltage of alkaline electrolysis or proton exchange membrane (PEM) electrolysis is usually above 1.8 V. In addition, SOEC has the characteristics of high ionic conductivity and electronic insulation, enabling the solid oxide electrolytic cell to achieve high-efficiency electrolysis reactions.

[0006] However, the main drawback of SOEC is that due to the high-temperature environment and the characteristics of solid oxides, its cells require water vapor as the main input for the water electrolysis reaction. So far, most of the existing technologies are based on the method of evaporating fresh water to provide the water vapor. However, this solution has two important problems. First, since water evaporation is a latent heat process, it means that a large amount of energy is required to provide the heat needed for the latent heat. Second, the hydrogen production process consumes a large amount of fresh water. As one of the most precious and crucial resources on Earth, fresh water plays an irreplaceable role in human survival, economic development, and the balance of the ecosystem. Therefore, its application will put great pressure on the local water supply.

[0007] As of now, seawater occupies approximately 97% of the total natural water resources on Earth and is thus regarded as an extremely abundant resource, naturally becoming a worthy alternative option to explore in the field of water electrolysis. However, seawater contains a wide variety of dissolved and suspended impurities. If these impurities are directly introduced into the water electrolysis process, they will not only significantly reduce the efficiency of the water electrolysis reaction but also cause corrosion to the materials of the electrolysis device and even lead to permanent damage. In this context, although using seawater desalination technology to obtain the required fresh water is a way to solve the above problems, this solution requires expensive seawater desalination equipment, and the desalination process itself also consumes a large amount of energy. In summary, the current solutions for providing the required water vapor resources for solid oxide electrolysis cells (SOECs) urgently need a more effective and economical alternative in terms of reliability and cost-effectiveness.

[0008] For example, the patent application with the publication number CN110904464A in the prior art requires additional wind power generation and does not maximize the utilization of tail gas. Therefore, a solid oxide electrolysis system based on waste heat-driven seawater evaporation recovery is needed to solve the above technical problems. Summary of the Invention

[0009] In view of this, the present invention provides a solid oxide electrolysis system based on waste heat-driven seawater evaporation recovery. Different from traditional water electrolysis devices, the present invention avoids the need to involve fresh water and can directly use the more abundant seawater in nature as the main input. In addition, except for the starting water vapor required at startup, the present invention realizes the evaporation of seawater through the heat generated during the water electrolysis reaction process during normal operation. Therefore, no additional energy input is required for the water supply. Finally, the present invention realizes an efficient new hydrogen production scheme for water electrolysis with seawater as the main input for the water electrolysis reaction process through the utilization of the waste heat of the tail gas of the solid oxide electrolysis cell.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A solid oxide electrolysis system for seawater evaporation recovery driven by waste heat, comprising: a seawater evaporation device for evaporating seawater into water vapor;

[0012] A steam compressor for increasing the pressure ratio and thus raising the temperature of the water vapor;

[0013] A solid oxide electrolyzer for electrolyzing water vapor into hydrogen and oxygen;

[0014] A steam turbine for reducing the pressure ratio and thus lowering the evaporation temperature of water, and generating output electricity using the tail gas other than hydrogen generated by the solid oxide electrolyzer;

[0015] The water vapor outlet of the seawater evaporation device is connected to the water vapor inlet of the steam compressor, the water vapor outlet of the steam compressor is connected to the water vapor inlet of the solid oxide electrolyzer, the tail gas outlet of the solid oxide electrolyzer is connected to the tail gas inlet of the steam turbine, the tail gas outlet of the steam turbine is connected to the seawater evaporation device, and the power output terminal of the steam turbine is electrically connected to the power input terminals of the steam compressor and the solid oxide electrolyzer respectively.

[0016] Further, the seawater evaporation device includes a seawater evaporation area, a regenerative heat exchanger, and a tail gas heat exchange tube. The input end of the regenerative heat exchanger is connected to natural seawater through a feed water pump, the output end of the regenerative heat exchanger is connected to the inlet of the seawater evaporation area through a pipeline, a water vapor outlet is provided above the seawater evaporation area for inputting water vapor to the steam compressor, the outlet of the seawater evaporation area is connected to another input end of the regenerative heat exchanger through a circulation end to preheat the natural seawater with the undistilled brine in the seawater evaporation area, the other output end of the regenerative heat exchanger discharges brine from a brine discharge port through a brine drain pump, the tail gas outlet of the steam turbine is connected to the tail gas heat exchange tube, the natural seawater in the seawater evaporation area is heated by the tail gas in the tail gas heat exchange tube, and the tail gas is discharged from a tail gas discharge port through the tail gas heat exchange tube.

[0017] Further, a starting water vapor inlet is also provided on the steam compressor, and the starting water vapor inlet is in parallel with the water vapor inlet of the steam compressor.

[0018] Further, a hydrogen gas outlet is provided above the solid oxide electrolyzer.

[0019] Further, the reaction temperature in the solid oxide electrolyzer is 650 °C to 850 °C.

[0020] Further, the reaction pressure in the seawater evaporation device is 0.15 bar to 0.25 bar.

[0021] Further, the evaporation temperature of water in the seawater evaporation device is 55 °C to 65 °C.

[0022] Further, the temperature of the starting water vapor is 100°C to 120°C.

[0023] Further, the actual voltage of the solid oxide electrolysis cell is three times the open-circuit voltage.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. In the present invention, the waste heat brought by the tail gas generated during the electrolysis of water is utilized to realize the evaporation of seawater. Subsequently, the generated water vapor serves as the main input during the water electrolysis reaction, ultimately avoiding the need for fresh water.

[0026] 2. The cascade utilization of waste heat of the solid oxide electrolysis cell is realized. Electricity is generated from high-grade heat through a steam turbine, and then water vapor required during the water electrolysis reaction is generated through a seawater evaporation device.

[0027] 3. Since the evaporation of seawater occurs outside the solid oxide electrolysis cell, the present invention can ensure that impurities in seawater will not be input into the solid oxide electrolysis cell, thus not affecting the normal operation of the solid oxide electrolysis cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0029] Figure 1 It is a schematic diagram of the overall structural flow of the present invention;

[0030] Figure 2 It is a classic I-V trend diagram of the water electrolysis cell;

[0031] Among them, in the figure:

[0032] 1 - Solid oxide electrolysis cell; 2 - Steam turbine; 3 - Seawater evaporation device; 4 - Steam compressor; 5 - Tail gas heat exchange tube; 6 - Seawater evaporation area; 7 - Regenerative heat exchanger; 8 - Feed water pump; 9 - Brine drain pump; 10 - Water vapor; 11 - Input electricity one; 12 - Input electricity two; 13 - Output electricity; 14 - Tail gas; 15 - Natural seawater; 16 - Brine; 17 - Brine discharge port; 18 - Tail gas discharge port; 19 - Starting water vapor; 20 - Hydrogen. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to the attached Figure 1-2 , the present invention provides a solid oxide electrolysis system for seawater evaporation recovery based on waste heat drive, including: a seawater evaporation device 3 for evaporating seawater into water vapor 10;

[0035] A steam compressor 4 for increasing the pressure ratio and thus increasing the temperature of the water vapor 10. The pressure ratio of the steam compressor 4 can be controlled so that the temperature of the water vapor 10 when input into the solid oxide electrolyzer 1 is close to the normal operating temperature range (650°C to 850°C) of the solid oxide electrolyzer 1;

[0036] A solid oxide electrolyzer 1 for electrolyzing the water vapor 10 into hydrogen 20 and oxygen;

[0037] A steam turbine 2 for reducing the pressure ratio and thus reducing the evaporation temperature of water, and generating output electricity 13 using the tail gas 14 other than hydrogen 20 generated by the solid oxide electrolyzer 1;

[0038] The water vapor outlet of the seawater evaporation device 3 is connected to the water vapor inlet of the steam compressor 4, the water vapor outlet of the steam compressor 4 is connected to the water vapor inlet of the solid oxide electrolyzer 1, the tail gas outlet of the solid oxide electrolyzer 1 is connected to the tail gas inlet of the steam turbine 2, the tail gas outlet of the steam turbine 2 is connected to the seawater evaporation device 3, and the power output terminal of the steam turbine 2 is electrically connected to the power input terminals of the steam compressor 4 and the solid oxide electrolyzer 1 respectively. According to the chemical reaction of water electrolysis (2H 2 O → O 2 + 2H 2 ), hydrogen 20 and a tail gas 14 containing moisture and oxygen will be generated in this process.

[0039] Preferably, the seawater evaporation device 3 includes a seawater evaporation area 6, a regenerative heat exchanger 7, and an exhaust gas heat exchange tube 5. The input end of the regenerative heat exchanger 7 is connected to natural seawater 15 through a feed water pump 8. The output end of the regenerative heat exchanger 7 is connected to the inlet of the seawater evaporation area 6 through a pipeline. A steam outlet is provided above the seawater evaporation area 6 for inputting water vapor 10 to the steam compressor 4. The outlet of the seawater evaporation area 6 is connected to another input end of the regenerative heat exchanger 7 through a circulation end, and the unevaporated brine 16 in the seawater evaporation area 6 is used to preheat the natural seawater 15. Another output end of the regenerative heat exchanger 7 discharges the brine 16 from a brine discharge port 17 through a brine drain pump 9. The exhaust gas outlet of the steam turbine 2 is connected to the exhaust gas heat exchange tube 5. The natural seawater 15 in the seawater evaporation area 6 is heated by the exhaust gas 14 in the exhaust gas heat exchange tube 5, and the exhaust gas 14 is discharged from an exhaust gas discharge port 18 through the exhaust gas heat exchange tube 5. The feed water pump 8 pumps the natural seawater 15 into the seawater evaporation device 3, and in the seawater evaporation area 6, through the heating of the exhaust gas heat exchange tube 5, the natural seawater 15 (along with other small amounts of non-condensable gases) is evaporated, and then flows through the solid oxide electrolytic cell 1, the steam turbine 2, and the exhaust gas heat exchange tube 5 once driven by the steam compressor 4 and is discharged at the exhaust gas discharge port 18. In order to ensure that the circulation end in the seawater evaporation area 6 can maintain the output of high-temperature (and liquid) seawater, it can be achieved by adjusting the seawater flow rate (i.e., the input flow rate) provided by the feed water pump 8. The specific flow rate needs to match the flow rate of the exhaust gas 14 in the entire system.

[0040] Preferably, a starting water vapor 19 inlet is also provided on the steam compressor 4. The starting water vapor 19 inlet is in parallel with the water vapor inlet of the steam compressor 4. The starting water vapor 19 is a temporary resource pre-prepared at approximately 110 °C under atmospheric pressure and can be obtained by methods such as evaporating the water in seawater in a boiler.

[0041] Preferably, a hydrogen gas outlet is provided above the solid oxide electrolytic cell 1.

[0042] Preferably, the reaction temperature in the solid oxide electrolytic cell 1 is 650 °C to 850 °C.

[0043] Preferably, the reaction pressure in the seawater evaporation device 3 is 0.15 bar to 0.25 bar, so that the evaporation temperature of seawater can be approximately 55 °C to 65 °C.

[0044] Preferably, the evaporation temperature of water in the seawater evaporation device 3 is 55 °C to 65 °C.

[0045] Preferably, the temperature of the starting water vapor 19 is 100 °C to 120 °C.

[0046] Preferably, the actual voltage of the solid oxide electrolyzer 1 is three times the open-circuit voltage. Although water electrolysis is an endothermic reaction process, in an actual water electrolysis process, heat will be generated due to various factors such as Ohmic losses and activation losses. Generally, the actual working voltage of water electrolysis must be much greater than the ideal (i.e., no voltage loss) open-circuit voltage. Especially at higher currents (e.g., 400 mA / cm2), the actual voltage can reach three times the open-circuit voltage. This means that the heat generated during the water electrolysis reaction process is much greater than the heat absorbed by the reaction, ultimately leading to an increase in the temperature of the electrolyzer and the exhaust gas. Thus, the exhaust gas 14 will pass through the steam turbine 2 under high temperature (e.g., 650 °C) and high pressure states to generate output electricity 13, and the output electricity 13 is converted into input electricity one 11 and input electricity two 12. The input electricity one 11 can be used to drive the steam compressor 4, the input electricity two 12 can be used to drive the steam turbine 2, and the output electricity 13 can also supply power to users.

[0047] Since not all of the seawater in the seawater evaporation area 6 will evaporate, the unevaporated part becomes brine 16, which will be output through the circulation end. Since the brine 16 output through the circulation end has also experienced the above heating process, its temperature is close to the boiling point (about 60 °C). When this part of the brine 16 passes through the regenerative heat exchanger 7 again, the waste heat in the brine 16 will exchange heat with the input natural seawater 15, thereby realizing the preheating of the natural seawater 15. This process is equivalent to recovering part of the high-temperature heat in the brine 16 and is an effective way to improve energy efficiency.

[0048] The exhaust gas 14 in the exhaust gas heat exchange tube 5 is in an approximately atmospheric pressure state after passing through the steam turbine 2, so the water condensation temperature is about 100 °C. When the temperature of the exhaust gas 14 drops to 100 °C, the condensation of water vapor 10 will occur, causing the exhaust gas 14 to be in a gas-liquid two-phase state. At this time, due to the temperature difference between the exhaust gas 14 and the seawater evaporation area 6 (100 °C and 60 °C respectively), not only can the seawater evaporation area 6 be heated, but also the latent heat of condensation of the water vapor 10 can be utilized, thus greatly improving the energy efficiency of the entire seawater evaporation process.

[0049] The specific usage method of the present invention is as follows:

[0050] When starting work, the solid oxide electrolyzer 1 needs to be preheated to the operating temperature range (650 °C to 850 °C), and at the same time, a stable water vapor 10 flow is required between the solid oxide electrolyzer 1, the steam turbine 2, and the seawater evaporation device 3. First, the starting water vapor 19 input from the outside is input into the steam compressor 4 to achieve its pressurization. At this time, due to the thermodynamic properties of the gas or steam, the compression process will increase the temperature of the starting water vapor 19. The phenomenon that the starting water vapor 19 flows through the solid oxide electrolyzer 1 will cause it to exchange heat with the three-dimensional structure (electrolyte, catalyst, electrode, etc.) of the solid oxide electrolyzer 1, thereby increasing the temperature of the three-dimensional structure of the solid oxide electrolyzer 1 over time; Second, in order to avoid the thermal shock problem of the three-dimensional structure material of the solid oxide electrolyzer 1, a lower pressure ratio can be used first, so that the starting water vapor 19 is at a lower temperature (for example, 100 °C); over time, when the temperature in the solid oxide electrolyzer 1 rises to a certain level (for example, 80 °C), the pressure ratio of the compressor can be gradually increased to gradually increase the temperature of the starting water vapor 19. Repeating the above operations can make the temperature of the solid oxide electrolyzer 1 approach the normal operating temperature range (650 °C to 850 °C), thereby starting the water electrolysis reaction to produce hydrogen and oxygen; at this time, the solid oxide electrolyzer 1 will have a self-heating phenomenon. The tail gas 14 generated by the solid oxide electrolyzer 1 passes through the steam turbine 2, and the generated output electricity 13 further drives the steam compressor 4 and the steam turbine 2. Subsequently, the tail gas 14 is input into the seawater evaporation area 6 in the seawater evaporation device 3, and the high-temperature heat on the tail gas 14 is transferred to the seawater evaporation area 6 through the tail gas heat exchange tube 5. When the natural seawater 15 is input into the seawater evaporation area 6, the natural seawater 15 will be evaporated due to the high-temperature heat brought by the tail gas 14, and the evaporated water vapor 10 will be input into the steam compressor 4; at this time, the input amount of the starting water vapor 19 can be gradually reduced until the generated water vapor 10 flow is sufficient for the normal operation of the solid oxide electrolyzer 1, and then the input of the starting water vapor 19 can be closed, thus completing the startup process of the entire system.

[0051] The water vapor 10 sequentially passes through the cycle semi-loop of the steam compressor 4 → solid oxide electrolyzer 1 → steam turbine 2 → seawater evaporation device 3.

[0052] In the seawater evaporation device 3, there is a cycle semi-loop of natural seawater 15 → regenerative heat exchanger 7 → seawater evaporation area 6 → circulation end → regenerative heat exchanger 7 → brine drain pump 9 → brine discharge port 17.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still, without conflict and without creative efforts, combine, add or delete the features in the embodiments of the present invention according to the situation or make other adjustments, so as to obtain different technical solutions that essentially do not deviate from the concept of the present invention, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling, characterized in that: include: A seawater evaporation device (3) for evaporating seawater into water vapor (10); A steam compressor (4) for increasing the pressure ratio and thus the temperature of the water vapor (10); A solid oxide electrolysis cell (1) for electrolyzing water vapor (10) into hydrogen (20) and oxygen; A steam turbine (2) for reducing the pressure ratio and thus reducing the evaporation temperature of water, and utilizing the tail gas (14) other than the hydrogen (20) generated by the solid oxide electrolytic cell (1) to generate output electricity (13); The water vapor outlet of the seawater evaporation device (3) is connected to the water vapor inlet of the steam compressor (4), the water vapor outlet of the steam compressor (4) is connected to the water vapor inlet of the solid oxide electrolysis cell (1), the tail gas outlet of the solid oxide electrolysis cell (1) is connected to the tail gas inlet of the steam turbine (2), the tail gas outlet of the steam turbine (2) is connected to the seawater evaporation device (3), and the power output end of the steam turbine (2) is electrically connected to the power input ends of the steam compressor (4) and the solid oxide electrolysis cell (1), respectively.

2. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 is characterized in that: The seawater evaporation device (3) comprises a seawater evaporation area (6), a regenerative heat exchanger (7) and an exhaust gas heat exchange pipe (5); the input end of the regenerative heat exchanger (7) is connected to natural seawater (15) via a water supply pump (8); the output end of the regenerative heat exchanger (7) is connected to the inlet of the seawater evaporation area (6) via a pipeline; a water vapor outlet is provided above the seawater evaporation area (6) for inputting water vapor (10) to the steam compressor (4); the outlet of the seawater evaporation area (6) is connected to another inlet of the regenerative heat exchanger (7) via a circulation end. The steam turbine (2) is connected to an inlet end of the steam turbine (2), and the natural seawater (15) is preheated by using the unevaporated salt water (16) in the seawater evaporation area (6). The other output end of the regenerative heat exchanger (7) discharges the salt water (16) from the salt water discharge port (17) through the salt water sewage pump (9). The tail gas outlet of the steam turbine (2) is connected to the tail gas heat exchange pipe (5). The natural seawater (15) in the seawater evaporation area (6) is heated by the tail gas (14) in the tail gas heat exchange pipe (5), and the tail gas (14) is discharged from the tail gas discharge port (18) through the tail gas heat exchange pipe (5).

3. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 is characterized in that: The steam compressor (4) is also provided with a starting water vapor (19) inlet, and the starting water vapor (19) inlet is connected in parallel with the water vapor inlet of the steam compressor (4).

4. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 is characterized in that: A hydrogen outlet is provided on the top of the solid oxide electrolytic cell (1).

5. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 is characterized in that: The reaction temperature in the solid oxide electrolytic cell (1) is 650°C to 850°C.

6. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 is characterized in that: The reaction pressure in the seawater evaporation device (3) is 0.15 bar to 0.25 bar.

7. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1 or 6, characterized in that: The evaporation temperature of water in the seawater evaporation device (3) is 55°C to 65°C.

8. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 3 is characterized in that: The temperature of the starting steam (19) is 100°C to 120°C.

9. The solid oxide electrolysis system based on waste heat driven seawater evaporation and recycling according to claim 1, characterized in that: The actual voltage of the solid oxide electrolytic cell (1) is three times the open circuit voltage.

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