Off-grid photovoltaic coupling electrolyzed water comprehensive control system and method

Abstract

The invention discloses an off-grid photovoltaic coupling electrolyzed water comprehensive control system and method. According to the off-grid photovoltaic coupling electrolyzed water comprehensive control system, hydrogen energy serves as an intermediate medium, renewable energy power generation and thermal power generation are organically combined, and photovoltaic power generation and hydrogen gas turbine power generation cooperate to supply power to a hydrogen production system and a user. Effective conversion of electricity, hydrogen and electricity can be achieved, hydrogen is stably absorbed, and the technical effects that stable electric power can be continuously provided for the system through coordination of the control system, and carbon emission is reduced are achieved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology application, and in particular to an off-grid photovoltaic coupled water electrolysis integrated control system and method. Background Art

[0002] Due to the volatility of photovoltaic power generation, a large amount of abandoned power has occurred, and photovoltaic power is not fully utilized. In the context of dual carbon, it is urgent to find a new method that can reduce both abandoned power and carbon emissions.

[0003] Hydrogen energy is a high-quality resource with abundant sources, clean, low carbon and wide applications. It has become an important strategic choice for my country to accelerate energy transformation and upgrading and cultivate new economic growth points. The "Medium- and Long-Term Plan for the Development of the Hydrogen Energy Industry (2021-2035)" regards hydrogen energy as "an important part of the future national energy system" and emphasizes "focusing on the development of renewable energy hydrogen production" (i.e. green hydrogen). Renewable energy electrolysis hydrogen production can convert volatile and intermittent photovoltaics into hydrogen energy, making hydrogen a clean and efficient energy carrier and one of the key technologies to solve global warming and achieve energy transformation.

[0004] Photovoltaic hydrogen production technology is also limited by natural conditions. For example, at night or on cloudy days, the irradiance is weak and the output is volatile, which causes the hydrogen production equipment to start and stop frequently, affecting the service life of the electrolyzer, as well as low equipment utilization and hydrogen production, which increases the cost of hydrogen production and affects economic benefits.

[0005] At present, most of the renewable energy water electrolysis hydrogen production systems built in China are mainly grid-connected hydrogen production, using the stable power supply of the power grid, and the equipment is also mature. However, after being connected to the grid, it needs to go through multiple conversions such as inversion, boosting, and rectification, which not only increases the cost of various equipment, but also leads to large losses and reduces the utilization rate of electricity.

[0006] The off-grid water electrolysis hydrogen production system is affected by various factors such as seasons and weather, which affect the stability and continuity of water electrolysis hydrogen production and the life of the electrolyzer. How to ensure stable power supply between the photovoltaic power generation system and the electrolyzer, and how to optimize the operation strategy of the control system to improve the overall efficiency of the system are still difficult problems to be solved.

[0007] Currently, no effective solution has been proposed to address the problems of unstable power supply and low overall operating efficiency due to defects in existing off-grid water electrolysis hydrogen production systems. Summary of the invention

[0008] In order to solve the above technical problems, the embodiments of the present invention hope to provide an off-grid photovoltaic-coupled water electrolysis integrated control system and method, so as to at least solve the problems of unstable power supply and low overall operating efficiency caused by the defects of the existing off-grid water electrolysis hydrogen production system itself.

[0009] The technical solution of the present invention is achieved in this way:

[0010] The embodiment of the present invention provides an off-grid photovoltaic coupled water electrolysis integrated control system, including: a photovoltaic power generation device, a power converter, a control system, an energy storage device, a water electrolysis hydrogen production system, an auxiliary system, a hydrogen storage tank and a hydrogen gas turbine, wherein the photovoltaic power generation device is connected to the control system and the power converter respectively, and is used to supply power by converting the radiation energy of sunlight into electrical energy; the power converter is connected to the energy storage device, the water electrolysis hydrogen production system and the auxiliary system respectively, and is used to convert the electrical energy into power according to the business demand type, and send the converted electrical energy to the energy storage device, the water electrolysis hydrogen production system and the auxiliary system respectively; the water electrolysis hydrogen production system is connected to the power converter, the control system, the energy storage device, the auxiliary system and the hydrogen storage tank respectively, and is used to receive the control command sent by the control system according to the operating state of the photovoltaic power generation device detected by the control system, and according to the control command, electrolyze water to produce hydrogen according to the electrical energy input by the power converter or the energy storage device, and produce the produced hydrogen. The hydrogen is separated, purified and dried to obtain treated hydrogen, and the treated hydrogen is transmitted to the hydrogen storage tank; the energy storage device is used to store the electric energy converted by the power converter; the auxiliary system is linked to the water electrolysis hydrogen production system to assist the water electrolysis hydrogen production system in producing hydrogen; one end of the hydrogen storage tank is connected to the water electrolysis hydrogen production system, and the other end of the hydrogen storage tank is connected to the hydrogen gas turbine, which is used to transmit the stored hydrogen to the hydrogen gas turbine according to the control instruction of the control module; one end of the hydrogen gas turbine is connected to the hydrogen storage tank, and the other end of the hydrogen gas turbine is connected to the power converter, which is used to use hydrogen as fuel to generate electricity and / or provide heat energy; the control system is respectively connected to the photovoltaic power generation device, the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine, which is used to monitor the operating status of the photovoltaic power generation device, the energy storage device, the water electrolysis hydrogen production system and the hydrogen storage tank, and control the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business needs according to the operating status.

[0011] Optionally, the photovoltaic power generation device includes: a photovoltaic array.

[0012] Further, optionally, the power converter includes: a DC bus, a first DC / DC converter, a second DC / DC converter, a third DC / DC converter, a first inverter, a second inverter and a third inverter, wherein one end of the first DC / DC converter is connected to the output end of the photovoltaic array, and the other end of the first DC / DC converter is connected to the DC bus, and is used to convert the electric energy generated by the photovoltaic array to obtain the converted electric energy, and transmit it through the DC bus; one end of the second DC / DC converter is connected to the DC bus, and the other end of the second DC / DC converter is connected to the energy storage device, and is used to convert the converted electric energy transmitted by the DC bus, and transmit the converted electric energy to the energy storage device; one end of the third DC / DC converter is connected to the DC bus, and the third DC / DC converter is connected to the DC bus. The other end of the C converter is connected to the water electrolysis hydrogen production system, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the water electrolysis hydrogen production system; one end of the first inverter is connected to the DC bus, and the other end of the first inverter is connected to the auxiliary system, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the auxiliary system; one end of the second inverter is connected to the DC bus, and the other end of the second inverter is connected to the user load, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the user load; one end of the third inverter is connected to the DC bus, and the other end of the third inverter is connected to the hydrogen gas turbine, and is used for converting the electric energy generated by the hydrogen gas turbine, and transmitting the converted electric energy to the DC bus.

[0013] Optionally, the water electrolysis hydrogen production system includes: a PEM electrolyzer, a gas-liquid separation system and a purification system, wherein the PEM electrolyzer is used to utilize electrical energy to electrolyze water to produce hydrogen, thereby obtaining hydrogen after electrolysis; the gas-liquid separation system is connected to the PEM electrolyzer, and is used to perform gas-liquid separation on the hydrogen after electrolysis, thereby obtaining separated hydrogen; the purification system is connected to the gas-liquid separation system, and is used to purify and dry the separated hydrogen, thereby obtaining purified and dried hydrogen.

[0014] Optionally, the control system is also used to control the water electrolysis hydrogen production system to execute the maximum power hydrogen production mode when the power output of the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system. The water electrolysis hydrogen production system separates, purifies, and dryly stores the prepared hydrogen in the hydrogen storage tank. The control system changes the operation mode of the energy storage device to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device; the control system is also used to control the water electrolysis hydrogen production system to execute the rated power hydrogen production mode when the power output of the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system, and the power output of the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system, separates, purifies, and dryly stores the hydrogen prepared by the water electrolysis hydrogen production system in the hydrogen storage tank. The control system changes the operation mode of the energy storage device to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device; the control system is also used to control the water electrolysis hydrogen production system to execute the rated power hydrogen production mode when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the rated hydrogen production power. The rated power hydrogen production mode is carried out, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, and the control system changes the operation mode of the energy storage device to the discharge mode to supply power to the water electrolysis hydrogen production system; the control system is also used to control the water electrolysis hydrogen production system to execute the minimum power hydrogen production mode when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output power of the photovoltaic array and the energy storage device is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, the control system sets the water electrolysis hydrogen production system to the minimum power, changes the operation mode of the energy storage device to the discharge mode, and supplies power to the water electrolysis hydrogen production system; the control system is also used to change the operation mode of the energy storage device to the discharge mode when the photovoltaic array needs maintenance, and supplies power to the water electrolysis hydrogen production system, so that the water electrolysis hydrogen production system remains in a hot standby state; the control system is also used to keep the PEM electrolyzer in the water electrolysis hydrogen production system in a hot standby state by controlling the power output of the hydrogen gas turbine when the photovoltaic array needs maintenance and the energy storage device is out of power.

[0015] Further, optionally, the control system is also used to monitor the state of the water electrolysis hydrogen production system; when the state of the water electrolysis hydrogen production system does not meet the safe operation state, an alarm is issued.

[0016] Optionally, the states of the water electrolysis hydrogen production system include: temperature, pressure, current, voltage, and concentrations of oxygen in hydrogen and hydrogen in oxygen.

[0017] The embodiment of the present invention provides an off-grid photovoltaic-coupled water electrolysis comprehensive control method, which is applied to an off-grid photovoltaic-coupled water electrolysis comprehensive control system, including: monitoring the operating status of a photovoltaic power generation device, an energy storage device, a water electrolysis hydrogen production system and a hydrogen storage tank; and controlling the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business requirements according to the operating status.

[0018] Optionally, the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine are controlled to execute corresponding business requirements according to the operating status, including: when the power output of the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the maximum power hydrogen production mode, the water electrolysis hydrogen production system separates, purifies and dryly stores the prepared hydrogen in the hydrogen storage tank, the operation mode of the energy storage device is changed to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device; when the power output of the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system, and the power output of the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the hydrogen prepared by the water electrolysis hydrogen production system is separated, purified and dryly stored in the hydrogen storage tank, the operation mode of the energy storage device is changed to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device; when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the output power of the photovoltaic array is greater than the output power of the energy storage device. When the sum is greater than the rated hydrogen production power, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system; when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the minimum power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, the water electrolysis hydrogen production system is set to the minimum power, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system; when the photovoltaic array needs maintenance, the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system, so that the water electrolysis hydrogen production system remains in a hot standby state; when the photovoltaic array needs maintenance and the energy storage device is out of power, the PEM electrolyzer in the water electrolysis hydrogen production system is kept in a hot standby state by controlling the power output of the hydrogen gas turbine.

[0019] Further, optionally, the method also includes: monitoring the state of the water electrolysis hydrogen production system; when the state of the water electrolysis hydrogen production system does not conform to the safe operation state, issuing an alarm; wherein the state of the water electrolysis hydrogen production system includes: temperature, pressure, current, voltage, and the concentration of oxygen in hydrogen and hydrogen in oxygen.

[0020] The embodiment of the present invention provides an off-grid photovoltaic-coupled water electrolysis integrated control system and method, which monitors the operating status of a photovoltaic power generation device, an energy storage device, a water electrolysis hydrogen production system and a hydrogen storage tank; controls the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business needs according to the operating status, thereby achieving effective conversion of electricity to hydrogen and ensuring stable consumption of hydrogen. After coordination by the control module, it can sustainably provide stable electricity to the system, achieving the technical effect of reducing carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0022] Figure 1 A schematic diagram of an off-grid photovoltaic coupled water electrolysis integrated control system provided by an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of another off-grid photovoltaic coupled water electrolysis integrated control system provided by an embodiment of the present invention;

[0024] Figure 3 A schematic flow chart of an off-grid photovoltaic coupled water electrolysis comprehensive control method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second" and the like in the specification, claims and drawings of the present invention are used to distinguish different objects rather than to limit a specific order.

[0027] It should also be noted that the following embodiments of the present invention may be executed separately, or in combination with each other, and the embodiments of the present invention do not impose specific limitations on this.

[0028] The embodiment of the present invention provides an off-grid photovoltaic coupled water electrolysis integrated control system. Figure 1 A schematic diagram of an off-grid photovoltaic coupled water electrolysis integrated control system provided by an embodiment of the present invention; Figure 1As shown, the off-grid photovoltaic coupled water electrolysis integrated control system provided in the embodiment of the present application includes:

[0029] Photovoltaic power generation device 10, power converter 11, control system 12, energy storage device 13, water electrolysis hydrogen production system 14, auxiliary system 15, hydrogen storage tank 16 and hydrogen gas turbine 17, wherein the photovoltaic power generation device 10 is connected to the control system 12 and the power converter 11 respectively, and is used to convert the radiation energy of sunlight into electrical energy for power supply; the power converter 11 is connected to the energy storage device 13, the water electrolysis hydrogen production system 14 and the auxiliary system 15 respectively, and is used to convert the electrical energy into power according to the business demand type, and convert the converted electrical energy into electrical energy. The electric energy is sent to the energy storage device 13, the water electrolysis hydrogen production system 14 and the auxiliary system 15 respectively; the water electrolysis hydrogen production system 14 is connected to the power converter 11, the control system 12, the energy storage device 13, the auxiliary system 15 and the hydrogen storage tank 16 respectively, and is used to receive the control instruction sent by the control system 12 according to the operating state of the photovoltaic power generation device 10 detected by the control system 12, and perform water electrolysis hydrogen production according to the electric energy input by the power converter 11 or the energy storage device 13 according to the control instruction, and separate, purify and dry the produced hydrogen to obtain The treated hydrogen is then transferred to the hydrogen storage tank 16; the energy storage device 13 is used to store the electric energy converted by the power converter 11; the auxiliary system 15 is connected to the water electrolysis hydrogen production system 14 to assist the water electrolysis hydrogen production system 14 in producing hydrogen; one end of the hydrogen storage tank 16 is connected to the water electrolysis hydrogen production system 14, and the other end of the hydrogen storage tank 16 is connected to the hydrogen gas turbine 17 to transfer the stored hydrogen to the hydrogen gas turbine 17 according to the control instruction of the control module; one end of the hydrogen gas turbine 17 is connected to the hydrogen storage tank 16, and the hydrogen gas turbine 17 is connected to the hydrogen storage tank 16. The other end of the machine 17 is connected to the power converter 11, which is used to use hydrogen as fuel to generate electricity and / or provide heat energy; the control system 12 is respectively connected to the photovoltaic power generation device 10, the energy storage device 13, the water electrolysis hydrogen production system 14, the hydrogen storage tank 16 and the hydrogen gas turbine 17, and is used to monitor the operating status of the photovoltaic power generation device 10, the energy storage device 13, the water electrolysis hydrogen production system 14 and the hydrogen storage tank 16, and control the energy storage device 13, the water electrolysis hydrogen production system 14, the hydrogen storage tank 16 and the hydrogen gas turbine 17 to execute corresponding business needs according to the operating status.

[0030] Optionally, the photovoltaic power generation device 10 includes: a photovoltaic array.

[0031] Further, optionally, the power converter 11 includes: a DC bus, a first DC / DC converter, a second DC / DC converter, a third DC / DC converter, a first inverter, a second inverter and a third inverter, wherein one end of the first DC / DC converter is connected to the output end of the photovoltaic array, and the other end of the first DC / DC converter is connected to the DC bus, and is used to convert the electric energy generated by the photovoltaic array to obtain the converted electric energy, and transmit it through the DC bus; one end of the second DC / DC converter is connected to the DC bus, and the other end of the second DC / DC converter is connected to the energy storage device 13, and is used to convert the converted electric energy transmitted by the DC bus, and transmit the converted electric energy to the energy storage device 13; one end of the third DC / DC converter is connected to the DC bus, and the third DC / DC converter The other end of the inverter is connected to the water electrolysis hydrogen production system 14, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the water electrolysis hydrogen production system 14; one end of the first inverter is connected to the DC bus, and the other end of the first inverter is connected to the auxiliary system 15, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the auxiliary system 15; one end of the second inverter is connected to the DC bus, and the other end of the second inverter is connected to the user load, and is used for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the user load; one end of the third inverter is connected to the DC bus, and the other end of the third inverter is connected to the hydrogen gas turbine 17, and is used for converting the electric energy generated by the hydrogen gas turbine 17, and transmitting the converted electric energy to the DC bus.

[0032] Optionally, the water electrolysis hydrogen production system 14 includes: a PEM electrolyzer, a gas-liquid separation system and a purification system, wherein the PEM electrolyzer is used to utilize electrical energy to electrolyze water to produce hydrogen to obtain hydrogen after electrolysis; the gas-liquid separation system is connected to the PEM electrolyzer and is used to perform gas-liquid separation on the hydrogen after electrolysis to obtain separated hydrogen; the purification system is connected to the gas-liquid separation system and is used to purify and dry the separated hydrogen to obtain purified and dried hydrogen.

[0033] Optionally, the control system 12 is also used to control the water electrolysis hydrogen production system 14 to execute the maximum power hydrogen production mode when the power output of the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system 14. The water electrolysis hydrogen production system 14 separates, purifies, dries and stores the prepared hydrogen in the hydrogen storage tank 16. The control system 12 changes the operation mode of the energy storage device 13 to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device 13. The control system 12 is also used to control the water electrolysis hydrogen production system 14 to execute the maximum power hydrogen production mode when the power output of the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system 14, and the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system 14. When the maximum hydrogen production power of the water hydrogen production system 14 is reached, the water electrolysis hydrogen production system 14 is controlled to execute the rated power hydrogen production mode, the hydrogen prepared by the water electrolysis hydrogen production system 14 is separated, purified, dried and stored in the hydrogen storage tank 16, and the control system 12 changes the operation mode of the energy storage device 13 to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device 13; the control system 12 is also used to control the water electrolysis hydrogen production system 14 to execute the rated power hydrogen production mode when the power output of the photovoltaic array is less than the rated hydrogen production power of the water hydrogen production system 14, and the sum of the output powers of the photovoltaic array and the energy storage device 13 is greater than the rated hydrogen production power. In the rated power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank 16, and the control system 12 changes the operation mode of the energy storage device 13 to the discharge mode to supply power to the water electrolysis hydrogen production system 14; the control system 12 is also used to control the water electrolysis hydrogen production system 14 to execute the minimum power hydrogen production mode when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system 14, and the sum of the output power of the photovoltaic array and the energy storage device 13 is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system 14, and the control system 12 separates and purifies the prepared hydrogen and stores it in the hydrogen storage tank 16. The water electrolysis hydrogen production system 14 is set to the minimum power, and the operation mode of the energy storage device 13 is changed to the discharge mode to supply power to the water electrolysis hydrogen production system 14; the control system 12 is also used to change the operation mode of the energy storage device 13 to the discharge mode to supply power to the water electrolysis hydrogen production system 14 when the photovoltaic array needs maintenance, so as to keep the water electrolysis hydrogen production system 14 in a hot standby state; the control system 12 is also used to keep the PEM electrolyzer in the water electrolysis hydrogen production system 14 in a hot standby state by controlling the power generated by the hydrogen gas turbine 17 when the photovoltaic array needs maintenance and the power of the energy storage device 13 is used up.

[0034] Further, optionally, the control system 12 is also used to monitor the state of the water electrolysis hydrogen production system 14; when the state of the water electrolysis hydrogen production system 14 does not meet the safe operation state, an alarm is issued.

[0035] Optionally, the states of the water electrolysis hydrogen production system 14 include: temperature, pressure, current, voltage, and concentrations of oxygen in hydrogen and hydrogen in oxygen.

[0036] In summary, Figure 2A schematic diagram of another off-grid photovoltaic coupled water electrolysis integrated control system provided by an embodiment of the present invention; Figure 2 As shown, the photovoltaic power generation device 10 is a device for generating electricity through a photovoltaic array. It uses the photoelectric effect to convert the radiation energy of sunlight into direct current electricity to power the system. The output end of the photovoltaic power generation device 10 is connected to a power converter 11 and a control system 12.

[0037] The power converter 11 is used to convert the direct current generated by the photovoltaic power generation device 10 into an adapted alternating current or direct current. The input end of the power converter 11 is connected to the photovoltaic power generation device 10, and the output end is connected to the control system 12, the water electrolysis hydrogen production system 14, the energy storage device 13, the hydrogen gas turbine 17, the auxiliary system 15 and the user load. Among them, the power converter 11 includes a DC bus, a DC / DC converter 1, a DC / DC converter 2, a DC / DC converter 3, an inverter 1, an inverter 2 and an inverter 3.

[0038] The water electrolysis hydrogen production system 14 includes a PEM electrolyzer, a gas-liquid separation system and a purification system, and utilizes electric energy to electrolyze water to produce hydrogen, and separates, purifies and dries the produced hydrogen before sending it to the hydrogen storage tank 16. The input end of the water electrolysis hydrogen production system 14 is connected to the power converter 11, and the output end is connected to the hydrogen storage tank 16.

[0039] The hydrogen storage tank 16 is used to store the hydrogen produced, separated, purified and dried by the water electrolysis hydrogen production system 14, and select a suitable pressure, and provide hydrogen to the hydrogen gas turbine 17 and hydrogen users. The input end of the hydrogen storage tank 16 is connected to the water electrolysis hydrogen production system 14, and the output end is connected to the hydrogen gas turbine and the hydrogen user.

[0040] The energy storage device 13 is used to store the generated electric energy as a backup power source, and a lithium battery is selected to provide backup electric energy for the water electrolysis hydrogen production system 14, the auxiliary system 15, and the user. The input end of the energy storage device 13 is connected to the power converter 11, and the output end is connected to the water electrolysis hydrogen production system 14, the auxiliary system 15, and the user load.

[0041] The auxiliary system 15 is an auxiliary system 15 of the water electrolysis hydrogen production system 14 , such as a water supply system, a cooling system, etc. An input end of the auxiliary system 15 is connected to the power converter 11 .

[0042] The hydrogen gas turbine 17 uses the hydrogen stored in the hydrogen storage tank 16 as fuel to generate electricity and provide heat energy to meet the user's load needs and realize the conversion of electric hydrogen to electricity and electric hydrogen to heat. The input end of the hydrogen gas turbine 17 is connected to the hydrogen storage tank 16, and the output end is connected to the power converter 11.

[0043] The control system 12 is used for data collection, data transmission, power distribution, safety protection and power control of the photovoltaic power generation device 10, the water electrolysis hydrogen production system 14, the energy storage device 13, the hydrogen gas turbine 17, the user module and the auxiliary system 15 in the off-grid photovoltaic coupled water electrolysis hydrogen production / storage / use system. The system power generation, hydrogen production and power consumption are controlled in a hierarchical manner to ensure safe and stable operation of the system.

[0044] The off-grid photovoltaic-coupled water electrolysis integrated control system provided in the embodiment of the present application enables the system to execute a corresponding working mode according to the power generation, hydrogen production, and electricity consumption conditions monitored by the control system.

[0045] When the power output by the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system 14, the water electrolysis hydrogen production system 14 is controlled to execute the maximum power hydrogen production mode, the water electrolysis hydrogen production system 14 separates and purifies the prepared hydrogen and stores it in the hydrogen storage tank 16, and the control system 12 changes the operation mode of the energy storage device 13 to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device 13;

[0046] When the power output by the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system 14, and the power output by the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system 14, the water electrolysis hydrogen production system 14 is controlled to execute the rated power hydrogen production mode, the hydrogen produced by the water electrolysis hydrogen production system 14 is separated, purified, dried and stored in the hydrogen storage tank 16, and the control system 12 changes the operation mode of the energy storage device 13 to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device 13;

[0047] When the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system 14, and the sum of the output powers of the photovoltaic array and the energy storage device 13 is greater than the rated hydrogen production power, the water electrolysis hydrogen production system 14 is controlled to execute the rated power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank 16, and the control system 12 changes the operation mode of the energy storage device 13 to the discharge mode to supply power to the water electrolysis hydrogen production system 14;

[0048] When the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system 14, and the sum of the output powers of the photovoltaic array and the energy storage device 13 is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system 14, the water electrolysis hydrogen production system 14 is controlled to execute the minimum power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank 16, the control system 12 sets the water electrolysis hydrogen production system 14 to the minimum power, and changes the operation mode of the energy storage device 13 to the discharge mode to supply power to the water electrolysis hydrogen production system 14;

[0049] When the photovoltaic array needs maintenance, the operation mode of the energy storage device 13 is changed to the discharge mode to supply power to the water electrolysis hydrogen production system 14 so that the water electrolysis hydrogen production system 14 remains in a hot standby state;

[0050] When the photovoltaic array needs maintenance and the energy storage device 13 runs out of power, the PEM electrolyzer in the water electrolysis hydrogen production system 14 is kept in a hot standby state by controlling the power generated by the hydrogen gas turbine 17.

[0051] In the embodiment of the present application, the electric energy generated by the hydrogen gas turbine is used to meet the electricity demand of users, and the extra hydrogen energy is also sold.

[0052] Further, optionally, the control system 12 is also used to monitor the state of the water electrolysis hydrogen production system 14; when the state of the water electrolysis hydrogen production system 14 does not conform to the safe operation state, an alarm is issued; wherein the state of the water electrolysis hydrogen production system 14 includes: temperature, pressure, current, voltage, and the concentration of oxygen in hydrogen and hydrogen in oxygen.

[0053] The off-grid photovoltaic coupled water electrolysis integrated control system provided by the embodiment of the present application can intelligently execute different hydrogen production / use modes according to weather conditions and system operating status, so that the electrolyzer can maintain a hot standby state to the greatest extent, solve the impact of volatile photovoltaics on the start-stop performance of the electrolyzer, reduce the number of starts and stops, increase the utilization rate of hydrogen production equipment, and monitor the operating status of the electrolyzer system in real time, issue early warnings in time, and maintain in time, effectively improve the working life of the electrolyzer, and make the system operate safely, reducing the cost of hydrogen production and maintenance costs. The off-grid photovoltaic coupled water electrolysis integrated control system provided by the embodiment of the present application can directly use the electricity generated by photovoltaic power generation for hydrogen production, realize the on-site consumption of photovoltaics, and reduce the impact of new energy power generation on the power grid. The hydrogen gas turbine module is added to the system, and hydrogen is used as the intermediate medium to achieve effective conversion of electricity and hydrogen, so that hydrogen is stably consumed. After coordination of the control module, it can sustainably provide stable electricity for the system and reduce carbon emissions. It also provides a clean and sustainable power system for areas not covered by the power grid, such as remote mountainous areas and isolated islands.

[0054] In the off-grid photovoltaic-coupled water electrolysis integrated control system provided in the embodiment of the present application, hydrogen energy is used as an intermediate medium to organically combine renewable energy power generation with thermal power generation. The synergy of photovoltaic power generation and hydrogen gas turbine power generation provides power for the hydrogen production system and users, realizes the mutual conversion of solar energy, hydrogen energy and electrical energy, and forms a new mode of electricity-hydrogen-electricity conversion. This system can be used in remote areas, mountainous areas, isolated islands and other areas to form a distributed energy microgrid for continuous power supply, fully absorb fluctuating renewable energy power, convert fluctuating renewable energy power generation into stable power output, and realize intelligent control in the process of water electrolysis to produce hydrogen, reduce the number of starts and stops of the electrolyzer, extend the service life of the electrolyzer, increase hydrogen production, and reduce costs.

[0055] The embodiment of the present invention provides an off-grid photovoltaic-coupled water electrolysis integrated control system, which monitors the operating status of a photovoltaic power generation device, an energy storage device, a water electrolysis hydrogen production system and a hydrogen storage tank; controls the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business needs according to the operating status, thereby achieving effective conversion of electricity to hydrogen and ensuring stable consumption of hydrogen. After coordination by the control module, it can sustainably provide stable electricity to the system, achieving the technical effect of reducing carbon emissions.

[0056] The embodiment of the present invention provides an off-grid photovoltaic coupled water electrolysis comprehensive control method, which is applied to Figure 1 or Figure 2 Off-grid photovoltaic coupled water electrolysis integrated control system, Figure 3 A schematic flow chart of an off-grid photovoltaic coupled water electrolysis comprehensive control method provided by an embodiment of the present invention; Figure 3 As shown, the off-grid photovoltaic coupled water electrolysis comprehensive control method provided in the embodiment of the present application includes:

[0057] Step S302, monitoring the operating status of the photovoltaic power generation device, the energy storage device, the water electrolysis hydrogen production system and the hydrogen storage tank;

[0058] Step S304, controlling the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business requirements according to the operating status.

[0059] Optionally, in step S304, the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine are controlled to execute corresponding business requirements according to the operating status, including: when the power output of the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the maximum power hydrogen production mode, the water electrolysis hydrogen production system separates, purifies, and dryly stores the prepared hydrogen in the hydrogen storage tank, the operation mode of the energy storage device is changed to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device; when the power output of the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system, and the power output of the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the hydrogen prepared by the water electrolysis hydrogen production system is separated, purified, and dryly stored in the hydrogen storage tank, the operation mode of the energy storage device is changed to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device; when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the photovoltaic array and the energy storage device output When the sum of the powers is greater than the rated hydrogen production power, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system; when the power output of the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the minimum power hydrogen production mode, the prepared hydrogen is separated, purified and dried and stored in the hydrogen storage tank, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system. The hydrogen produced by water electrolysis is dried and stored in a hydrogen storage tank, the water electrolysis hydrogen production system is set to minimum power, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system; when the photovoltaic array needs maintenance, the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system, so that the water electrolysis hydrogen production system remains in a hot standby state; when the photovoltaic array needs maintenance and the energy storage device is out of power, the PEM electrolyzer in the water electrolysis hydrogen production system is kept in a hot standby state by controlling the power generated by the hydrogen gas turbine.

[0060] Further, optionally, the off-grid photovoltaic-coupled water electrolysis comprehensive control method provided in the embodiment of the present application also includes: monitoring the state of the water electrolysis hydrogen production system; when the state of the water electrolysis hydrogen production system does not meet the safe operation state, issuing an alarm; wherein the state of the water electrolysis hydrogen production system includes: temperature, pressure, current, voltage, and the concentration of oxygen in hydrogen and hydrogen in oxygen.

[0061] The embodiment of the present invention provides an off-grid photovoltaic-coupled water electrolysis comprehensive control method, which monitors the operating status of a photovoltaic power generation device, an energy storage device, a water electrolysis hydrogen production system and a hydrogen storage tank; controls the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business needs according to the operating status, thereby achieving effective conversion of electricity to hydrogen and ensuring stable consumption of hydrogen. After coordination by the control module, it can sustainably provide stable electricity to the system, achieving the technical effect of reducing carbon emissions.

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. An off-grid photovoltaic coupled water electrolysis integrated control system, characterized in that: include: Photovoltaic power generation device, power converter, control system, energy storage device, water electrolysis hydrogen production system, auxiliary system, hydrogen storage tank and hydrogen gas turbine, among which, The photovoltaic power generation device is connected to the control system and the power converter respectively, and is used to provide power by converting the radiation energy of sunlight into electrical energy; The power converter is connected to the energy storage device, the water electrolysis hydrogen production system and the auxiliary system respectively, and is used to convert the electric energy according to the business demand type, and send the converted electric energy to the energy storage device, the water electrolysis hydrogen production system and the auxiliary system respectively; The water electrolysis hydrogen production system is respectively connected to the power converter, the control system, the energy storage device, the auxiliary system and the hydrogen storage tank, and is used to receive a control instruction sent by the control system according to the operating state of the photovoltaic power generation device detected by the control system, and to perform water electrolysis hydrogen production according to the control instruction and the electric energy input by the power converter or the energy storage device, and to separate, purify and dry the produced hydrogen to obtain treated hydrogen, and to transmit the treated hydrogen to the hydrogen storage tank; The energy storage device is used to store the electric energy converted by the power converter; The auxiliary system is linked to the water electrolysis hydrogen production system and is used to assist the water electrolysis hydrogen production system in producing hydrogen; One end of the hydrogen storage tank is connected to the water electrolysis hydrogen production system, and the other end of the hydrogen storage tank is connected to the hydrogen gas turbine, so as to transmit the stored hydrogen to the hydrogen gas turbine according to the control instruction of the control module; One end of the hydrogen gas turbine is connected to the hydrogen storage tank, and the other end of the hydrogen gas turbine is connected to the power converter, so as to use the hydrogen as fuel to generate electricity and / or provide heat energy; The control system is respectively connected to the photovoltaic power generation device, the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine, and is used to monitor the operating status of the photovoltaic power generation device, the energy storage device, the water electrolysis hydrogen production system and the hydrogen storage tank, and control the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business requirements according to the operating status.

2. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 1 is characterized in that: The photovoltaic power generation device comprises: a photovoltaic array.

3. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 2 is characterized in that: The power converter includes: a DC bus, a first DC / DC converter, a second DC / DC converter, a third DC / DC converter, a first inverter, a second inverter and a third inverter, wherein: One end of the first DC / DC converter is connected to the output end of the photovoltaic array, and the other end of the first DC / DC converter is connected to the DC bus, and is used to convert the electric energy generated by the photovoltaic array to obtain the converted electric energy, and transmit it through the DC bus; One end of the second DC / DC converter is connected to the DC bus, and the other end of the second DC / DC converter is connected to the energy storage device, for converting the converted electric energy transmitted by the DC bus and transmitting the converted electric energy to the energy storage device; One end of the third DC / DC converter is connected to the DC bus, and the other end of the third DC / DC converter is connected to the water electrolysis hydrogen production system, for converting the converted electric energy transmitted by the DC bus, and transmitting the converted electric energy to the water electrolysis hydrogen production system; One end of the first inverter is connected to the DC bus, and the other end of the first inverter is connected to the auxiliary system, for converting the converted electric energy transmitted by the DC bus and transmitting the converted electric energy to the auxiliary system; One end of the second inverter is connected to the DC bus, and the other end of the second inverter is connected to the user load, for converting the converted electric energy transmitted by the DC bus and transmitting the converted electric energy to the user load; One end of the third inverter is connected to the DC bus, and the other end of the third inverter is connected to the hydrogen gas turbine, and is used to convert the electric energy generated by the hydrogen gas turbine and transmit the converted electric energy to the DC bus.

4. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 3 is characterized in that: The water electrolysis hydrogen production system comprises: a PEM electrolyzer, a gas-liquid separation system and a purification system, wherein: The PEM electrolyzer is used to produce hydrogen by electrolyzing water using electrical energy to obtain hydrogen after electrolysis; The gas-liquid separation system is connected to the PEM electrolyzer and is used to separate the hydrogen after the electrohydrolysis into gas and liquid to obtain separated hydrogen; The purification system is connected to the gas-liquid separation system and is used to purify and dry the separated hydrogen to obtain purified and dried hydrogen.

5. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 4 is characterized in that: The control system is also used to control the water electrolysis hydrogen production system to execute the maximum power hydrogen production mode when the power output by the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system. The water electrolysis hydrogen production system separates, purifies, dries and stores the prepared hydrogen in the hydrogen storage tank. The control system changes the operation mode of the energy storage device to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device. The control system is further used for controlling the water electrolysis hydrogen production system to execute the rated power hydrogen production mode when the power output by the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system and the power output by the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system, separating, purifying, drying and storing the hydrogen prepared by the water electrolysis hydrogen production system in the hydrogen storage tank, and the control system changes the operation mode of the energy storage device to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device; The control system is also used to control the water electrolysis hydrogen production system to execute the rated power hydrogen production mode, separate and purify the prepared hydrogen and store it in the hydrogen storage tank when the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the rated hydrogen production power, and the control system changes the operation mode of the energy storage device to the discharge mode to supply power to the water electrolysis hydrogen production system; The control system is also used for controlling the water electrolysis hydrogen production system to execute the minimum power hydrogen production mode, separating, purifying, drying and storing the prepared hydrogen in the hydrogen storage tank, when the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system, and the control system sets the water electrolysis hydrogen production system to the minimum power, changes the operation mode of the energy storage device to the discharge mode, and supplies power to the water electrolysis hydrogen production system; The control system is also used to change the operation mode of the energy storage device to a discharge mode when the photovoltaic array needs maintenance, to supply power to the water electrolysis hydrogen production system, so that the water electrolysis hydrogen production system remains in a hot standby state; The control system is also used to keep the PEM electrolyzer in the water electrolysis hydrogen production system in a hot standby state by controlling the power generated by the hydrogen gas turbine when the photovoltaic array needs maintenance and the energy storage device is out of power.

6. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 5, characterized in that: The control system is also used to monitor the state of the water electrolysis hydrogen production system; when the state of the water electrolysis hydrogen production system does not meet the safe operation state, an alarm is issued.

7. The off-grid photovoltaic coupled water electrolysis integrated control system according to claim 6, characterized in that: The states of the water electrolysis hydrogen production system include: temperature, pressure, current, voltage, and the concentrations of oxygen in hydrogen and hydrogen in oxygen.

8. An off-grid photovoltaic coupled water electrolysis comprehensive control method, characterized in that: Applied to off-grid photovoltaic coupled water electrolysis integrated control system, including: Monitor the operating status of photovoltaic power generation devices, energy storage devices, water electrolysis hydrogen production systems and hydrogen storage tanks; The energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine are controlled to execute corresponding business requirements according to the operating status.

9. The off-grid photovoltaic coupled water electrolysis comprehensive control method according to claim 8, characterized in that: The controlling of the energy storage device, the water electrolysis hydrogen production system, the hydrogen storage tank and the hydrogen gas turbine to execute corresponding business requirements according to the operating state includes: When the power output by the photovoltaic array is greater than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the maximum power hydrogen production mode, the water electrolysis hydrogen production system separates, purifies, dries and stores the prepared hydrogen in the hydrogen storage tank, changes the operation mode of the energy storage device to the charging mode, and stores the excess electric energy generated by the photovoltaic array in the energy storage device; When the power output by the photovoltaic array is greater than the rated hydrogen production power of the water electrolysis hydrogen production system, and the power output by the photovoltaic array is less than the maximum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the hydrogen prepared by the water electrolysis hydrogen production system is separated, purified, dried and stored in the hydrogen storage tank, the operation mode of the energy storage device is changed to the charging mode, and the excess electric energy generated by the photovoltaic array is stored in the energy storage device; When the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the rated hydrogen production power, the water electrolysis hydrogen production system is controlled to execute the rated power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, and the operation mode of the energy storage device is changed to the discharge mode to supply power to the water electrolysis hydrogen production system; When the power output by the photovoltaic array is less than the rated hydrogen production power of the water electrolysis hydrogen production system, and the sum of the output powers of the photovoltaic array and the energy storage device is greater than the minimum hydrogen production power of the water electrolysis hydrogen production system, the water electrolysis hydrogen production system is controlled to execute the minimum power hydrogen production mode, the prepared hydrogen is separated, purified, dried and stored in the hydrogen storage tank, the water electrolysis hydrogen production system is set to the minimum power, the operation mode of the energy storage device is changed to the discharge mode, and the water electrolysis hydrogen production system is powered; When the photovoltaic array needs maintenance, the operation mode of the energy storage device is changed to a discharge mode to supply power to the water electrolysis hydrogen production system so that the water electrolysis hydrogen production system remains in a hot standby state; When the photovoltaic array needs maintenance and the power of the energy storage device is used up, the PEM electrolyzer in the water electrolysis hydrogen production system is kept in a hot standby state by controlling the power generated by the hydrogen gas turbine.

10. The off-grid photovoltaic coupled water electrolysis comprehensive control method according to claim 9, characterized in that: The method further comprises: Monitoring the state of the water electrolysis hydrogen production system; when the state of the water electrolysis hydrogen production system does not meet the safe operation state, issuing an alarm; The states of the water electrolysis hydrogen production system include: temperature, pressure, current, voltage, and the concentrations of oxygen in hydrogen and hydrogen in oxygen.

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