Solar energy electrolysis energy storage system and control method thereof

Abstract

This invention discloses a solar electrolysis energy storage system and its control method. The system includes a photovoltaic electrolysis control module, a water circulation module, and an energy storage module. The photovoltaic electrolysis control module includes a photovoltaic system, a control system, and an electrolytic cell. The water circulation module includes a heat exchanger, a turbine, a condenser, and a water pump. The energy storage module includes an inverter controller, an energy storage device, and a hydrogen storage device. The water supply module is connected to a hot water pump, and the heat exchanger is connected to the turbine and the photovoltaic system. The turbine is connected to the condenser, the electrolytic cell, and the inverter controller. The condenser and the electrolytic cell are connected to the water pump, and the water pump is connected to the heat exchanger. The photovoltaic system is connected to the energy storage device through the inverter controller, and both the photovoltaic system and the energy storage device are connected to the control system. The hydrogen energy generated by the electrolytic cell is stored through the hydrogen storage device. This invention improves the utilization rate of photovoltaic power while enhancing the electrolysis performance of the electrolytic cell, reducing the impact of the volatility of photovoltaic power generation on the electrolytic cell, and improving the efficiency of photovoltaic power generation.

Description

Technical Field

[0001] This invention relates to the field of renewable energy conversion and energy storage, specifically to a solar electrolysis energy storage system and its control method. Background Technology

[0002] Renewable energy has many advantages over fossil fuels, such as being clean and pollution-free. However, due to intermittency and other issues, renewable energy cannot be directly connected to the power grid. Hydrogen energy, as a secondary energy source, is currently an ideal alternative to fossil fuels. Using renewable energy to produce hydrogen is an important means to improve the efficiency of renewable energy utilization and achieve energy cascade utilization.

[0003] Proton exchange membrane electrolysis for hydrogen production is easier to integrate with renewable energy sources due to its fast dynamic response, ease of achieving high-pressure hydrogen storage, and suitability for high-voltage hydrogen storage. Meanwhile, solar energy currently suffers from low utilization efficiency, and photovoltaic electrolysis coupling is difficult, creating an urgent need for integrated systems with higher photovoltaic utilization and electrolysis efficiency to achieve energy storage and utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a solar electrolysis energy storage system and its control method, which aims to solve the problems of low efficiency and photovoltaic electrolysis coupling caused by heat accumulation in photovoltaic electrolysis systems by constructing a thermodynamic cycle system and specifying the control method, so as to achieve efficient conversion of renewable energy into electricity and hydrogen energy.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A solar electrolysis energy storage system includes a photovoltaic electrolysis control module, a water circulation module, and an energy storage module;

[0007] The photovoltaic electrolysis control module includes a photovoltaic system, a control system, and an electrolytic cell;

[0008] The water circulation module includes a heat exchanger, turbine, condenser, and water pump;

[0009] The energy storage module includes an inverter controller, an energy storage device, and a hydrogen storage device;

[0010] The water supply module is connected to a hot water pump, and the heat exchanger is connected to a turbine and a photovoltaic system. The turbine is connected to a condenser, an electrolyzer, and an inverter controller. The condenser and the electrolyzer are connected to a water pump, and the water pump is connected to a heat exchanger. The photovoltaic system is connected to an energy storage device through the inverter controller. Both the photovoltaic system and the energy storage device are connected to the control system. The hydrogen energy generated by the electrolyzer is stored through a hydrogen storage device.

[0011] Furthermore, the photovoltaic system is used for photoelectric and photothermal conversion, and the generated electrical energy is used as the input to the energy storage module and electrolytic cell. It also removes the heat accumulated in the photovoltaic system in a timely manner through forced heat exchange with the water circulation module.

[0012] Furthermore, the control system is used to set the working voltage and current of the electrolytic cell, the temperature and pressure of the liquid electrolyte flowing into the electrolytic cell through the water circulation module, set the number of series and parallel connections of the electrolytic cells, and control the energy storage module to select the storage of electrical energy and hydrogen energy.

[0013] Furthermore, the electrolytic cell is a proton exchange membrane electrolytic cell, and the unreacted liquid electrolyte in the electrolytic cell is transported through pipelines to a water pump for pressurization before entering the heat exchanger.

[0014] Furthermore, in the water circulation module, the heat exchanger is installed at the bottom of the photovoltaic cells of the photovoltaic system, and the heat exchanger, turbine, water pump and condenser constitute a thermodynamic cycle;

[0015] The water supply module provides liquid water, and the water pump pressurizes the liquid water before supplying it to the heat exchanger. The heat exchanger uses the circulating working fluid to exchange heat with the waste heat from the photovoltaic cells to convert the liquid water into superheated steam. The turbine uses the superheated steam to perform work, and the electrical energy converted from the work is stored in an energy storage device after voltage regulation by the inverter controller. Part of the steam generated after the work is performed flows into an electrolytic cell for electrolysis, and the remaining steam enters the condenser to form liquid water. This liquid water is then supplied to the heat exchanger by the water pump.

[0016] Furthermore, the inverter controller is used to regulate the voltage of the electrical energy generated by the photovoltaic system and the electrical energy generated by the turbine in the water circulation module and then store it using an energy storage device.

[0017] A control method for a solar electrolytic energy storage system includes:

[0018] Step 1: The control system records the irradiance, photovoltaic module temperature, and liquid water temperature of the photovoltaic system, and estimates the output power and photovoltaic cell efficiency P of the photovoltaic system. PV :

[0019] P PV =E PV ×A PV ×η m ×η pv

[0020]

[0021] In the formula: E PV It is the intensity of photovoltaic irradiance, A PV It is the irradiated area, η m It is the product of the photovoltaic module efficiency and the optical efficiency, η pv η0 is the photovoltaic cell efficiency; T is the photovoltaic cell efficiency at room temperature. WΔT and T0 represent the temperatures of the liquid water after being pressurized by the water pump, the photovoltaic cell temperature, and T, respectively. W Temperature difference, room temperature It is a corrected temperature coefficient, with a value ranging from -0.002 to -0.003;

[0022] Step 2: The control system compares whether the output power of the photovoltaic system meets the power requirements of the energy storage system. If so, the energy storage device of the energy storage system is used for storage after voltage regulation by the inverter controller; otherwise, proceed to step 3.

[0023] Step 3: Based on the requirements of the electrolysis voltage and current of a single electrolytic cell, the control system determines the number of electrolytic cells in operation and the series-parallel connection method according to the voltage and current output of the photovoltaic system at this time;

[0024] The open-circuit voltage and short-circuit current of a photovoltaic system are also known as the photovoltaic output voltage V. pv and photovoltaic output current I pv The operating voltage and current of a single electrolytic cell are V0 and I0, respectively. The number of cells connected in series and parallel are Series and Parallel, respectively. The total electrolysis voltage is V. ec and total electrolysis current I ec They are Series*V0 and Parallel*I0, respectively;

[0025] Initially, the number of electrolytic cells is set to 1, and then the cycle is performed:

[0026] 3-1 If the output voltage V of the photovoltaic system pv With the total electrolysis voltage V ec If the difference is greater than the electrolysis voltage V0 of a single electrolytic cell, connect an electrolytic cell Series+1 in series; otherwise, jump to 3-3.

[0027] 3-2 If the photovoltaic output current I is connected in series with the cells in 3-1, pv With the total electrolysis current I ec If the difference is greater than the electrolytic current I0 of the electrolytic cell, then another electrolytic cell Parallel+1 is connected in parallel; otherwise, the series-connected electrolytic cell Series-1 is canceled. After parallel connection, return to 3-1.

[0028] 3-3 Compare the output voltage V of the photovoltaic system pv The relative magnitude of V with the total electrolysis voltage Vec, if V pv ≤V ec If V pv >V ec When comparing the output current I of the photovoltaic system pv with I ec +I0's size, if I pv >I ecIf +I0, then connect one electrolytic cell in parallel (Parallel+1), and then return 3-1; otherwise, if the number of electrolytic cells in series is greater than 1, then subtract one electrolytic cell (Series-1) and end the loop; if the number of electrolytic cells in series is equal to 1, then end the loop directly.

[0029] After exiting the loop, the values ​​of Series and Parallel in the system are the number of electrolytic cells connected in series and parallel.

[0030] Step 4: Compare the polarization curves of the electrolytic cell at different temperatures and pressures with the current-voltage characteristic curves of the photovoltaic system to obtain the optimal electrolysis temperature and pressure, thereby achieving photovoltaic-electrolysis coupling;

[0031] Step 5: Connect the electrolytic cells in series and parallel according to the values ​​of series and parallel connection determined in Step 3, and control the inlet water temperature and pressure of the electrolytic cells using the water supply flow rate and pump working pressure based on the working pressure and working temperature obtained in Step 4.

[0032] Furthermore, the comparison of the polarization curves of the electrolytic cell at different temperatures and pressures with the current-voltage characteristic curves of the photovoltaic system to obtain the optimal electrolysis temperature and pressure includes:

[0033] Plot the polarization curves of the electrolytic cell at different temperatures and pressures and the volt-ampere characteristic curves of the photovoltaic system on the same graph. Select the polarization curve of the electrolytic cell that is closest to the maximum power point on the volt-ampere characteristic curve of the photovoltaic system, and observe the working pressure and working temperature of the polarization curve of the electrolytic cell to determine the optimal electrolysis temperature and pressure.

[0034] Furthermore, a magnetic control device is connected to the positive and negative poles of the electrolytic cell. The magnetic control device opens and closes the switch by sensing changes in the magnetic field under the control of electric power. When energized, the switch closes due to the opposite magnetic properties and connects to the electrolytic cell, thereby connecting the series and parallel of the electrolytic cell. The water supply module and water circulation module control the inlet water temperature and pressure of the electrolytic cell. The water pressure is increased by adjusting the working pressure of the water pump. When the temperature of the water vapor is still high after the turbine has done work, the water temperature is reduced by adjusting the water flow rate of the water supply module.

[0035] Compared with the prior art, the present invention has the following technical features:

[0036] This invention improves the utilization rate of photovoltaic power generation and enhances the electrolytic performance of the electrolytic cell by comprehensively utilizing photovoltaic and photothermal technologies. It also reduces the impact of the volatility of photovoltaic power generation on the electrolytic cell through dynamic control, thereby further improving the efficiency of photovoltaic power generation. Attached Figure Description

[0037] Figure 1 This is a block diagram of the overall structure of the system of the present invention;

[0038] Figure 2 This is a schematic diagram of the control flow of the present invention. Detailed Implementation

[0039] See Figure 1 This invention provides a solar electrolysis energy storage system, comprising: a photovoltaic electrolysis control module, a water circulation module, and an energy storage module, wherein:

[0040] 1. Photovoltaic electrolysis control module

[0041] The photovoltaic electrolysis control module is mainly used to realize the photothermal and hydrothermal cycle through the photovoltaic system, and to use the electrolysis cell to produce hydrogen by electrolysis, and to transmit the electrical energy and hydrogen energy to the energy storage module for storage.

[0042] like Figure 1 As shown, in this embodiment, the photovoltaic electrolysis control module includes three parts: a photovoltaic system, a control system, and an electrolytic cell. The photovoltaic system is used for photoelectric and photothermal conversion, and the generated electrical energy serves as the input to the energy storage module and the electrolytic cell. It also exchanges heat with the water circulation module in a timely manner to remove the heat accumulated in the photovoltaic system.

[0043] The control system is used to set the working voltage and current of the electrolytic cell, the temperature and pressure of the liquid electrolyte flowing into the electrolytic cell through the water circulation module, the number of series and parallel connections of the electrolytic cell, and to set the energy storage module to select the storage of electrical energy and hydrogen energy.

[0044] The electrolytic cell is a proton exchange membrane electrolytic cell. The unreacted liquid electrolyte in the electrolytic cell is transported again through pipelines to a water pump for pressurization before entering the heat exchanger.

[0045] 2. Water circulation module

[0046] The liquid water in the water circulation module is heated by the heat supplied by the photovoltaic system before being supplied to the electrolysis cell. The water circulation module includes a heat exchanger, a turbine, a water pump, and a condenser. The water supply module is connected to the hot water pump, the heat exchanger is connected to the turbine and the photovoltaic system in the photovoltaic electrolysis control module, the turbine is connected to the condenser, the electrolysis cell, and the inverter controller, and the condenser and the electrolysis cell are connected to the water pump.

[0047] In the water circulation module, the heat exchanger is installed at the bottom of the photovoltaic cells of the photovoltaic system. The heat exchanger, turbine, water pump, and condenser form a thermodynamic cycle. Liquid water supplied by the water supply module is pressurized by the water pump to lower the vaporization point of the water before being supplied to the heat exchanger. The heat exchanger uses the circulating working fluid to exchange heat with the waste heat of the photovoltaic cells to convert the liquid water into superheated steam. The superheated steam enters the turbine and performs work. The converted electrical energy is stored by the energy storage device in the energy storage module after the voltage is regulated by the inverter controller. The low-grade water vapor after the work is performed flows into the electrolytic cell for electrolysis, and the remaining water vapor enters the condenser to form liquid water. This liquid water is then supplied to the heat exchanger by the water pump. The circulating working fluid is a mixture of isopentane and pentafluoropropane.

[0048] In a specific implementation case, a water supply module provides circulating liquid water. Through an isentropic and isobaric process constructed by a heat exchanger, turbine, water pump, and condenser, the working fluid absorbs and releases heat. The heat exchanger transfers waste heat from the photovoltaic system to the liquid water, converting it into high-grade water vapor. This high-grade water vapor is then processed by the turbine into low-grade water vapor before flowing to the electrolytic cell for electrolysis to obtain hydrogen. Simultaneously, because the circulating working fluid transfers waste heat from the photovoltaic system to the liquid water via the heat exchanger, excess heat from the photovoltaic cells is carried away, thereby improving the energy storage efficiency of the photovoltaic cells.

[0049] 3. Energy storage module

[0050] The energy storage module is used to store the electrical energy and hydrogen energy generated by the photovoltaic electrolysis control module. The energy storage module consists of three parts: an inverter controller, an energy storage device, and a hydrogen storage device. Specifically: the inverter controller is used to regulate the voltage of the electrical energy generated by the photovoltaic system and the turbine in the water circulation module before storing it using the energy storage device; the hydrogen storage device is used to store the hydrogen produced by the electrolysis cell.

[0051] The control module utilizes photovoltaic characteristics for energy storage optimization and energy cascade utilization, and its implementation steps are as follows:

[0052] Step 1: The control system records the irradiance, module temperature, and liquid water temperature of the photovoltaic system, and approximates the output power and photovoltaic cell efficiency of the photovoltaic system using the following formula.

[0053] P PV =E PV ×A PV ×η m ×η pv

[0054]

[0055] In the formula: E PV It is the intensity of photovoltaic irradiance, A PV It is the irradiated area, ηm It is the product of the photovoltaic module efficiency and the optical efficiency, η pv η0 is the photovoltaic cell efficiency; T is the photovoltaic cell efficiency at room temperature. W ΔT and T0 represent the temperatures of the liquid water after being pressurized by the water pump, the photovoltaic cell temperature, and T, respectively. W Temperature difference, room temperature It is a corrected temperature coefficient, typically between -0.002 and -0.003.

[0056] Step 2: The control system compares whether the output power of the photovoltaic system meets the power requirements of the energy storage system. If so, the power storage of the battery is guaranteed first, and the energy is stored using the energy storage device of the energy storage system after voltage regulation by the inverter controller. Otherwise, proceed to step 3.

[0057] like Figure 2 As shown, in a specific implementation case, when the photovoltaic system output power P pv Greater than the set power P ref And the stable duration T is greater than the set time T. ref In this case, photovoltaic power can be directly stored through the energy storage module ESS. That is, when photovoltaic power generation is highly volatile, the energy storage efficiency is low, so hydrogen electrolysis is used in this situation; while when the volatility is low, it is used for energy storage.

[0058] Step 3: Based on the requirements of the electrolysis voltage and current of a single electrolytic cell, the control system determines the number of electrolytic cells in operation and the series-parallel connection method according to the voltage and current output of the photovoltaic system at this time.

[0059] like Figure 2 As shown in a specific implementation case, when the photovoltaic system's power generation cannot be directly stored, the photovoltaic system's output voltage is the main source of electrolytic energy. The open-circuit voltage and short-circuit current of the photovoltaic system are the photovoltaic output voltage V. pv and photovoltaic output current I pv The operating voltage and current of a single electrolytic cell are V0 and I0, respectively. The number of cells connected in series and parallel are Series and Parallel, respectively. The total electrolysis voltage is V. ec and total electrolysis current I ec They are Series*V0 and Parallel*I0, respectively;

[0060] Initially, the number of electrolytic cells is set to 1, and then the cycle is performed:

[0061] 3-1 If the output voltage V of the photovoltaic system pv With the total electrolysis voltage V ec If the difference is greater than the electrolysis voltage V0 of a single electrolytic cell, connect an electrolytic cell Series+1 in series; otherwise, jump to 3-3.

[0062] 3-2 If the photovoltaic output current I is connected in series with the cells in 3-1, pv With the total electrolysis current I ec If the difference is greater than the electrolytic current I0 of the electrolytic cell, then connect another electrolytic cell, Parallel+1, in parallel; otherwise, cancel the series connection of the electrolytic cells, Series-1. After parallel connection, return to 3-1. Series-1 is mainly because I... pv with I ec When the difference is less than I0, the number of electrolytic cells connected in series may become mismatched with the voltage of the common electrolytic cell. Reducing one electrolytic cell can help prevent electrolytic instability.

[0063] 3-3 Compare the output voltage V of the photovoltaic system pv The relative magnitude of V with the total electrolysis voltage Vec, if V pv ≤V ec If V pv >V ec When comparing the output current I of the photovoltaic system pv with I ec +I0's size, if I pv >I ec If +I0, then connect one electrolytic cell in parallel (Parallel+1), and then return 3-1; otherwise, if the number of electrolytic cells in series is greater than 1, then subtract one electrolytic cell (Series-1) and end the loop; if the number of electrolytic cells in series is equal to 1, then end the loop directly.

[0064] After exiting the loop, the values ​​of Series and Parallel in the system represent the number of electrolytic cells connected in series and parallel.

[0065] Step 4: Compare the polarization curves of the electrolytic cell at different temperatures and pressures with the current-voltage characteristic curves of the photovoltaic system to obtain the optimal electrolysis temperature and pressure, thereby achieving photovoltaic-electrolysis coupling.

[0066] The electrolysis voltage of a single electrolytic cell can be composed of the following three parts:

[0067] V cell =E ocv +V act +V ohm +V diff

[0068] In the formula: E ocv V act V ohm V diffThese are the open-circuit voltage, activation overpotential, ohmic overpotential, and diffusion overpotential of a single electrolytic cell. The open-circuit voltage, activation overpotential, and diffusion overpotential are affected by the electrolysis temperature, while the ohmic overpotential is affected by the water content of the proton exchange membrane; the water content of the membrane is thus changed by adjusting the activity of the liquid water through pressure regulation.

[0069] In a specific implementation case, the polarization curves of the electrolytic cell under different temperatures and pressures and the photovoltaic IV characteristic curves are plotted on the same graph. The polarization curve of the electrolytic cell that is closest to the maximum power point on the photovoltaic system's current-voltage characteristic curve is selected. The working pressure and working temperature of the electrolytic cell polarization curve are viewed, and the water pressure and temperature are adjusted in step 5.

[0070] Step 5: Connect the electrolytic cells in series and parallel according to the values ​​of series and parallel connection determined in Step 3, and control the inlet water temperature and pressure of the electrolytic cells using the water supply flow rate and pump working pressure based on the working pressure and working temperature obtained in Step 4.

[0071] In a specific implementation case, a magnetic control device can be connected to the positive and negative poles of the electrolytic cell. The magnetic control device can open and close the switch by sensing changes in the magnetic field under the control of electric current. When energized, the switch closes due to the opposite magnetic field, connecting to the electrolytic cell and thus connecting the series and parallel connections of the electrolytic cells. The inlet water temperature and pressure of the electrolytic cell are controlled by the water supply module and the water circulation module. The water pressure is increased by adjusting the working pressure of the water pump. If the temperature of the water vapor is still high after the turbine has done its work, the water temperature is reduced by adjusting the water flow rate of the water supply module.

[0072] The energy storage system and its control method can convert all electrical energy into hydrogen energy as needed, and the power regulation is mainly carried out by the control module based on system monitoring.

[0073] In a specific implementation case, if the demand for hydrogen energy is greater than that for electricity, the electrical energy stored in the energy storage device can be delivered to the electrolyzer through the control system, and the charging switch of the storage battery can be disconnected so that the electrical energy generated by the photovoltaic system can be used for electrolysis to produce hydrogen.

[0074] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A control method for a solar electrolytic energy storage system, characterized in that, The solar electrolysis energy storage system includes a photovoltaic electrolysis control module, a water circulation module, and an energy storage module; The photovoltaic electrolysis control module includes a photovoltaic system, a control system, and an electrolytic cell; The water circulation module includes a heat exchanger, turbine, condenser, and water pump; The energy storage module includes an inverter controller, an energy storage device, and a hydrogen storage device; The water supply module is connected to a water pump, and the heat exchanger is connected to a turbine and a photovoltaic system. The turbine is connected to a condenser, an electrolyzer, and an inverter controller. The condenser and the electrolyzer are connected to the water pump, and the water pump is connected to the heat exchanger. The photovoltaic system is connected to an energy storage device through the inverter controller. Both the photovoltaic system and the energy storage device are connected to the control system. The hydrogen energy generated by the electrolyzer is stored through a hydrogen storage device. The photovoltaic system is used for photoelectric and photothermal conversion. The generated electrical energy is used as the input of the energy storage module and electrolytic cell, and the water circulation module removes the heat accumulated in the photovoltaic system in a timely manner through forced heat exchange. The control system is used to set the working voltage and current of the electrolytic cell, the temperature and pressure of the liquid electrolyte flowing into the electrolytic cell through the water circulation module, set the number of series and parallel connections of the electrolytic cells, and control the energy storage module to select the storage of electrical energy and hydrogen energy. The electrolytic cell is a proton exchange membrane electrolytic cell. The unreacted liquid electrolyte in the electrolytic cell is transported through pipelines to a water pump for pressurization and then enters the heat exchanger. In the water circulation module, the heat exchanger is installed at the bottom of the photovoltaic cells of the photovoltaic system, and the heat exchanger, turbine, water pump and condenser constitute a thermodynamic cycle; The water supply module provides liquid water, and the water pump pressurizes the liquid water before supplying it to the heat exchanger. The heat exchanger uses the circulating working fluid to exchange heat with the waste heat from the photovoltaic cells to convert the liquid water into superheated steam. The turbine uses the superheated steam to do work, and the electrical energy converted after the work is done is stored using an energy storage device after the voltage is regulated by the inverter controller. The water vapor formed after the superheated steam does work flows into the electrolytic cell for electrolysis, and the other part enters the condenser to form liquid water. The liquid water is then supplied to the heat exchanger by the water pump. The inverter controller is used to regulate the voltage of the electrical energy generated by the photovoltaic system and the electrical energy generated by the turbine in the water circulation module and then store it using an energy storage device. Control methods include: Step 1: The control system records the irradiance, photovoltaic module temperature, and liquid water temperature of the photovoltaic system, and estimates the output power and photovoltaic cell efficiency of the photovoltaic system. : ； ； In the formula: It is the intensity of photovoltaic irradiance. It is the irradiated area. It is the product of the photovoltaic module efficiency and the optical efficiency. It refers to the efficiency of photovoltaic cells; This refers to the efficiency of photovoltaic cells at room temperature. These represent the temperatures of the liquid water after being pressurized by the water pump, the photovoltaic cell temperature, and... Temperature difference, room temperature This is the corrected temperature coefficient, with a value ranging from -0.002 to -0.

003. Step 2: The control system compares whether the output power of the photovoltaic system meets the power requirements of the energy storage system. If so, the energy storage device of the energy storage system is used for storage after voltage regulation by the inverter controller; otherwise, proceed to step 3. Step 3: Based on the requirements of the electrolysis voltage and current of a single electrolytic cell, the control system determines the number of electrolytic cells in operation and the series-parallel connection method according to the voltage and current output of the photovoltaic system at this time; The open-circuit voltage and short-circuit current of a photovoltaic system are also known as the photovoltaic output voltage V. pv and photovoltaic output current I pv The operating voltage and current of a single electrolytic cell are V0 and I0, respectively. The number of cells connected in series and parallel is Series and Parallel, respectively. The total electrolysis voltage is V. ec and total electrolysis current I ec These are Series* V0 and Parallel* I0, respectively; Initially, the number of electrolytic cells is set to 1, and then the cycle is performed: Step 3-1: If the difference between the output voltage Vpv of the photovoltaic system and the total electrolysis voltage Vec is greater than the electrolysis voltage V0 of a single electrolysis cell, connect an electrolysis cell Series+1 in series; otherwise, proceed to step 3-3. Step 3-2: If the difference between the photovoltaic output current Ipv and the total electrolysis current Iec after connecting the cells in series in Step 3-1 is greater than the electrolysis current I0 of the electrolysis cell, then connect another electrolysis cell Parallel+1 in parallel; otherwise, cancel the series electrolysis cell Series-1. After parallel connection, return to Step 3-1. Step 3-3: Compare the relative magnitudes of the photovoltaic system output voltage Vpv and the total electrolysis voltage Vec. If Vpv ≤ Vec, end the loop. If Vpv > Vec, compare the magnitudes of the photovoltaic system output current Ipv and Iec + I0. If Ipv > Iec + I0, connect one electrolytic cell (Parallel + 1) in parallel and return to step 3-1. Otherwise, if the number of electrolytic cells connected in series is greater than 1, subtract one electrolytic cell (Series - 1) and end the loop. If the number of electrolytic cells connected in series is equal to 1, end the loop directly. After exiting the loop, the values ​​of Series and Parallel in the system are the number of electrolytic cells connected in series and parallel. Step 4: Compare the polarization curves of the electrolytic cell at different temperatures and pressures with the current-voltage characteristic curves of the photovoltaic system to obtain the optimal electrolysis temperature and pressure, thereby achieving photovoltaic-electrolysis coupling; Step 5: Connect the electrolytic cells in series and parallel according to the values ​​of series and parallel connection determined in Step 3, and control the inlet water temperature and pressure of the electrolytic cells using the water supply flow rate and pump working pressure based on the working pressure and working temperature obtained in Step 4.

2. The control method for the solar electrolytic energy storage system according to claim 1, characterized in that, The step of comparing the polarization curves of the electrolytic cell at different temperatures and pressures with the current-voltage characteristic curves of the photovoltaic system to obtain the optimal electrolysis temperature and pressure includes: Plot the polarization curves of the electrolytic cell at different temperatures and pressures and the volt-ampere characteristic curves of the photovoltaic system on the same graph. Select the polarization curve of the electrolytic cell that is closest to the maximum power point on the volt-ampere characteristic curve of the photovoltaic system, and check the working pressure and working temperature of the polarization curve of the electrolytic cell as the optimal electrolysis temperature and pressure.

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