Renewable energy hydrogen energy storage system for closed-loop use

Abstract

The utility model provides a renewable energy hydrogen energy storage system for closed-loop use, which comprises a renewable energy power generation unit, a proton exchange membrane water electrolysis hydrogen production unit, a magnesium hydride hydrogen storage and release unit, a proton exchange membrane fuel cell power generation unit, a water storage unit and a heat supply system, the renewable energy power generation unit is electrically connected with the proton exchange membrane water electrolysis hydrogen production unit, and the proton exchange membrane water electrolysis hydrogen production unit, the magnesium hydride hydrogen storage and release unit and the proton exchange membrane fuel cell power generation unit are sequentially connected through a hydrogen conveying pipeline. The proton exchange membrane fuel cell power generation unit, the water storage unit and the proton exchange membrane water electrolysis hydrogen production unit are sequentially connected through water pipes, and the heat supply system is connected with the magnesium hydride hydrogen storage and release unit through a heat-conducting medium pipeline. The hydrogen energy storage system can recycle water generated by power generation of the proton exchange membrane fuel cell, the water is supplied to the proton exchange membrane to electrolyze water for hydrogen production, and a closed loop that water is generated by water electrolysis for hydrogen production and power generation and then recycled to electrolyzed water for use is formed.

Description

Technical Field

[0001] The utility model relates to hydrogen energy storage technology, in particular to a closed-loop renewable energy hydrogen energy storage system. Background Art

[0002] As wind and solar power generation increases, the amount of unused wind and solar power curtailed also increases, making it more difficult to absorb. By 2022, the curtailment rate in the Tibet Autonomous Region reached 20%, while in Qinghai, the rates were 7.3% and 8.9% respectively. This curtailment stems from the system's inability to support large-scale renewable energy development in the region due to its peak-shaving capacity. Curtailed wind and solar power can be used for long-term energy storage, storing it for use in unexpected power needs, such as power outages, balancing grid demand, or providing temporary power to businesses and services that cannot sustain power outages.

[0003] On the other hand, hydrogen energy storage technology, which has many advantages, has received widespread attention in recent years. The advantages of hydrogen energy storage include: (1) Long-term: Pumped hydropower storage can be used as long-term energy storage, but it is subject to geographical restrictions. Hydrogen energy storage is more suitable for long-term charging and discharging of more than 4 hours, and can complete seasonal transition power. The self-discharge rate of hydrogen energy storage is almost zero, and it can adapt to energy storage for more than 1 year without geographical restrictions; (2) Cross-regional: Hydrogen can be transported in a variety of ways and is not restricted by the power transmission and distribution network, thus achieving cross-regional peak regulation. Battery energy storage power stations are restricted by the power transmission and distribution network and are difficult to play a cross-regional peak regulation role.

[0004] Current renewable energy hydrogen storage technologies include: generating electricity from renewable energy, producing hydrogen through water electrolysis, storing the hydrogen, and releasing it for fuel cell power generation when electricity is needed. Compared to lithium battery storage, this storage technology offers longer storage durations, such as seasonal storage; it is not restricted by geographical location, compared to hydroelectric storage; and it is easier to deploy than flow battery storage.

[0005] In renewable energy hydrogen storage technologies, water electrolysis for hydrogen production, such as proton exchange membrane electrolysis, has high water requirements and requires pure water. Renewable energy-abundant areas, such as the Northwest, are often loess or desert areas, and water supply becomes a major problem for water electrolysis for hydrogen production. In addition, in renewable energy hydrogen storage technologies, after photovoltaic water electrolysis for hydrogen production, there is also a problem with the long-term storage of hydrogen. For long-term storage of hydrogen, high-pressure hydrogen storage can be used, but the hydrogen storage process requires hydrogen pressurization. The use of a hydrogen compressor is energy-consuming and usually requires two stages of pressure increase to 70MPa. Furthermore, when using hydrogen to generate electricity, the hydrogen needs to be reduced to 0.5MPa before it can be supplied to fuel cells for power generation. Pressurization and then decompression is a completely redundant process and has energy-consuming issues. For low-pressure hydrogen storage, room-temperature hydrogen storage materials can be used, such as AB5 (rare earth hydrogen storage alloy), AB2, AB (FeTi hydrogen storage alloy), or BCC hydrogen storage alloy, which can store and release hydrogen at room temperature. However, these hydrogen storage alloys have problems to varying degrees, such as low hydrogen storage capacity, limited material resources, and high costs. Utility Model Content

[0006] The purpose of this utility model is to address the problems existing in current renewable energy hydrogen storage technology by proposing a closed-loop renewable energy hydrogen storage system. This system recycles water generated by proton exchange membrane fuel cells for use in proton exchange membrane water electrolysis to produce hydrogen. This forms a closed-loop system in which water electrolysis produces hydrogen, electricity is generated to produce water, and water is recycled for use in water electrolysis. This closed-loop renewable energy hydrogen storage system is not restricted by water sources and can operate independently in a closed-loop storage / power generation operation in the field.

[0007] It should be noted that, in the present utility model, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, as well as closed-ended "composed of", "composed of" and similar meanings.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a closed-loop renewable energy hydrogen storage system, comprising a renewable energy power generation unit, a proton exchange membrane water electrolysis hydrogen production unit, a magnesium hydride hydrogen storage and desorption unit, a proton exchange membrane fuel cell power generation unit, a water storage unit and a heating system, wherein the renewable energy power generation unit is electrically connected to the proton exchange membrane water electrolysis hydrogen production unit, the proton exchange membrane water electrolysis hydrogen production unit, the magnesium hydride hydrogen storage and desorption unit and the proton exchange membrane fuel cell power generation unit are connected in sequence through a hydrogen transmission pipeline, the proton exchange membrane fuel cell power generation unit, the water storage unit and the proton exchange membrane water electrolysis hydrogen production unit are connected in sequence through a water pipe, and the heating system is connected to the magnesium hydride hydrogen storage and desorption unit through a heat transfer medium pipeline.

[0009] Furthermore, the renewable energy power generation unit is a photovoltaic power generation device, a wind power generation device or a biomass power generation device.

[0010] Furthermore, the PEM electrolysis unit and the PEM fuel cell power generation unit can be a single device. The reactions within the PEM electrolysis unit and the PEM fuel cell power generation unit are reversible, so the same device can perform both functions, reducing system costs.

[0011] Furthermore, the magnesium hydride hydrogen storage and desorption unit is filled with magnesium hydride. The use of magnesium hydride to store hydrogen has the advantages of high hydrogen storage density (7.6wt.%), large hydrogen storage capacity, and stability. The working pressure of magnesium hydride when storing hydrogen or releasing hydrogen is low pressure (can be less than 12 bar), and the working pressure is easy to match with the hydrogen production unit and the proton exchange membrane, that is, no pressure pump is required and the pipeline container can be designed for low pressure. Both the storage and desorption of magnesium hydride require high temperature (180℃-400℃), and the heating system of the utility model (such as a concentrating solar collector) can provide the working temperature required for magnesium hydride to store and desorb hydrogen. The hydrogen storage material of the utility model is magnesium hydride, which has the advantages of low cost and long storage time compared with traditional hydrogen storage materials.

[0012] Furthermore, the proton exchange membrane fuel cell power generation unit is a static drainage fuel cell, and the water recovery rate of the static drainage is as high as 99%.

[0013] Furthermore, the water storage unit includes a water storage container, a valve, and a water pump. The water storage container is provided with a valve that is connected to the water pump via a pipeline. The air side of the proton exchange membrane fuel cell produces water through condensation. This water is then injected into the water storage container by controlling the gas pressure at the hydrogen and oxygen terminals and the opening and closing of the valve. The water in the water storage container is then injected into the proton exchange membrane water electrolysis hydrogen production unit via the water pump and the opening and closing of the valve, providing the water required for hydrogen production by electrolysis.

[0014] Furthermore, the heating system includes a concentrating solar thermal collector and a heat storage device, which are connected by a heat transfer medium pipeline. In areas where wind and solar power are curtailed, the concentrating solar thermal collector can be used when there is sufficient sunlight to provide the operating temperature (280°C-400°C) required for magnesium hydride to store and release hydrogen.

[0015] Furthermore, the concentrating solar collector and the magnesium hydride hydrogen storage and desorption unit are connected via a heat-conducting medium pipeline;

[0016] And / or the heat storage device and the magnesium hydride hydrogen storage and dehydrogenation unit are connected via a heat conducting medium pipeline.

[0017] Furthermore, the heat storage device can store heat from a concentrated solar collector and provide heat energy to the magnesium hydride hydrogen storage and dehydrogenation unit when it needs to release hydrogen. The heat storage device is a thermochemical heat storage device that uses a reversible CaCO3 / CaO reaction.

[0018] Furthermore, the heat transfer medium is a heat energy exchange medium between the concentrated solar thermal collector, the heat storage device and the magnesium hydride hydrogen storage and desorption unit. The heat transfer medium of the present invention is molten salt.

[0019] Furthermore, the molten salt is preferably a binary molten salt, which includes 60 wt % sodium nitrate and 40 wt % potassium nitrate, and has a maximum operating temperature of 600° C., which is very suitable for the operating temperature of magnesium hydride for storing and releasing hydrogen.

[0020] The working principle of the closed-loop renewable energy hydrogen storage system is as follows:

[0021] Renewable energy storage: the renewable energy power generation unit generates electricity to supply the proton exchange membrane water electrolysis hydrogen production unit to produce hydrogen, and the hydrogen produced by the proton exchange membrane water electrolysis hydrogen production unit is transported to the magnesium hydride hydrogen storage and desorption unit for storage;

[0022] Storage and release of hydrogen: the heat supply system provides the heat energy required by the magnesium hydride hydrogen storage and dehydrogenation unit to store or release hydrogen;

[0023] Energy storage and power generation: the hydrogen released by the magnesium hydride hydrogen storage and dehydrogenation unit is supplied to the proton exchange membrane fuel cell power generation unit for power generation;

[0024] Water resources are recycled. The water generated by the proton exchange membrane fuel cell power generation unit is collected and transported to the water storage unit for storage. The water stored in the water storage unit can be supplied to the proton exchange membrane water electrolysis hydrogen production unit to produce hydrogen.

[0025] Furthermore, the concentrating solar collector in the heating system provides the heat energy required for the magnesium hydride hydrogen storage and dehydrogenation unit to store or release hydrogen;

[0026] And / or the heat storage device in the heat supply system provides the thermal energy required for the magnesium hydride hydrogen storage and dehydrogenation unit to store hydrogen or release hydrogen.

[0027] Compared with the existing technology, the closed-loop renewable energy hydrogen storage system of this utility model has the following advantages:

[0028] 1) The present invention solves the problem of water source for hydrogen production by electrolysis through the recycling of water resources. The proton exchange membrane fuel cell power generation unit of the present invention is a static drainage fuel cell. The static drainage mainly refers to drainage by capillary action, pressure difference, concentration, and gravity. The static drainage helps to increase the system's water recovery rate to 99%. Compared with dynamic drainage in terms of battery performance, static drainage: at high current density (>500mA / cm2), the water generation rate of the static structure is higher than the water discharge rate. The present invention recycles the water generated by the proton exchange membrane fuel cell power generation and uses it to supply the proton exchange membrane water electrolysis to produce hydrogen, thus forming a closed loop of water electrolysis to produce hydrogen, power generation to generate water, and then recycling water for electrolysis. Moreover, the water generated by the proton exchange membrane fuel cell power generation is pure water and can be used for hydrogen production by proton exchange membrane water electrolysis without filtering or purification. For the small amount of water loss in the hydrogen energy storage system of the present invention, the water required for system operation can be guaranteed by pre-storing a certain amount of water in the water storage unit or adding a water replenishment device. The renewable energy hydrogen storage system used in a closed loop of the utility model is easy to deploy and can independently operate in a closed loop to store energy / generate electricity in the wild, eliminating the problem of finding a water source.

[0029] 2) The present invention uses magnesium hydride hydrogen storage material to store hydrogen, which can achieve long-term storage of hydrogen. The principle of magnesium hydride (MgH2) hydrogen storage: Under certain temperature and pressure conditions, magnesium can react with hydrogen to form magnesium hydride, and this reaction is reversible; when magnesium hydride is heated, it can decompose and release the stored hydrogen. Because magnesium hydride has a high volume hydrogen storage density (110g / L) and mass hydrogen storage density (7.6wt.%), and a low platform hydrogen pressure (<1MPa), it provides a convenient solution for the pressure of hydrogen production by electrolysis of water and the hydrogen pressure used in fuel cell power generation, that is, no hydrogen pressurization process is required. Magnesium is one of the most abundant light metal elements on the earth. Magnesium reserves are abundant, with an abundance of 2% in the earth's crust. China is the country with the richest magnesium resources in the world. Magnesium resource ore types are complete and widely distributed, and its reserves and production are both ranked first in the world. Therefore, magnesium hydride hydrogen storage materials have the advantages of low cost and long storage time.

[0030] 3) The present invention adopts a concentrating solar thermal collector to provide the working temperature (280°C-400°C) required for magnesium hydride to store and release hydrogen. The concentrating solar thermal collector uses molten salt as a heat transfer medium. The molten salt has a high working temperature and can overcome the problem that the working temperature is not suitable for magnesium hydride to store and release hydrogen when thermal oil is used as the heat transfer medium. The working temperature of thermal oil is up to 400°C, and there is a temperature gradient, so that the working temperature of most areas in a large-scale magnesium hydride hydrogen storage system will be lower than 400°C, and hydrogen cannot be stored or released. The molten salt of the present invention is preferably a binary molten salt. The binary molten salt containing 60wt% sodium nitrate and 40wt% potassium nitrate has a melting point of 220°C and a maximum working temperature of 600°C, which is very suitable for the working temperature of magnesium hydride to store and release hydrogen.

[0031] 4) The hydrogen energy storage system of the present invention can achieve long-term heat storage. The heat storage device of the present invention is a thermochemical heat storage device using the reversible calcination / carbonation reaction of CaCO3 / CaO. The thermochemical heat storage technology of the reversible calcination / carbonation reaction of CaCO3 / CaO: CaCO3 absorbs solar thermal energy and is decomposed into CaO and CO2. The released CO2 is compressed and stored, and CaO is stored at room temperature and pressure. This is a thermal energy storage process; CaO and CO2 are reacted in a carbonation reactor to form CaCO3, which is an exothermic reaction. This is a thermal energy release process. The reversible calcination / carbonation reaction of CaCO3 / CaO has a high exothermic temperature (650℃~1000℃), which is suitable for the release of hydrogen from magnesium hydride. This calcium-based material has the advantages of wide distribution, low price and good compatibility with the CO2 cycle, and can achieve long-term heat storage in concentrating solar collectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of a renewable energy hydrogen storage system for closed-loop use. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0034] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two elements or an interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly specified and specifically limited. The disclosure below provides many different implementation methods or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application.

[0035] Example 1

[0036] This embodiment discloses a closed-loop renewable energy hydrogen storage system, such as Figure 1As shown, it includes a renewable energy power generation unit 1, a proton exchange membrane water electrolysis hydrogen production unit 2, a magnesium hydride hydrogen storage and dehydrogenation unit 3, a proton exchange membrane fuel cell power generation unit 4, a water storage unit 5 and a heating system.

[0037] The renewable energy power generation unit 1 is electrically connected to the proton exchange membrane water electrolysis hydrogen production unit 2 by an electric wire. The proton exchange membrane water electrolysis hydrogen production unit 2 uses the electric energy provided by the renewable energy power generation unit 1 to electrolyze water to produce hydrogen. The renewable energy power generation unit 1 is a photovoltaic power generation device, a wind power generation device, or a biomass power generation device.

[0038] Described proton exchange membrane electrolysis water production hydrogen unit 2, magnesium hydride hydrogen storage and dehydrogenation unit 3 and proton exchange membrane fuel cell power generation unit 4 are connected in sequence by hydrogen delivery pipeline.The hydrogen (pressure can reach 15-25bar) that described proton exchange membrane electrolysis water production hydrogen unit 2 electrolysis water produces can be transported to magnesium hydride hydrogen storage and dehydrogenation unit 3 via pressure regulating valve and hydrogen pipeline and stored.When there is power demand (such as cross-season adjustment), magnesium hydride hydrogen storage and dehydrogenation unit 3 can discharge the hydrogen stored (this moment hydrogen pressure 8-12bar), provides hydrogen to proton exchange membrane fuel cell power generation unit 4 via pressure regulating valve and hydrogen pipeline to generate electricity, namely completes renewable energy power generation, to cross-season reuse.

[0039] The proton exchange membrane water electrolysis hydrogen production unit 2 and the proton exchange membrane fuel cell power generation unit 3 can be the same set of devices. The magnesium hydride hydrogen storage and dehydrogenation unit 3 is filled with magnesium hydride. The hydrogen storage material of this embodiment is magnesium hydride, which has the advantages of low cost and long storage time compared with traditional hydrogen storage materials. The proton exchange membrane fuel cell power generation unit 4 is a static drainage fuel cell. The static drainage mainly refers to drainage by relying on capillary, pressure difference, concentration and gravity. The water recovery rate of the static drainage is as high as 99%. Compared with dynamic drainage in terms of battery performance: high current density (>500mA / cm 2 ), the water generation rate of the static structure is higher than the water discharge rate.

[0040] The proton exchange membrane fuel cell power generation unit 4, the water storage unit 5 and the proton exchange membrane water electrolysis hydrogen production unit 2 are connected in sequence through water pipes. The water generated by the proton exchange membrane fuel cell power generation unit 4 during power generation can be injected into the water storage unit 5 through the pressure of hydrogen and air. The stored water can be supplied to the proton exchange membrane water electrolysis hydrogen production unit 2 for hydrogen production next time through a water pump and a water pipe. The water generated by the next power generation can be recycled for use in proton exchange membrane water electrolysis hydrogen production, thus forming a closed-loop use of water.

[0041] The heating system is connected to the magnesium hydride storage and degassing unit 3 via a heat transfer medium pipeline. The heating system can provide the heat energy required for hydrogen storage and release in the magnesium hydride. The heating system of this embodiment includes a concentrating solar thermal collector 6 and a heat storage device 7, which are connected via a heat transfer medium pipeline. The concentrating solar thermal collector 6 is connected to the magnesium hydride storage and degassing unit 3 via a heat transfer medium pipeline; the heat storage device 7 is also connected to the magnesium hydride storage and degassing unit 3 via a heat transfer medium pipeline.

[0042] The concentrating solar thermal collector 6 utilizes reflectors and lenses to redirect sunlight and focus it onto a receiver, thereby collecting and supplying heat. In areas with curtailed wind and solar power, concentrating solar thermal collectors can be used to maintain the required operating temperature (280°C-400°C) for the magnesium hydride storage and decomposition unit 3 when sufficient sunlight is available.

[0043] The heat storage device 7 can store heat from the concentrating solar collector 6 and provide heat energy to the magnesium hydride hydrogen storage and dehydrogenation unit 3 when it needs to release hydrogen. The heat storage device is a thermochemical heat storage device that uses a reversible CaCO3 / CaO reaction.

[0044] The concentrating solar collector 6 provides heat energy to the heat storage device 7. The heat storage device 7 has CaCO3 that absorbs solar heat energy and is decomposed into CaO and CO2. The released CO2 is compressed and stored, and CaO is stored at room temperature and pressure. This is thermal energy storage; when magnesium hydride releases hydrogen, the heat storage device 7 converts CaO and CO2 into CaCO3 in the carbonation reactor, and at the same time releases heat energy to supply the heat energy required for magnesium hydride to release hydrogen.

[0045] The heat transfer medium is a heat energy exchange medium between the concentrating solar collector 6, the magnesium hydride hydrogen storage and decomposition unit 3, and the heat storage device 7. In this embodiment, the heat transfer medium is a binary molten salt comprising 60 wt% sodium nitrate and 40 wt% potassium nitrate, with a maximum operating temperature of 600°C, which is very suitable for the operating temperature of magnesium hydride hydrogen storage and decomposition.

[0046] This embodiment uses proton exchange membrane electrolysis to produce hydrogen. The hydrogen is stored by magnesium metal to form magnesium hydride. When electricity is needed, the magnesium hydride releases the hydrogen to the proton exchange membrane fuel cell to generate electricity. The water generated by the electricity is recovered and used for proton exchange membrane electrolysis to produce hydrogen, thus forming a closed-loop use of water. At the same time, the hydrogen stored and released by magnesium hydride is provided by the heating system to provide the required heat energy.

[0047] The working steps of the closed-loop renewable energy hydrogen storage system are as follows:

[0048] Renewable energy storage: 500kW photovoltaic power generation unit generates electricity to supply 500kW proton exchange membrane water electrolysis hydrogen production unit 2 with a hydrogen production rate of 1200L / min and a pressure of 10bar, continuously for 4 hours / day for three months. The total hydrogen volume is 2000kg, which is transported through the hydrogen pipeline to the 50-ton magnesium hydride hydrogen storage and dehydrogenation unit 3 for storage;

[0049] After a three-month period, 2,000 kg of hydrogen (equivalent to 30,000 kWh of electricity) can be released through magnesium hydride. The concentrated solar collectors in the heating system provide the heat required for the magnesium hydride storage and release units to store or release hydrogen, maintaining the system's operating temperature between 280°C and 400°C.

[0050] Energy storage and power generation: the hydrogen released by the magnesium hydride hydrogen storage and dehydrogenation unit 3 is supplied to the proton exchange membrane fuel cell power generation unit 4 for power generation;

[0051] Water resources are recycled. The water generated by the proton exchange membrane fuel cell power generation unit 4 is transported to the water storage unit 5 for storage; the water stored in the water storage unit 5 is supplied to the proton exchange membrane water electrolysis hydrogen production unit 2 for hydrogen production using a water pump. The proton exchange membrane fuel cell power generation unit of this embodiment is a static drainage fuel cell. The static drainage mainly refers to drainage by capillary, pressure difference, concentration and gravity. The static drainage is conducive to increasing the system's water recovery rate to 99%. This embodiment recycles the water generated by the proton exchange membrane fuel cell power generation and uses it to supply the proton exchange membrane water electrolysis hydrogen production, thus forming a closed loop of water electrolysis hydrogen production, power generation to generate water, and then recycling it for electrolysis water use. Moreover, the water generated by the proton exchange membrane fuel cell power generation is pure water and can be used for proton exchange membrane water electrolysis hydrogen production without filtering or purification.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A closed-loop renewable energy hydrogen storage system, characterized in that: The invention comprises a renewable energy power generation unit (1), a proton exchange membrane water electrolysis hydrogen production unit (2), a magnesium hydride hydrogen storage and desorption unit (3), a proton exchange membrane fuel cell power generation unit (4), a water storage unit (5) and a heat supply system; the renewable energy power generation unit (1) is electrically connected to the proton exchange membrane water electrolysis hydrogen production unit (2); the proton exchange membrane water electrolysis hydrogen production unit (2), the magnesium hydride hydrogen storage and desorption unit (3) and the proton exchange membrane fuel cell power generation unit (4) are connected in sequence through a hydrogen transmission pipeline; the proton exchange membrane fuel cell power generation unit (4), the water storage unit (5) and the proton exchange membrane water electrolysis hydrogen production unit (2) are connected in sequence through a water pipe; and the heat supply system is connected to the magnesium hydride hydrogen storage and desorption unit (3) through a heat transfer medium pipeline.

2. The closed-loop renewable energy hydrogen storage system according to claim 1 is characterized in that: The renewable energy power generation unit (1) is a photovoltaic power generation device, a wind power generation device or a biomass power generation device.

3. The closed-loop renewable energy hydrogen storage system according to claim 1 is characterized in that: The magnesium hydride hydrogen storage and dehydrogenation unit (3) is filled with magnesium hydride.

4. The closed-loop renewable energy hydrogen storage system according to claim 1 is characterized in that: The proton exchange membrane fuel cell power generation unit (4) is a static drainage fuel cell.

5. The closed-loop renewable energy hydrogen storage system according to claim 1 is characterized in that: The water storage unit (5) comprises a water storage container, a valve and a water pump. The water storage container is provided with a valve, and the valve is connected to the water pump through a pipeline.

6. The closed-loop renewable energy hydrogen storage system according to claim 1 is characterized in that: The heat supply system comprises a concentrating solar heat collector (6) and a heat storage device (7), wherein the concentrating solar heat collector (6) and the heat storage device (7) are connected via a heat-conducting medium pipeline.

7. The closed-loop renewable energy hydrogen storage system according to claim 6 is characterized in that: The concentrating solar collector (6) and the magnesium hydride hydrogen storage and dehydrogenation unit (3) are connected via a heat-conducting medium pipeline; And / or the heat storage device (7) and the magnesium hydride hydrogen storage and dehydrogenation unit (3) are connected via a heat-conducting medium pipeline.

8. The closed-loop renewable energy hydrogen storage system according to claim 6 is characterized in that: The heat storage device (7) is a thermochemical heat storage device using a reversible reaction of CaCO3 / CaO.

9. The closed-loop renewable energy hydrogen storage system according to any one of claims 1 to 8, characterized in that: The heat conducting medium is molten salt.

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