Island multi-energy integrated light heat and power cogeneration system

Abstract

The invention discloses an island multi-energy integrated light heat and power cogeneration system, relates to the technical field of new energy utilization, and solves the problem of electricity, heat and fresh water supply under the conditions that an island is relatively closed and resources are deficient by utilizing rich renewable energy sources of the island, so that energy waste is reduced to the maximum extent, and the utilization rate of clean energy is improved. The system comprises a multi-energy integrated power generation module, a water electrolysis hydrogen production module, a combined heat and power supply module based on hydrogen energy and a multi-stage flash evaporation seawater desalination module based on solar photo-thermal, and offshore wind energy, solar energy, wave energy and a fuel cell technology are fused to cope with energy challenges in island regions. By introducing a fuel cell, a heat pump technology and a multi-stage flash evaporation seawater desalination technology, not only can electric power be provided, but also heat energy for heating and fresh water can be produced, and meanwhile, the system has good performance in the aspect of quick response starting through utilization and redistribution of waste heat of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy utilization, and particularly relates to a sea-island multi-energy integrated combined heat and power supply system. BACKGROUND

[0002] With the increasing environmental problems and energy security issues, energy development and utilization play a crucial role in modern society, aiming to address the increasingly urgent environmental problems and energy security challenges. The use of traditional fossil fuels has led to air pollution and greenhouse gas emissions, threatening the global ecological balance. In this context, the development and utilization of new energy has become one of the key strategies to promote sustainable development.

[0003] The development of islands requires safe, reliable electricity and sufficient water resources as a guarantee. However, isolated island areas, due to geographical location and resource constraints, their energy supply usually relies on imported fossil fuels, which may lead to instability of energy security and supply. At the same time, the use of traditional fossil fuels (such as coal, oil and natural gas) to generate electricity will release a large amount of carbon dioxide (CO2) and other harmful gases, causing air pollution and greenhouse gas emissions, exacerbating climate change. In order to achieve sustainable development in these regions, it is particularly urgent to develop innovative energy solutions.

[0004] Islands are usually located in marine environments and have abundant solar, wind and wave energy resources. Efficient use of these energy resources can provide stable electricity, heat and fresh water for islands in a cleaner way, reducing dependence on external energy, while promoting the balance of marine ecology.

[0005] Hydrogen is considered a clean energy with great development potential, which can be used as a transportation fuel in fuel cell vehicles or hydrogen internal combustion engine vehicles to meet the clean energy needs of road transportation on islands. In addition, hydrogen can also produce heat energy in the combustion process for heating or refrigeration systems to meet the temperature comfort needs of residents and facilities on the island. There are various technical paths for hydrogen production, among which the technology of using PEM electrolyzer to electrolyze water is widely favored due to its high efficiency, fast response, low operating temperature, small space occupation, high purity of hydrogen produced, and integration. Proton exchange membrane fuel cell is a high-efficiency, environmentally friendly energy conversion technology that is gradually attracting widespread attention. Its basic working principle is to convert hydrogen and oxygen into electrical energy in an electrochemical reaction, with the only emission being water vapor, which is pollution-free and zero-emission. This makes fuel cells an important choice to replace traditional combustion methods, providing a new way for energy transformation and environmental protection. At the same time, in the island scenario, based on the heat generated during the operation of the fuel cell, heat energy can be utilized through heat storage tanks and heat pumps.

[0006] Besides the thermal power supply, fresh water plays a key role in the survival and sustainable development of island communities. For island application scenarios, the most suitable method for long-term fresh water supply is seawater desalination. From a broad classification, it is mainly divided into two categories: distillation method (thermal method) and membrane method. Among them, the low-temperature multi-effect distillation method, multi-stage flash distillation method and reverse osmosis membrane method are the global mainstream technologies. Generally speaking, the low-temperature multi-effect distillation method has the advantages of energy saving, low seawater pretreatment requirement and high quality of desalination water; the reverse osmosis membrane method has the advantages of low investment and low energy consumption, but has a higher requirement for seawater pretreatment; the multi-stage flash distillation method has advantages in technology maturity, reliable operation and large device output, but has a higher energy consumption. Given the high salinity of seawater on islands and the abundance of wind, light and wave energy, the multi-stage flash distillation method is more suitable for seawater desalination under island conditions.

[0007] Currently, there are many patent applications that attempt to design energy supply systems for islands. For example, the invention patent CN114784861A discloses a "system and method for using offshore renewable energy for island water, electricity and heating supply" which uses offshore renewable energy to generate electricity and applies it to water, electricity and heating combined supply. The core technology of this invention is to use the fluctuating power generated by offshore renewable energy to electrolyze fresh water to generate hydrogen, then use the hydrogen to react with carbon dioxide to generate hydrocarbon fuel, and then use the fuel generator to generate electricity again, and use the waste heat in the process of generating electricity to provide heating. Although this invention is clear, the intermediate links in the process of preparing hydrocarbon fuel are numerous, which can easily cause energy waste. For example, the invention patent CN114640127A discloses a "comprehensive energy supply device suitable for islands" which designs a comprehensive energy supply device including various power generation equipment and seawater desalination equipment to meet the demand for electricity and fresh water for island development. The core technology is to use renewable energy to generate electricity first, and use diesel generators to generate electricity when the demand for electricity is large, and use electricity for water and heat combined supply. Although this invention is clear, it still cannot get rid of the dependence on traditional fuels in island areas because it needs to use diesel generators to generate electricity, and a large amount of waste heat generated by fuel cells is not utilized, causing energy waste. SUMMARY

[0008] In this context, the present invention proposes a multi-energy integrated fresh-heat-electricity combined supply system for islands, which aims to utilize the abundant renewable energy on islands to solve the problems of electricity, heat and fresh water supply in the relatively closed and resource-poor conditions on islands, thereby minimizing energy waste and improving the utilization rate of clean energy.

[0009] The present invention proposes a multi-energy integrated fresh-heat-electricity combined supply system for islands, which includes: a multi-energy integrated power generation module, an electrolytic water hydrogen production module, a heat and electricity combined supply module based on hydrogen energy, and a multi-stage flash seawater desalination module based on solar photothermal energy, wherein:

[0010] Multi-energy integrated power generation module: convert offshore solar, wind and wave energy into electricity through an integrated energy conversion device and store it through energy storage equipment;

[0011] Further, the integrated energy conversion device includes photovoltaic power generation equipment, wind turbine units and wave energy generator units. The photovoltaic power generation equipment selects high-efficiency and durable solar photovoltaic panels, such as monocrystalline silicon or polycrystalline silicon solar panels. These solar panels have good durability and performance in offshore environments. Adjustable angle supports can be used during installation to make optimal adjustments according to the angle of the sun. The wind turbine unit selects a vertical axis wind turbine suitable for offshore environments. Vertical axis wind turbines can produce good results in different wind directions, and are also more suitable for harsh offshore weather conditions. Ensure that the blade design of the wind turbine can remain stable at high wind speeds to avoid damage. Wave energy generators are used to capture wave energy. A wave energy device based on the float or swing arm principle can be selected. These devices can convert the up-and-down motion of the sea waves into mechanical energy, which is then converted into electrical energy by the generator.

[0012] Further, the electrical energy output of photovoltaic, wind and wave energy is integrated into an electrical energy storage system, such as a lithium ion battery storage system. To balance energy fluctuations and maintain stable power output. At the same time, in order to realize the coordination and optimization of the whole system, the intelligent controller monitors the output of different energy sources for electrical energy, and adjusts and distributes according to the demand, to ensure that the supply of electricity, heat and fresh water can always meet the needs of the island community.

[0013] Electrolytic water hydrogen production module: uses a proton exchange membrane electrolyzer as a hydrogen production device. In the system, the anode of the energy storage system is connected to the anode of the electrolyzer, and the cathode is connected to the cathode of the electrolyzer. The source of water for electrolysis is water in the fresh water tank after deionization, filtration, degassing and other operations. Electrolysis decomposes water into hydrogen and oxygen through an electrolysis reaction. The generated hydrogen and oxygen are released from the electrolyzer and separated by a gas-water separation device. The hydrogen (oxygen) is purified and compressed and stored in a high-pressure hydrogen storage tank (oxygen storage tank) or directly used for application.

[0014] Further, the oxygen storage tank uses a high-pressure gas cylinder, and the high-pressure hydrogen storage tank uses a metal compound hydrogen storage tank. The gas flow direction of hydrogen and oxygen is controlled by a gas flow meter, a pressure gauge and a controller.

[0015] Further, in order to maintain the stability and efficiency of the electrolysis process, appropriate electrolysis load control is required, and the hydrogen-based cogeneration module provides certain heat support for its reaction to run the PEM electrolyzer at the best operating point, which will help to improve the hydrogen production efficiency and make the system run in the best state.

[0016] Further, hot water is delivered from the hydrogen-based combined heat and power module to the electrolyzer to provide heat for the electrolysis process.

[0017] The hydrogen-based combined heat and power module includes a fuel cell module, a water source heat pump module, and a hydrogen combustion heat exchanger module. Stored hydrogen gas is supplied from the hydrogen storage tank to the fuel cell for electrochemical reaction to generate electricity and heat. In the electrochemical reaction, hydrogen gas reacts with oxygen at the anode of the fuel cell to generate electricity and heat. Electrons flow through the external circuit to power, while protons pass through the proton exchange membrane to the cathode, combine with oxygen and electrons to form water, releasing heat. The heat generated from the fuel cell is recovered and upgraded by the heat pump, which is used for heating, providing hot water or other required heat energy. Part of the hydrogen gas is combusted through the hydrogen combustion heat exchanger to generate additional heat energy, which is supplied to the heat pump.

[0018] The fuel cell unit is composed of multiple proton exchange membrane fuel cells with a rated power of 130 kW and a rated voltage of 700 V arranged in parallel to form a stack. Each stack is provided with gas inlets and outlets and cooling water inlets and outlets to receive hydrogen and oxygen, forming a liquid-cooled heat exchange cycle. The generated electricity is fed into the AC power grid via a DC-AC inverter device to supply the load. The anode gas outlet of the stack is configured with a gas pump and a gas-water separator to transport excess reaction gas back to the gas inlet.

[0019] The fuel cell and the heat pump system constitute a cooling water circulation and waste heat utilization system. The waste heat generated by the fuel cell stack is transferred to the heat exchanger through the internal circulating cooling water, and then to the circulating cooling working medium of the water source heat pump through the heat exchanger, realizing the cooling of the fuel cell. The heat pump absorbs heat and redistributes it to achieve heating.

[0020] The water source heat pump module includes an evaporator, a compressor, a condenser, and an expansion valve. The refrigerant changes state to achieve heat energy upgrading and transfer. First, in the evaporator, the refrigerant changes from liquid to gas, absorbing heat from the environment to lower the ambient temperature. Then, through the compressor, the gaseous refrigerant is compressed into high-pressure high-temperature gas, and the internal heat energy gradually increases. In the condenser, the high-temperature gaseous refrigerant releases heat, transferring the upgraded heat energy. Finally, through the expansion valve, the high-pressure refrigerant enters the evaporator, the pressure drops sharply, and the refrigerant reverts to low-pressure gas, starting to absorb heat, and the cycle continues.

[0021] The circulating working medium of the water source heat pump is R134a.

[0022] When the fuel cell is cold-starting, the hydrogen combustion heat exchanger can burn part of the hydrogen to generate heat energy, which is used to heat the fuel cell and the system, thereby facilitating rapid cold-starting. When the user's demand for heat is large and the fuel cell's waste heat is insufficient, additional heat can also be provided by burning hydrogen.

[0023] In addition, the heat stored in the heat storage tank has multiple uses: for heating the proton exchange membrane fuel cell stack to facilitate its rapid cold-starting; for increasing the water temperature for hydrogen production by electrolysis of water, thereby improving the electrolysis efficiency; for improving the efficiency of the evaporation process in the seawater desalination device, thereby achieving efficient freshwater production; and for meeting the user's daily heating needs.

[0024] Further, the medium that stores heat in the heat storage tank is deionized water.

[0025] Multi-stage flash evaporation seawater desalination module based on solar thermal energy: seawater is pumped into the desalination plant, pretreated, and heated by a solar trough collector. The heated seawater is then desalinated through a multi-stage flash evaporation process and stored in a freshwater tank.

[0026] Further, the solar trough collector module is designed to collect heat from solar energy to drive the desalination process of seawater. It consists of two main parts: a collector and a heat pump. The task of the collector is to convert solar energy into heat energy and transfer it to seawater to facilitate evaporation. The trough collector is usually composed of a series of pipes or channels, in which the flowing working medium can absorb heat radiation from the sun. These collectors are usually located in the open sunlight to maximize the capture of solar energy. When solar radiation shines on the collector, the temperature inside the working medium rises, releasing heat. The heat pump is a key part of upgrading and transferring the heat collected by the solar collector to the desired location. The heat pump works on the principle of thermodynamic cycle, which changes the state of the refrigerant to achieve the upgrading and transfer of heat energy. The entire heat pump working cycle is repeated continuously, and through the continuous transformation of the state of the refrigerant, the heat absorbed by the solar collector is upgraded from low temperature to high temperature, and then the upgraded heat energy is transferred to the multi-stage flash evaporation device to drive the flash evaporation process. In this way, the solar collector and heat pump work together to convert solar energy into heat energy and transfer the heat energy to seawater for desalination, thereby achieving the goal of seawater desalination. At the same time, this module can also improve energy utilization efficiency by using the recovered heat to preheat the seawater entering the device.

[0027] Further, the circulating working medium used in the solar trough collector cycle is heat conducting oil, and the circulating working medium used in the heat pump cycle is R134a.

[0028] Further, the multi-stage flash distillation device is composed of multiple flash evaporators, each operating at a different pressure. Inside the device, evaporators and condensers are arranged, as well as heat exchangers connected to the heat pump system. The heat pump system transfers the stored heat energy to the multi-stage flash distillation device through the heat exchangers, driving the evaporation and condensation processes. The heat pump system transfers high-temperature heat energy to the flash evaporators, promoting the evaporation process.

[0029] Further, in the first-stage evaporator, due to the input of heat energy, part of the water in the seawater evaporates into steam. The steam passes through the condenser and condenses into desalinated water, thus achieving the preliminary desalination of seawater. The remaining seawater enters the next evaporator under high pressure, and the subsequent evaporation-condensation process continues. In each evaporator, the pressure of the flash evaporator gradually decreases, thus reducing the boiling point of seawater and promoting more water evaporation. The steam generated by evaporation is condensed into desalinated water through the condenser, and similar condensation processes occur in each evaporator. After each stage of evaporation-condensation process, the produced desalinated water is collected to form the desalinated water product.

[0030] Further, the heat energy generated in the multi-stage flash distillation device can be recovered through the heat exchanger to preheat the seawater entering the device, thus improving the overall thermal efficiency.

[0031] Further, the collected fresh water has two usage ways, one is to provide fresh water for island residents; the other is to provide water source for electrolytic water hydrogen production.

[0032] The present application combines offshore wind energy, solar energy, wave energy and fuel cell technology to address the energy challenges in island areas. This innovative system comprehensively utilizes multiple renewable energy sources, overcoming the problems of traditional fuel supply, achieving energy diversification and efficient utilization. By introducing fuel cells, heat pump technology and multi-stage flash seawater desalination technology, not only electricity can be provided, but also heat energy for heating and fresh water can be produced. At the same time, through the utilization and redistribution of system waste heat, the system has good performance in rapid response start, realizes multi-energy flow coordination and complementary power generation, and has rich types of energy utilization and high energy utilization rate. This system not only has wide application prospects in the field of energy, but also injects new vitality into the sustainable development of island areas. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1is a kind of island multi-energy integrated hydrogen heat and power supply system structural schematic diagram provided by the present application:

[0035] Figure 1 Each reference number: photovoltaic generator set (1), wind power generator set (2), wave power generator set (3), DC-AC inverter I (4), hybrid DC-DC converter (5), intelligent controller (6), relay I (7), lithium ion battery pack (8), DC-DC converter I (9), DC-AC inverter II (10), relay II (11), proton exchange membrane electrolytic cell (12), gas-water separator I (13), gas-water separator II (14), electronic three-way valve I (15), metal compound hydrogen storage tank (16), oxygen storage steel cylinder (17), safety valve (18), pressure regulating valve (19), mixer I (20), proton exchange membrane fuel cell (21), gas-water separator III (22), hydrogen circulation pump (23), air compressor (24), intercooler (25), humidifier (26), mixer II (27), electronic three-way valve II (28), heat exchanger I (29), electronic three-way valve III (30), cooling water tank (31), cooling water circulating pump (32), electronic three-way valve IV (33), heat exchanger II (34), evaporator I (35), compressor I (36), hydrogen combustion heat exchanger (37), compressor II (38), condenser I (39), expansion valve I (40), heat storage tank (41), electronic five-way valve (42), circulating pump (43), electronic three-way valve V (44), electronic three-way valve VI (45), heat exchanger III (46), mixer III (47), mixer IV (48), seawater pump I (49), electronic three-way valve VII (50), mixer V (51), multi-stage flash evaporator (52), condenser tube (53), fresh water collector (54), seawater pump II (55), electronic three-way valve VIII (56), mixer VI (57), fresh water pump (58), check valve I (59), electronic three-way valve IX (60), check valve II (61), concentrated brine pump (62), heat exchanger IV (63), condenser II (64), compressor III (65), evaporator II (66), expansion valve II (67), heat conducting oil circulating pump (68), trough type solar collector (69), electronic three-way valve X (70), mixer VII (71), evaporator III (72), compressor IV (73), condenser III (74), expansion valve III (75), DC-AC inverter III (76), fresh water pool (77), circulating pump II (78), heat exchanger V (79). DETAILED DESCRIPTION

[0036] The application will be further described in conjunction with the following examples, but the application is not limited to the following examples.

[0037] Example 1: as Figure 1The island multi-energy integrated hydrogen heat and power cogeneration system is shown. It includes a multi-energy integrated power generation module, a water electrolysis hydrogen production module, a hydrogen energy-based heat and power cogeneration module, and a multi-stage flash seawater desalination module based on solar heat supply.

[0038] The multi-energy integrated power generation system refers to the conversion of offshore wind energy and wave energy into fluctuating electric energy through a wind energy generator set (2) and a wave energy generator set (3). The fluctuating electric energy is converted into alternating current through a DC-AC inverter I (4), and then combined with the electric energy generated by a solar power generator set (1). The electric energy is regulated and rectified through a hybrid DC-DC converter (5), and then distributed through an intelligent controller (6). When there is a power demand, the electric energy enters the lithium ion battery pack (8) through relay I (7), is regulated through DC-DC converter I (9), is converted into alternating current through DC-AC inverter II (10), and is finally connected to the alternating current grid to achieve power supply. In addition, when there is a water electrolysis demand or the energy storage device is fully charged, the electric energy enters the water electrolysis as the electric energy input for the preparation of hydrogen and oxygen through relay II (11). At the same time, when the offshore energy is insufficient, the electric energy stored in the lithium ion battery pack (8) can be regulated through DC-DC converter I (9) and used as the electric energy input for the preparation of hydrogen and oxygen.

[0039] The water electrolysis hydrogen production module uses a proton exchange membrane electrolyzer (12) as the hydrogen production equipment, which is directly connected with relay II (11) and DC-DC converter I (9). The water electrolysis of the proton exchange membrane electrolyzer is extracted from the freshwater pool (77) by the freshwater pump (58), mixed with the liquid water separated by gas-water separator I (13) and gas-water separator II (14) in electronic three-way valve I (15) through check valve I (59) and electronic three-way valve IX (60), and then obtained. The hydrogen obtained by water electrolysis enters the metal compound hydrogen storage tank (16) after removing water through gas-water separator I (13) for standby. The oxygen obtained by water electrolysis enters the oxygen storage steel cylinder (17) after removing water through gas-water separator II (14) for standby. At the same time, the proton exchange membrane electrolyzer (12) is heated by the hydrogen energy-based heat and power cogeneration module. Specifically, the heat fluid enters the heat exchanger V (79) through the electronic five-way valve (42) to heat the freshwater required for electrolysis of the proton exchange membrane electrolyzer (12) to provide the required heat for the reaction and accelerate the reaction efficiency.

[0040] The hydrogen energy-based heat and power cogeneration module includes a proton exchange membrane fuel cell unit and a heat pump heat storage unit. The heat pump utilizes the waste heat of the fuel cell while cooling the fuel cell to keep its working temperature at the optimal temperature. In the cold start process, the heat pump provides the necessary heat for the fuel cell to achieve rapid cold start.

[0041] Specifically: when the proton exchange membrane fuel cell (21) is required to provide electrical energy, hydrogen gas flows out of the metal compound hydrogen storage tank (16) through the safety valve (18), and then the pressure and mass flow are adjusted through the pressure regulating valve (19). After these adjustments, the hydrogen gas flows through the mixer I (20) and mixes with the unreacted hydrogen gas at the anode outlet before entering the anode region. At the same time, oxygen is extracted from the oxygen storage steel cylinder (17), the pressure is adjusted through the air compressor (24), and after being cooled through the intercooler (25), it enters the cathode region. Before entering the cathode, the oxygen also increases the humidity through the humidifier (26). The working principle of the proton exchange membrane fuel cell (21) is to decompose the hydrogen gas supplied to the anode into protons and electrons. The protons are transmitted through the proton exchange membrane to the cathode side, and water is generated when reacting with oxygen. At the same time, the electrons flow through the external circuit to generate current. In this way, chemical energy is converted into electrical energy, accompanied by the release of a large amount of heat energy. The generated direct current is converted into alternating current through the DC-AC inverter III (76) to supply external loads. At the anode outlet, unreacted hydrogen gas is discharged. These unreacted hydrogen gas enters the hydrogen circulation pump (23) through the gas-water separator III (22), and then reenters the mixer I (20), and finally reenters the anode region of the proton exchange membrane fuel cell. The heat released by the fuel cell is carried away by the cooling water, and mixed with the cooling water passing through the intercooler (25) in the mixer II (27). When the temperature of the fuel cell stack is too high, part of the cooling water enters the heat exchanger II (34) to exchange heat with the coolant. The cooled cooling water enters the cooling water tank (31) from the electronic three-way valve III (30), and then enters the electronic three-way valve IV (33) through the cooling water circulation pump (32) to flow to the proton exchange membrane fuel cell (21) and the intercooler (25) for cooling the proton exchange membrane fuel cell (21) and oxygen.

[0042] In particular, during the cold start of the fuel cell stack, the cooling water enters the heat exchanger I (29) from the electronic three-way valve II (28), and then is heated by the heat pump assembly. The heated cooling water is sent to the proton exchange membrane fuel cell (21). This method aims to quickly bring the fuel cell to the ideal working temperature to achieve efficient and rapid cold start.

[0043] Driven by circulating pump II (78), the coolant absorbs heat from heat exchanger II (34) and then transfers the heat to evaporator I (35). The heat pump cycle absorbs heat from the fuel cell waste heat through evaporator I (35), evaporating the liquid refrigerant into vapor. Then, compressor I (36) compresses the vapor into high-temperature, low-pressure vapor at a temperature of 60-65°C and a pressure of 1.5-1.7 MPa, and then further heats it to 70-75°C through hydrogen heat exchanger (37). Subsequently, compressor II (38) further compresses the vapor into high-temperature, high-pressure vapor at a temperature of 75-80°C and a pressure of 2.2-2.5 MPa. Finally, heat is released in condenser I (39), causing the refrigerant to condense from a vapor state into a liquid state. After the expansion valve I (40) reduces the refrigerant pressure, it re-enters evaporator I (35), completing the cycle. Through this process, the heat pump cycle transfers fuel cell waste heat from the low-temperature region to the high-temperature region that needs heating, thereby achieving thermal management and temperature control.

[0044] It is worth noting that when the waste heat from the fuel cell is insufficient to meet the system's heat demand, or during a cold start of the fuel cell, hydrogen enters the hydrogen combustion heat exchanger (37) from the metal compound hydrogen storage tank (16) and then undergoes combustion to generate heat energy, providing heat for the heat pump's working fluid. This process is designed to ensure that the system can maintain normal operation when additional heat is required.

[0045] The heat pump circulating fluid passes through condenser I (39), transferring heat to the condensate on the other side of the condenser. The condensate is heated and stored in a heat storage tank (41) at 75-80°C via a circulation pump (43). When the system has a heat demand, the circulation pump (43) drives the hot water through an electronic five-channel valve (42) to deliver the heat to the required location. The destinations of the hot water are as follows: 1. It enters heat exchanger V (79) to provide the heat required for the water electrolysis reaction. After cooling, the water enters mixer IV (48) and mixes with the hot water used to heat the fuel cell before flowing into mixer III (47). 2. It enters heat exchanger I (29) to provide heat for the cold start process of the fuel cell. The hot water flowing out of heat exchanger I (29) flows into mixer IV (48) and mixes with the hot water entering heat exchanger V (79) before flowing into mixer III (47). Third, the water flows through the electronic three-way valve VI (45) to heat exchanger IV (63) and heat exchanger III (46) respectively to provide heat for domestic heating and to heat the seawater flowing out of the condenser tube (53). After cooling, the water is mixed in mixer III (47) and then enters the electronic three-way valve V (44) and enters the condenser I (39) again to absorb heat.

[0046] The multi-stage flash seawater desalination module based on solar heating includes: a parabolic trough solar collector unit, two heat pump units, and an MSF multi-stage flash seawater desalination unit. The solar collector unit absorbs solar energy and transfers the heat to the two heat pump units via heat transfer oil. After the heat pumps upgrade the heat quality, part of the heat is used to provide heat for the multi-stage flash seawater desalination process, and the other part is used to meet domestic heating needs.

[0047] Specifically: The heat transfer oil absorbs heat in the trough solar collector (69), and the temperature rises to 55-60℃. Driven by the heat transfer oil circulation pump (68), it enters the evaporator III (72) through the electronic three-way valve X (70) to release heat. The heat pump circulation working fluid is heated in the evaporator III (72) to evaporate the liquid refrigerant into steam. The compressor IV (73) compresses the steam into high-temperature and high-pressure steam with a temperature of 65-70℃ and a pressure of 1.7-2.1MPa. In the condenser III (74), it is condensed by the low-temperature heating water or domestic water at 24-26℃ to release heat, condensing the refrigerant into liquid. After the pressure is reduced by the expansion valve III (75), it re-enters the evaporator for circulation. In addition, the heat transfer oil is mixed with the heat transfer oil after heat exchange in evaporator Ⅲ (72) through electronic three-way valve Ⅹ (70) in mixer Ⅶ (71), and then enters evaporator Ⅱ (66) to heat the heat pump circulation working fluid. The heat pump circulation working fluid is heated and evaporated into steam in evaporator Ⅱ (66). Compressor Ⅲ (65) compresses the steam into high temperature and high pressure steam with a temperature of 75-80℃ and a pressure of 2.2-2.5MPa. The steam is condensed by seawater at 40-45℃ in condenser Ⅱ (64) to release heat and condense the refrigerant into liquid. After the pressure is reduced by expansion valve Ⅱ (67), the refrigerant re-enters evaporator Ⅱ (66) for circulation.

[0048] In the MSF multi-stage flash seawater desalination process: Seawater is drawn by seawater pump I (49) and transported to electronic three-way valve VII (50), then enters mixer V (51) to mix with seawater heated to 60-65°C, and then enters condenser II (64) to be further heated to 70-75°C. In addition, seawater passes through electronic three-way valve VII (50) and then through electronic three-way valve VIII (56) to enter the condenser tubes of the last two flash evaporators to act as condenser and to replenish seawater in the last two flash tanks. The heated seawater flowing out of condenser II (64) is introduced into the first-stage flash evaporator. In the first-stage evaporator, the pressure is 0.03 MPa, which is lower than the saturated vapor pressure of the seawater at this temperature, and some of the water in the seawater evaporates into steam. The steam passes through condenser tube (53) and condenses into desalinated water, thus achieving the initial desalination of seawater. The remaining seawater enters the next evaporator, and then the evaporation-condensation process continues. In each evaporator, the pressure of the flash evaporator is gradually reduced, thereby lowering the boiling point of the seawater and promoting the evaporation of more water. The steam generated by evaporation is condensed into desalinated water through the condenser tube (53), and a similar condensation process occurs in each evaporator. After each stage of evaporation-condensation process, the desalinated water produced is collected by the freshwater collector (54) to form desalinated water products. When the seawater reaches the last stage flash evaporator, the temperature is 30-35℃, close to the temperature of natural seawater, and the concentration reaches 30-40g / L. After the concentrated brine is separated, it enters the mixer VI (57) and mixes with the cooled seawater from the next two flash evaporators. Then, it is discharged into the sea by the seawater pump through the check valve II (61). The remaining low-temperature seawater with low salt concentration that has not been evaporated enters the condenser tube (53) in the first six-stage flash evaporator again via seawater pump II (55) to serve as condensate. After absorbing heat through the condenser tube, the seawater is further heated to 60-65°C by heat exchanger III (46) and enters mixer V (51) to mix with seawater from electronic three-way valve VII (50). After mixing, it enters condenser II (64) and is further heated to 70-75°C. Then it enters the multi-stage flash evaporator (52) again, thus repeating the process to achieve seawater desalination.

[0049] All the above equipment parts are as follows Figure 1 After connection and installation are complete, purge the hydrogen pipeline with hydrogen gas. Purge the remaining pipelines with nitrogen gas. After evacuating all pipelines, introduce the following into the corresponding pipelines according to the above requirements: deionized water, R134a, heat transfer oil, and seawater.

Claims

1. A multi-energy integrated desalination combined heat and power system for islands, characterized in that: Wind power generator (2) and wave power generator (3) convert wind and wave energy at sea into wave power. The wave power is converted from AC to DC by DC-AC inverter I (4) and then combined with the power generated by solar generator (1). The power is regulated and rectified by hybrid DC-DC converter (5) and then distributed by intelligent controller (6). When the load has a power demand, the power enters the lithium-ion battery pack (8) through relay I (7). After being regulated by DC-DC converter I (9), the DC power is converted into AC by DC-AC inverter II (10) and finally connected to the AC grid to provide power. In addition, when there is a demand for water electrolysis or the energy storage device is fully charged, the power is used as the power input for water electrolysis through relay II (11) to produce hydrogen and oxygen. When the energy at sea is insufficient, the power stored in the lithium-ion battery pack (8) can be regulated by DC-DC converter I (9) and then used as the power input for water electrolysis. The hydrogen production module uses a proton exchange membrane electrolyzer (12) as the hydrogen production equipment, which is directly connected to relay II (11) and DC-DC converter I (9). The electrolyzed water in the proton exchange membrane electrolyzer is extracted from the freshwater pool (77) by a freshwater pump (58), and after passing through check valve I (59) and electronic three-way valve IX (60), it is separated from the liquid water separated by gas-water separator I (13) and gas-water separator II (14) in electronic three-way valve I (15). After mixing, the hydrogen obtained from water electrolysis is removed by gas-water separator I (13) and then enters the metal compound hydrogen storage tank (16) for later use; the oxygen obtained from water electrolysis is removed by gas-water separator II (14) and then enters the oxygen storage cylinder (17) for later use; the proton exchange membrane electrolyzer (12) is heated by a hydrogen-based cogeneration module, and the hot fluid enters the heat exchanger V (79) from the electronic five-channel valve (42) to heat the proton exchange membrane electrolyzer (12) to electrolyze the required fresh water.

2. The system according to claim 1, characterized in that: When the proton exchange membrane fuel cell (21) needs to provide power, hydrogen flows out from the metal compound hydrogen storage tank (16) via the safety valve (18), and then the pressure and mass flow rate are regulated by the pressure regulating valve (19). After these regulation, the hydrogen flows through mixer I (20) and mixes with the unreacted hydrogen at the anode outlet before entering the anode region. Meanwhile, oxygen is drawn from the oxygen storage cylinder (17), the pressure is adjusted by the air compressor (24), and after being cooled by the intercooler (25), it enters the cathode region. Before entering the cathode, the oxygen is also humidified by the humidifier (26). The direct current generated by the proton exchange membrane fuel cell (21) is converted into alternating current by the DC-AC inverter III (76) to supply the external load. At the anode outlet, the unreacted hydrogen is discharged. The unreacted hydrogen enters the hydrogen circulation pump (23) through the gas-water separator III (22), then re-enters the mixer I (20), and finally re-enters the anode region of the proton exchange membrane fuel cell. The heat released by the fuel cell is carried away by the cooling water and mixed with the cooling water that has passed through the intercooler (25) in the mixer II (27). When the stack temperature is too high, some of the cooling water will enter the heat exchanger II (34) to exchange heat with the coolant. The cooled water enters the cooling water tank (31) through the electronic three-way valve III (30), and then enters the electronic three-way valve IV (33) through the cooling water circulation pump (32) before flowing to the proton exchange membrane fuel cell (21) and the intercooler (25) to cool the proton exchange membrane fuel cell (21) and oxygen.

3. The system according to claim 1, characterized in that: During the cold start process of the fuel cell stack, cooling water enters heat exchanger I (29) through electronic three-way valve II (28), and is then heated by the heat pump assembly before being sent into the proton exchange membrane fuel cell (21).

4. The system according to claim 1, characterized in that: Driven by the circulating pump II (78), the coolant absorbs heat from the heat exchanger II (34) and then transfers the heat to the evaporator I (35). The heat pump cycle absorbs heat from the waste heat of the fuel cell through the evaporator I (35) and evaporates the liquid refrigerant into steam. Then, the compressor I (36) compresses the steam into high-temperature, low-pressure steam at a temperature of 60-65°C and a pressure of 1.5-1.7 MPa, and then further heats it to 70-75°C through the hydrogen heat exchanger (37). After that, the compressor II (38) further compresses the steam into high-temperature, high-pressure steam at a temperature of 75-80°C and a pressure of 2.2-2.5 MPa. Finally, the heat is released in the condenser I (39), causing the refrigerant to condense from a vapor state to a liquid state. The expansion valve I (40) reduces the pressure of the refrigerant and it re-enters the evaporator I (35) to complete the cycle.

5. The system according to claim 1, characterized in that: When the waste heat from the fuel cell is insufficient to meet the system's heat demand, or during the cold start of the fuel cell, hydrogen enters the hydrogen combustion heat exchanger (37) from the metal compound hydrogen storage tank (16) and then undergoes combustion to generate heat energy, providing heat for the heat pump circulation working fluid; the heat pump circulation working fluid passes through condenser I (39) and transfers heat to the condensate on the other side of the condenser. The condensate is heated and stored in the heat storage tank (41) at 75-80°C via the circulation pump (43). When the system has a heat demand, the circulation pump (43) drives the hot water through the electronic five-channel valve (42) to deliver the heat to the required location; the destination of the hot water is as follows:

1. Entering heat exchanger V (79) to provide the heat required for the water electrolysis reaction, After cooling, the water enters mixer IV (48) and mixes with the hot water used to heat the fuel cell before flowing into mixer III (47). Second, it enters heat exchanger I (29) to provide heat for the cold start process of the fuel cell. The hot water flowing out of heat exchanger I (29) flows into mixer IV (48) and mixes with the hot water entering heat exchanger V (79) before flowing into mixer III (47). Third, it flows through electronic three-way valve VI (45) to heat exchanger IV (63) and heat exchanger III (46) respectively to provide heat for domestic heating and to heat the seawater flowing out of the condenser tube (53). After cooling, the water is mixed in mixer III (47) and then enters electronic three-way valve V (44) before entering condenser I (39) again to absorb heat.

6. The system according to claim 1, characterized in that: The heat transfer oil absorbs heat in the trough solar collector (69), and its temperature rises to 55-60℃. Driven by the heat transfer oil circulation pump (68), it enters the evaporator III (72) through the electronic three-way valve X (70) to release heat. The heat pump circulating working fluid is heated in the evaporator III (72) to evaporate the liquid refrigerant into vapor. The compressor IV (73) compresses the vapor into high-temperature and high-pressure vapor with a temperature of 65-70℃ and a pressure of 1.7-2.1MPa. In the condenser III (74), it is condensed by low-temperature heating water or domestic water at 24-26℃ to release heat, condensing the refrigerant into a liquid state. The pressure is then reduced through the expansion valve III (75) before... The heat transfer oil enters the evaporator cycle again; in addition, the heat transfer oil is mixed with the heat transfer oil after heat exchange in evaporator Ⅲ (72) through electronic three-way valve Ⅹ (70) and then enters evaporator Ⅱ (66) to heat the heat pump cycle working fluid. The heat pump cycle working fluid is heated and evaporated into steam in evaporator Ⅱ (66). Compressor Ⅲ (65) compresses the steam into high temperature and high pressure steam with a temperature of 75-80℃ and a pressure of 2.2-2.5MPa. The steam is condensed by seawater at 40-45℃ in condenser Ⅱ (64) to release heat and condense the refrigerant into liquid. After the pressure is reduced by expansion valve Ⅱ (67), the refrigerant re-enters evaporator Ⅱ (66) for circulation.

7. The system according to claim 1, characterized in that: In the MSF multi-stage flash desalination process: seawater is drawn by seawater pump I (49) and transported to electronic three-way valve VII (50), then enters mixer V (51) to mix with seawater heated to 60-65℃, and then enters condenser II (64) to be further heated to 70-75℃; in addition, seawater passes through electronic three-way valve VII (50) and then through electronic three-way valve VIII (56) to enter the condenser tubes of the last two flash evaporators to act as condensate and to replenish seawater in the last two flash tanks; The heated seawater flowing out of condenser II (64) is introduced into the first-stage flash evaporator. In the first-stage evaporator, the pressure is 0.03 MPa, which is lower than the saturated vapor pressure of the seawater at this temperature. Some of the water in the seawater evaporates into steam. The steam passes through the condenser tube (53) and is condensed into desalinated water, thus achieving the initial desalination of the seawater. The remaining seawater enters the next evaporator and continues the evaporation-condensation process. In each evaporator, the steam generated by evaporation is condensed into desalinated water through the condenser tube (53). After each stage of evaporation-condensation process, the desalinated water is collected by the freshwater collector (54) to form desalinated water products. When the seawater reaches the last-stage flash evaporator, the temperature is 30-35℃, close to the temperature of natural seawater, and the concentration reaches 30-40 g / L. After the concentrated brine is separated, the concentrated brine enters the mixer VI (57) and mixes with the cooled seawater of the last two flash evaporators. After passing through the check valve II (61), it is discharged into the sea by the seawater pump. The remaining unevaporated salt has a low concentration. Low-temperature seawater is pumped again by seawater pump II (55) into the condenser tube (53) in the first six-stage flash evaporator to act as condensate. After absorbing heat through the condenser tube, the seawater is further heated by heat exchanger III (46) to 60-65°C and then enters mixer V (51) to mix with seawater from electronic three-way valve VII (50). After mixing, it enters condenser II (64) to be further heated to 70-75°C and then enters the multi-stage flash evaporator (52) again, thus repeating the process to achieve seawater desalination.

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