Waste heat recovery device based on megawatt high-power fuel cell

Abstract

The invention discloses a waste heat recovery device based on a megawatt high-power fuel cell, and relates to the technical field of waste heat recovery. By recycling the waste heat of the fuel cell stack and the heat of the air source in the environment, the waste of energy in the fuel cell combined heat and power system is reduced, the energy utilization efficiency is improved, and the purpose of saving energy is achieved. The waste heat recovery device based on the megawatt high-power fuel cell comprises a cooling system, a heat pump system and a waste heat recovery system, the cooling system can cool an electric pile of the fuel cell, the current converter and the tail exhaust condensation plate heat exchanger; the heat pump system can absorb heat of an air source, the waste heat recovery system is coupled with the cooling system and the heat pump system, and the waste heat recovery system can recycle waste heat of the electric pile, heat of the current converter, heat of the tail exhaust condensation plate type heat exchanger and heat of the air source. The performance of the battery waste heat recovery device is improved.

Description

Technical Field

[0001] The present application relates to the field of waste heat recovery technology, and in particular to a waste heat recovery device based on a megawatt-class high-power fuel cell. Background Art

[0002] A fuel cell is an electrochemical device that can directly convert chemical energy stored in fuel and oxidant into electrical energy. Theoretically, the thermal-electric conversion efficiency of a fuel cell can reach 85% to 90%, but in reality, the battery is subject to various polarization restrictions during operation. The actual energy conversion efficiency of most batteries is between 40% and 60%, and the remaining energy is expressed in the form of heat energy, which is usually called waste heat. If the waste heat is not dissipated in time, it will cause the battery to lose temperature, seriously affecting the normal operation and service life of the battery.

[0003] In order to ensure that the fuel cell stack can operate efficiently under any load conditions, the system usually oversupplies hydrogen. If the heat energy in the tail exhaust hydrogen that does not participate in the reaction during operation is not utilized, the waste heat recovery rate of the fuel cell will be low.

[0004] The AD / DC (AC / DC) converter in the fuel cell system generates a certain amount of waste heat when converting the DC power generated by the fuel cell into the AC power required for vehicles or other applications. If it is not dissipated in time, it will cause system failure and safety problems.

[0005] Heat pump technology is a highly efficient energy conversion technology that absorbs heat from a low-temperature heat source and transfers it to a high-temperature heat source by compressing and expanding a circulating working fluid (usually a refrigerant). In a fuel cell system, heat pump technology can be used to recover and utilize waste heat from the fuel cell, improving the energy efficiency of the entire system. Summary of the invention

[0006] The embodiments of the present application provide a waste heat recovery device based on a megawatt-class high-power fuel cell, which can recycle the waste heat of the fuel cell stack and the heat from the air source in the environment, reduce the energy waste in the fuel cell cogeneration system, improve the energy utilization efficiency, and achieve the purpose of saving energy.

[0007] To achieve the above-mentioned objectives, an embodiment of the present application provides a waste heat recovery device based on a megawatt-class high-power fuel cell, including a cooling system, a heat pump system and a waste heat recovery system; the cooling system can cool the fuel cell stack, the current converter and the tail-discharge condensing plate heat exchanger; the heat pump system can absorb heat from the air source, and the waste heat recovery system is coupled with the cooling system and the heat pump system, and the waste heat recovery system can realize the recovery and utilization of the waste heat of the fuel cell stack, the heat of the current converter, the heat of the tail-discharge condensing plate heat exchanger and the heat of the air source.

[0008] Furthermore, the cooling system includes a main cooling system, an auxiliary cooling system and a tail exhaust cooling system arranged in parallel; the main cooling system, the auxiliary cooling system and the tail exhaust cooling system all include three cooling modes: air cooling, water cooling, and air cooling and water cooling operating together.

[0009] Furthermore, the main cooling system includes a first circulating water pump, a main heat exchanger and a first air radiator which are connected in sequence along the flow direction of the liquid; the inlet of the first circulating water pump and the outlet of the first air radiator are both connected to the fuel cell stack; the auxiliary cooling system includes a second circulating water pump, an auxiliary heat exchanger and a second air radiator which are connected in sequence along the flow direction of the liquid; the inlet of the second circulating water pump and the outlet of the second air radiator are both connected to the current converter; the tail exhaust cooling system includes a third circulating water pump, a tail exhaust heat exchanger and a third air radiator which are connected in sequence along the flow direction of the liquid; the inlet of the third circulating water pump and the outlet of the third air radiator are both connected to the tail exhaust condensing plate heat exchanger.

[0010] Furthermore, the heat pump system comprises an air evaporator, a compressor, a heat storage plate heat exchanger and an expansion valve which are connected end to end in sequence.

[0011] Furthermore, the waste heat recovery system includes a first waste heat recovery subsystem, a second waste heat recovery subsystem and a heat storage tank; the first waste heat recovery subsystem is coupled to the cooling system through a main heat exchanger, an auxiliary heat exchanger and a tail heat exchanger respectively; the second waste heat recovery subsystem is coupled to the heat pump system through a heat storage plate heat exchanger; the first waste heat recovery subsystem and the second waste heat recovery subsystem are both connected to the heat storage tank.

[0012] Furthermore, the first waste heat recovery subsystem includes a first cold water source; the cold water from the first cold water source is divided into three paths; the three paths of cold water flow into the heat storage tank after passing through the main heat exchanger, the auxiliary heat exchanger or the tail heat exchanger respectively; the second waste heat recovery subsystem includes a second cold water source; the cold water from the second cold water source also flows into the heat storage tank after passing through the heat storage plate heat exchanger.

[0013] Furthermore, the first cold water source is connected to the main heat exchanger, the auxiliary heat exchanger and the tail heat exchanger via a branch valve.

[0014] Furthermore, the heat storage tank is connected to the main heat exchanger, the auxiliary heat exchanger, the tail heat exchanger, and the heat storage plate heat exchanger through a confluence valve.

[0015] Furthermore, the outlet of the heat storage tank is connected to the inlet of the first circulating water pump.

[0016] Furthermore, the medium of the cooling system and the waste heat recovery system are both water.

[0017] Compared with the prior art, this application has the following beneficial effects:

[0018] 1. The embodiment of the present application optimizes the structure of the waste heat recovery system in the existing fuel cell waste heat recovery device. Most of the heat is carried by the main cooling system, the auxiliary cooling system and the tail exhaust cooling system. The three cooling systems are connected in parallel and are coupled to the waste heat recovery system through a heat exchanger respectively, thereby reducing the heat load of a single heat exchanger. In addition, since the function of the heat pump system is positioned as a heat supplement function, in the heat pump system, only a single-stage compression is used to achieve the function that can only be completed by multi-stage compression in a conventional megawatt-class high-power fuel cell waste heat recovery system, which greatly reduces the structural complexity of the waste heat recovery system and improves the economy of the system.

[0019] 2. The embodiment of the present application takes into account the control effect of the cooling system in the fuel cell waste heat recovery device. The main cooling system, the auxiliary cooling system and the tail exhaust cooling system are all equipped with independent heat exchangers and air radiators, and the heat dissipation method can realize free switching between water cooling and air cooling according to actual needs. When the water level in the heat storage tank is too high, the user's heat demand is small at this time, and the air cooling mode is adopted. At this time, no cold water is introduced, and the three heat exchangers stop working. The air cooling method only needs to rely on the fan to adjust the wind speed; when the water level in the heat storage tank is too low, the user's heat demand is large at this time, and the water cooling mode is adopted. At this time, the three heat exchangers enter the working mode, and the water cooling only needs to rely on the heat exchanger outlet water temperature to adjust the cold water inlet flow; when the water level in the heat storage tank is moderate, the joint operation of the water cooling and air cooling modes can be dynamically adjusted according to the actual needs of the user, and the control of the wind speed or cold water flow is convenient, efficient and accurate. In addition, when considering the change in power size when the fuel cell is working, the control change of the heat dissipation mode can also be carried out in the same way.

[0020] 3. The embodiment of the present application takes into account the integration effect in the waste heat recovery device of the fuel cell. The waste heat recovery device can recover heat from four heat sources, namely the three heat sources of the fuel cell system and the external air heat source. The three heat sources of the fuel cell system are the stack heat source, the current converter heat source, and the tail exhaust heat source. Through this waste heat recovery device, the waste heat of the four heat sources can be recovered and integrated into one loop, which not only realizes the cooling function of the fuel cell components, so that each component maintains the normal working temperature, but also realizes the heating function for the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1This is a schematic diagram of the structure of a waste heat recovery device based on a megawatt-class high-power fuel cell according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] 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 described embodiments 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 ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0025] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, they can understand the specific meanings of the above terms in this application according to specific circumstances.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" can explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0027] Reference Figure 1 , an embodiment of the present application provides a waste heat recovery device based on a megawatt-class high-power fuel cell, including a cooling system, a heat pump system and a waste heat recovery system. The cooling system can cool the fuel cell stack 9, the current converter 5 and the tail condensing plate heat exchanger 1. The heat pump system can absorb heat from the air source, and the waste heat recovery system is coupled to the cooling system and the heat pump system through a heat exchanger. The waste heat recovery system can realize the recovery and utilization of waste heat from the stack, heat from the current converter, heat from the tail condensing plate heat exchanger and heat from the air source.

[0028] During the operation of the fuel cell system, the stack 9, the tail condensing plate heat exchanger 1, and the current converter 5 will generate a large amount of heat that needs to be cooled to maintain an ideal operating temperature. The circulating water pump in the heat pump system can pump cold water into the stack 9, the tail condensing plate heat exchanger 1, and the current converter 5 to carry out excess heat and exchange heat with the medium of the waste heat recovery system.

[0029] The cooling system includes a main cooling system, an auxiliary cooling system and a tail exhaust cooling system which are arranged in parallel.

[0030] The main cooling system includes a first circulating water pump 10, a main heat exchanger 11 and a first air radiator 12 which are sequentially connected along the flow direction of the liquid. The inlet of the first circulating water pump 10 and the outlet of the first air radiator 12 are both connected to the fuel cell stack 9.

[0031] The auxiliary cooling system includes a second circulating water pump 6 , an auxiliary heat exchanger 7 and a second air radiator 8 which are sequentially connected along the flow direction of the liquid. The inlet of the second circulating water pump 6 and the outlet of the second air radiator 8 are both connected to the current converter 5 .

[0032] The tail cooling system includes a third circulating water pump 2, a tail heat exchanger 3, and a third air radiator 4 which are sequentially connected along the flow direction of the liquid. The inlet of the third circulating water pump 2 and the outlet of the third air radiator 4 are both connected to the tail condensing plate heat exchanger 1.

[0033] The main cooling system, auxiliary cooling system and tail cooling system all include three cooling modes: air cooling, water cooling, and air cooling and water cooling. The cooling methods of the three cooling systems can be switched independently according to usage requirements. The three cooling systems do not affect each other, and the cooling medium is water.

[0034] When the air cooling mode is in operation, the main heat exchanger 11, the auxiliary heat exchanger 7 and the tail heat exchanger 3 do not work. When the medium in the cooling system flows through the heat exchanger, no heat exchange occurs with the medium in the waste heat recovery system. When flowing through the air radiator, the speed of the fan is adjusted to exchange heat with the air by forced convection, and the heat is dissipated into the environment, thereby achieving heat dissipation.

[0035] When the water cooling mode is in operation, the first air radiator 12, the second air radiator 8, and the third air radiator 4 do not work. When the medium in the cooling system flows through the heat exchanger, heat is exchanged with the medium in the waste heat recovery system, and the waste heat is transferred to the waste heat recovery system. When the air cooling and water cooling are in operation together, the two modes are operated simultaneously to achieve heat dissipation.

[0036] The waste heat recovery system includes a first waste heat recovery subsystem, a second waste heat recovery subsystem and a heat storage tank 21. The first waste heat recovery subsystem is coupled to the cooling system through the main heat exchanger 11, the auxiliary heat exchanger 7 and the tail heat exchanger 3 respectively. The second waste heat recovery subsystem is coupled to the heat pump system through the heat storage plate heat exchanger in the heat pump system. The first waste heat recovery subsystem and the second waste heat recovery subsystem are both connected to the heat storage tank 21.

[0037] The first waste heat recovery subsystem includes a first cold water source 17. The cold water from the first cold water source 17 is divided into three paths after being diverted by a branch valve 18. The three paths of cold water flow through the main heat exchanger 11, the auxiliary heat exchanger 7 or the tail heat exchanger 3 respectively, and then flow into the heat storage tank 21 through a confluence valve 20. The second waste heat recovery subsystem includes a second cold water source 19. The cold water from the second cold water source 19 flows through the heat storage plate heat exchanger 15 and also flows into the heat storage tank 21 through a confluence valve 20. The outlet of the heat storage tank 21 is connected to the inlet of the first circulating water pump 10.

[0038] The heat pump system includes an air evaporator 13, a compressor 14, a heat storage plate heat exchanger 15 and an expansion valve 16 which are connected end to end in sequence.

[0039] The medium of the heat pump system is refrigerant. When the low-temperature liquid refrigerant flowing out of the expansion valve 16 flows through the evaporator 13, it absorbs the heat of the air in the environment and the temperature rises because the temperature is lower than the ambient temperature. After being compressed by the compressor 14, the temperature is even higher. Then, after passing through the heat storage plate heat exchanger 15, the heat in the high-temperature refrigerant vapor is transferred to the second cold water source 19 through the heat storage plate heat exchanger 15. After the cold water absorbs heat, the temperature rises and becomes hot water, and enters the heat storage tank 21 for storage, thereby realizing heat recovery and utilization. After passing through the heat storage plate heat exchanger 15, the refrigerant passes through the expansion valve 16 again, and finally completes a cycle, realizing the recovery and utilization of the heat of the air in the environment over and over again.

[0040] The temperature of the hot water entering the heat storage tank 21 needs to be greater than 60°C to meet the heat demand. When the battery stack 9 is running at low power, the temperature of the hot water in the waste heat recovery system flowing out of the main heat exchanger 11, the auxiliary heat exchanger 7, and the tail heat exchanger 3 may not reach 60°C. At this time, the water flow rate of the first cold water source 17 can be adjusted to increase the temperature of the hot water at the outlet. At the same time, the temperature of the second cold water source 19 rises after flowing through the heat storage plate heat exchanger 15 and the temperature is greater than 60°C. After merging with the hot water flowing out of the main heat exchanger 11, the auxiliary heat exchanger 7, and the tail heat exchanger 3 through the confluence valve 20, the hot water temperature will be increased. By adjusting the working power of the heat pump system, this temperature can be made to reach above 60°C, thereby achieving the hot water temperature standard for heating demand.

[0041] The bottom of the heat storage tank 21 is connected to the main cooling system through the return pipe 22. In winter or cold climate conditions, the hot water in the heat storage tank 21 can be returned to the main cooling system according to actual usage to prevent the medium temperature in the main cooling system from dropping to the freezing point, which is beneficial to improving the temperature stability of the fuel cell stack 9 and facilitating the low-temperature cold start of the fuel cell stack 9.

[0042] To summarize, the embodiment of the present application recycles and utilizes the waste heat of the fuel cell stack 9 and the waste heat of the current converter 5, which helps to maintain the ideal operating temperature of the fuel cell while greatly reducing heat loss and reducing the heat dissipation heat load of the fuel cell stack 9 and the current converter 5. The cooling system is innovatively coupled with the waste heat recovery system through a heat exchanger, and this part of heat is stored in the hot water of the waste heat recovery system, thereby achieving effective recovery of the overall waste heat of the fuel cell cogeneration, which not only reduces the cost of the waste heat recovery device, but also solves the problems of low efficiency and waste of heat energy in the existing waste heat recovery.

[0043] In addition, since air source heat pump technology has the advantages of high efficiency and energy saving, multi-purpose use, environmental friendliness and strong applicability, the embodiment of the present application uses air source heat pump technology to recover and utilize air source heat, and innovatively converts low-grade thermal energy in the ambient air into hot water in the form of high-grade thermal energy, which not only greatly improves the energy utilization efficiency, but also helps to improve the heat-to-electricity ratio of fuel cell cogeneration, and to a certain extent realizes the effective collection and redistribution of waste heat generated during the operation of the fuel cell.

[0044] In addition, the embodiment of the present application proposes a multi-mode operation of the cooling system. The cooling system is divided into three parts for independent operation and high-temperature water return from the heat storage tank. Compared with the existing technology, it has many technical advantages and highlights.

[0045] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A waste heat recovery device based on a megawatt-class high-power fuel cell, characterized in that: It includes a cooling system, a heat pump system and a waste heat recovery system; the cooling system can cool the fuel cell stack, the current converter and the tail condensing plate heat exchanger; the heat pump system can absorb heat from the air source, and the waste heat recovery system is coupled with the cooling system and the heat pump system. The waste heat recovery system can realize the recovery and utilization of waste heat from the fuel cell stack, heat from the current converter, heat from the tail condensing plate heat exchanger and heat from the air source.

2. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 1 is characterized in that: The cooling system includes a main cooling system, an auxiliary cooling system and a tail exhaust cooling system which are arranged in parallel; the main cooling system, the auxiliary cooling system and the tail exhaust cooling system all include three cooling modes: air cooling, water cooling, and air cooling and water cooling in combination.

3. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 2 is characterized in that: The main cooling system includes a first circulating water pump, a main heat exchanger and a first air radiator which are sequentially connected along the flow direction of the liquid; the inlet of the first circulating water pump and the outlet of the first air radiator are both connected to the fuel cell stack; The auxiliary cooling system includes a second circulating water pump, an auxiliary heat exchanger and a second air radiator which are sequentially connected along the flow direction of the liquid; the inlet of the second circulating water pump and the outlet of the second air radiator are both connected to the current converter; The tail exhaust cooling system includes a third circulating water pump, a tail exhaust heat exchanger, and a third air radiator which are sequentially connected along the flow direction of the liquid; the inlet of the third circulating water pump and the outlet of the third air radiator are both connected to the tail exhaust condensing plate heat exchanger.

4. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 3 is characterized in that: The heat pump system comprises an air evaporator, a compressor, a heat storage plate heat exchanger and an expansion valve which are connected end to end in sequence.

5. The waste heat recovery device based on megawatt-class high-power fuel cell according to claim 4 is characterized in that: The waste heat recovery system includes a first waste heat recovery subsystem, a second waste heat recovery subsystem and a heat storage tank; the first waste heat recovery subsystem is coupled to the cooling system through a main heat exchanger, an auxiliary heat exchanger and a tail heat exchanger respectively; the second waste heat recovery subsystem is coupled to the heat pump system through a heat storage plate heat exchanger; the first waste heat recovery subsystem and the second waste heat recovery subsystem are both connected to the heat storage tank.

6. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 5 is characterized in that: The first waste heat recovery subsystem comprises a first cold water source; the cold water from the first cold water source is divided into three paths; the three paths of cold water flow into the heat storage tank after passing through the main heat exchanger, the auxiliary heat exchanger or the tail heat exchanger respectively; The second waste heat recovery subsystem includes a second cold water source; the cold water from the second cold water source flows through the heat storage plate heat exchanger and also flows into the heat storage tank.

7. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 6 is characterized in that: The first cold water source is connected to the main heat exchanger, the auxiliary heat exchanger and the tail heat exchanger through a branch valve.

8. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 6 is characterized in that: The heat storage tank is connected with the main heat exchanger, the auxiliary heat exchanger, the tail heat exchanger, and the heat storage plate heat exchanger through a confluence valve.

9. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 5, characterized in that: The outlet of the heat storage tank is communicated with the inlet of the first circulating water pump.

10. The waste heat recovery device based on a megawatt-class high-power fuel cell according to claim 1, characterized in that: The medium of the cooling system and the waste heat recovery system is water.

Images