High-efficiency flexible low-medium temperature fuel cell waste heat refrigeration system

Abstract

The present application belongs to hydrogen energy technical field, and particularly relates to a high-efficiency flexible medium-low temperature fuel cell waste heat refrigeration system.The technical scheme is as follows: a high-efficiency flexible medium-low temperature fuel cell waste heat refrigeration system, comprising a CO2 transcritical heat pump system, a lithium bromide absorption refrigeration system and a fuel cell power generation system, hot water generated by the CO2 transcritical heat pump system and hot water generated by the fuel cell power generation system are mixed and supplied to the lithium bromide absorption refrigeration system, and hot water generated by the lithium bromide absorption refrigeration system is sent back to the fuel cell power generation system.The present application provides a high-efficiency flexible medium-low temperature fuel cell waste heat refrigeration system, which fully utilizes fuel cell power and utilizes low-grade heat, can greatly improve the temperature range of the fuel cell, and improves the overall energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy technology, and specifically relates to a high-efficiency and flexible waste heat cooling system for medium and low temperature fuel cells. Background Technology

[0002] With the development and maturation of hydrogen energy and fuel cell utilization technologies, hydrogen fuel cell distributed energy supply technology is one of the comprehensive utilization technologies for hydrogen energy. Compared with traditional distributed energy supply technologies, it has the advantages of zero carbon emissions and high efficiency, and is expected to play an important role in the development of the hydrogen energy industry. The main working principle of a distributed energy supply system based on a proton exchange membrane fuel cell (PEMFC) is as follows: Hydrogen is supplied upstream and enters the fuel cell system. Through electrochemical reaction, current is generated to achieve power generation. At the same time as power generation, the electrochemical reaction generates heat, which is captured by externally supplied cooling water to produce hot water at ~70°C, thus achieving combined heat and power (CHP). The application of a simple fuel cell CHP system has certain limitations. For example, the demand for hot water will decrease in the hot summer, and the hot water produced by the fuel cell power generation system will be wasted, thus significantly reducing the system's energy utilization efficiency. In this case, if the low-grade heat produced by the fuel cell system is converted into high-grade cooling energy to provide cooling for the high-temperature environment, a hydrogen fuel cell CHP system can be constructed, which will greatly improve the overall energy utilization efficiency of the system. However, due to current technological limitations, the outlet hot water temperature of PEM fuel cells is below 70°C, or even as low as 65°C. Because of the low heat quality, absorption refrigeration is difficult to utilize effectively. Summary of the Invention

[0003] In order to solve the above-mentioned problems in the existing technology, the purpose of this invention is to provide a high-efficiency and flexible waste heat cooling system for medium and low temperature fuel cells, which can make full use of the fuel cell power while utilizing low-grade heat, thereby greatly increasing the temperature range of the fuel cell and improving the overall energy utilization efficiency.

[0004] The technical solution adopted in this invention is as follows:

[0005] A high-efficiency and flexible medium-low temperature fuel cell waste heat cooling system includes a CO2 transcritical heat pump system, a lithium bromide absorption cooling system, and a fuel cell power generation system. The hot water generated by the CO2 transcritical heat pump system and the hot water generated by the fuel cell power generation system are mixed and supplied to the lithium bromide absorption cooling system. The hot water generated by the lithium bromide absorption cooling system is returned to the fuel cell power generation system.

[0006] This invention utilizes a CO2 transcritical heat pump with a large temperature glide heating method to raise the temperature of warm water, so that the warm water meets the conditions for the formation of water-lithium bromide solution. This allows low-temperature heat sources to also adapt to water-lithium bromide absorption refrigeration, overcoming the disadvantage that even if lithium bromide can be generated at low-temperature heat sources, low-temperature circulating water cooling is still required.

[0007] This invention utilizes the low-temperature waste heat generated during fuel cell power generation, achieving energy cascade utilization through heating and cooling. By coupling a CO2 transcritical heat pump with refrigeration, it can provide cooling in summer and heating in winter, and, when necessary, a combined heat, cooling, and power (CHP) system. This improves waste heat recovery and utilization rates, reduces energy input, and enhances the overall system energy efficiency. The heat pump air cooler provides heating while simultaneously cooling via a heat pump evaporator, increasing the energy utilization efficiency of the heat pump system, reducing energy consumption, and improving economic efficiency.

[0008] The CO2 transcritical heat pump coupled with lithium bromide absorption refrigeration increases the system's operability and makes operation more flexible; the heat pump and lithium bromide absorption refrigeration serve as backups for each other, increasing the redundancy of the refrigeration system, so that even if one device fails, the other device can still provide cooling independently.

[0009] As a preferred embodiment of the present invention, the CO2 transcritical heat pump system includes a compressor, an air cooler, a regenerator, a heat pump system throttling valve, and a heat pump system evaporator connected in sequence by pipelines. The compressor is connected to the shell side of the regenerator by pipelines. Cold water is fed into the tube side inlet of the air cooler, and the hot water at the tube side outlet of the air cooler is mixed with the hot water generated by the fuel cell power generation system and then supplied to the lithium bromide absorption refrigeration system.

[0010] As a preferred embodiment of the present invention, the tube-side inlet of the heat pump system evaporator is supplied with cold water return water, and the tube-side outlet of the heat pump system evaporator is supplied with cold water supply water.

[0011] As a preferred embodiment of the present invention, the lithium bromide absorption refrigeration system includes a high-pressure stage generator, the lithium bromide aqueous solution outlet of the high-pressure stage generator is connected to a low-pressure stage absorber via a pipeline, the water vapor outlet of the high-pressure stage generator is connected to a condenser, the condenser is connected to a refrigeration system evaporator via a pipeline, the refrigeration system evaporator is connected to the high-pressure stage absorber via a pipeline, the lithium bromide aqueous solution outlet of the high-pressure stage absorber is connected to a first circulation pump via a pipeline, and the outlet of the first circulation pump is connected to the low-pressure stage generator via a pipeline.

[0012] The lithium bromide aqueous solution outlet of the low-pressure stage generator is connected to the high-pressure stage absorber through a pipeline. The water vapor outlet of the low-pressure stage generator is connected to the low-pressure stage absorber through a pipeline. The lithium bromide aqueous solution outlet of the low-pressure stage absorber is connected to a second circulation pump through a pipeline. The outlet of the second circulation pump is connected to the high-pressure stage generator through a pipeline.

[0013] The hot water generated by the CO2 transcritical heat pump system and the hot water generated by the fuel cell power generation system are mixed and sent to the hot water inlet of the low-pressure stage generator. The hot water outlet of the low-pressure stage generator is connected to the hot water inlet of the high-pressure stage generator through a pipeline. The hot water outlet of the high-pressure stage generator sends the hot water back to the fuel cell power generation system.

[0014] In a preferred embodiment of the present invention, the condenser, the low-pressure stage absorber, and the high-pressure stage absorber are all supplied with circulating water.

[0015] As a preferred embodiment of the present invention, cold water is introduced into the tube side of the evaporator.

[0016] As a preferred embodiment of the present invention, a first throttling valve is connected to the pipeline between the condenser and the evaporator, a second throttling valve is connected to the pipeline between the lithium bromide aqueous solution outlet of the high-pressure stage generator and the low-pressure stage absorber, and a third throttling valve is connected to the pipeline between the lithium bromide aqueous solution outlet of the low-pressure stage generator and the high-pressure stage absorber.

[0017] As a preferred embodiment of the present invention, the fuel cell power generation system includes a fuel cell stack, which is connected to a hydrogen supply module, an air supply module and a cooling module. The fuel cell stack is electrically connected to a power conversion module, which is electrically connected to a battery. The power conversion module supplies alternating current.

[0018] As a preferred embodiment of the present invention, the hydrogen supply module includes a hydrogen pipeline, which is connected to a hydrogen circulation pump, and the hydrogen circulation pump is connected to the fuel cell stack via a pipeline.

[0019] As a preferred embodiment of the present invention, the air supply module includes an air pump, the outlet of which is connected to a humidifier via a pipeline, and the humidifier is connected to the fuel cell stack via a pipeline.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. Improve system adaptability. This invention utilizes a CO2 transcritical heat pump with large temperature glide heating to raise the temperature level of the warm water, enabling the warm water to meet the conditions for the formation of water-lithium bromide solution. This allows low-temperature heat sources to also adapt to water-lithium bromide absorption refrigeration, overcoming the disadvantage that even if lithium bromide can be generated with a low-temperature heat source, low-temperature circulating water cooling is still required.

[0022] 2. Improve energy utilization and heat pump economy. This invention utilizes the low-temperature waste heat from fuel cell power generation, achieving energy cascade utilization through heating and cooling. By coupling a CO2 transcritical heat pump with refrigeration, it can provide cooling in summer and heating in winter, and, when necessary, a combined heat-cooling-electricity system (CHP) can be implemented, improving waste heat recovery and utilization, reducing energy input, and increasing the overall system energy efficiency. The heat pump air cooler provides heating while simultaneously cooling via a heat pump evaporator, increasing the energy utilization efficiency of the heat pump system, reducing energy consumption, and improving economic efficiency.

[0023] 3. Enhanced system operability and redundancy. The CO2 transcritical heat pump coupled with lithium bromide absorption refrigeration increases the system's operability and makes operation more flexible; the heat pump and lithium bromide absorption refrigeration serve as backups for each other, increasing the redundancy of the refrigeration system, so that even if one device fails, the other device can still provide cooling independently. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a flow chart of a transcritical CO2 heat pump;

[0026] Figure 3 This is a pH diagram of a CO2 transcritical heat pump system;

[0027] Figure 4 This is a flow chart of a water-lithium bromide absorption refrigeration system;

[0028] Figure 5 This is a flowchart of a fuel cell power generation system.

[0029] In the diagram: 1-CO2 transcritical heat pump system; 2-lithium bromide absorption refrigeration system; 3-fuel cell power generation system; 11-compressor; 12-air cooler; 13-regenerator; 14-heat pump system throttle valve; 15-heat pump system evaporator; 21-high pressure stage generator; 22-low pressure stage absorber; 23-condenser; 24-refrigeration system evaporator; 25-high pressure stage absorber; 26-first circulation pump; 27-second circulation pump; 28-first throttle valve; 29-second throttle valve; 210-third throttle valve; 211-low pressure stage generator; 31-fuel cell stack; 32-hydrogen circulation pump; 33-air pump; 34-humidifier; 35-plate heat exchanger; 36-DC / DC module; 37-DC / AC module; 38-battery. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0032] like Figure 1 As shown, the efficient and flexible medium-low temperature fuel cell waste heat cooling system of this embodiment includes a CO2 transcritical heat pump system 1, a lithium bromide absorption cooling system 2, and a fuel cell power generation system 3. The hot water generated by the CO2 transcritical heat pump system 1 and the hot water generated by the fuel cell power generation system 3 are mixed and supplied to the lithium bromide absorption cooling system 2. The hot water generated by the lithium bromide absorption cooling system 2 is returned to the fuel cell power generation system 3.

[0033] Specifically, such as Figure 2 As shown, the CO2 transcritical heat pump system 1 includes a compressor 11, an air cooler 12, a regenerator 13, a heat pump system throttling valve 14, and a heat pump system evaporator 15, which are connected in sequence via pipelines. The compressor 11 is connected to the shell side of the regenerator 13 via pipelines. Cold water is fed into the tube side inlet of the air cooler 12, and the hot water from the tube side outlet of the air cooler 12 is mixed with the hot water generated by the fuel cell power generation system 3 and supplied to the lithium bromide absorption refrigeration system 2. Cold water return water is fed into the tube side inlet of the heat pump system evaporator 15, and cold water supply water is discharged from the tube side outlet of the heat pump system evaporator 15.

[0034] Specifically, such as Figure 4 As shown, the lithium bromide absorption refrigeration system 2 includes a high-pressure stage generator 21. The lithium bromide aqueous solution outlet of the high-pressure stage generator 21 is connected to a low-pressure stage absorber 22 via a pipeline. The water vapor outlet of the high-pressure stage generator 21 is connected to a condenser 23. The condenser 23 is connected to a refrigeration system evaporator 24 via a pipeline. The refrigeration system evaporator 24 is connected to a high-pressure stage absorber 25 via a pipeline. The lithium bromide aqueous solution outlet of the high-pressure stage absorber 25 is connected to a first circulation pump 26 via a pipeline. The outlet of the first circulation pump 26 is connected to a low-pressure stage generator 211 via a pipeline.

[0035] The lithium bromide aqueous solution outlet of the low-pressure stage generator 211 is connected to the high-pressure stage absorber 25 through a pipeline. The water vapor outlet of the low-pressure stage generator 211 is connected to the low-pressure stage absorber 22 through a pipeline. The lithium bromide aqueous solution outlet of the low-pressure stage absorber 22 is connected to the second circulation pump 27 through a pipeline. The outlet of the second circulation pump 27 is connected to the high-pressure stage generator 21 through a pipeline.

[0036] The hot water generated by the CO2 transcritical heat pump system 1 and the hot water generated by the fuel cell power generation system 3 are mixed and sent to the hot water inlet of the low-pressure stage generator 211. The hot water outlet of the low-pressure stage generator 211 is connected to the hot water inlet of the high-pressure stage generator 21 through a pipeline. The hot water outlet of the high-pressure stage generator 21 sends the hot water back to the fuel cell power generation system 3.

[0037] The condenser 23, the low-pressure stage absorber 22, and the high-pressure stage absorber 25 are all circulated with water. The tube side of the evaporator is circulated with cold water.

[0038] A first throttle valve 28 is connected to the pipeline between the condenser 23 and the evaporator. A second throttle valve 29 is connected to the pipeline between the lithium bromide aqueous solution outlet of the high-pressure stage generator 21 and the low-pressure stage absorber 22. A third throttle valve 210 is connected to the pipeline between the lithium bromide aqueous solution outlet of the low-pressure stage generator 211 and the high-pressure stage absorber 25.

[0039] Specifically, such as Figure 5 As shown, the fuel cell power generation system 3 includes a fuel cell stack 31, which is connected to a hydrogen supply module, an air supply module, and a cooling module. The fuel cell stack 31 is electrically connected to a power conversion module, which is electrically connected to a battery 38. The power conversion module supplies AC power.

[0040] The hydrogen supply module includes a hydrogen pipeline connected to a hydrogen circulation pump 32, which is connected to the fuel cell stack 31 via a pipeline. The air supply module includes an air pump 33, whose outlet is connected to a humidifier 34 via a pipeline, which is also connected to the fuel cell stack 31 via a pipeline. The cooling module includes a plate heat exchanger 35, whose inlet is connected to a shared water network. Cooled water is pumped into the fuel cell stack 31. Cooling water from the fuel cell stack 31 is fed into the plate heat exchanger 35, and the heated hot water is mixed with hot water generated by the CO2 transcritical heat pump system 1 before being supplied to the lithium bromide absorption refrigeration system 2. The power conversion module includes a DC / DC module 36 and a DC / AC module 37. The electrical energy generated by the fuel cell stack 31 is delivered to the DC / DC module 36. The DC / DC module 36 is connected to the battery 38 for charging and discharging. The DC / DC module 36 is also connected to the DC / AC module 37. The DC / AC module 37 outputs 380V AC and 220V AC after conversion.

[0041] In the CO2 transcritical heat pump system 1, since there is no phase change in the heat release process, the condenser is a gas cooler, or simply gas cooler 12. For example... Figure 2 and Figure 3As shown, in a conventional transcritical CO2 heat pump system 1, in process 1-2 (S106→S101), the CO2 working fluid is isentropically compressed by the compressor 11; in process 2-3 (S101→S102), CO2 isobarically releases heat in the air cooler 12, heating room temperature water and providing hot water to the outside; after releasing heat, CO2 further releases heat in the regenerator 13 (S102→S103), reheating the CO2 working fluid to room temperature; in process 3-4 (S103→S104), isenthalpic expansion is achieved through the expansion valve, forming a partial liquid phase CO2; in process 4-1 (S104→S105), after expansion, the liquid phase CO2 evaporates isobarically and absorbs heat in the evaporator 15 of the heat pump system, cooling the circulating cold water; after evaporation, the working fluid CO2 is entirely in the gas phase, and after being reheated by the regenerator 13, it returns to the inlet of the compressor 11, forming a complete cycle. In process S107→S108, cold water is heated by air cooler 12, and the hot water is mixed with the hot water generated by fuel cell power generation system 3 and supplied to lithium bromide absorption refrigeration system 2. In process S109→S110, cold water return water is sent out as cold water supply water through heat pump system evaporator 15.

[0042] like Figure 3 As shown, in the high-pressure stage, in process S201→S202 or S206, the lithium bromide aqueous solution is heated by heat source water in the high-pressure stage generator 21, and the water in the solution continuously vaporizes; in process S206→S207, as the water continues to vaporize, the concentration of the lithium bromide aqueous solution in the high-pressure stage generator 21 continuously increases, and it enters the low-pressure stage absorber 22, controlled by the second throttle valve 29; in process S202→S203, the water vapor enters the condenser 23, is cooled by the cooling water in the condenser 23, and condenses into high-pressure, low-temperature liquid water; in process S203→S204… 204. When the water in the condenser 23 enters the evaporator 24 of the refrigeration system through the first throttle valve 28, in process S204→S205, it rapidly expands and vaporizes, and absorbs a large amount of heat from the refrigerant water in the evaporator during the vaporization process, thereby achieving the purpose of cooling; in process S205→S208, the low-temperature water vapor enters the high-pressure stage absorber 25 and is absorbed by the lithium bromide aqueous solution from the low-pressure stage in the absorber, and the solution concentration gradually decreases; in process S208→S210, it is sent back to the low-pressure stage generator 211 by the first circulation pump 26 to complete the high-pressure stage cycle.

[0043] In the low-pressure stage, process S210→S211 or S212, the lithium bromide aqueous solution is heated by heat source water in the low-pressure stage generator 211, and the water in the solution continuously vaporizes; process S212→S213, as the water continues to vaporize, the concentration of the lithium bromide aqueous solution in the generator continuously increases, and enters the high-pressure stage absorber 25, controlled by the third throttle valve 210; process S211→S214, water vapor enters the low-pressure stage absorber 22, is absorbed by the lithium bromide aqueous solution from the high-pressure stage in the absorber, and the solution concentration gradually decreases; process S214→S201, and then is sent back to the low-pressure stage generator 211 by the second circulation pump 27, completing the low-pressure stage cycle.

[0044] In process S220→S221→S222, the hot water generated by the CO2 transcritical heat pump system 1 and the hot water generated by the fuel cell power generation system 3 are mixed and sent to the low-pressure stage generator 211. The high-pressure stage generator 21 sends out hot water return water, which can be supplied to the fuel cell power generation system 3. In processes S223→S224, S231→S232, and S233→S234, circulating water is fed in and circulating water return water is sent out. In process S225→S226, cold water return water is fed in and cold water feed water is sent out.

[0045] like Figure 5 As shown, fuel cell power generation system 3 refers to the entire fuel cell power generation system 3. The hydrogen supply module and air supply module provide the reactants hydrogen and oxygen to the power generation system. The oxygen required for the reaction is obtained directly from the ambient air by air pump 33, and the air is humidified before entering the fuel cell stack. The hydrogen gas is provided by an external hydrogen supply system. The cooling module exchanges the heat generated during the chemical reaction inside the fuel cell to the outside through a radiator. The fuel cell stack 31 is the core of the entire system, the site where hydrogen and oxygen react to generate electricity. The power conversion module converts the electricity generated by the fuel cell through a DC / DC converter and inverter before connecting it to the terminal for use. The monitoring module realizes real-time monitoring and control of the fuel cell system's operating conditions, ensuring the automatic and stable operation of the fuel cell power generation system 3. The hot water generated by the fuel cell is heated by a heat exchanger and returned to the outside for hot water supply, such as... Figure 5 As shown.

[0046] like Figure 1 As shown, this invention obtains high-temperature hot water through a CO2 transcritical heat pump, mixes it with warm water from a self-fuel cell, and then uses the mixed hot water for lithium bromide absorption refrigeration. This allows the system to meet the requirements of absorption refrigeration for warm water, and the CO2 transcritical heat pump evaporator refrigeration combined with absorption refrigeration increases the total cooling capacity of the system, improves the overall energy utilization efficiency of the system, or reduces the energy consumption per unit cooling capacity.

[0047] Example 1:

[0048] This embodiment provides a solution for a 100kW warm water absorption cooling system, aiming to complete the development of an absorption-type low-temperature waste heat cooling system suitable for hydrogen fuel cell combined cooling, heating, and power (CCHP). This system ensures that the refrigerant evaporation process is completed when the fuel cell stack outlet hot water (~70℃) is available, and also achieves complete absorption of the refrigerant by the working fluid in a concentrated solution under cooling water conditions at around 30℃, thus realizing a complete cycle of the cooling system. A CO2 transcritical heat pump coupled with a lithium bromide absorption cooling system 2 is used. The system mainly includes: a CO2 transcritical heat pump system 1 and a water-lithium bromide absorption cooling system 22. The specific design of each system is as follows:

[0049] CO2 transcritical heat pump system 1:

[0050] In the CO2 transcritical heat pump system 1 of this embodiment, the key control point parameters are as follows: compressor 11 inlet and outlet pressure: 3.0~4.0 / 9.5~11.5MPag, air cooler 12 (inlet and outlet) cold and hot side temperature: (15~25.0 / 100~115℃) / (120~105 / 55~45℃), regenerator 13 (inlet and outlet) cold and hot side temperature: (3~9 / 15~25℃) / (45~55 / 40~50℃), heat pump system throttle valve 14 pressure drop: 6.0~7.0MPa, heat pump system evaporator 15 (inlet and outlet) cold and hot side temperature: (15 / 10.0℃) / (3~9 / 3~9℃).

[0051] Lithium bromide absorption refrigeration system 2:

[0052] The key control parameters of the lithium bromide absorption refrigeration system 2 in this embodiment are as follows: high-pressure side operating pressure 6-9 kPaa, low-pressure side operating pressure 1.0-3.0 kPaa, evaporator 24 pressure 0.8-1.4 kPaa, inlet water-lithium bromide absorption refrigeration hot water temperature ≥70℃, evaporator 24 cold water (inlet and outlet) temperature (15 / 10.1℃), circulating cooling water (inlet and outlet) temperature (32 / 37℃).

[0053] Example 2:

[0054] The process flow is the same as in Example 1. When the hot water at the outlet of the hydrogen fuel cell is 65°C, in order to ensure that the mixed hot water completes the refrigerant evaporation process, and also to achieve complete absorption of the concentrated solution by the working fluid under cooling water conditions of around 30°C, thus realizing the full cycle of the refrigeration system, the output of the CO2 transcritical heat pump needs to be increased accordingly, based on Example 1.

[0055] CO2 transcritical heat pump system 1:

[0056] In this embodiment of the CO2 transcritical heat pump system 1, the key control point parameters are the same as in Example 1, except that the CO2 circulation rate is increased from 1050 kg / h to 2116 kg / h, the power of compressor 11 is increased from 17.4 kW to 35 kW, and the cooling load is increased from 26.61 kW to 53.94 kW.

[0057] Lithium bromide absorption refrigeration system 2:

[0058] The key control point parameters of the lithium bromide absorption refrigeration system 2 in this embodiment are the same as those in Example 1.

[0059] Regarding the water-lithium bromide absorption refrigeration, which may not occur at low temperatures (~70°C) or may occur, but requires low-temperature cooling water (~18°C) due to the low solution temperature after absorption, this invention uses a CO2 transcritical heat pump coupled with a lithium bromide absorption refrigeration system 2 to raise the temperature of the low-temperature cooling water from 18°C ​​to 30°C.

[0060] When generating electricity from fuel cells, this invention achieves an energy efficiency of 52%. If the fuel cell generates electricity and then provides 100kW of cooling capacity through compression refrigeration, it would consume internal electrical energy, reducing the utilization rate of external electrical energy. By integrating energy utilization through heating and cooling, and coupling a CO2 transcritical heat pump with refrigeration, cooling can be provided in summer and heating in winter. Through this "heat-cool-electricity" tri-generation system, while ensuring 100kW of cooling capacity, the external power supply efficiency is improved by 2% to 18% compared to a 100-500kW fuel cell + compression refrigeration system, significantly improving the overall energy supply efficiency of the fuel cell.

[0061] This invention utilizes a transcritical carbon dioxide heat pump to significantly increase the waste heat temperature of fuel cells from over 70°C, expanding the hot water temperature to 65-70°C. This improves the operational flexibility of the fuel cell system while extending its lifespan.

[0062] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A high-efficiency and flexible waste heat cooling system for medium- and low-temperature fuel cells, characterized in that: The system includes a CO2 transcritical heat pump system (1), a lithium bromide absorption refrigeration system (2), and a fuel cell power generation system (3). The hot water generated by the CO2 transcritical heat pump system (1) and the hot water generated by the fuel cell power generation system (3) are mixed and supplied to the lithium bromide absorption refrigeration system (2). The hot water generated by the lithium bromide absorption refrigeration system (2) is returned to the fuel cell power generation system (3). The CO2 transcritical heat pump system (1) includes a compressor (11), an air cooler (12), a regenerator (13), a heat pump system throttle valve (14), and a heat pump system evaporator (15) connected in sequence by pipelines. The compressor (11) is connected to the shell side of the regenerator (13) by pipelines. Cold water is fed into the tube side inlet of the air cooler (12), and the hot water at the tube side outlet of the air cooler (12) is mixed with the hot water generated by the fuel cell power generation system (3) and then supplied to the lithium bromide absorption refrigeration system (2). The lithium bromide absorption refrigeration system (2) includes a high-pressure stage generator (21), the lithium bromide aqueous solution outlet of the high-pressure stage generator (21) is connected to a low-pressure stage absorber (22) through a pipeline, the water vapor outlet of the high-pressure stage generator (21) is connected to a condenser (23), the condenser (23) is connected to a refrigeration system evaporator (24) through a pipeline, the refrigeration system evaporator (24) is connected to a high-pressure stage absorber (25) through a pipeline, the lithium bromide aqueous solution outlet of the high-pressure stage absorber (25) is connected to a first circulation pump (26) through a pipeline, and the outlet of the first circulation pump (26) is connected to a low-pressure stage generator (211) through a pipeline. The lithium bromide aqueous solution outlet of the low-pressure stage generator (211) is connected to the high-pressure stage absorber (25) through a pipeline. The water vapor outlet of the low-pressure stage generator (211) is connected to the low-pressure stage absorber (22) through a pipeline. The lithium bromide aqueous solution outlet of the low-pressure stage absorber (22) is connected to the second circulation pump (27) through a pipeline. The outlet of the second circulation pump (27) is connected to the high-pressure stage generator (21) through a pipeline. The hot water generated by the CO2 transcritical heat pump system (1) and the hot water generated by the fuel cell power generation system (3) are mixed and sent to the hot water inlet of the low-pressure stage generator (211). The hot water outlet of the low-pressure stage generator (211) is connected to the hot water inlet of the high-pressure stage generator (21) through a pipeline. The hot water outlet of the high-pressure stage generator (21) sends the hot water back to the fuel cell power generation system (3). The fuel cell power generation system (3) includes a fuel cell stack (31), which is connected to a hydrogen supply module, an air supply module and a cooling module. The fuel cell stack (31) is electrically connected to a power conversion module, which is electrically connected to a battery (38). The power conversion module supplies AC power.

2. The efficient and flexible waste heat cooling system for medium- and low-temperature fuel cells according to claim 1, characterized in that: The evaporator (15) of the heat pump system has cold water return water sent into its tube side inlet and cold water supply water sent out of its tube side outlet.

3. The efficient and flexible waste heat cooling system for medium- and low-temperature fuel cells according to claim 1, characterized in that: The condenser (23), the low-pressure stage absorber (22), and the high-pressure stage absorber (25) are all supplied with circulating water.

4. The efficient and flexible waste heat cooling system for medium- and low-temperature fuel cells according to claim 1, characterized in that: Cold water is introduced into the tube side of the evaporator.

5. The efficient and flexible waste heat cooling system for medium and low temperature fuel cells according to claim 1, characterized in that: A first throttle valve (28) is connected to the pipeline between the condenser (23) and the evaporator. A second throttle valve (29) is connected to the pipeline between the lithium bromide aqueous solution outlet of the high-pressure generator (21) and the low-pressure absorber (22). A third throttle valve (210) is connected to the pipeline between the lithium bromide aqueous solution outlet of the low-pressure generator (211) and the high-pressure absorber (25).

6. The efficient and flexible waste heat cooling system for medium- and low-temperature fuel cells according to claim 1, characterized in that: The hydrogen supply module includes a hydrogen pipeline connected to a hydrogen circulation pump (32), which is connected to the fuel cell stack (31) via a pipeline.

7. The efficient and flexible waste heat cooling system for medium- and low-temperature fuel cells according to claim 1, characterized in that: The air supply module includes an air pump (33), the outlet of which is connected to a humidifier (34) via a pipe, and the humidifier (34) is connected to the fuel cell stack (31) via a pipe.

Images