Cross-time multi-energy complementary heat supply system and operation method

Abstract

The cross-time multi-energy complementary heat supply system at least comprises a CO2 transcritical heat pump system and a heat exchange system, and the CO2 transcritical heat pump system is configured to store heat within a first preset time period on the basis of renewable energy power peak-valley difference; and the heat exchange system is configured to supply heat to the target in a second preset time period based on heat storage of the CO2 transcritical heat pump system and low-temperature waste heat generated during power generation of the hydrogen fuel cell system. Through the coupling CO2 transcritical heat pump technology, a cross-time, multi-source coupling and multi-source complementary heat supply system is constructed. The CO2 transcritical heat pump technology has the advantages of being environmentally friendly, free of toxicity, high in working pressure, good in heat exchange performance and the like, high COP (coefficient of performance) can still be kept under the low-temperature heat source condition, and the CO2 transcritical heat pump technology is very suitable for the heat supply link in an off-grid type heat and power cogeneration system. In addition, waste heat generated in the operation process of the hydrogen fuel cell is utilized, and the energy efficiency of the whole system is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel cells, and in particular to a time-spanning multi-energy complementary heating system and an operating method thereof. Background Art

[0002] With the development of hydrogen energy technology, the application of hydrogen fuel cells has expanded from the traditional transportation field to more diversified comprehensive energy supply projects. Such projects combine renewable energy such as wind energy and solar energy with PEM (proton exchange membrane) water electrolysis hydrogen production technology, and then use hydrogen fuel cells to generate electricity, thus realizing a pure off-grid combined heat and power system. This system not only solves the energy supply problem in remote areas, but also realizes the cross-time storage of electricity, providing a new way for sustainable development.

[0003] The pure off-grid combined heat and power system is mainly composed of renewable energy collection devices, PEM water electrolysis hydrogen production equipment, hydrogen storage devices, hydrogen fuel cells and energy management systems. In the energy collection stage, renewable energy such as wind energy and solar energy is used. During the day, solar panels are like energy catchers, converting sunlight into electricity; wind turbines rotate at high speed in the wind, converting wind energy into electricity. Part of the generated electricity directly meets the local real-time electricity demand, and the other part enters the PEM water electrolysis hydrogen production equipment. In the PEM water electrolysis hydrogen production equipment, electricity causes water to decompose into hydrogen and oxygen, and hydrogen is stored, becoming the key to subsequent energy conversion. When night falls or energy demand reaches a peak, the stored hydrogen is transported to the hydrogen fuel cell. The hydrogen fuel cell converts the chemical energy of hydrogen into electricity through electrochemical reactions to power the load. At the same time, this reaction process will generate a lot of heat energy, which is not wasted but fully utilized. Through heat exchange devices, thermal energy can be used for heating to meet the heating needs of residents or industrial facilities during cold periods; it can also be used to prepare hot water to ensure the supply of hot water for daily life and production, thus realizing the combined supply of heat and electricity.

[0004] However, in the actual project implementation process, due to the different installation locations and the equipment's tolerance requirements for ambient temperature, HVAC design is required for PEM hydrogen production equipment and hydrogen fuel cell containers. Especially considering that the main heating period is concentrated at night, the mismatch of heat energy in time and space becomes particularly prominent. In order to solve this problem, electric heaters are usually used to consume electricity for heating, but this is obviously not the best choice for pure off-grid systems that pursue high energy efficiency and sustainability. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a cross-time multi-energy complementary heating system and operation method, and constructs a cross-time, multi-source coupled, and multi-source complementary heating system by coupling CO2 transcritical heat pump technology. CO2 transcritical heat pump technology is environmentally friendly and non-toxic, has high working pressure, and has good heat exchange performance. It can still maintain a high COP (energy efficiency ratio) under low-temperature heat source conditions, and is very suitable for the heating link in off-grid combined heat and power systems. In addition, the present invention uses the waste heat generated by hydrogen fuel cells during operation to further improve the energy efficiency of the entire system.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A multi-energy complementary heating system across time, comprising at least:

[0008] The CO2 transcritical heat pump system is configured to store heat in a first preset time period based on the peak-to-valley difference of renewable energy electricity;

[0009] The heat exchange system is configured to provide heat to the target in a second preset time period based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system.

[0010] Furthermore, the heat exchange system includes a hot water circulation pump, a waste heat exchanger, a hot water storage tank and a main heat exchanger, and the hot water circulation pump, the waste heat exchanger, the hot water storage tank and the main heat exchanger are connected in sequence.

[0011] Furthermore, the hot water circulation pump is configured to boost the low-temperature water into high-pressure low-temperature water, and the high-pressure low-temperature water is exchanged with the hot side stream from the hydrogen fuel cell system through the waste heat exchanger to become medium-temperature water, and then exchanged with the hot side stream from the CO2 transcritical heat pump system to become high-temperature water and stored in the heat storage tank. The stored high-temperature water becomes low-temperature water after supplying heat to the target through the main heat exchanger, and enters the hot water circulation pump again for circulation.

[0012] Furthermore, the CO2 transcritical heat pump system includes a compressor, a gas cooler, a regenerator, a throttle valve and an evaporator, wherein the compressor, the gas cooler, the regenerator, the throttle valve and the evaporator are connected in sequence, and the evaporator, the regenerator and the compressor are connected in sequence.

[0013] Furthermore, the compressor is configured to perform isentropic compression on CO2, and the CO2 after isentropic compression releases heat isobarically through a gas cooler to provide a heat source for the heat exchange system; the CO2 after isobaric heat release further releases heat through a regenerator and is reheated to room temperature; the reheated CO2 undergoes isenthalpic expansion through a throttle valve to form partial liquid CO2; the liquid CO2 absorbs heat isobarically in the evaporator to cool the circulating cold water; after the liquid CO2 evaporates, the gaseous CO2 is reheated through the regenerator and returns to the compressor inlet, forming a complete cycle.

[0014] A multi-energy complementary heating operation method across time, comprising:

[0015] In the first preset time period, heat is stored through a CO2 transcritical heat pump system based on the peak-to-valley difference of renewable energy electricity;

[0016] In the second preset time period, the heat exchange system is used to heat the target based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system.

[0017] Furthermore, the heat exchange system includes a hot water circulation pump, a waste heat exchanger, a hot water storage tank and a main heat exchanger, and the hot water circulation pump, the waste heat exchanger, the hot water storage tank and the main heat exchanger are connected in sequence.

[0018] Furthermore, the heat storage based on the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system are used to heat the target through a heat exchange system, including:

[0019] The low-temperature water is pressurized into high-pressure low-temperature water through a hot water circulation pump. The high-pressure low-temperature water is exchanged with the hot side stream from the hydrogen fuel cell system through a waste heat exchanger to become medium-temperature water. The water is then exchanged with the hot side stream from the CO2 transcritical heat pump system to become high-temperature water and stored in a heat storage tank. The stored high-temperature water is converted into low-temperature water after supplying heat to the target through a main heat exchanger and enters the hot water circulation pump again for circulation.

[0020] Furthermore, the CO2 transcritical heat pump system includes a compressor, a gas cooler, a regenerator, a throttle valve and an evaporator, wherein the compressor, the gas cooler, the regenerator, the throttle valve and the evaporator are connected in sequence, and the evaporator, the regenerator and the compressor are connected in sequence.

[0021] Furthermore, the heat storage by the CO2 transcritical heat pump system includes:

[0022] CO2 is isentropically compressed by a compressor, and the isentropically compressed CO2 isobarically releases heat through a gas cooler to provide a heat source for the heat exchange system; the isobarically released CO2 further releases heat through a regenerator and is reheated to room temperature; the reheated CO2 is isenthalpically expanded through a throttle valve to form partial liquid CO2; the liquid CO2 isobarically absorbs heat in the evaporator to cool the circulating cold water; after the liquid CO2 evaporates, the gaseous CO2 is reheated through the regenerator and returns to the compressor inlet, forming a complete cycle.

[0023] The beneficial effects of the present invention are:

[0024] 1. Thermal energy is stored across time. The present invention utilizes surplus renewable energy electricity during the day, and heats the water through a large temperature glide of a CO2 transcritical heat pump to raise the temperature of the warm water to the rated temperature. After the warm water temperature drops due to heat loss such as heat dissipation and heating (including daytime and nighttime), it can be supplemented to the rated temperature through a heat pump to prepare for use by the air conditioning system. When the temperature is maintained near the rated temperature, the heat pump is in a hot standby state, saving electricity.

[0025] 2. Multi-source coupling and multi-source complementation. The present invention utilizes renewable energy electricity and low-temperature waste heat from fuel cell power generation, and organically combines them through a CO2 transcritical heat pump to achieve mutual backup and mutual complementation of multiple energy sources. This not only enhances the operational flexibility and redundancy of the system, but also enables the heating system to adapt to the instability of renewable energy electricity, operate completely off-grid, have zero carbon emissions, and output heat stably according to user needs.

[0026] 3. Improve energy utilization and economy. The present invention utilizes the peak-valley difference of renewable energy power during the day, and stores heat in a planned manner through a CO2 transcritical heat pump, thereby reducing wind and power abandonment and improving utilization. At night, the low-temperature waste heat generated by fuel cells during power generation can be used to improve the utilization of fuel cell waste heat through a heat pump, thereby enhancing economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a time-spanning multi-energy complementary heating system according to Example 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of a CO2 transcritical heat pump system according to Example 1 of the present invention.

[0029] Figure symbols: P1-1 is a hot water circulation pump, EX1-2 is a waste heat exchanger, EX1-3 is a main heat exchanger, V1-1 is a hot water storage tank, VAL1-1, VAL1-2, VAL1-3 are flow regulating valves, TC-temperature control, FC-flow control; COMP2 is a compressor, EX2-1 is a gas cooler, EX2-2 is a regenerator, EX2-3 is an evaporator, and VAL2-1 is a throttle valve. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment provides a cross-time multi-energy complementary heating system, which includes at least a CO2 transcritical heat pump system and a heat exchange system, wherein the CO2 transcritical heat pump system is configured to store heat in a first preset time period based on the peak-to-valley difference of renewable energy electricity; the heat exchange system is configured to heat a target (such as a PEM water electrolysis hydrogen production system, a hydrogen fuel cell system) in a second preset time period based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system.

[0033] Preferably, the heat exchange system includes a hot water circulation pump P1-1, a waste heat exchanger EX1-2, a hot water storage tank V1-1 and a main heat exchanger EX1-3, and the hot water circulation pump P1-1, the waste heat exchanger EX1-2, the hot water storage tank V1-1 and the main heat exchanger EX1-3 are connected in sequence. Among them, the hot water circulation pump P1-1 is configured to boost the low-temperature water into high-pressure low-temperature water, and the high-pressure low-temperature water is heat-exchanged with the hot side stream from the hydrogen fuel cell system through the waste heat exchanger EX1-2 to form medium-temperature water, and then heat-exchanged with the hot side stream from the CO2 transcritical heat pump system to form high-temperature water and stored in the hot water storage tank V1-1. The stored high-temperature water is converted into low-temperature water after supplying heat to the target through the main heat exchanger EX1-3, and enters the hot water circulation pump P1-1 again for circulation.

[0034] It should be noted that the waste heat exchanger EX1-2 receives warm water from the hydrogen fuel cell system, and after temperature control and heat exchange, it becomes warm water return water and then circulates to the fuel cell; the main heat exchanger EX1-3 receives hot water from the hot water storage tank V1-1, which can heat the circulating hot water of user 1, user 2, and user 3 respectively.

[0035] Preferably, if Figure 2 As shown, the CO2 transcritical heat pump system includes a compressor COMP2, a gas cooler EX2-1, a regenerator EX2-2, a throttle valve VAL2-1 and an evaporator EX2-3. The compressor COMP2, the gas cooler EX2-1, the regenerator EX2-2, the throttle valve VAL2-1 and the evaporator EX2-3 are connected in sequence, and the evaporator EX2-3, the regenerator EX2-2 and the compressor COMP2 are connected in sequence. Among them, the compressor COMP2 is configured to perform isentropic compression on CO2. The CO2 after isentropic compression is isobaric heat release through the gas cooler EX2-1 to provide a heat source for the heat exchange system; the CO2 after isobaric heat release further releases heat through the regenerator EX2-2 and is reheated to room temperature; the reheated CO2 is isenthalpic expansion through the throttle valve VAL2-1 to form partial liquid CO2; the liquid CO2 absorbs heat isobarically in the evaporator EX2-3 to cool the circulating cold water; after the liquid CO2 evaporates, the gaseous CO2 is reheated through the regenerator EX2-2 and returns to the inlet of the compressor COMP2, forming a complete cycle.

[0036] Example 2

[0037] This embodiment is based on embodiment 1:

[0038] This embodiment provides a cross-time multi-energy complementary heating system, which is suitable for megawatt-level hydrogen fuel cell comprehensive energy supply, and aims to achieve cross-time storage of thermal energy, while realizing multi-source coupling and multi-source complementarity of renewable energy power and low-temperature waste heat during fuel cell power generation. The cross-time multi-energy complementary heating system of this embodiment mainly includes: a heat exchange system, a CO2 transcritical heat pump system, a PEM water electrolysis hydrogen production system, and a hydrogen fuel cell system.

[0039] The heat exchange system of this embodiment is as described in Example 1, wherein the key control point parameters are as follows: inlet and outlet pressures of the hot water circulation pump P1-1: 0.2.0~0.3 / 0.5~0.6MPag; (inlet and outlet) cold and hot side temperatures of the waste heat exchanger EX1-2: (45~65 / 65~70°C) / (70~80 / 55~45°C); (inlet and outlet) cold and hot side temperatures of the main heat exchanger EX1-3: (40~60 / 100~110°C) / (45~65 / 100~115°C).

[0040] The CO2 transcritical heat pump system of this embodiment is as described in Example 1, wherein the key control point parameters are as follows:

[0041] Inlet and outlet pressures of compressor COMP2: 3.0~4.0 / 9.5~11.5MPag; (inlet and outlet) cold and hot side temperatures of gas cooler EX2-1: (15~25.0 / 100~115℃) / (120~105 / 55~45℃); (inlet and outlet) cold and hot side temperatures of regenerator EX2-2: (3~9 / 15~25℃) / (45~55 / 40~50℃); pressure drop of throttle valve VAL2-1: 6.0~7.0MPa; (inlet and outlet) cold and hot side temperatures of evaporator EX2-3: (15 / 10.0℃) / (3~9 / 3~9℃).

[0042] Example 3

[0043] This embodiment is based on Embodiment 2:

[0044] The present embodiment provides a cross-time multi-energy complementary heating operation method, including: in a first preset time period, based on the peak-to-valley difference of renewable energy electricity, heat is stored through a CO2 transcritical heat pump system; in a second preset time period, based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system, heating the target is provided through a heat exchange system.

[0045] Preferably, in the heat storage stage, when the system water temperature is not detected to be <110°C (adjustable) and the hydrogen fuel cell system has no heat recovery, the CO2 transcritical heat pump system is used for planned heat storage, wherein the flow control loop of the flow regulating valve VAL1-3 and the temperature control loop of the flow regulating valve VAL1-1 form a cascade control to control the water temperature of the system; in the heat release stage, if the hydrogen fuel cell system has no heat recovery, the heat storage tank V1-1 is used to release heat to the outside first, and when the system water temperature is <50°C (adjustable), it can be supplemented to 110°C through the CO2 transcritical heat pump system; if the hydrogen fuel cell system has heat recovery, it is preferentially supplemented to 65°C (adjustable) through the hydrogen fuel cell system. If the water temperature of the system cannot be maintained, it can continue to be supplemented to 110°C through the CO2 transcritical heat pump system.

[0046] It should be noted that the present invention has the following advantages by coupling the heat exchange system with a CO2 transcritical heat pump:

[0047] 1. In the pure off-grid combined heat and power system, the HVAC demand for thermal energy of the PEM water electrolysis hydrogen production system and the hydrogen fuel cell system container is mismatched in time, space, and quantity. Electric heaters are usually used to consume electricity for heating, but the energy consumption is high and higher requirements are placed on the energy storage redundancy design. The present invention couples the CO2 transcritical heat pump technology to construct a cross-time heat exchange system, which can achieve the effect of heating during the day and using it at night. The megawatt-level energy supply system can reduce the proportion of chemical energy storage by 10-20%.

[0048] 2. The multi-source coupling and multi-source complementarity of low-temperature waste heat from renewable energy power and fuel cell power generation are achieved through CO2 transcritical heat pumps. The waste heat temperature of the fuel cell is raised from 70°C to 110°C by heat pumps, realizing the cascade utilization of waste heat from the fuel cell. Under the condition of hot water return at 50°C, the heat capacity increases by 67.3%.

[0049] 3. Through CO2 transcritical heat pumps, the peak-valley difference of renewable energy power during the day can be utilized. Through CO2 transcritical heat pumps, planned heat storage can be used to increase the flexibility of the power system, timely smooth out the peak-valley difference, reduce wind and power abandonment, and improve utilization. At night, the low-temperature waste heat from fuel cell power generation can be timely raised to 110°C through heat pumps to meet user needs, improve the utilization rate of fuel cell waste heat, and enhance economic efficiency.

[0050] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A multi-energy complementary heating system across time, characterized in that: At least: The CO2 transcritical heat pump system is configured to store heat in a first preset time period based on the peak-to-valley difference of renewable energy electricity; The heat exchange system is configured to provide heat to the target in a second preset time period based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system.

2. The multi-energy complementary heating system across time according to claim 1, characterized in that: The heat exchange system comprises a hot water circulation pump (P1-1), a waste heat exchanger (EX1-2), a hot water storage tank (V1-1) and a main heat exchanger (EX1-3), and the hot water circulation pump (P1-1), the waste heat exchanger (EX1-2), the hot water storage tank (V1-1) and the main heat exchanger (EX1-3) are connected in sequence.

3. The multi-energy complementary heating system across time according to claim 2 is characterized in that: The hot water circulation pump (P1-1) is configured to boost the pressure of low-temperature water into high-pressure low-temperature water. The high-pressure low-temperature water is exchanged with the hot side stream from the hydrogen fuel cell system through the waste heat exchanger (EX1-2) to become medium-temperature water, and then exchanged with the hot side stream from the CO2 transcritical heat pump system to become high-temperature water and stored in the hot water storage tank (V1-1). The stored high-temperature water is converted into low-temperature water after supplying heat to the target through the main heat exchanger (EX1-3), and enters the hot water circulation pump (P1-1) again for circulation.

4. The multi-energy complementary heating system across time according to claim 1, characterized in that: The CO2 transcritical heat pump system includes a compressor (COMP2), a gas cooler (EX2-1), a regenerator (EX2-2), a throttle valve (VAL2-1) and an evaporator (EX2-3); the compressor (COMP2), the gas cooler (EX2-1), the regenerator (EX2-2), the throttle valve (VAL2-1) and the evaporator (EX2-3) are connected in sequence; and the evaporator (EX2-3), the regenerator (EX2-2) and the compressor (COMP2) are connected in sequence.

5. The multi-energy complementary heating system across time according to claim 4 is characterized in that: The compressor (COMP2) is configured to perform isentropic compression on CO2. The isentropically compressed CO2 isobarically releases heat through a gas cooler (EX2-1) to provide a heat source for the heat exchange system. The isobarically released CO2 is further released heat through a regenerator (EX2-2) to be reheated to room temperature. The reheated CO2 is isenthalpically expanded through a throttle valve (VAL2-1) to form part of liquid CO2. The liquid CO2 isobarically absorbs heat in an evaporator (EX2-3) to cool the circulating cold water. After the liquid CO2 evaporates, the gaseous CO2 is reheated through the regenerator (EX2-2) and returns to the inlet of the compressor (COMP2), forming a complete cycle.

6. A method for operating a multi-energy complementary heating system across time, characterized in that: include: In the first preset time period, heat is stored through a CO2 transcritical heat pump system based on the peak-to-valley difference of renewable energy electricity; In the second preset time period, the heat exchange system is used to heat the target based on the heat storage of the CO2 transcritical heat pump system and the low-temperature waste heat of the hydrogen fuel cell system during power generation.

7. A multi-energy complementary heating operation method across time according to claim 6, characterized in that: The heat exchange system comprises a hot water circulation pump (P1-1), a waste heat exchanger (EX1-2), a hot water storage tank (V1-1) and a main heat exchanger (EX1-3), and the hot water circulation pump (P1-1), the waste heat exchanger (EX1-2), the hot water storage tank (V1-1) and the main heat exchanger (EX1-3) are connected in sequence.

8. A multi-energy complementary heating operation method across time according to claim 7, characterized in that: The heat storage based on the CO2 transcritical heat pump system and the low-temperature waste heat during power generation of the hydrogen fuel cell system provide heat to the target through a heat exchange system, including: The low-temperature water is pressurized into high-pressure low-temperature water by the hot water circulation pump (P1-1), and the high-pressure low-temperature water is heat-exchanged with the hot side stream from the hydrogen fuel cell system through the waste heat exchanger (EX1-2) to become medium-temperature water, and then heat-exchanged with the hot side stream from the CO2 transcritical heat pump system to become high-temperature water and stored in the hot water storage tank (V1-1). The stored high-temperature water is converted into low-temperature water after supplying heat to the target through the main heat exchanger (EX1-3), and enters the hot water circulation pump (P1-1) again for circulation.

9. A multi-energy complementary heating operation method across time according to claim 6, characterized in that: The CO2 transcritical heat pump system includes a compressor (COMP2), a gas cooler (EX2-1), a regenerator (EX2-2), a throttle valve (VAL2-1) and an evaporator (EX2-3); the compressor (COMP2), the gas cooler (EX2-1), the regenerator (EX2-2), the throttle valve (VAL2-1) and the evaporator (EX2-3) are connected in sequence; and the evaporator (EX2-3), the regenerator (EX2-2) and the compressor (COMP2) are connected in sequence.

10. A multi-energy complementary heating operation method across time according to claim 9, characterized in that: The heat storage by the CO2 transcritical heat pump system comprises: CO2 is isentropically compressed by a compressor (COMP2), and the isentropically compressed CO2 is isobarically released through a gas cooler (EX2-1), providing a heat source for the heat exchange system; the isobarically released CO2 is further released through a regenerator (EX2-2) and reheated to room temperature; the reheated CO2 is isenthalpically expanded through a throttle valve (VAL2-1) to form partial liquid CO2; the liquid CO2 isobarically absorbed in an evaporator (EX2-3) to cool the circulating cold water; after the liquid CO2 evaporates, the gaseous CO2 is reheated through the regenerator (EX2-2) and returns to the inlet of the compressor (COMP2), forming a complete cycle.

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