A liquid hydrogen power system for balanced heat utilization and a method for balanced heat utilization thereof

Abstract

The present invention discloses a liquid hydrogen power system with balanced heat utilization and a balanced heat utilization method thereof, and relates to the technical field of hydrogen energy application. The liquid hydrogen power system comprises: a liquid hydrogen storage tank, a buffer tank, a fuel cell (or an engine), an intercooler, an air compressor, a liquid hydrogen pump and a coil; the balanced heat utilization method thereof can effectively utilize the coldness of liquid hydrogen to cool the fuel cell (or the engine), and utilize the heat of the fuel cell (or the engine) to vaporize the liquid hydrogen, replacing the function of a traditional vaporizer, thereby realizing balanced heat utilization inside the system and improving the energy utilization efficiency of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen energy application, and in particular to a liquid hydrogen power system for balanced heat utilization and a balanced heat utilization method thereof. Background Art

[0002] In traditional liquid hydrogen power systems, there is often an imbalance in local heat and cold, resulting in a large amount of energy waste. Among them, the temperature of liquid hydrogen is extremely low, about -253°C. Before it is supplied to the fuel cell (or engine), it needs to absorb heat and vaporize through the vaporizer to increase the operating temperature. Hydrogen energy utilization devices such as fuel cells (or engines) release a lot of heat during operation and require additional cooling media for circulating cooling, such as liquid-cooled fuel cell stacks; or require additional structural design to use air for cooling, such as air-cooled fuel cell stacks. In summary, the liquid hydrogen vaporization endothermic process requires the absorption of a large amount of heat, and the cooling of the fuel cell (or engine) requires a large amount of cold. Through reasonable process and structural design, the liquid hydrogen system and the fuel cell (or engine) can achieve complementary utilization of cold and heat to improve overall efficiency.

[0003] Existing fuel cell cooling technology mainly uses air or circulating water to perform thermal management on the fuel cell system. The existing liquid hydrogen supply system requires a vaporizer to vaporize the liquid hydrogen. The heat of the traditional vaporizer also comes from heat exchange with air or circulating water. For example, the patent with application number CN201611056763.3 uses circulating water to perform thermal management on the fuel cell system, and uses the heat carried by the circulating water to heat up the liquid hydrogen storage tank, thereby accelerating the vaporization of liquid hydrogen. This process introduces additional working fluids, and a radiator is still required to dissipate the heat from the circulating water used for cooling. The water tank for storing the circulating water also increases the volume and weight of the overall system.

[0004] In summary, it is particularly important to achieve balanced utilization of heat in the overall power system where liquid hydrogen and fuel cells (or engines) are located through system process design to avoid energy waste. Summary of the invention

[0005] In view of this, the present invention provides a liquid hydrogen power system with balanced heat utilization and a method for balanced heat utilization, which can effectively utilize the coldness of liquid hydrogen to cool the fuel cell (or engine), and utilize the heat of the fuel cell (or engine) to vaporize the liquid hydrogen, replacing the function of the traditional vaporizer, achieving balanced heat utilization within the system, and improving the energy utilization efficiency of the system.

[0006] The technical solution of the present invention is: a liquid hydrogen power system for balanced utilization of heat, comprising: a liquid hydrogen storage tank, a buffer tank, a fuel cell, an intercooler, an air compressor, a liquid hydrogen pump and a coil;

[0007] The liquid hydrogen storage tank, buffer tank, fuel cell, intercooler and air compressor are connected in sequence through a delivery pipeline, and a gas phase valve I is provided on the delivery pipeline between the liquid hydrogen storage tank and the buffer tank, and a gas phase valve II is provided on the delivery pipeline between the buffer tank and the fuel cell;

[0008] The liquid hydrogen storage tank and the intercooler are connected by two parallel delivery pipelines, and a liquid hydrogen pump is provided on one delivery pipeline, and a liquid phase valve is provided on the other delivery pipeline; a coil is surrounded by the outer surface of the fuel cell, which is connected to the intercooler through the delivery pipeline; at the same time, the coil on the outer surface of the fuel cell is connected to the buffer tank through the delivery pipeline.

[0009] A liquid hydrogen power system for balanced heat utilization, comprising: a liquid hydrogen storage tank, a buffer tank, an engine, an air compressor, a liquid hydrogen pump and a coil;

[0010] The liquid hydrogen storage tank, buffer tank, engine and air compressor are connected in sequence through a delivery pipeline, and a gas phase valve I is provided on the delivery pipeline between the liquid hydrogen storage tank and the buffer tank, and a gas phase valve II is provided on the delivery pipeline between the buffer tank and the engine;

[0011] The outer surface of the engine is surrounded by a coil, and the liquid hydrogen storage tank and the coil are connected by two parallel delivery pipelines, one of which is provided with a liquid hydrogen pump, and the other is provided with a liquid phase valve; at the same time, the coil on the outer surface of the engine is connected to the buffer tank by a delivery pipeline.

[0012] Preferably, the shape of the liquid hydrogen storage tank may be spherical or cylindrical.

[0013] A method for balanced utilization of heat in a liquid hydrogen power system comprises the following steps:

[0014] Step 1: A rated amount of liquid hydrogen is stored in the liquid hydrogen storage tank, and a certain volume and pressure of hydrogen is stored in the buffer tank. At this time, the gas phase valve I and the liquid phase valve are closed, the gas phase valve II is opened, and the hydrogen in the buffer tank enters the fuel cell; at the same time, the air compressor starts working, and the compressed air is sent to the fuel cell after being cooled by the intercooler;

[0015] Step 2: The liquid hydrogen pump starts working, and the liquid hydrogen passes through the intercooler and coil to exchange heat with the compressed air and the fuel cell. The liquid hydrogen absorbs heat and vaporizes before entering the buffer tank, while cooling the fuel cell at the same time.

[0016] Step 3: The fuel cell continuously generates heat, and the liquid hydrogen flow is adjusted by the liquid hydrogen pump to maintain the working temperature of the fuel cell. When the pressure of the hydrogen formed by the vaporization of the liquid hydrogen in the coil is greater than the pressure in the liquid hydrogen storage tank, the gas phase valve I and the liquid phase valve are both opened, and the liquid hydrogen in the liquid hydrogen storage tank is continuously squeezed out under the action of the hydrogen pressure. The outflow flow of the liquid hydrogen is controlled by adjusting the valve opening of the gas phase valve I and the liquid phase valve. When the pressure of the liquid hydrogen storage tank satisfies that the outflow flow of the liquid hydrogen is greater than or equal to the delivery flow of the liquid hydrogen pump, the liquid hydrogen pump is turned off;

[0017] Step 4: When the liquid hydrogen power system is ready to stop working, close the liquid phase valve and the gas phase valve II, shut down the fuel cell and then close the gas phase valve I.

[0018] A method for balanced utilization of heat in a liquid hydrogen power system comprises the following steps:

[0019] Step 1: A rated amount of liquid hydrogen is stored in the liquid hydrogen storage tank, and a certain volume and pressure of hydrogen is stored in the buffer tank. At this time, the gas phase valve I and the liquid phase valve are closed, and the gas phase valve II is opened, and the hydrogen in the buffer tank enters the engine; at the same time, the air compressor starts working, so that the compressed air enters the engine, and the engine starts working;

[0020] Step 2: The liquid hydrogen pump starts working, and the liquid hydrogen exchanges heat with the engine through the coil. The liquid hydrogen absorbs heat and vaporizes before entering the buffer tank, while cooling the engine at the same time.

[0021] Step 3: The engine continuously generates heat, and the liquid hydrogen flow is adjusted by the liquid hydrogen pump to maintain the operating temperature of the engine. When the pressure of the hydrogen formed by the vaporization of the liquid hydrogen in the coil is greater than the pressure in the liquid hydrogen storage tank, the gas phase valve I and the liquid phase valve are both opened, and the liquid hydrogen in the liquid hydrogen storage tank is continuously squeezed out under the action of the hydrogen pressure. The outflow flow of liquid hydrogen is controlled by adjusting the valve opening of the gas phase valve I and the liquid phase valve. When the pressure of the liquid hydrogen storage tank satisfies that the outflow flow of liquid hydrogen is greater than or equal to the delivery flow of the liquid hydrogen pump, the liquid hydrogen pump is turned off;

[0022] Step 4: When the liquid hydrogen power system is ready to stop working, close the liquid phase valve and gas phase valve II, and then close the gas phase valve I after the engine is shut down.

[0023] Beneficial effects:

[0024] 1. The present invention arranges liquid hydrogen pipelines reasonably, regulates the flow of liquid hydrogen, and adds a buffer tank for storing hydrogen, thereby utilizing the coldness of liquid hydrogen to cool the fuel cell and utilizing the heat of the fuel cell to vaporize the liquid hydrogen, thereby achieving a balanced utilization of the coldness of liquid hydrogen with the heat of compressed air and the heat of the fuel cell. The liquid hydrogen pipeline is directly exchanged with the fuel cell, replacing the function of the traditional vaporizer, and can effectively achieve the heat balance inside the system. At the same time, the coordination of the valve and the buffer tank can be used to realize liquid hydrogen transportation, reduce the use of liquid hydrogen pumps, and improve the energy utilization efficiency of the system.

[0025] 2. The present invention arranges liquid hydrogen pipelines reasonably, regulates the flow of liquid hydrogen, and adds a buffer tank for storing hydrogen, thereby utilizing the coldness of liquid hydrogen to cool the engine and utilizing the heat of the engine to vaporize the liquid hydrogen, thereby achieving a balanced utilization of the coldness of liquid hydrogen and the heat of the engine, replacing the function of a traditional vaporizer, reducing energy loss, effectively achieving heat balance within the system, and improving the energy utilization efficiency of the system; at the same time, by utilizing the coordinated effect of valves and buffer tanks, liquid hydrogen transportation can be achieved, reducing the use of liquid hydrogen pumps, and further improving the energy utilization efficiency of the system.

[0026] 3. The existing thermal management method of liquid hydrogen power system mainly uses circulating water and utilizes the cooling capacity of liquid hydrogen to cool the fuel cell, which introduces additional working fluid and increases the volume and weight of the system. The vaporization of liquid hydrogen is often carried out by heat exchange with air or circulating water through a vaporizer. The method of the present invention adopts a method of direct heat exchange between a liquid hydrogen pipeline and a fuel cell or an engine to make liquid hydrogen absorb heat and vaporize, thereby replacing the traditional vaporizer. By utilizing the cooling capacity of liquid hydrogen and the heat balance of the fuel cell or the engine, the introduction of additional working fluid is avoided and the heat utilization efficiency is improved. At the same time, the present invention also adopts a liquid hydrogen supply method in which a buffer tank and a valve are coordinated with each other, and different hydrogen supply methods are adopted for the startup, operation, shutdown and other states of the liquid hydrogen power system, thereby saving energy and improving system efficiency while meeting the hydrogen demand of the power system and the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of an embodiment of the liquid hydrogen power system of the present invention.

[0028] Figure 2 FIG. 4 is a schematic diagram of another embodiment of the liquid hydrogen power system of the present invention.

[0029] Among them, 1-liquid hydrogen storage tank, 2-gas phase valve I, 3-buffer tank, 4-transmission pipeline, 5-gas phase valve II, 6-fuel cell, 7-intercooler, 8-air compressor, 9-liquid hydrogen pump, 10-liquid phase valve, 11-power line, 12-motor, 13-coil, 14-engine. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0031] Embodiment 1:

[0032] The present embodiment provides a liquid hydrogen power system with balanced heat utilization and a method for balanced heat utilization thereof, which can effectively utilize the coldness of liquid hydrogen to cool the fuel cell, and utilize the heat of the fuel cell to vaporize the liquid hydrogen, replacing the function of the traditional vaporizer, achieving balanced heat utilization within the system, and improving the energy utilization efficiency of the system.

[0033] like Figure 1 As shown, the liquid hydrogen power system includes: a liquid hydrogen storage tank 1, a buffer tank 3, a fuel cell 6, an intercooler 7, an air compressor 8, a liquid hydrogen pump 9, a motor 12 and a coil 13;

[0034] The liquid hydrogen storage tank 1, the buffer tank 3, the fuel cell 6, the intercooler 7 and the air compressor 8 are connected in sequence through a delivery pipeline 4, and a gas phase valve I2 is provided on the delivery pipeline 4 between the liquid hydrogen storage tank 1 and the buffer tank 3, and a gas phase valve II5 is provided on the delivery pipeline 4 between the buffer tank 3 and the fuel cell 6;

[0035] The liquid hydrogen storage tank 1 and the intercooler 7 are connected by two parallel delivery pipelines 4, and a liquid hydrogen pump 9 is provided on one delivery pipeline 4, and a liquid phase valve 10 is provided on the other delivery pipeline 4; a coil 13 is surrounded on the outer surface of the fuel cell 6, and the coil 13 is connected to the intercooler 7 through the delivery pipeline 4, and is communicated with the two delivery pipelines 4 connected in parallel between the liquid hydrogen storage tank 1 and the intercooler 7. The delivery pipeline 4 between the coil 13 and the intercooler 7 and the two delivery pipelines 4 connected in parallel between the liquid hydrogen storage tank 1 and the intercooler 7 together constitute a liquid hydrogen pipeline; at the same time, the coil 13 on the outer surface of the fuel cell 6 is connected to the buffer tank 3 through the delivery pipeline 4;

[0036] Among them, the shape of the liquid hydrogen storage tank 1 can be spherical or cylindrical or other traditional or special-shaped structures; the gas phase valve I2, the gas phase valve II5 and the liquid phase valve 10 are all controlled by an external control system; the buffer tank 3 is used to store vaporized hydrogen; the coil 13 surrounding the outer surface of the fuel cell 6 is used to cool the fuel cell 6; the air compressor 8 is used to compress the incoming air, and the intercooler 7 is used to cool the compressed air, and its cooling capacity comes from the cooling capacity carried by the liquid hydrogen pipeline between the liquid hydrogen storage tank 1 and the intercooler 7; the liquid hydrogen pump 9 is used to regulate the flow of liquid hydrogen out of the liquid hydrogen storage tank 1.

[0037] In this embodiment, the fuel cell 6 provides electric energy to the motor 12 through the power line 11, thereby providing power for other external systems or equipment.

[0038] The working principle or method of the liquid hydrogen power system is:

[0039] In the initial state (i.e. the state where the liquid hydrogen power system is not started), the liquid hydrogen storage tank 1 stores a rated amount of liquid hydrogen, and the buffer tank 3 stores hydrogen of a certain capacity and pressure. At this time, the gas phase valve I2 and the liquid phase valve 10 are in a closed state, and the gas phase valve II5 is opened, and the hydrogen in the buffer tank 3 enters the fuel cell 6 through the delivery pipeline 4; at the same time, the air compressor 8 starts to work, and the compressed air is sent to the fuel cell 6 after being cooled by the intercooler 7, and the fuel cell 6 starts to work and can provide electric energy for the motor 12;

[0040] After the fuel cell 6 starts working, the liquid hydrogen pump 9 starts working, and the liquid hydrogen with a small flow rate (i.e., the flow rate that satisfies the outlet temperature of the coil 13 to be the ambient temperature) is transferred through the intercooler 7 and the coil 13 on the outer surface of the fuel cell 6 to exchange heat with the compressed air and the fuel cell 6. The liquid hydrogen absorbs heat and vaporizes before entering the buffer tank 3, and the fuel cell 6 is cooled at the same time. At this point, the liquid hydrogen power system is started and starts working. Among them, the cooling capacity of the intercooler 7 is provided by the liquid hydrogen (i.e., the cooling capacity of the intercooler 7 is the cooling capacity carried by the liquid hydrogen entering the intercooler 7). The liquid hydrogen vaporization heat absorption process needs to absorb a large amount of heat, and the cooling of the fuel cell 6 requires a large amount of cooling capacity.

[0041] After the liquid hydrogen power system is started and begins to work, the fuel cell 6 continues to work and generates a large amount of heat. The liquid hydrogen flow is adjusted by the liquid hydrogen pump 9 to maintain the operating temperature of the fuel cell 6 within a reasonable range (generally 25-90°C, preferably 70-85°C). As the liquid hydrogen in the coil 13 is vaporized and formed, the hydrogen is stored in the buffer tank 3 in large quantities. When the pressure in the buffer tank 3 is greater than the pressure in the liquid hydrogen storage tank 1, the gas phase valve Ⅰ2 and the liquid phase valve 10 are both opened, and the liquid hydrogen in the liquid hydrogen storage tank 1 is continuously squeezed out under the pressure generated by the hydrogen in the buffer tank 3. The outflow flow of liquid hydrogen can be controlled by adjusting the valve opening of the gas phase valve Ⅰ2 and the liquid phase valve 10. When the pressure of the liquid hydrogen storage tank 1 satisfies that the outflow flow of liquid hydrogen is greater than or equal to the delivery flow of the liquid hydrogen pump 9, the liquid hydrogen pump 9 is closed, thereby reducing the energy consumption of the liquid hydrogen pump 9 and improving the overall efficiency of the system;

[0042] When the liquid hydrogen power system is ready to stop working, the liquid phase valve 10 and the gas phase valve II5 are closed to ensure that the fuel cell 6 is safely shut down before closing the gas phase valve I2 to avoid damage to the fuel cell 6 due to excessively high or low temperatures.

[0043] Embodiment 2:

[0044] The present embodiment provides a liquid hydrogen power system with balanced heat utilization and a method for balanced heat utilization thereof, which can effectively utilize the coldness of liquid hydrogen to cool the engine and utilize the heat of the engine to vaporize the liquid hydrogen, replacing the function of a traditional vaporizer, achieving balanced heat utilization within the system, and improving the energy utilization efficiency of the system.

[0045] like Figure 2 As shown, the liquid hydrogen power system includes: a liquid hydrogen storage tank 1, a buffer tank 3, an engine 14, an air compressor 8, a liquid hydrogen pump 9 and a coil 13;

[0046] The liquid hydrogen storage tank 1, the buffer tank 3, the engine 14 and the air compressor 8 are connected in sequence through a delivery pipeline 4, and a gas phase valve I2 is provided on the delivery pipeline 4 between the liquid hydrogen storage tank 1 and the buffer tank 3, and a gas phase valve II5 is provided on the delivery pipeline 4 between the buffer tank 3 and the engine 14;

[0047] The outer surface of the engine 14 is surrounded by a coil 13, and the liquid hydrogen storage tank 1 and the coil 13 are connected by two parallel delivery pipelines 4, and a liquid hydrogen pump 9 is provided on one delivery pipeline 4, and a liquid phase valve 10 is provided on the other delivery pipeline 4; here, the two parallel delivery pipelines 4 constitute a liquid hydrogen pipeline; at the same time, the coil 13 on the outer surface of the engine 14 is connected to the buffer tank 3 through the delivery pipeline 4;

[0048] Among them, the shape of the liquid hydrogen storage tank 1 can be spherical or cylindrical or other traditional or special-shaped structures; the gas phase valve I2, the gas phase valve II5 and the liquid phase valve 10 are all controlled by an external control system; the buffer tank 3 is used to store vaporized hydrogen; the coil 13 surrounding the outer surface of the engine 14 can be used to cool the engine 14; the air compressor 8 is used to compress the incoming air as the oxygen source of the engine 14; the liquid hydrogen pump 9 can regulate the flow of liquid hydrogen out of the liquid hydrogen storage tank 1; the engine 14 provides power for other external systems or equipment.

[0049] The working principle of the liquid hydrogen power system is:

[0050] In the initial state (i.e., the state in which the liquid hydrogen power system is not started), the liquid hydrogen storage tank 1 stores a rated amount of liquid hydrogen, and the buffer tank 3 stores hydrogen of a certain capacity and pressure. At this time, the gas phase valve I2 and the liquid phase valve 10 are closed, and the gas phase valve II5 is opened, and the hydrogen in the buffer tank 3 enters the engine 14 through the delivery pipeline 4; at the same time, the air compressor 8 starts to work, so that the compressed air enters the engine 14, and the engine 14 starts to work, thereby providing power for other external systems or equipment;

[0051] After the engine 14 starts to work, the liquid hydrogen pump 9 starts to work, and the liquid hydrogen with a small flow rate (i.e., the flow rate that satisfies the outlet temperature of the coil 13 to be the ambient temperature) is sent through the coil 13 on the outer surface of the engine 14 to exchange heat with the engine 14, and the liquid hydrogen enters the buffer tank 3 after absorbing heat and vaporizing, and the engine 14 is cooled at the same time; at this point, the liquid hydrogen power system is started and starts to work; wherein, the liquid hydrogen vaporization heat absorption process needs to absorb a large amount of heat, and the cooling of the engine 14 requires a large amount of cold;

[0052] After the liquid hydrogen power system is started and begins to work, the engine 14 continues to work and generates a large amount of heat. The liquid hydrogen flow is adjusted by the liquid hydrogen pump 9 to maintain the operating temperature of the engine 14 within a preset range (that is, the engine 14 is cooled to a preset range to ensure that it can operate stably). As the liquid hydrogen in the coil 13 is vaporized and formed, the hydrogen gas is stored in a large amount in the buffer tank 3. When the pressure in the buffer tank 3 is greater than the pressure in the liquid hydrogen storage tank 1, the gas phase valve Ⅰ2 and the liquid phase valve 10 are both opened, and the liquid hydrogen in the liquid hydrogen storage tank 1 is continuously squeezed out under the pressure generated by the hydrogen in the buffer tank 3. The outflow flow of liquid hydrogen can be controlled by adjusting the valve opening of the gas phase valve Ⅰ2 and the liquid phase valve 10. When the pressure of the liquid hydrogen storage tank 1 satisfies that the outflow flow of liquid hydrogen is greater than or equal to the delivery flow of the liquid hydrogen pump 9, the liquid hydrogen pump 9 is turned off, thereby reducing the energy consumption of the liquid hydrogen pump 9 and improving the overall efficiency of the system;

[0053] When the liquid hydrogen power system is ready to stop working, the liquid phase valve 10 and the gas phase valve II5 are closed to ensure that the engine 14 is safely shut down before closing the gas phase valve I2 to avoid damage to the engine 14 due to excessively high or low temperatures.

[0054] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid hydrogen power system with balanced heat utilization, characterized in that: include: Liquid hydrogen storage tank (1), buffer tank (3), fuel cell (6), intercooler (7), air compressor (8), liquid hydrogen pump (9) and coil (13); The liquid hydrogen storage tank (1), the buffer tank (3), the fuel cell (6), the intercooler (7) and the air compressor (8) are connected in sequence via a delivery pipeline (4), and a gas phase valve I (2) is provided on the delivery pipeline (4) between the liquid hydrogen storage tank (1) and the buffer tank (3), and a gas phase valve II (5) is provided on the delivery pipeline (4) between the buffer tank (3) and the fuel cell (6); The liquid hydrogen storage tank (1) and the intercooler (7) are connected via two parallel delivery pipelines (4), one of the delivery pipelines (4) is provided with a liquid hydrogen pump (9), and the other delivery pipeline (4) is provided with a liquid phase valve (10); a coil (13) is surrounded on the outer surface of the fuel cell (6), and is connected to the intercooler (7) via the delivery pipeline (4); at the same time, the coil (13) on the outer surface of the fuel cell (6) is connected to the buffer tank (3) via the delivery pipeline (4).

2. A liquid hydrogen power system with balanced heat utilization, characterized in that: include: A liquid hydrogen storage tank (1), a buffer tank (3), an engine (14), an air compressor (8), a liquid hydrogen pump (9) and a coil (13); The liquid hydrogen storage tank (1), the buffer tank (3), the engine (14) and the air compressor (8) are connected in sequence via a delivery pipeline (4), and a gas phase valve I (2) is provided on the delivery pipeline (4) between the liquid hydrogen storage tank (1) and the buffer tank (3), and a gas phase valve II (5) is provided on the delivery pipeline (4) between the buffer tank (3) and the engine (14); The outer surface of the engine (14) is surrounded by a coil (13); the liquid hydrogen storage tank (1) and the coil (13) are connected via two parallel delivery pipelines (4); one delivery pipeline (4) is provided with a liquid hydrogen pump (9), and the other delivery pipeline (4) is provided with a liquid phase valve (10); at the same time, the coil (13) on the outer surface of the engine (14) is connected to the buffer tank (3) via the delivery pipeline (4).

3. The liquid hydrogen power system with balanced heat utilization according to claim 1 or 2, characterized in that: The shape of the liquid hydrogen storage tank (1) is spherical or cylindrical.

4. A method for balanced utilization of heat in a liquid hydrogen power system, characterized in that: It uses the liquid hydrogen power system as claimed in claim 1, comprising the following steps: Step 1: A rated amount of liquid hydrogen is stored in the liquid hydrogen storage tank (1), and a certain volume and pressure of hydrogen is stored in the buffer tank (3). At this time, the gas phase valve I (2) and the liquid phase valve (10) are closed, the gas phase valve II (5) is opened, and the hydrogen in the buffer tank (3) enters the fuel cell (6); at the same time, the air compressor (8) starts to work, and the compressed air is cooled by the intercooler (7) and then sent to the fuel cell (6); Step 2: the liquid hydrogen pump (9) starts to work, and the liquid hydrogen is transferred through the intercooler (7) and the coil (13) to exchange heat with the compressed air and the fuel cell (6). The liquid hydrogen absorbs heat and vaporizes, and then enters the buffer tank (3), while cooling the fuel cell (6); Step 3: The fuel cell (6) continuously operates to generate heat, and the liquid hydrogen flow rate is adjusted by the liquid hydrogen pump (9) to maintain the operating temperature of the fuel cell (6). When the pressure of the hydrogen gas formed by the vaporization of the liquid hydrogen in the coil (13) is greater than the pressure in the liquid hydrogen storage tank (1), the gas phase valve I (2) and the liquid phase valve (10) are both opened, and the liquid hydrogen in the liquid hydrogen storage tank (1) is continuously squeezed out under the action of the hydrogen pressure. The outflow flow rate of the liquid hydrogen is controlled by adjusting the valve opening of the gas phase valve I (2) and the liquid phase valve (10). When the pressure in the liquid hydrogen storage tank (1) satisfies that the outflow flow rate of the liquid hydrogen is greater than or equal to the delivery flow rate of the liquid hydrogen pump (9), the liquid hydrogen pump (9) is closed; Step 4: When the liquid hydrogen power system is ready to stop working, the liquid phase valve (10) and the gas phase valve II (5) are closed, the fuel cell (6) is shut down, and then the gas phase valve I (2) is closed.

5. A method for balanced utilization of heat in a liquid hydrogen power system, characterized in that: It uses the liquid hydrogen power system as claimed in claim 2, comprising the following steps: Step 1: A rated amount of liquid hydrogen is stored in the liquid hydrogen storage tank (1), and a certain volume and pressure of hydrogen is stored in the buffer tank (3). At this time, the gas phase valve I (2) and the liquid phase valve (10) are closed, and the gas phase valve II (5) is opened, and the hydrogen in the buffer tank (3) enters the engine (14); at the same time, the air compressor (8) starts to work, so that the compressed air enters the engine (14), and the engine (14) starts to work; Step 2: the liquid hydrogen pump (9) starts to work, and the liquid hydrogen is exchanged with the engine (14) through the coil (13). The liquid hydrogen absorbs heat and vaporizes, and then enters the buffer tank (3), while cooling the engine (14); Step 3: The engine (14) continuously operates to generate heat, and the liquid hydrogen flow rate is adjusted by the liquid hydrogen pump (9) to maintain the operating temperature of the engine (14). When the pressure of the hydrogen gas formed by the vaporization of the liquid hydrogen in the coil (13) is greater than the pressure in the liquid hydrogen storage tank (1), the gas phase valve I (2) and the liquid phase valve (10) are both opened, and the liquid hydrogen in the liquid hydrogen storage tank (1) is continuously squeezed out under the action of the hydrogen pressure. The outflow flow rate of the liquid hydrogen is controlled by adjusting the valve opening of the gas phase valve I (2) and the liquid phase valve (10). When the pressure in the liquid hydrogen storage tank (1) satisfies that the outflow flow rate of the liquid hydrogen is greater than or equal to the delivery flow rate of the liquid hydrogen pump (9), the liquid hydrogen pump (9) is closed; Step 4: When the liquid hydrogen power system is ready to stop working, the liquid phase valve (10) and the gas phase valve II (5) are closed, and the engine (14) is shut down before closing the gas phase valve I (2).

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