Ammonia-electric hybrid system for a marine vessel with reversible fuel cell

Abstract

The application aims to provide an ammonia-electric hybrid power system of a ship with a reversible fuel cell, comprising an ammonia fuel engine, a double-fed induction motor, a propeller, a gear box, a diesel generator set, a fuel cell, a hydrogen storage and supply system, a power transformation device, a ship power grid and hydraulic elements, etc. The application can realize hybrid propulsion of the ammonia fuel engine and the double-fed induction motor, coordinated power supply of the diesel generator set and the reversible fuel cell and lithium battery, coupling of the reversible fuel cell and the diesel generator set in the gas path, and further improves the whole-ship propulsion efficiency. The application proposes a gas path coordination scheme of the engine and the fuel cell, can realize complementary advantages of the work of the two, simplifies the gas path design redundancy, and improves the integration of the system.

Description

Technical Field

[0001] The present invention relates to a marine propulsion system, specifically a marine hybrid power system. Background Technology

[0002] Currently, marine power systems, which are mainly based on diesel engines, have the disadvantages of high pollution, low energy consumption, and high carbon emissions. Therefore, there is an urgent need to find a low-carbon and efficient power system to meet the increasingly stringent carbon reduction requirements and adapt to the future goals of low-carbonization and even zero carbon.

[0003] Ammonia fuel, as a clean fuel, is widely used in the chemical industry. As a zero-carbon fuel, it has also attracted increasing attention in the marine propulsion field in recent years. Although the concept of ammonia fuel engines has been proposed in the shipbuilding industry, mature products are still lacking due to technological limitations. On the one hand, there is a lack of comprehensive research on the performance of ammonia fuel engines; on the other hand, there is no clear technical solution for matching ammonia fuel engines with appropriate power systems. Therefore, the research and development of ammonia fuel engines is still in its initial stage, and hybrid power systems for ammonia fuel engines are currently a technological void.

[0004] Marine hybrid power systems combine the advantages of traditional internal combustion engine propulsion and pure electric propulsion. Hybrid systems offer significant advantages in overall energy efficiency, energy conservation and emission reduction, and vibration and noise reduction. Furthermore, compared to pure electric propulsion systems, they can achieve long driving ranges with smaller capacity batteries at a lower cost. Hybrid systems based on ammonia fuel engines can meet the requirements of zero-carbon power while mitigating the low efficiency and cold-start difficulties of ammonia fuel engines. The introduction of an electric motor can also improve the dynamic characteristics of ammonia fuel engines, achieving complementary advantages from multiple power sources. Hybrid systems based on ammonia fuel engines will become one of the best power forms for future zero-carbon power. Therefore, securing intellectual property rights for ammonia fuel engine hybrid systems is of great significance for gaining a competitive edge in international technology and protecting key technologies related to ammonia fuel engine hybrid power. Summary of the Invention

[0005] The purpose of this invention is to provide a marine ammonia-electric hybrid propulsion system with a reversible fuel cell that overcomes the shortcomings of single ammonia engine propulsion technology and realizes hybrid propulsion of ammonia fuel engine, electric motor, ammonia diesel generator set, energy storage device, and reversible fuel cell.

[0006] The objective of this invention is achieved as follows:

[0007] This invention discloses a marine ammonia-electric hybrid power system with a reversible fuel cell, characterized by comprising: a variable-pitch propeller, an ammonia engine, an ammonia-diesel generator set, a doubly-fed induction motor, a reversible hydrogen fuel cell, a lithium-ion battery, a power grid, a first hydrogen storage tank, and a first oxygen storage tank. The ammonia engine is connected to the doubly-fed induction motor and the variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the power grid via a doubly-fed induction motor frequency converter. The stator winding of the doubly-fed induction motor is directly connected to the power grid. The lithium-ion battery is connected to the power grid via a lithium-ion battery inverter. The reversible hydrogen fuel cell... The fuel cell is connected to the power grid via a reversible hydrogen fuel cell inverter and a bidirectional transformer, while the ammonia-diesel generator is directly connected to the power grid. The first hydrogen storage tank is connected to the reversible hydrogen fuel cell via a first shut-off valve, a pressure regulating valve, a flame-retardant valve, and the first outlet of a seventh three-way valve. The hydrogen outlet of the reversible hydrogen fuel cell is connected to the ammonia-diesel generator via a second fuel pump, the first outlet of an eighth three-way valve, and a second flow meter. The first oxygen storage tank is connected to the reversible hydrogen fuel cell via a second shut-off valve, a fourth three-way valve, and a third flow meter. A portion of the oxygen passes through a fifth three-way valve, a purification device, and a second heat exchanger. The third exhaust gas recirculation pump and the ninth three-way valve enter the intake pipe to regulate the exhaust gas recirculation rate. Oxygen generated in the electrolysis mode of the reversible hydrogen fuel cell enters the first oxygen storage tank through the first centrifugal pump, the fourth three-way valve, and the fourth shut-off valve. A portion of the exhaust gas from the ammonia-diesel generator unit's exhaust pipe enters the reversible hydrogen fuel cell through the second outlet of the sixth three-way valve and the first outlet of the second three-way valve. The exhaust gas generated by the reversible hydrogen fuel cell and the exhaust gas generated by the ammonia-diesel generator unit are combined through the first three-way valve and returned to the exhaust pipe of the ammonia-diesel generator unit. A portion of the exhaust gas from the exhaust pipe passes through… The fifth three-way valve, the third three-way valve, the purification device, the second heat exchanger, and the third exhaust gas recirculation pump enter the intake pipe of the ammonia-diesel generator unit through the ninth three-way valve. After the air is compressed by the turbocharger of the ammonia-diesel generator unit, part of it enters the exhaust pipe through the third switch shut-off valve, and part of it enters the intake pipe through the first outlet of the third heat exchanger and the ninth three-way valve. The exhaust gas in the exhaust pipe is discharged into the atmosphere through the turbine, part of it is directly discharged into the atmosphere through the sixth three-way valve, and another part enters the reversible hydrogen fuel cell through the sixth three-way valve and the second three-way valve.

[0008] The present invention may also include:

[0009] 1. When the reversible hydrogen fuel cell operates in electrolysis mode, the power required for electrolysis is supplied by the ship's power grid. The exhaust gas generated by the ammonia diesel generator passes through the exhaust pipe and exchanges heat with water in the fourth heat exchanger to supply the heat required for electrolysis of the reversible fuel cell. The heating water comes from a water storage tank, flows through a water pump, catalyst, and evaporator, passes through the fourth heat exchanger, and enters the reversible hydrogen fuel cell. The hydrogen and water mixture generated by the electrolysis of the reversible hydrogen fuel cell evaporates in the evaporator and enters the condenser. The condensed water enters the water storage tank, and the generated hydrogen enters the second hydrogen storage tank. The oxygen generated by the electrolysis of the reversible fuel cell enters the environment through the evaporator. When the reversible hydrogen fuel cell operates in power generation mode, the hydrogen in the second hydrogen storage tank enters the anode of the reversible hydrogen fuel cell through the fifth heat exchanger, and the oxygen in the second oxygen storage tank enters the cathode of the reversible hydrogen fuel cell. The generated electricity is then fed into the grid through a power conversion device.

[0010] 2. In startup mode, the doubly-fed induction motor is controlled by the frequency converter to drag the ammonia fuel engine. The power source for the doubly-fed induction motor is the ship's power grid. The ship's power grid is supplied by the reversible hydrogen fuel cell, lithium-ion battery, and ammonia diesel generator set individually or in combination. The hydrogen fuel required by the fuel cell in the power grid enters the hydrogen fuel cell through the first hydrogen storage tank, the first shut-off valve, the pressure regulating valve, the flame retardant valve, the seventh three-way valve, and the first flow meter. In cold environments, the ammonia diesel generator set starts first. A portion of the exhaust gas produced by the exhaust pipe enters the reversible hydrogen fuel cell for preheating through the fourth three-way valve, the second three-way valve, or the third three-way valve. After the reversible hydrogen fuel cell is preheated to the preset temperature, it starts up again.

[0011] 3. In mechanical mode, the clutch is engaged, the doubly fed induction motor does not work, and the ammonia fuel engine drives the variable pitch propeller.

[0012] 4. In electric propulsion mode, the doubly-fed induction motor starts, the clutch disengages, the ammonia engine stops working, and the variable-pitch propeller is driven by the doubly-fed induction motor. The control rules are as follows: when the ship speed is low, the gearbox selects a high speed ratio gear; when the ship speed is high, a low speed ratio gear is selected. When the ship is docked or berthed, the pitch of the variable-pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the gearbox speed ratio is selected at a high speed ratio gear.

[0013] 5. In hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller. In this mode, the doubly fed induction motor is controlled by the ship's electrical network via a frequency converter, and the ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the variable pitch propeller pitch ratio and the speed of the doubly fed induction motor.

[0014] 6. In power generation mode, the clutch engages, and part of the power from the ammonia fuel engine drives the doubly-fed induction motor to generate electricity, while the other part drives the variable-pitch propeller. At this time, the doubly-fed induction motor feeds power to the grid in two ways: when the variable-pitch propeller pitch ratio is adjusted to make the ammonia engine speed reach the rated speed and generate 50Hz frequency power, it directly feeds power to the ship's power grid. At this time, the frequency converter does not work, and the doubly-fed induction motor acts as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, it feeds power to the ship's power grid through the frequency converter.

[0015] 7. The ship's electrical grid, ammonia-diesel generator set, hydrogen fuel cell, and lithium-ion battery include individual working modes and combined working modes. In individual working mode, the ammonia-diesel generator set, hydrogen fuel cell, or lithium-ion battery supplies power to the ship's electrical grid independently based on the power demand of the ship's electrical grid. In combined working mode, when the ship's power demand exceeds that of one of the generators, the two or three generators work together to supply power.

[0016] The advantages of this invention are:

[0017] 1. This invention proposes a marine ammonia-electric hybrid power system with a reversible fuel cell. It includes an ammonia fuel engine, a doubly-fed induction motor, a dual-ratio gearbox, and a clutch. With a wide power range, it can meet the power needs of ships under various operating conditions, reducing pollutant and carbon dioxide emissions. The significant technical advantages are as follows: First, the use of a doubly-fed induction motor reduces the inverter capacity by 50% compared to traditional PTO induction or synchronous motors used in ships. Simultaneously, due to the inclusion of a hydrogen fuel cell and a lithium-ion battery, the doubly-fed induction motor does not require a starter generator set during startup. The AC power required for the rotor windings of the doubly-fed induction motor is directly obtained from the DC power of the hydrogen fuel cell and converted by the inverter. Compared to traditional doubly-fed induction motors, this eliminates the AC-DC-AC conversion stage, improving energy transfer efficiency. The dual-ratio gearbox design overcomes the limitation of the small slip range of the doubly-fed induction motor, which makes it difficult to meet the needs of low-speed navigation. Furthermore, the variable-pitch propeller design avoids the problem of low torque at low speeds, better meeting the high torque requirements of low-speed navigation and improving the propulsion efficiency of the power system. The combination of an ammonia fuel engine and a doubly-fed induction motor serves two purposes. First, the doubly-fed induction motor can adjust the working space of the ammonia fuel engine, thereby improving its efficiency. Second, it can solve the problem of starting difficulties in high-power ammonia fuel engines due to the high ignition point of ammonia fuel. Furthermore, ammonia fuel engines suffer from incomplete combustion and poor dynamic characteristics under low-load conditions. The doubly-fed induction motor can utilize rapid torque response for torque coordination control to meet navigation requirements.

[0018] 2. The ship's power grid utilizes an ammonia-diesel generator set equipped with lithium-ion batteries and a hydrogen fuel cell. The lithium-ion batteries can perform peak shaving and valley filling of the power grid, ensuring the ammonia-diesel generator set operates at its optimal efficiency point, thus improving the grid system efficiency. Simultaneously, the hydrogen fuel cell, as one of the energy sources, can coordinate with the lithium-ion batteries to optimize the efficiency of the ammonia-diesel generator set, and can also be used by the lithium-ion batteries to optimize the operating point. This combined optimization approach improves the overall efficiency of the power grid and meets the grid's electricity demand. The specific technical effects are as follows: When grid power demand is low, the hydrogen fuel cell and ammonia-diesel generator set operate in a high-efficiency range, with the remaining power charging the lithium-ion batteries. When grid power demand is high or exceeds the rated power of the ammonia-diesel generator set and hydrogen fuel cell, the lithium-ion batteries discharge to meet the power demand, ensuring high-efficiency output from both the ammonia-diesel generator set and the hydrogen fuel cell. The lithium-ion battery configuration leverages its high power output response to meet the dynamic power needs of the ship, thereby reducing operating fluctuations of the ammonia-diesel generator set and preventing increased engine emissions under extreme operating conditions. Moreover, lithium-ion batteries and hydrogen fuel cells can serve as backup power sources when diesel generators fail, meeting the requirements for black start in the power grid; the hydrogen fuel cell is directly connected to the doubly-fed induction generator through an inverter, making black start more reliable.

[0019] 3. The doubly-fed induction motor has two power feeding modes to the ship's power grid. First, when the ammonia-fueled engine operates at a constant speed, the ship can change speeds via variable pitch propellers, and the doubly-fed motor can be directly connected to the ship's power grid. Second, when both the ammonia-fueled engine and the variable-pitch propeller operate at variable speeds, the doubly-fed motor achieves grid connection by adjusting the frequency and phase of synchronous power generation in the rotor excitation windings via a frequency converter. Significant technical advantages can be seen in these two feeding methods. Both methods avoid power losses and rely solely on software control for grid connection. Furthermore, using a small-capacity frequency converter to control the doubly-fed induction motor rotor windings enables variable-speed power generation, improving power generation efficiency and cost. Selecting between these two modes allows for optimal efficiency optimization of the ammonia-fueled engine.

[0020] 4. This invention proposes a marine ammonia-electric hybrid power system with a reversible fuel cell. It integrates the gas path design of the ammonia-diesel generator and the reversible hydrogen fuel cell, employing a shared hydrogen fuel supply circuit to simplify the redundancy of the supply pipeline. Simultaneously, the exhaust gas generated by the fuel cell is introduced into the exhaust pipe of the ammonia-diesel generator, resulting in more efficient waste heat utilization and increased turbine power, which is beneficial for optimizing the performance of the ammonia-diesel generator by increasing compressed air. The exhaust gas recirculation circuit design solves the problem of excessive nitrogen oxide emissions from the ammonia-diesel generator, while the cylinder bypass circuit prevents compressor surge under partial load.

[0021] 5. Another advantage of the present invention is that by introducing the exhaust gas after the turbine of the ammonia-diesel generator into the preheating circuit of the hydrogen fuel cell, the cold start and electrolysis of the reversible hydrogen fuel cell can be achieved without the need for an additional heat source, thus realizing the reuse of exhaust energy.

[0022] 6. Reversible hydrogen fuel cells can not only feed power to the grid in conjunction with lithium-ion batteries and ammonia diesel generators when power demand is high, but also absorb excess power from the grid in electrolysis mode when power demand is low, keeping the ammonia diesel generator in its high-efficiency operating range while producing and storing hydrogen; the hydrogen produced by the electrolysis of the reversible fuel cell can ignite the ammonia in the ammonia diesel generator, realizing the hydrogen-ignited ammonia combustion mode.

[0023] 7. The hybrid power system provided by this system is suitable for the power system of large ocean-going vessels. It can meet the requirements of zero-carbon navigation, ensure low emissions of pollutants such as nitrogen oxides, and guarantee the range of ocean voyages. Attached Figure Description

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

[0025] Figure 2 This is a schematic diagram of a reversible fuel cell in operation. Detailed Implementation

[0026] The invention will now be described in more detail with reference to the accompanying drawings:

[0027] Combination Figure 1-2The present invention discloses a marine ammonia-electric hybrid power system with a reversible fuel cell, comprising a variable pitch propeller 1, a gearbox 2, a clutch 3, an ammonia engine 4, an ammonia-diesel generator set 5, a doubly-fed induction motor 6, a hydrogen fuel cell inverter 7, a bidirectional transformer 8, a reversible hydrogen fuel cell 9, three-way valves 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, heat exchangers 11a, 11b, 11c, a doubly-fed induction motor frequency converter 12, a lithium-ion battery inverter 13, and a lithium-ion battery... The system includes: battery 14, flow meters 15a and 15b, flame-retardant valve 16, pressure regulating valve 17, on / off valves 18a, 18b and 18c, hydrogen storage tank 19a, oxygen storage tank 19b, oxygen pump 20a, fuel pump 20b, exhaust gas recirculation pump 20c, purification device 21, exhaust pipe 22, intake pipe 23, turbocharger 24; water storage tank 25a, hydrogen storage tank 25b, oxygen storage tank 25c, water pump 26, catalyst tank 27, condenser 28, evaporator 29a, heat exchangers 29b and 29c. The connections are as follows: the output of the ammonia fuel engine 4 is mechanically connected to the doubly-fed induction motor 6 and the variable-pitch propeller 1 via the clutch 3 in the gearbox 2; the rotor excitation winding of the doubly-fed induction motor 6 is connected to the ship's power grid via the frequency converter 12, and the stator winding is directly connected to the power grid. The lithium-ion battery 14 is connected to the power grid via the lithium-ion battery inverter 13. The reversible hydrogen fuel cell 9 is connected to the power grid via the hydrogen fuel cell inverter 7 and the bidirectional transformer 8. The ammonia-diesel generator unit 5 is directly connected to the power grid. The hydrogen fuel in the hydrogen storage tank 19a enters the fuel cell 9 through the first outlet of the three-way valve 10g via the switch shut-off valve 18a, the pressure regulating valve 17, and the flame retardant valve 16. The hydrogen produced by the hydrogen fuel cell 9 in electrolysis mode or the residual hydrogen enters the ammonia-diesel generator unit 23 through the hydrogen outlet, fuel pump 20b, the first outlet of the three-way valve 10h, and the fuel flow meter 15b to ignite the ammonia. Oxygen from oxygen storage tank 19b enters hydrogen fuel cell 9 via shut-off valve 18b, three-way valve 10d, and flow meter 15c. A portion of the oxygen enters intake pipe 23 via three-way valve 10e, purification device 21, heat exchanger 11b, exhaust gas recirculation pump 20c, and three-way valve 10i to regulate the exhaust gas recirculation rate. Oxygen generated in electrolysis mode in hydrogen fuel cell 9 enters oxygen storage tank 19b via centrifugal pump 20a, three-way valve 10d, and shut-off valve 18d. A portion of the exhaust gas from ammonia-diesel generator exhaust pipe 22 enters hydrogen fuel cell via the second outlet of three-way valve 10f and the first outlet of three-way valve 10b for cold start or electrolysis mode. The exhaust gas generated by hydrogen fuel cell 9 and ammonia-diesel generator 5 are combined via three-way valve 10a and returned to exhaust pipe 22. A portion of the exhaust gas in the exhaust pipe 22 passes through three-way valves 10e and 10c, purification device 21, heat exchanger 11b, exhaust gas recirculation pump 20c, and then enters the intake pipe 23 through three-way valve 10i. This is the exhaust gas recirculation loop.After being compressed by the turbocharger 24, part of the ambient air enters the exhaust pipe through the shut-off valve 18c, which is the cylinder bypass circuit; another part enters the intake pipe 23 through the heat exchanger 11c and the first outlet of the three-way valve 10i. Most of the exhaust gas in the exhaust pipe 22 is discharged into the atmosphere through the turbine in the turbocharger 24. Part of it is directly discharged into the atmosphere through the three-way valve 10f, and another part enters the fuel cell through the three-way valves 10f and 10b, which is the hydrogen fuel cell cold start preheating circuit.

[0028] See Figure 2 When the reversible hydrogen fuel cell 9 operates in electrolysis mode, the electricity required for electrolysis is supplied by the ship's power grid. The exhaust gas generated by the ammonia-diesel generator 5 is discharged through exhaust pipe 22, passing through heat exchanger 29b to exchange heat with water, providing the heat required for the electrolysis of the reversible fuel cell. The heated water originates from water storage tank 25a, flows through water pump 26, catalyst 27, heat exchanger 29a, and heat exchanger 29b before entering the reversible hydrogen fuel cell 9. The hydrogen and water mixture generated by the electrolysis of the reversible hydrogen fuel cell 9 evaporates through heat exchanger 29a and enters condenser 28. The condensed water enters water storage tank 25a, and the generated hydrogen enters hydrogen storage tank 25b. The oxygen generated by the electrolysis of the reversible hydrogen fuel cell 9 enters the environment through heat exchanger 29a. When the reversible hydrogen fuel cell operates in power generation mode, the hydrogen from the hydrogen storage tank enters the anode of the reversible hydrogen fuel cell through heat exchanger 29c, and the oxygen from oxygen storage tank 25c enters the cathode of the reversible hydrogen fuel cell. The generated electricity is then fed into the grid through a power conversion device.

[0029] In this embodiment, the ammonia fuel engine 4 is preferably a compression ignition engine, the ammonia diesel generator set 5 is preferably a spark ignition engine, and the lithium-ion battery 14 is preferably a lithium iron phosphate battery with high power density and small size and weight.

[0030] The main working modes of this invention are as follows:

[0031] In the ship's standby mode, the start-up mode is controlled by the frequency converter 12, which controls the doubly-fed induction motor 6 to drag the ammonia fuel engine 4. The power source for the doubly-fed induction motor 6 is provided by the ship's electrical grid. The ship's electrical grid can be powered individually or in combination by the reversible fuel cell 9, the lithium-ion battery 14, and the ammonia-diesel generator 5. The hydrogen fuel required by the fuel cell in the grid enters the hydrogen fuel cell through the hydrogen storage tank 19a, the shut-off valve 18a, the pressure regulating valve 17, the flame retardant valve 16, the three-way valve 10g, and the flow meter 15a. It should be noted that in cold environments, the ammonia-diesel generator 5 starts first. A portion of the exhaust gas produced by the exhaust pipe 22 enters the hydrogen fuel cell 9 through the three-way valves 10d, 10b, or 10c for preheating. After the fuel cell 9 has been preheated to a suitable temperature, it starts up.

[0032] In mechanical mode, clutch 3 is engaged, at which time doubly fed induction motor 6 is not working, and ammonia fuel engine 4 drives variable pitch propeller 1 through gearbox 2.

[0033] In electric propulsion mode, the doubly-fed induction motor 6 starts, the clutch 3 disengages, and the ammonia engine 4 stops operating. The variable-pitch propeller 1 is driven by the doubly-fed induction motor 6. At this time, the speed ratio of the gearbox 2 can be selected according to the ship's speed and pitch ratio. The control rule is as follows: when the ship's speed is low, the gearbox 2 selects a high speed ratio gear; when the ship's speed is high, a low speed ratio gear is selected. When the ship is docked or berthed, the pitch of the variable-pitch propeller 1 is reduced to meet the speed range of the doubly-fed induction motor 6, and the speed ratio of the gearbox 2 should also be selected at a high speed ratio.

[0034] In the hybrid propulsion mode, clutch 3 engages, and the doubly-fed induction motor 6 and the ammonia fuel engine 4 jointly drive the variable-pitch propeller 1 via gearbox 2. In this mode, the doubly-fed induction motor 6 is controlled by the ship's electrical network via frequency converter 12. In this mode, the ammonia fuel engine 4 can operate in constant power mode or optimal economic curve mode, and the engine operating range is optimized by adjusting the pitch ratio of the variable-pitch propeller 1 and the speed of the doubly-fed induction motor 6.

[0035] In power generation mode, clutch 3 engages, and part of the power from the ammonia fuel engine 4 drives the doubly-fed induction motor 6 to generate electricity. Part of the power drives the variable-pitch propeller 1 through gearbox 2. At this time, the doubly-fed induction motor 6 can feed power to the grid in two ways. When the pitch ratio of the variable-pitch propeller 1 is adjusted so that the speed of the ammonia engine 4 is at the rated speed and generates 50Hz frequency power, it directly feeds power to the ship's power grid. At this time, the frequency converter 12 does not work, and the doubly-fed induction motor 6 can act as an asynchronous motor. When the speed of the doubly-fed induction motor 6 is less than the rated speed, it feeds power to the ship's power grid through the frequency converter 12.

[0036] The ship's electrical system includes 5 ammonia-diesel generators, 9 hydrogen fuel cells, and 14 lithium-ion batteries. Its main operating modes are divided into individual operating mode and combined operating mode.

[0037] In standalone mode, the ammonia-diesel generator 5, hydrogen fuel cell 9, or lithium-ion battery 14 supply power to the ship's power grid independently, based on the power demand of the ship's power grid. In joint operation mode, when the ship's power demand exceeds that of one of the generators, the two or three generators supply power together, and the power output of each generator is optimized according to the energy management strategy.

[0038] The reversible hydrogen fuel cell 9 operates primarily in two modes: electrolysis mode and power generation mode. In electrolysis mode, the ship's electrical grid supplies the power required for electrolysis. The exhaust gas from the ammonia-diesel generator 5 passes through exhaust pipe 22 and heats water via heat exchanger 29b, providing the heat needed for electrolysis in the reversible fuel cell 9. The heated water originates from water storage tank 25a, flows through water pump 26, catalyst 27, heat exchanger 29a, and heat exchanger 29b before entering the reversible hydrogen fuel cell 9. The hydrogen and water mixture produced by electrolysis in the reversible hydrogen fuel cell 9 evaporates in heat exchanger 29a and enters condenser 28. The condensed water enters water storage tank 25a, and the produced hydrogen enters hydrogen storage tank 25b. The oxygen produced by electrolysis in the reversible fuel cell 9 enters the environment via heat exchanger 29a. In power generation mode, hydrogen from the hydrogen storage tank enters the anode of the reversible hydrogen fuel cell via heat exchanger 29c, and oxygen from oxygen storage tank 25c enters the cathode of the reversible hydrogen fuel cell. The generated electricity is then fed into the grid via a power conversion device.

[0039] When the ship's grid power demand is low, the ammonia-diesel generator unit 5 operates at its optimal power under the control of the energy management unit. A portion of the power is used to meet the power demand, while the remaining power is used to store hydrogen in the electrolysis mode of the reversible hydrogen fuel cell 9 and in the lithium-ion battery 14, thus performing peak shaving and valley filling. When the ship's grid power demand is high, the ammonia-diesel generator unit 5, the lithium-ion battery 14, and the reversible hydrogen fuel cell 9 need to operate in power generation mode, with all three supplying power jointly or in pairs. In this case, the energy management strategy optimizes the power output.

Claims

1. A marine ammonia-electric hybrid power system with a reversible fuel cell, characterized in that: The system includes a variable-pitch propeller, an ammonia engine, an ammonia-diesel generator set, a doubly-fed induction motor, a reversible hydrogen fuel cell, a lithium-ion battery, a power grid, a first hydrogen storage tank, and a first oxygen storage tank. The ammonia engine is connected to the doubly-fed induction motor and the variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the power grid via a doubly-fed induction motor frequency converter, and the stator winding of the doubly-fed induction motor is directly connected to the power grid. The lithium-ion battery is connected to the power grid via a lithium-ion battery inverter. The reversible hydrogen fuel cell is connected to the power grid via a reversible hydrogen fuel cell inverter and a bidirectional transformer. The ammonia-diesel generator set is directly connected to the power grid. The first hydrogen storage tank is connected to the reversible hydrogen fuel cell via a first shut-off valve, a pressure regulating valve, a flame-retardant valve, and the first outlet of a seventh three-way valve. The hydrogen outlet of the reversible hydrogen fuel cell is connected to the ammonia-diesel generator set via a second fuel pump, the first outlet of an eighth three-way valve, and a second flow meter. The first oxygen storage tank is connected to the reversible hydrogen fuel cell via a second shut-off valve, a fourth three-way valve, and a third flow meter. A portion of the oxygen passes through a fifth three-way valve, a purification device, a second heat exchanger, a third exhaust gas recirculation pump, and a ninth three-way valve. The air enters the intake pipe, and the exhaust gas recirculation rate is adjusted. Oxygen generated in the electrolysis mode of the reversible hydrogen fuel cell enters the first oxygen storage tank through the first centrifugal pump, the fourth three-way valve, and the fourth shut-off valve. Part of the exhaust gas in the exhaust pipe of the ammonia diesel generator enters the reversible hydrogen fuel cell through the second outlet of the sixth three-way valve and the first outlet of the second three-way valve. The exhaust gas generated by the reversible hydrogen fuel cell and the exhaust gas generated by the ammonia diesel generator are combined through the first three-way valve to the exhaust pipe of the ammonia diesel generator. Part of the exhaust gas in the exhaust pipe passes through the fifth three-way valve, the third three-way valve, the purification device, the second heat exchanger, and the third exhaust gas recirculation pump, and enters the intake pipe of the ammonia diesel generator through the ninth three-way valve. After the air is compressed by the turbocharger of the ammonia diesel generator, part of it enters the exhaust pipe through the third shut-off valve, and part of it enters the intake pipe through the third heat exchanger and the first outlet of the ninth three-way valve. The exhaust gas in the exhaust pipe is discharged into the atmosphere through the turbine, part of it is directly discharged into the atmosphere through the sixth three-way valve, and the other part enters the reversible hydrogen fuel cell through the sixth three-way valve and the second three-way valve. In hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller. In this mode, the doubly fed induction motor is controlled by the ship's electrical grid via a frequency converter, and the ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the variable pitch propeller pitch ratio and the speed of the doubly fed induction motor. In power generation mode, the clutch engages, and part of the power from the ammonia fuel engine drives the doubly-fed induction motor to generate electricity, while the other part drives the variable-pitch propeller. At this time, the doubly-fed induction motor feeds power to the grid in two ways. When the variable-pitch propeller pitch ratio is adjusted to make the ammonia engine speed reach the rated speed and generate 50Hz frequency power, it feeds power directly to the ship's power grid. At this time, the frequency converter does not work, and the doubly-fed induction motor acts as an asynchronous motor. When the speed of the doubly-fed induction motor is less than the rated speed, it feeds power to the ship's power grid through the frequency converter.

2. The marine ammonia-electric hybrid power system with a reversible fuel cell according to claim 1, characterized in that: When the reversible hydrogen fuel cell operates in electrolysis mode, the power required for electrolysis is supplied by the ship's power grid. The exhaust gas generated by the ammonia diesel generator passes through the exhaust pipe and exchanges heat with water in the fourth heat exchanger to supply the heat required for electrolysis of the reversible fuel cell. The heating water comes from a water storage tank, flows through a water pump, catalyst, and evaporator, and enters the reversible hydrogen fuel cell through the fourth heat exchanger. The hydrogen and water mixture generated by the electrolysis of the reversible hydrogen fuel cell evaporates in the evaporator and enters the condenser. The condensed water enters the water storage tank, and the generated hydrogen enters the second hydrogen storage tank. The oxygen generated by the electrolysis of the reversible fuel cell enters the environment through the evaporator. When the reversible hydrogen fuel cell operates in power generation mode, the hydrogen in the second hydrogen storage tank enters the anode of the reversible hydrogen fuel cell through the fifth heat exchanger, and the oxygen in the second oxygen storage tank enters the cathode of the reversible hydrogen fuel cell. The generated electricity is then fed into the grid through a power conversion device.

3. A marine ammonia-electric hybrid power system with a reversible fuel cell according to claim 1, characterized in that: In startup mode, the doubly-fed induction motor is controlled by the frequency converter to drag the ammonia fuel engine. The power source for the doubly-fed induction motor is the ship's power grid, which is powered individually or in combination by the reversible hydrogen fuel cell, lithium-ion battery, and ammonia diesel generator. The hydrogen fuel required by the fuel cell in the power grid enters the hydrogen fuel cell through the first hydrogen storage tank, the first shut-off valve, the pressure regulating valve, the flame retardant valve, the seventh three-way valve, and the first flow meter. In cold environments, the ammonia diesel generator starts first. A portion of the exhaust gas produced by the exhaust pipe enters the reversible hydrogen fuel cell for preheating through the fourth three-way valve, the second three-way valve, or the third three-way valve. After the reversible hydrogen fuel cell is preheated to the preset temperature, it starts up again.

4. A marine ammonia-electric hybrid power system with a reversible fuel cell according to claim 1, characterized in that: In mechanical mode, the clutch engages, the doubly fed induction motor does not work, and the ammonia fuel engine drives the variable pitch propeller.

5. A marine ammonia-electric hybrid power system with a reversible fuel cell according to claim 1, characterized in that: In electric propulsion mode, the doubly-fed induction motor starts, the clutch disengages, the ammonia engine stops working, and the variable-pitch propeller is driven by the doubly-fed induction motor. The control rules are as follows: when the ship speed is low, the gearbox selects a high speed ratio gear; when the ship speed is high, a low speed ratio gear is selected. When the ship is docked or berthed, the pitch of the variable-pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the gearbox speed ratio is selected at a high speed ratio gear.

6. A marine ammonia-electric hybrid power system with a reversible fuel cell according to claim 1, characterized in that: The ship's electrical grid, ammonia-diesel generator, hydrogen fuel cell, and lithium-ion battery include individual and combined operating modes. In individual mode, the ammonia-diesel generator, hydrogen fuel cell, or lithium-ion battery supplies power to the ship's electrical grid independently, based on the power demand of the ship's electrical grid. In combined operating mode, when the ship's power demand exceeds that of one of the generators, the two or three generators work together to supply power.

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