Ammonia-electric hybrid power system for ships based on comprehensive waste heat gradient utilization

Abstract

The purpose of this invention is to provide a marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization, including an ammonia fuel engine, a doubly-fed induction motor, a propeller, a gearbox, a clutch, a waste heat recovery system, a power conversion unit, a fuel cell, a thermoelectric power generation module, and a condenser. The technical solution of this invention enables hybrid propulsion of the ammonia fuel engine and the doubly-fed induction motor, while simultaneously achieving gradient utilization of waste heat from the hybrid power system, significantly improving energy efficiency and further enhancing the overall propulsion efficiency of the ship.

Description

TECHNICAL FIELD

[0001] The present application relates to a ship power system, in particular to a ship hybrid power system. BACKGROUND

[0002] At present, the ship power system mainly based on diesel engine has the disadvantages of high pollution, low energy consumption and high carbon emission, so it is urgent to seek a low-carbon and high-efficiency power system to meet the increasingly stringent carbon reduction demand and adapt to the future low-carbonization and even zero-carbon target.

[0003] Ammonia fuel, as a clean fuel, is widely used in the chemical industry. As a zero-carbon fuel, ammonia fuel has gradually attracted widespread attention in the field of ship power in recent years. Although the concept of ammonia fuel engine has been proposed in the ship industry, there is still no mature product due to technical limitations. On the one hand, the performance of ammonia fuel engine lacks comprehensive research, and on the other hand, there is no clear technical solution for matching the ammonia fuel engine with a power system. Therefore, the research and development of ammonia fuel engine is still in the preliminary stage, and the hybrid power system of ammonia fuel engine is still in the technical blank stage.

[0004] The ship hybrid power system has the advantages of both traditional internal combustion engine propulsion and pure electric propulsion. The hybrid power system has obvious advantages in comprehensive energy efficiency, energy saving and emission reduction, and vibration and noise. Compared with the pure electric propulsion system, a small capacity battery can meet the long endurance mileage, and the cost is low. The hybrid power system based on ammonia fuel engine can not only meet the requirement of zero-carbon power, but also make up for the problems of low efficiency at low load, difficult cold start and other problems of ammonia fuel engine. The introduction of the motor can improve the dynamic characteristics of the ammonia fuel engine and realize the complementary advantages of multiple power sources. The waste heat recovery technology can recover the waste heat generated by the engine, which is one of the important means of energy saving and carbon reduction. Due to the characteristics of integration of multiple energy devices, the hybrid power system also has multiple heat sources that can be recycled. At present, there are still few application technologies of waste heat recovery system in ship hybrid power system.

[0005] The hybrid power system based on ammonia fuel engine will become one of the best power forms of future zero-carbon power. Therefore, the layout of ammonia fuel engine hybrid power system intellectual property has very important significance for occupying the international technology highland in advance and protecting the key technology of ammonia fuel engine hybrid power. SUMMARY

[0006] The purpose of the present application is to provide a ship ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization, which can realize ammonia fuel engine and motor hybrid propulsion and reduce ship carbon emission by applying gradient waste heat recovery and utilization system.

[0007] The object of the present invention is achieved in that:

[0008] The ship ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization is characterized by comprising a variable pitch propeller, a clutch, a double-fed induction motor, an ammonia fuel cell, an ammonia fuel engine, an evaporation superheater, a heat exchange plate, a high-pressure steam drum, a steam turbine, a steam turbine, a generator, a thermoelectric module, an electric grid, and an organic Rankine medium.

[0009] The present invention can also include:

[0010] 1. The water cooled by the second condenser is pumped into the ammonia fuel engine by the first water pump to exchange heat with the lubricating oil and the cylinder jacket water.

[0011] 2. In the starting mode, the frequency converter controls the double-fed induction motor to drag the ammonia fuel engine for starting.

[0012] 3. In the mechanical mode, the clutch is engaged, the double-fed induction motor is not working, and the ammonia fuel engine drives the variable pitch propeller through the gear box.

[0013] 4. In the electric propulsion mode, the doubly-fed induction motor is started, the clutch is disconnected, the ammonia engine is not working, the doubly-fed induction motor drives the variable pitch propeller, when the ship speed is low, the gearbox selects the high speed ratio gear, when the ship speed is high, the low speed ratio gear is selected; when the ship is at the shore or the berth, the pitch of the variable pitch propeller is reduced to meet the speed range of the doubly-fed induction motor, and the high speed ratio gear is selected at the same time.

[0014] 5. In the hybrid propulsion mode, the clutch is connected, the doubly-fed induction motor and the ammonia engine drive the variable pitch propeller through the gearbox, the doubly-fed induction motor is powered by the ship power grid through the frequency converter, the ammonia engine works in the constant power mode or the optimal economic curve mode, and the engine working interval is optimized by adjusting the pitch ratio of the variable pitch propeller and the speed of the doubly-fed induction motor.

[0015] 6. In the power generation mode, the clutch is connected, the ammonia engine drives the doubly-fed induction motor to generate power, and a part of the power drives the variable pitch propeller through the gearbox, the doubly-fed induction motor includes two ways to feed the power grid, when the ammonia engine speed is adjusted to the rated speed to generate 50HZ frequency power, the power is directly fed to the ship power grid, at this time, the frequency converter does not work, and the doubly-fed induction motor works as an asynchronous motor; when the speed of the doubly-fed induction motor is less than the rated speed, the frequency and voltage of the output power are controlled by the voltage frequency converter to feed the power grid.

[0016] The advantages of the application are:

[0017] 1. This invention proposes a marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization. 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 an ammonia fuel cell and a thermoelectric module, 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 ammonia 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 doubly-fed induction motor (DFIG) provides power to the ship's electrical grid in two modes. First, when the ammonia-fueled engine operates at a constant speed, the ship can change speeds via variable pitch propellers, allowing the DFIG to directly connect to the grid. Second, when both the ammonia-fueled engine and the variable-pitch propeller operate at variable speeds, the DFIG achieves grid connection by adjusting the frequency and phase of synchronous power generation in the rotor excitation windings via a frequency converter. This demonstrates significant technological advantages. Both power supply methods avoid power losses and rely solely on software control for grid connection. Furthermore, using a small-capacity frequency converter to control the DFIG rotor windings enables variable-speed power generation, improving power generation efficiency and reducing costs. Selecting between these different modes allows for optimal efficiency optimization of the ammonia-fueled engine.

[0019] 3. This invention proposes a marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization, realizing the cascade utilization of thermal energy in the marine hybrid power system. Based on the temperature of different waste heat sources in the system, a dual-loop waste heat recovery system of organic Rankine cycle and steam Rankine cycle is designed. The steam Rankine cycle utilizes the waste heat from ammonia fuel engine lubricating oil and cylinder liner water, and exhaust superheat; the organic Rankine cycle utilizes ammonia fuel cell exhaust preheating and ammonia fuel engine compressed intercooled air superheating. This fully considers the utilization of heat sources of different qualities, improving the energy and efficiency of waste heat recovery. Simultaneously, the introduction of a thermoelectric power generation module further utilizes low-temperature heat sources, reducing system energy consumption.

[0020] 4. 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

[0021] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0022] The invention will now be described in more detail with reference to the accompanying drawings:

[0023] Combination Figure 1 This invention discloses a marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization, comprising a variable pitch propeller 1, a gearbox 2, a clutch 3, a doubly fed induction motor 4, a doubly fed induction motor frequency converter 5, an ammonia fuel cell 6, an ammonia fuel engine 7, a compressed air heat exchanger 8, a turbocharger 9, an exhaust pipe 10, an intake pipe 11, an intercooler 12, lubricating oil and cylinder liner water 13, an evaporative superheater 14, a heat exchange plate 15, three-way valves 16a, 16b, and 16c, a high-pressure steam drum 17, a low-pressure steam drum 18, a steam turbine 19a, an organic working fluid steam turbine 19b, one-way valves 20a and 20b, a generator 21, a condenser 22a and 22b, a water pump 23a, an organic working fluid pump 23b, and a thermoelectric module 24. The output of the ammonia fuel engine 7 is mechanically connected to the doubly fed induction motor 4 and the variable pitch propeller 1 via the clutch 3 in the gearbox 2; the rotor excitation winding of the doubly fed induction motor 4 is connected to the output of the ammonia fuel cell 6 via the frequency converter 5, and the stator winding is directly connected to the power grid.

[0024] In the low-pressure organic Rankine loop, a portion of the organic Rankine medium exchanges heat with the ammonia fuel cell 6 via heat exchange plate 15, while another portion exchanges heat with the cooling water inside the doubly-fed induction motor 4 via three-way valves 16a and 16b and heat exchanger 8. This results in the final collection of an organic Rankine fluid at a certain temperature, which then exchanges heat with the compressed air after being pressurized and intercooled by the ammonia engine 7. The fluid evaporates and becomes superheated organic Rankine saturated steam, which enters the low-pressure steam drum 12. Afterward, it passes through a one-way valve 20b and enters the organic Rankine turbine 19a to drive the generator 21, which outputs electricity for grid connection. A portion of the expanded organic medium, after performing work, passes through a three-way valve 16d to the hot end of the thermoelectric module 24 for heat exchange, generating electricity to power the doubly-fed motor 4. The organic working fluid exiting the thermoelectric module 24 and the working fluid exiting the organic working fluid turbine 19a exchange heat with the cooling water via condenser 22a, and finally undergoes a new organic Rankine cycle via the organic working fluid pump 23b for waste heat recovery. The steam Rankine cycle is as follows: Water cooled by condenser 22b is pumped by water pump 23a to the ammonia fuel engine 7 for heat exchange with lubricating oil and cylinder liner water 13. After being preheated by these two components, the water, now at a certain temperature, enters the evaporative superheater 14 for heat exchange with the high-temperature exhaust gas from the ammonia fuel engine 7. The exhaust gas from the ammonia fuel engine 7, which exchanges heat with the water, is divided into two parts: one part is the exhaust gas after the turbocharger 9, and the other part is the exhaust gas during the exhaust gas recirculation process. After heat exchange with the exhaust gas, the preheated water becomes high-temperature superheated steam. The superheated steam enters the high-pressure steam drum 17 and then enters the steam turbine 19b through one-way valve 20a to perform work. The turbine 19b drives the generator 21 to generate electricity and connect to the grid. Part of the expanded steam enters the hot end of the thermoelectric module 24 through 16c for further heat energy utilization and power generation, while the other part, together with the steam after heat exchange with the thermoelectric module, is cooled by condenser 22b and re-enters the steam Rankine cycle for waste heat recovery.

[0025] The main working modes of this invention are as follows:

[0026] In the ship's standby mode, the inverter 5 controls the doubly-fed induction motor 4 to tug the ammonia fuel engine 7 for startup. The power source for the doubly-fed induction motor 4 is directly provided by the power generated by the ammonia fuel cell 6 and the thermoelectric module 24 controlled by the inverter 5. This setup can prevent insufficient power due to ship grid failure and reduce energy loss during power transmission.

[0027] In mechanical mode, clutch 3 is engaged, at which time doubly fed induction motor 4 is not working, and ammonia fuel engine 7 drives variable pitch propeller 1 through gearbox 2.

[0028] In electric propulsion mode, the doubly-fed induction motor 4 starts, the clutch 3 disengages, and the ammonia engine 7 stops operating. The variable-pitch propeller 1 is driven by the doubly-fed induction motor 4. At this time, the gearbox speed ratio can be selected according to the ship speed and pitch ratio. The control rule is as follows: when the ship speed is low, the gearbox 2 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 1 is reduced to meet the speed range of the doubly-fed induction motor 4, and the gearbox 2 speed ratio should also be selected at a high speed ratio gear.

[0029] In the hybrid propulsion mode, clutch 3 engages, and the doubly-fed induction motor 4 and the ammonia fuel engine 7 jointly drive the variable-pitch propeller 1 via gearbox 2. In this mode, the doubly-fed induction motor 4 is powered by the ship's electrical grid and controlled by frequency converter 5. In this mode, the ammonia fuel engine 7 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 4.

[0030] In power generation mode, clutch 3 engages, and part of the power from the ammonia fuel engine 7 drives the doubly-fed induction motor 4 to generate electricity. Part of the power drives the variable-pitch propeller 1 through gearbox 2. At this time, the doubly-fed induction motor 4 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 7 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 5 does not work, and the doubly-fed induction motor 4 can act as an asynchronous motor. When the speed of the doubly-fed induction motor 4 is less than the rated speed, the frequency and voltage of the output power are controlled by the variable-voltage frequency converter 5 to feed power to the ship's power grid.

Claims

1. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization, characterized in that: The system includes a variable-pitch propeller, clutch, doubly-fed induction motor, ammonia fuel cell, ammonia fuel engine, evaporative superheater, heat exchange plates, high-pressure steam drum, steam turbine, steam turbine, generator, thermoelectric module, power grid, and organic Rankine medium. The ammonia fuel engine output is connected to the doubly-fed induction motor and variable-pitch propeller via a clutch. The rotor excitation winding of the doubly-fed induction motor is connected to the ammonia fuel cell output via a frequency converter. The stator winding of the doubly-fed induction motor is directly connected to the power grid. The organic Rankine medium consists of two parts: one part exchanges heat with the ammonia fuel cell via heat exchange plates, and the other part exchanges heat with... (The sentence is incomplete and requires further context to translate accurately.) The heat exchanger exchanges heat with the cooling water inside the doubly-fed induction motor, eventually generating an organic Rankine fluid. This fluid then exchanges heat with the compressed air after being pressurized and intercooled by the ammonia engine, evaporating and superheating into organic Rankine saturated steam, which enters the low-pressure steam drum. After passing through the second one-way valve, it enters the turbine to do work, driving the generator to output electrical energy and connect to the grid. A portion of the organic medium after expansion and work passes through the fourth three-way valve to enter the hot end of the thermoelectric module for heat exchange, generating electrical energy to power the doubly-fed motor. The organic working fluid flowing out of the thermoelectric module and the working fluid flowing out of the turbine exchange heat with the cooling water in the first condenser, and then undergoes a second organic working fluid pump to recycle organic Rankine for waste heat recovery.

2. The marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization according to claim 1, characterized in that: Water cooled by the second condenser is pumped by the first water pump into the ammonia fuel engine to exchange heat with lubricating oil and cylinder liner water. After being preheated by these two components, the water enters the evaporative superheater to exchange heat with the exhaust gas from the ammonia fuel engine. The exhaust gas from the ammonia fuel engine that exchanges heat with the water is divided into two parts: one part is the exhaust gas after the turbocharger, and the other part is the exhaust gas during the exhaust gas recirculation process. After exchanging heat with the exhaust gas, the preheated water becomes high-temperature superheated steam. The superheated steam enters the high-pressure steam drum and then enters the steam turbine through the first one-way valve to do work. The steam turbine drives the generator to generate electricity and connect to the grid. Part of the expanded steam enters the hot end of the thermoelectric module through the third three-way valve for further heat energy utilization and power generation. The other part, together with the steam after exchanging heat with the thermoelectric module, is cooled by the second condenser and re-enters the steam Rankine cycle for waste heat recovery.

3. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization as described in claim 1, characterized in that: In startup mode, the inverter controls the doubly fed induction motor to pull the ammonia fuel engine to start. The power source for the doubly fed induction motor is directly provided by the power generated by the ammonia fuel cell and thermoelectric module controlled by the inverter.

4. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization as described in claim 1, characterized in that: In mechanical mode, the clutch engages, the doubly fed induction motor does not operate, and the ammonia fuel engine drives the variable pitch propeller through the gearbox.

5. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization as described in 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 doubly-fed induction motor drives the variable-pitch propeller. When the ship's speed is low, the gearbox selects a high speed ratio gear, and when the ship's speed is high, it selects a low speed ratio gear. When the ship is docked or berthed, the pitch of the variable-pitch propeller decreases to meet the speed range of the doubly-fed induction motor, and the gearbox selects a high speed ratio gear.

6. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization according to claim 1, characterized in that: In the hybrid propulsion mode, the clutch engages, and the doubly fed induction motor and the ammonia fuel engine jointly drive the variable pitch propeller via a gearbox. The doubly fed induction motor is powered by the ship's electrical grid and controlled by a frequency converter. The ammonia fuel engine operates in constant power mode or optimal economic curve mode. The engine's operating range is optimized by adjusting the pitch ratio of the variable pitch propeller and the speed of the doubly fed induction motor.

7. A marine ammonia-electric hybrid power system based on comprehensive waste heat gradient utilization according to claim 1, characterized in that: 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 another part of the power drives the variable-pitch propeller through the gearbox. The doubly-fed induction motor feeds power to the grid in two ways: when the ammonia engine speed is adjusted to the rated speed by adjusting the pitch ratio of the variable-pitch propeller to generate 50Hz frequency power, it directly feeds power to the ship's 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, the frequency and voltage of the output power are controlled by the variable-voltage frequency converter before feeding power to the ship's grid.

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