Low temperature waste heat recovery thermal management system and method for marine pem fuel cells

Abstract

The application discloses a low-temperature waste heat recovery thermal management system and method of a PEM fuel cell for a ship. The method is based on an organic Rankine cycle for low-temperature waste heat recovery for thermal management and is used for a high-power PEM fuel cell ship. The system, through a compact and efficient coupling design, efficiently and stably converts the low-temperature waste heat generated by the PEMFC into additional electric energy, significantly improves the comprehensive energy utilization efficiency and endurance of the power system of the ship, and has good variable working condition adaptability and space adaptability.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, specifically relating to a thermal management system and method for low-temperature waste heat recovery based on organic Rankine cycle for PEM fuel cells used in high-power inland waterway vessels. Background Technology

[0002] Inland waterway transportation, as an important component of the green transportation system, is developing towards zero emissions and high efficiency. Proton exchange membrane fuel cells (PEMFCs), with their advantages of high energy conversion efficiency, zero pollutant emissions, and low noise, are considered one of the ideal power sources for future ships, especially inland waterway vessels. However, PEMFCs generate a large amount of low-temperature waste heat (40-80°C) during power generation. This heat is usually directly discharged or inefficiently utilized, resulting in low overall system energy utilization. Typically, only the electrical output is utilized, and the waste heat is not effectively converted into additional power.

[0003] On the other hand, inland waterway vessels, especially high-powered tugboats and container ships, have high demands for propulsion power and auxiliary electricity. Furthermore, the compact space of these vessels places stringent requirements on the energy density and overall efficiency of their power systems. Traditional steam Rankine cycles, when recovering such low-temperature thermal energy, suffer from system complexity, large equipment size, and poor adaptability to partial loads, making them unsuitable for the limited space and variable operating conditions of ships.

[0004] Organic Rankine cycle (ORC) technology is an ideal choice for recovering low- and medium-temperature thermal energy and efficiently converting it into electricity. It uses a low-boiling-point organic working fluid, enabling the generation of steam at relatively low temperatures to drive turbine power generation. It offers significant advantages such as system simplicity, high thermal efficiency, low operating pressure, flexible start-up and shutdown, and ease of modular integration. In particular, the ORC system is highly adaptable to changes in heat source temperature, enabling more effective recovery of sensible heat, which makes it highly promising for recovering waste heat from proton exchange membrane fuel cells (PEMFCs).

[0005] Currently, although some studies have combined PEMFCs with ORCs for building combined cooling, heating, and power (CCHP), their system configurations are designed to meet relatively stable electrical, thermal, and cooling loads, and the waste heat distribution method is fixed. This makes it difficult to adapt to the complex and variable operating conditions of ships, especially the requirements for "on-demand" waste heat generation and rapid system response. Therefore, there is an urgent need for an innovative thermoelectric conversion scheme specifically designed for the operating conditions of high-power inland waterway vessels, capable of deeply integrating PEMFCs and ORCs, and achieving efficient and stable conversion of waste heat into propulsion or auxiliary power. Summary of the Invention

[0006] To address the problems of low waste heat utilization efficiency in PEMFCs and the inability of traditional waste heat power generation systems to adapt to the space and variable operating conditions of ships in existing technologies, this invention aims to provide a thermoelectric conversion system and method based on the organic Rankine cycle for PEM fuel cells suitable for high-power inland waterway vessels. This system, through a compact and efficient coupling design, efficiently and stably converts the low-temperature waste heat generated by PEMFCs into additional electrical energy, significantly improving the overall energy utilization efficiency and range of the ship's propulsion system, and possessing good adaptability to variable operating conditions and space.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for low-temperature waste heat recovery and thermal management of PEM fuel cells for marine applications, characterized by comprising the following steps:

[0009] S1: The proton exchange membrane fuel cell power generation module is started to provide the main power for the ship. The waste heat generated is carried by the cooling medium and pressurized by the system water pump (2). It is then diverted through the system three-way valve (3). Part or all of the high-temperature cooling medium carries the waste heat to the waste heat recovery heat exchanger (7). If diverted through the outboard water three-way valve (11), the outboard water source (6) enters the outboard water heat exchanger (4) through the outboard water intake pump (5) to provide cooling water for the working fluid pump condenser (9). The outboard water three-way valve (11) adjusts the outboard water flow distribution according to the condensation load demand.

[0010] S2: The intelligent coupling and control system, based on the ship's current total power demand P... {total} PEMFC current output power P {PEMFC} and the outlet temperature T of the cooling medium {out} Calculate the optimal waste heat recovery rate Q. {recovery}^* The waste heat recovery temperature range is taken as T. {out} For temperatures ∈ [70, 85]℃, the waste heat recovery rate is determined by the following formula: Q {recovery}^* = f(P {total} , P {PEMFC} ,T {cool} ) = η {ORC} ρ {cool} Q {cool} · c p · (T {cool} - T {in} ); where ρ {cool} Q is the density of the cooling medium. {cool} c is the mass flow rate of the cooling medium. p Given the specific heat capacity of the cooling medium [approximately 4.18 kJ / (kg·℃) for deionized water], η {ORC} For the thermoelectric conversion efficiency of the ORC system, T {in}The inlet temperature of the cooling medium is used to determine the waste heat splitting ratio α ∈ [0, 1], where the waste heat splitting ratio α is the ratio of the flow rate at port A to the flow rate at port B of the three-way valve 3: when P {PEMFC} ≥P {min} And when the water temperature reaches the target temperature, α is taken as 1; when P {PEMFC} < P {min} When α is 0; P {min} To ensure that fuel cells meet the minimum power requirements for waste heat power generation;

[0011] S3: The intelligent coupling and control system adjusts the flow regulating valve on the cooling circuit of the proton exchange membrane fuel cell power generation module leading to the evaporator branch, so that the high-temperature cooling medium with a flow range of 0.5~5 m³ / h enters the waste heat recovery heat exchanger (7) at a temperature of 70~85℃, heating the organic working medium in the organic Rankine cycle ORC circuit and causing it to evaporate into superheated steam.

[0012] S4: High-pressure organic working fluid superheated steam (evaporation pressure 1.8 MPa) drives radial turbine generator set (10) to expand and do work, outputting additional AC power. The low-pressure steam after doing work enters the working fluid pump condenser (9) and is cooled and condensed into liquid working fluid by the overboard water source (6). The overboard water intake pump (5) draws water from the overboard and distributes it to the inlet of the condenser (9) through the overboard water three-way valve (11).

[0013] S5: The liquid organic working fluid is pressurized to 1.8 MPa by the working fluid pump (8) and then re-enters the waste heat recovery heat exchanger (7) to absorb heat and complete the cycle;

[0014] S6: The electrical energy generated by the organic Rankine cycle power generation module is processed by the power management unit and works in conjunction with the electrical energy of the proton exchange membrane fuel cell power generation module to meet the power needs of ship propulsion and auxiliary machinery. The control unit continuously monitors the system status and dynamically adjusts the waste heat diversion ratio to ensure that the system can operate efficiently and stably under different speeds and loads.

[0015] In the above method, in step S1, the cooling medium is deionized water, ethylene glycol-deionized water solution, or deionized water solution with added trimethylglycine.

[0016] In the above method, in step S2, Q {cool} It is 0.5~5 m³ / h; η {ORC} It ranges from 8% to 15%.

[0017] In the above method, in step S3, the organic working fluid is R245fa; the evaporation pressure of the superheated steam is 1.8 MPa, corresponding to a saturation temperature of 75~80℃.

[0018] A method for low-temperature waste heat recovery and thermal management of PEM fuel cells for marine applications, comprising the following modules:

[0019] Proton exchange membrane fuel cell power generation module: As a main or auxiliary power source for ships, its cooling circuit outlet is connected to a waste heat recovery heat exchanger.

[0020] Organic Rankine Cycle Power Generation Module: Radial turbine unit (power density 3.5kW / m³), working fluid R245fa, evaporation pressure 1.8MPa, suitable for waste heat of 70-85℃; includes an evaporator, turbine generator set, condenser, and working fluid pump. The evaporator serves as the waste heat recovery heat exchanger; its primary side is connected to the PEMFC cooling circuit to absorb waste heat generated by the PEMFC; its secondary side flows with the organic working fluid. The turbine generator set is connected to the evaporator outlet, utilizing the expansion of the organic working fluid vapor to generate electricity. The condenser cools the working fluid discharged from the turbine. The working fluid pump pressurizes the condensed liquid working fluid and returns it to the evaporator.

[0021] External heat exchange module: used to provide a low-temperature cold source for the ORC condenser and to perform the function of PEMFC waste heat discharge when the waste heat recovery system is bypassed.

[0022] The intelligent coupling and control system includes a flow regulating valve, temperature and pressure sensors, and a control unit. The flow regulating valve is located on the branch of the PEMFC cooling circuit leading to the evaporator. The sensors are respectively arranged at key nodes such as the PEMFC outlet, evaporator inlet and outlet, and turbine inlet and outlet. The control unit receives sensor signals and dynamically adjusts the opening of the flow regulating valve according to the ship's real-time power demand, PEMFC operating status, and environmental conditions to control the waste heat flow into the evaporator, thereby optimizing the ORC module's power generation and overall system efficiency.

[0023] The power management unit is used to rectify, invert, and control the grid connection of the DC power generated by the PEMFC and the AC power generated by the ORC turbine generator, and uniformly deliver them to the ship's propulsion motors and daily loads to achieve comprehensive management and optimized distribution of electrical energy.

[0024] Furthermore, the organic Rankine cycle power generation module adopts an integrated turbine generator set, preferably using magnetic levitation bearings or high-efficiency compact bearing technology to achieve low vibration, high speed and miniaturization, adapting to the vibration environment and space constraints of ships.

[0025] Furthermore, the organic working fluid is selected as R245fa, a low-boiling-point organic working fluid. It has advantages such as high density, small specific volume, low sound velocity, condensation pressure close to atmospheric pressure, and extremely low freezing point, which makes the turbine and condenser and other equipment more compact, eliminating the need for superheaters and complex antifreeze facilities, making it very suitable for marine applications and variable operating conditions.

[0026] Furthermore, the condenser is a plate or compact heat exchanger, and its cold source is the ship's outboard water (river water). Utilizing the abundant low-temperature water source of inland waterways can effectively reduce the condensation temperature and improve the thermal efficiency of the ORC cycle.

[0027] Furthermore, the system also includes a power management unit, which is used to rectify, invert, and control the DC power generated by the PEMFC and the AC power generated by the ORC turbine generator, and uniformly deliver them to the ship's propulsion motor and daily loads, so as to realize the comprehensive management and optimized distribution of electrical energy.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. Significantly improve overall energy efficiency: By efficiently recovering the low-grade heat energy that was originally discarded by PEMFC through ORC and converting it into electrical energy, the overall energy utilization efficiency of the ship's power system can be improved by 15%-25%, effectively extending the driving range or reducing the amount of fuel (hydrogen) carried.

[0030] 2. Enhanced system adaptability and flexibility: The system adopts intelligent control to dynamically adjust the waste heat recovery ratio, enabling it to respond quickly to the changing operating conditions of the ship. Whether it is constant speed cruising or frequent start-stop, acceleration and deceleration, it can maintain efficient operation, solving the problem of limited adjustment capability of traditional waste heat utilization systems.

[0031] 3. Highly Compact and Well-Adapted to Ships: The ORC system itself has a simple structure, employing an integrated turbine and a compact heat exchanger. The working fluid characteristics enable the equipment to be miniaturized. The entire coupling system occupies little space and is relatively lightweight, perfectly meeting the design requirements of inland waterway vessels with limited engine room space.

[0032] 4. Reliable operation and easy maintenance: The organic working fluid remains dry throughout the expansion process, avoiding water erosion and corrosion of the turbine blades, thus improving equipment lifespan and reliability. The system operates at near atmospheric pressure, ensuring high safety and requiring minimal maintenance.

[0033] 5. Win-win for environmental protection and economy: On the basis of achieving zero emissions from PEMFC, it further “turns waste into treasure”, increases the output of electricity without additional fuel consumption, reduces the equivalent electricity cost of ship operation, and improves the economic efficiency throughout the entire life cycle. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the thermoelectric conversion system of a PEM fuel cell coupled with an organic Rankine cycle, which is suitable for high-power inland waterway vessels according to the present invention.

[0035] The components shown in the diagram are as follows.

[0036] 1. Fuel cell stack; 2. System water pump; 3. System three-way valve; 4. Outboard water heat exchanger; 5. Outboard water intake pump; 6. Outboard water source; 7. Waste heat recovery heat exchanger; 8. Working fluid pump; 9. Working fluid pump condenser; 10. Turbine generator set; 11. Outboard water three-way valve. Detailed Implementation

[0037] The technical solutions described below, in conjunction with specific illustrations, are presented to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and similar extended embodiments made by those skilled in the art without inventive effort are all within the scope of protection of this invention.

[0038] Example 1

[0039] like Figure 1 As shown, this embodiment provides a low-temperature waste heat recovery thermal management system for PEM fuel cells used in ships, including the following modules: a proton exchange membrane fuel cell power generation module, an organic Rankine cycle power generation module, an external heat exchange module, a power management unit, and an intelligent coupling and control system;

[0040] Proton exchange membrane fuel cell power generation module: As the main power source or auxiliary power source of a ship, its cooling circuit outlet is connected to a waste heat recovery heat exchanger. In this embodiment, the proton exchange membrane fuel cell power generation module is stack 1.

[0041] Organic Rankine Cycle Power Generation Module: Radial turbine unit (power density 3.5kW / m³), working fluid R245fa, evaporation pressure 1.8MPa, suitable for waste heat of 70-85℃; includes an evaporator, turbine generator set, condenser, and working fluid pump. The evaporator serves as the waste heat recovery heat exchanger; its primary side is connected to the PEMFC cooling circuit to absorb waste heat generated by the PEMFC; its secondary side flows with the organic working fluid. The turbine generator set is connected to the evaporator outlet, utilizing the expansion of the organic working fluid vapor to generate electricity. The condenser cools the working fluid discharged from the turbine. The working fluid pump pressurizes the condensed liquid working fluid and returns it to the evaporator.

[0042] Outboard heat exchange module: used to provide a low-temperature cold source for the ORC condenser and to perform the function of PEMFC waste heat discharge when the waste heat recovery system is bypassed;

[0043] The power management unit is used to rectify, invert, and control the grid connection of the DC power generated by the PEMFC and the AC power generated by the ORC turbine generator, and uniformly deliver them to the ship's propulsion motors and daily loads to achieve comprehensive management and optimized distribution of electrical energy.

[0044] An intelligent coupling and control system is used to perform data acquisition, power optimization allocation, and fault diagnosis.

[0045] A waste heat recovery heat exchanger 7 is provided between the cooling medium outlet of the proton exchange membrane fuel cell power generation module and the organic Rankine cycle power generation module; a working fluid pump condenser 9 is provided between the outboard heat exchange module and the organic Rankine cycle power generation module; and an outboard water heat exchanger 4 is provided between the proton exchange membrane fuel cell power generation module and the outboard heat exchange module.

[0046] A system three-way valve 3 is installed between the cooling circuit main pipe of the proton exchange membrane fuel cell power generation module and the branch node of the outboard water heat exchanger 4 and the waste heat recovery heat exchanger 7. This valve is used to adjust the flow rate ratio of the waste heat medium entering the waste heat recovery heat exchanger 7 according to the control signal. The outboard water heat exchanger 4 is installed at the bypass end of the system three-way valve 3. When the ORC system is shut down or the condensation load is low, the high-temperature cooling medium of the proton exchange membrane fuel cell power generation module is directly exchanged with the outboard water through the outboard water heat exchanger 4 and then returned to the circuit to achieve auxiliary discharge of waste heat.

[0047] The organic Rankine cycle power generation module includes a turbine generator set 10, a working fluid pump condenser 9, and a working fluid pump 8; the outboard heat exchange module includes an outboard water intake pump 5, an outboard water source 6, and an outboard water three-way valve 11; the waste heat recovery heat exchanger 7, the working fluid pump 8, the working fluid pump condenser 9, and the turbine generator set 10 are connected sequentially to form a cycle; the outboard water three-way valve 11 includes three ports A, B, and C; the outboard water source 6 is connected to the outboard water intake pump 5 and the C port of the outboard water three-way valve 11; the B port of the outboard water three-way valve 11 is connected sequentially to the outboard water heat exchanger 4 and the outboard water source 6. The A end of the outboard water three-way valve 11 is sequentially connected to the working fluid pump condenser 9 and the outboard water source 6; the outboard water source 6 is river water and / or lake water; the cooling medium outlet of the proton exchange membrane fuel cell power generation module is sequentially connected to the waste heat recovery heat exchanger 7 of the organic Rankine cycle power generation module through the system water pump 2 and the system three-way valve 3, and the waste heat recovery heat exchanger 7 is connected to the cooling medium inlet of the proton exchange membrane fuel cell power generation module 1; the third port of the system three-way valve 3 is sequentially connected to the outboard water heat exchanger 4 and the cooling medium inlet of the proton exchange membrane fuel cell power generation module 1.

[0048] In this embodiment, the working fluid pump condenser 9 is a plate or compact heat exchanger, and its cold source is the ship's external water source. By utilizing the abundant low-temperature water source of the inland river, the condensation temperature can be effectively reduced and the thermal efficiency of the ORC cycle can be improved.

[0049] Example 2

[0050] This embodiment applies the above system, taking a 500kW inland waterway container ship as an example, and includes the following steps:

[0051] Marine PEMFC rated power P {rated} = 500 kW, ORC design waste heat recovery power Q{ORC} ≈ 150kW (based on 30% recovery of approximately 500 kW of total waste heat from PEMFC), ORC power generation efficiency η ORC ≈ 12%, which can output an additional electrical power of approximately 18 kW.

[0052] S1: The PEMFC operates at 250 kW power. The cooling medium (deionized water) temperature rises by about 8°C, and the temperature at the fuel cell outlet is about 73°C. It enters the system three-way valve 3 via system water pump 2.

[0053] S2: The intelligent control system detected the ship's real-time total power demand P. {total} = 480 kW, PEMFC current output P {PEMFC} = 250 kW, Cooling medium outlet temperature T {out} = 73℃, calculate the optimal waste heat recovery amount Q based on the optimization algorithm. {recovery}^* ≈ 75 kW, determine the waste heat diversion ratio α = 1.

[0054] S3: Cooling medium volumetric flow rate Q {cool} ≈ 2.3 m³ / h, high-temperature cooling medium enters the evaporator (7) and heats R245fa to 1.8 MPa, 78℃ superheated steam.

[0055] S4: High-pressure organic working fluid vapor drives the turbine generator set to expand and do work, outputting additional electrical energy. The low-pressure vapor after doing work enters the condenser and is cooled and condensed into liquid working fluid by the outboard water.

[0056] S5: After being pressurized by the working fluid pump, the liquid working fluid re-enters the evaporator to absorb heat, completing the cycle.

[0057] S6: The electrical energy generated by the ORC module is processed by the power management unit and works in conjunction with the PEMFC power to meet the power needs of ship propulsion and auxiliary machinery. The control unit continuously monitors the system status and dynamically adjusts the waste heat diversion ratio to ensure that the system can operate efficiently and stably under different speeds and loads.

[0058] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for low-temperature waste heat recovery and thermal management of PEM fuel cells for marine applications, characterized in that, Includes the following steps: S1: The proton exchange membrane fuel cell power generation module is started to provide the main power for the ship. The waste heat generated is carried by the cooling medium and pressurized by the system water pump (2). It is then diverted through the system three-way valve (3). Part or all of the high-temperature cooling medium carries the waste heat to the waste heat recovery heat exchanger (7). If diverted through the outboard water three-way valve (11), the outboard water source (6) enters the outboard water heat exchanger (4) through the outboard water intake pump (5) to provide cooling water for the working fluid pump condenser (9). The outboard water three-way valve (11) adjusts the outboard water flow distribution according to the condensation load demand. S2: Based on the ship's current total power demand P {total} PEMFC current output power P {PEMFC} and the outlet temperature T of the cooling medium {out} Calculate the optimal waste heat recovery rate Q. {recovery}^* The waste heat recovery temperature range is taken as T. {out} For temperatures ∈ [70, 85]℃, the waste heat recovery rate is determined by the following formula: Q {recovery}^* = f(P {total} , P {PEMFC} , T {cool} ) = η {ORC} ρ {cool} ·Q {cool} · c p · (T {cool} - T {in} ); where ρ {cool} Q is the density of the cooling medium. {cool} c is the mass flow rate of the cooling medium. p η is the specific heat capacity of the cooling medium. {ORC} For the thermoelectric conversion efficiency of the ORC system, T {in} The inlet temperature of the cooling medium is used as the basis for the control unit to determine the waste heat splitting ratio α ∈ [0, 1], where the waste heat splitting ratio α is the ratio of the flow rate at port A to the flow rate at port B of the three-way valve 3: when P {PEMFC} ≥ P {min} And when the water temperature reaches the target temperature, α is taken as 1; when P {PEMFC} < P {min} When α is 0; P {min} To ensure that fuel cells meet the minimum power requirements for waste heat power generation; S3: Adjust the flow regulating valve on the cooling circuit of the proton exchange membrane fuel cell power generation module leading to the evaporator branch so that the high-temperature cooling medium with a flow range of 0.5~5 m³ / h enters the waste heat recovery heat exchanger (7) at a temperature of 70~85℃, heats the organic working medium in the organic Rankine cycle ORC circuit, and makes it evaporate into superheated steam. S4: The high-pressure organic working fluid superheated steam drives the radial turbine generator set (10) to expand and do work, outputting additional AC power. The low-pressure steam after doing work enters the working fluid pump condenser (9) and is cooled and condensed into liquid working fluid by the overboard water source (6). The overboard water intake pump (5) draws water from the overboard and distributes it to the inlet of the condenser (9) through the overboard water three-way valve (11). S5: After the liquid organic working fluid is pressurized to 1.8 MPa by the working fluid pump (8), it re-enters the waste heat recovery heat exchanger (7) to absorb heat and complete the cycle; S6: The electrical energy generated by the organic Rankine cycle power generation module is processed by the power management unit and works in conjunction with the electrical energy of the proton exchange membrane fuel cell power generation module to meet the power needs of ship propulsion and auxiliary machinery. The control unit continuously monitors the system status and dynamically adjusts the waste heat diversion ratio to ensure that the system can operate efficiently and stably under different speeds and loads.

2. The method for low-temperature waste heat recovery and thermal management of marine PEM fuel cells as described in claim 1, characterized in that, In step S1, the cooling medium is deionized water, ethylene glycol-deionized water solution, or deionized water solution with added trimethylglycine.

3. The low-temperature waste heat recovery and thermal management method for marine PEM fuel cells as described in claim 1, characterized in that, In step S2, Q {cool} It is 0.5~5 m³ / h; η {ORC} It ranges from 8% to 15%.

4. The low-temperature waste heat recovery and thermal management method for marine PEM fuel cells as described in claim 1, characterized in that, In step S3, the organic working fluid is R245fa; the evaporation pressure of the superheated steam is 1.8 MPa, corresponding to a saturation temperature of 75~80℃.

5. The method according to any one of claims 1 to 4 employs a low-temperature waste heat recovery thermal management system for marine PEM fuel cells, characterized in that, include: The system includes a proton exchange membrane fuel cell power generation module, an organic Rankine cycle power generation module, and an external heat exchange module; a waste heat recovery heat exchanger (7) is provided between the cooling medium outlet of the proton exchange membrane fuel cell power generation module and the organic Rankine cycle power generation module; a working fluid pump condenser (9) is provided between the external heat exchange module and the organic Rankine cycle power generation module; and an external water heat exchanger (4) is provided between the proton exchange membrane fuel cell power generation module and the external heat exchange module. A system three-way valve (3) is provided between the cooling circuit main pipe of the proton exchange membrane fuel cell power generation module and the branch node of the outboard water heat exchanger (4) and the waste heat recovery heat exchanger (7). The valve is used to adjust the flow ratio of the waste heat medium entering the waste heat recovery heat exchanger (7) according to the control signal. The outboard water heat exchanger (4) is located at the bypass end of the system three-way valve (3). When the ORC system is shut down or the condensation load is low, the high temperature cooling medium of the proton exchange membrane fuel cell power generation module is directly exchanged with the outboard water through the outboard water heat exchanger (4) and then returned to the circuit to realize the auxiliary discharge of waste heat.

6. The cryogenic waste heat recovery thermal management system for marine PEM fuel cells according to claim 5, characterized in that, The organic Rankine cycle power generation module includes an evaporator (7), a turbine generator set (10), a working fluid pump condenser (9), and a working fluid pump (8); the outboard heat exchange module includes an outboard water intake pump (5), an outboard water source (6), and an outboard water three-way valve (11). The waste heat recovery heat exchanger (7), working fluid pump (8), working fluid pump condenser (9) and turbine generator set (10) are connected in sequence to form a cycle; The outboard water three-way valve (11) includes three ports: A, B, and C. The outboard water source (6) is connected to the outboard water intake pump (5) and the C end of the outboard water three-way valve (11). The B end of the outboard water three-way valve (11) is connected to the outboard water heat exchanger (4) and the outboard water source (6) in sequence. The A end of the outboard water three-way valve (11) is connected to the working fluid pump condenser (9) and the outboard water source (6) in sequence. The outboard water source (6) is river water and / or lake water. The cooling medium outlet of the proton exchange membrane fuel cell power generation module is connected in sequence to the waste heat recovery heat exchanger (7) of the organic Rankine cycle power generation module via the system water pump (2) and the system three-way valve (3). The waste heat recovery heat exchanger (7) is connected to the cooling medium inlet of the proton exchange membrane fuel cell power generation module (1). The third port of the system three-way valve (3) is connected in sequence to the outboard water heat exchanger (4) and the cooling medium inlet of the proton exchange membrane fuel cell power generation module (1).

7. The cryogenic waste heat recovery thermal management system for marine PEM fuel cells according to claim 5 or 6, characterized in that, The proton exchange membrane fuel cell power generation module is a stack (1).

8. The cryogenic waste heat recovery thermal management system for marine PEM fuel cells according to claim 5 or 6, characterized in that, The working fluid pump condenser (9) is a plate or compact heat exchanger. Its cold source is the ship's external water source. By utilizing the abundant low-temperature water source of the inland river, the condensation temperature can be effectively reduced and the thermal efficiency of the ORC cycle can be improved.

9. The cryogenic waste heat recovery thermal management system for marine PEM fuel cells according to claim 5, characterized in that, It also includes a power management unit, which is used to rectify, invert and control the DC power generated by PEMFC and the AC power generated by ORC turbine generator, and uniformly transmit them to the ship's propulsion motor and daily loads to realize the comprehensive management and optimized distribution of electrical energy.

10. The cryogenic waste heat recovery thermal management system for marine PEM fuel cells according to claim 5, characterized in that, It also includes an intelligent coupling and control system, which is used to perform data acquisition, power optimization allocation and fault diagnosis.

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