A low-grade heat energy recovery refrigeration and power generation integrated system and a working method thereof

Abstract

The application discloses a low-grade heat energy recycling refrigeration and power generation integrated system and a working method thereof. The system comprises a heat energy-mechanical energy conversion unit, an elastic heat refrigeration unit, a power generation energy storage and driving unit, a mode switching mechanism and a system control module. The heat energy-mechanical energy conversion unit is used for converting low-grade heat energy into reciprocating mechanical work; the elastic heat refrigeration unit is used for generating a refrigeration effect by using mechanical energy; the power generation energy storage and driving unit is used for converting mechanical energy into electrical energy storage and converting the electrical energy into mechanical energy output; the mode switching mechanism is used for realizing coupling and disconnection among the mechanisms; and the system control module is used for controlling the running state and mode switching of each executing mechanism. The application realizes efficient step-by-step utilization of low-grade heat energy by integrating the above executing mechanisms and flexibly switching three working modes. Moreover, all auxiliary equipment is driven by the electrical energy generated by the system itself, without external power grid input, so that off-grid independent operation is realized.

Description

Technical Field

[0001] This invention belongs to the field of energy utilization and thermal management technology, and particularly relates to an integrated system for low-grade heat energy recovery, refrigeration and power generation and its working method. Background Technology

[0002] In global final energy consumption, thermal energy accounts for as much as 50%, and more than 25% of global greenhouse gas emissions. Among these, low-grade thermal energy below 100°C accounts for as much as 63% of emissions from industrial production and the power industry. Meanwhile, renewable low-grade thermal energy such as geothermal and solar low-temperature thermal energy has not been utilized on a large scale. This type of low-grade thermal energy cannot be effectively converted using traditional steam turbines. Mainstream Organic Rankine Cycle (ORC) technology, when utilizing heat sources below 100°C, generally has a power generation efficiency of less than 5%, and suffers from problems such as the flammability and explosiveness of organic working fluids and system complexity. Thermal power generation (TEG) technology also has limited efficiency (commercial module efficiency is about 5%), high material costs, and is difficult to promote on a large scale.

[0003] At the same time, the refrigeration industry accounts for more than 20% of global electricity consumption. Traditional vapor compression refrigeration technology is highly dependent on grid power supply, and the refrigerants used have a strong greenhouse effect.

[0004] Elastic-thermal refrigeration technology based on shape memory materials is an emerging green refrigeration technology in recent years. This technology utilizes the endothermic / exothermic effect (i.e., the elasto-thermal effect) of shape memory materials during stress-induced phase transitions to achieve refrigeration. It boasts significant advantages such as refrigerant-free operation, high theoretical efficiency, all-solid-state operation, and environmental friendliness, and is considered one of the important technological pathways to replace traditional vapor compression refrigeration. However, existing elasto-thermal refrigeration systems heavily rely on external electrical energy input to drive mechanical loading / unloading devices, making it impossible to achieve on-site utilization of low-grade heat energy. This, to some extent, limits its application scope and energy-saving potential.

[0005] In summary, the industry urgently needs a technological solution that can efficiently recover low-grade heat energy below 100°C, while simultaneously meeting the needs of refrigeration and power generation, solving the problem of mismatch between supply and demand in time and space, and is environmentally friendly and efficient. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated system for low-grade heat energy recovery, refrigeration, and power generation, and its working method, in order to solve the problem that existing elasto-thermal refrigeration systems rely heavily on external electrical energy input to drive mechanical loading / unloading devices, and cannot achieve on-site consumption of low-grade heat energy.

[0007] This invention is implemented as follows: Firstly, it provides an integrated system for low-grade heat energy recovery, refrigeration, and power generation, comprising: A thermal-mechanical energy conversion unit is used to convert low-grade thermal energy into reciprocating mechanical work. It includes a low-grade heat source, a room-temperature cold source, a first water pump, a heat exchange pipe, and a shape memory material actuator. The shape memory material actuator has a first heat exchange channel inside, which is connected to the low-grade heat source and the room-temperature cold source through the heat exchange pipe. The first water pump is installed on the heat exchange pipe to control the alternating flow of heat transfer fluid between the low-grade heat source, the room-temperature cold source, and the shape memory material actuator. The elastic-thermal cooling unit is used to generate a cooling effect using mechanical energy. It includes a shape memory material cooler, a second water pump, a hot end heat dissipation circuit, and a cold end cooling circuit. The shape memory material cooler is provided with a second heat exchange channel. The hot end heat dissipation circuit and the cold end cooling circuit are respectively connected to the second heat exchange channel. The second water pump is installed on the hot end heat dissipation circuit and the cold end cooling circuit. A power generation, storage, and drive unit is used to convert mechanical energy into electrical energy for storage and to convert electrical energy back into mechanical energy for output when needed. It includes an electromagnetic induction power generation device, a rectifier and voltage regulator module, an energy storage battery, and a drive motor. The electromagnetic induction power generation device is selectively mechanically coupled to the shape memory material actuator. The rectifier and voltage regulator module is electrically connected to the electromagnetic induction power generation device. The energy storage battery is electrically connected to the rectifier and voltage regulator module. The drive motor is electrically connected to the energy storage battery and is selectively mechanically coupled to the shape memory material cooler. A mode switching mechanism is used to achieve selective mechanical coupling and disconnection between the shape memory material actuator and the shape memory material cooler, between the shape memory material actuator and the electromagnetic induction power generation device, and between the drive motor and the shape memory material cooler; The system control module is used to control the operating status and mode switching of each actuator.

[0008] Furthermore, the shape memory material actuator includes: The first shape memory material uses shape memory alloys or shape memory polymers; A piston-cylinder structure, wherein the first shape memory material is nested within the piston-cylinder structure, with one end connected to the piston and the other end fixed to the cylinder; The first heat exchange channel is disposed inside the cylinder wall or around the first shape memory material, for the heat transfer fluid to flow through; The first transmission mechanism, connected to the piston, is used to convert the reciprocating deformation of the first shape memory material into reciprocating linear motion or rotational motion output.

[0009] Furthermore, the shape memory material cooler includes: The second shape memory material uses shape memory alloys or shape memory polymers; The second transmission mechanism is used to apply an axial load or remove the load from the second shape memory material; The second heat exchange channel is disposed around the second shape memory material for the heat transfer fluid to flow through.

[0010] Furthermore, the mode switching mechanism includes: The first clutch is located on the transmission path between the shape memory material actuator and the shape memory material cooler; The second clutch is located on the transmission path between the shape memory material actuator and the electromagnetic induction power generation device; The third clutch is located on the transmission path between the drive motor and the shape memory material cooler; The first clutch, the second clutch, and the third clutch are one of the following: electromagnetic clutch, mechanical clutch, or hydraulic clutch.

[0011] Furthermore, the elastothermal cooling unit also includes: A hot-end radiator, connected to the hot-end heat dissipation circuit, is used to release the heat generated during the cooling process to the environment or external heat users. A cold-end radiator, connected to the cold-end refrigeration circuit, is used to deliver the generated cooling energy to the space to be refrigerated; The first water pump, the second water pump, the hot end radiator, and the cold end radiator are all electrically connected to the energy storage battery.

[0012] To achieve the above objectives, a second aspect of the present invention provides a method for operating a low-grade heat energy recovery refrigeration and power generation integrated system, the method comprising three switchable operating modes: Mode 1: Direct-drive thermal cooling mode When the supply of low-grade heat source is stable and there is a cooling demand, the mode switching mechanism is controlled to mechanically couple the shape memory material actuator with the shape memory material cooler, while disconnecting the shape memory material actuator from the electromagnetic induction power generation device. The first water pump is started to introduce hot water from a low-grade heat source into the first heat exchange channel of the shape memory material actuator. After the temperature of the shape memory material in the shape memory material actuator rises to its characteristic transformation temperature threshold, it spontaneously returns to its preset initial shape, producing macroscopic deformation. Mechanical work is output through the first transmission mechanism to drive the shape memory material cooler to complete the loading action. The shape memory material cooler undergoes a stress-induced phase transition during loading, releasing latent heat of phase transition and causing the temperature to rise. The hot end heat dissipation circuit is activated, and the heat transfer fluid is driven by the second water pump to flow through the second heat exchange channel of the shape memory material cooler, so as to transfer the heat to the hot end heat sink for release. After the shape memory material cooler has finished dissipating heat, the first water pump is switched to introduce room temperature cold source water into the first heat exchange channel of the shape memory material actuator. The shape memory material actuator cools down to below the characteristic transition temperature threshold and undergoes a reverse phase change, restoring its original state and driving the shape memory material cooler to complete the unloading action. The shape memory material cooler undergoes a reverse phase change during unloading, absorbing the latent heat of the phase change and thus lowering its temperature. The cold end refrigeration circuit is started, and the heat transfer fluid is driven by the second water pump to flow through the second heat exchange channel of the shape memory material refrigerator, so as to deliver the cold energy to the cold end heat sink and cool the space to be cooled. Repeat the above cycle to achieve continuous cooling output; Mode 2: Heat recovery power generation and energy storage mode When there is no cooling demand, the cooling demand is low, or the supply of low-grade heat source is excessive, the mode switching mechanism is controlled to mechanically couple the shape memory material actuator with the electromagnetic induction power generation device, while disconnecting the shape memory material actuator from the shape memory material cooler. The first water pump is started, and hot water from a low-grade heat source and cold water from a normal temperature source are alternately introduced into the first heat exchange channel of the shape memory material actuator, driving the shape memory material actuator to complete a reciprocating phase change cycle and continuously output mechanical work. The mechanical work output by the shape memory material actuator drives the electromagnetic induction power generation device to operate, converting mechanical energy into alternating current energy. The AC power is rectified, filtered, and regulated by the rectifier and voltage regulator module and then converted into DC power, which is stored in the energy storage battery. The electrical energy stored in the energy storage battery is preferentially supplied to the first water pump, the second water pump, the system control module, and other auxiliary equipment in the system, so as to realize the self-powered closed-loop operation of the system. Mode 3: Energy Storage and Cooling Mode When the supply of low-grade heat source is insufficient or interrupted, or when the cooling demand increases significantly and the direct-drive cooling capacity of heat energy cannot meet the demand, the mode switching mechanism is controlled to make the drive motor mechanically coupled with the shape memory material cooler, while disconnecting the shape memory material cooler from the shape memory material actuator. The energy storage battery supplies power to the drive motor, and the drive motor drives the shape memory material cooler to complete a continuous loading-unloading reciprocating cycle; The shape memory material cooler releases heat during loading and absorbs heat during unloading. Through the alternating switching of the hot end heat dissipation circuit and the cold end cooling circuit, a cooling effect is continuously generated. The cold-end refrigeration circuit directs the generated cooling energy to the space to be refrigerated, ensuring the continuity and sufficiency of refrigeration.

[0013] Furthermore, the low-grade heat source is industrial waste hot water, geothermal water, engine cooling water, solar hot water, or boiler flue gas waste heat, and the temperature of the low-grade heat source is below 100°C.

[0014] Furthermore, the ambient temperature cold source is tap water, cooling tower return water, ambient cooling water, or surface water.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: (1) It pioneered a full-chain integrated system architecture to realize the coordinated conversion and cascade utilization of multiple energy forms. This invention is the first to construct an integrated system for the entire "low-grade thermal energy-mechanical energy-refrigeration / electrical energy" chain based on a single shape memory material system. Compared with traditional technologies, this invention uses a single thermal-mechanical energy conversion unit (shape memory material actuator) to simultaneously connect a thermo-elastic cooling unit and a power generation and energy storage unit, achieving three core functions—efficient low-grade thermal energy recovery, continuous cooling, and power generation and energy storage—within a single system. This integrated architecture avoids the multi-stage conversion chains of "thermal energy → electrical energy → mechanical energy → cooling" or "thermal energy → mechanical energy → electrical energy → mechanical energy → cooling" in traditional technologies, significantly reducing energy losses in intermediate links and greatly improving the comprehensive utilization efficiency and scenario adaptability of low-grade thermal energy.

[0016] (2) Flexible switching between multiple modes to solve the problem of mismatch between supply and demand in time and space. This invention innovatively designs three automatically / manually switchable operating modes: direct-drive cooling with thermal energy, thermal energy recovery for power generation and storage, and energy storage-supplemented cooling, giving the system high flexibility and adaptability. When the heat source is abundant and cooling demand is high (Mode 1), thermal energy directly drives cooling, resulting in the shortest energy conversion path and highest efficiency. When the heat source is excessive or cooling demand is low (Mode 2), excess thermal energy is converted into electrical energy for storage, enabling time-shifted energy utilization. When the heat source is interrupted or cooling demand is high (Mode 3), the stored electrical energy is released to drive cooling, ensuring continuous cooling. This multi-mode collaborative mechanism fundamentally solves the contradiction between the intermittency and volatility of low-grade thermal energy supply and the continuity and stability of cooling demand, enabling the system to maintain efficient and stable operation under various complex conditions. This significantly improves the system's robustness and adaptability to different operating conditions.

[0017] (3) Achieve closed-loop self-powered system and get rid of dependence on external power grid. This invention achieves closed-loop self-powering of the system through the integrated design of power generation, energy storage, and drive units. In Mode 2 operation, the mechanical energy generated by the shape memory material actuator is converted into electrical energy via an electromagnetic induction power generation device, and then rectified and regulated before being stored in the energy storage battery. The energy storage battery prioritizes powering all auxiliary equipment within the system, including the first and second water pumps, the system control module, sensors, valves, etc. This means the system can operate independently without connecting to an external power grid, making it particularly suitable for remote areas, mobile platforms (ships, vehicles), and off-grid buildings. This energy self-sufficiency significantly expands the system's application scope and greatly reduces dependence on external infrastructure.

[0018] (4) All-solid-state operation significantly improves environmental friendliness, safety and reliability. This invention utilizes shape memory materials as the core functional material, enabling the entire system to operate in a completely solid state. It does not use any synthetic refrigerants such as hydrofluorocarbons (HFCs) or chlorofluorocarbons (CFCs), resulting in a zero global warming potential (GWP). Furthermore, the system has no high-pressure operating components (conventional compression refrigeration systems can reach high-pressure sides of 1.5-2.5 MPa) and contains no flammable or explosive organic refrigerants (conventional circulating systems commonly use flammable refrigerants such as isobutane and R245fa), significantly improving operational safety. In addition, shape memory materials exhibit excellent fatigue life (high-quality nickel-titanium alloys can withstand millions of cycles), resulting in low system maintenance costs and high reliability.

[0019] (5) Wide heat source adaptability, covering almost all low-grade heat energy scenarios below 100℃. This invention, by selecting shape memory materials with different phase transition temperatures and combining them with appropriate tempering treatments, can be adapted to low-grade heat sources with a wide temperature range below 100℃. Whether it's waste heat from factory cooling water (typically 40-80℃), boiler flue gas waste heat (typically 60-150℃, which this system can reduce to below 100℃ for utilization through heat exchange), or chemical reaction heat, or geothermal energy (low-temperature geothermal, typically 50-90℃), solar water heating (typically 40-80℃), or even engine cooling water waste heat (typically 70-95℃) in the renewable energy field, this system can efficiently recover and utilize them. This broad adaptability gives this invention enormous market potential and application value.

[0020] (6) Elastic-thermal refrigeration requires no refrigerant, and its theoretical energy efficiency far exceeds that of traditional refrigeration technology. The elasto-thermal cooling technology used in this invention is based on the solid-state phase change thermal effect of shape memory materials, with a theoretical cooling coefficient of 5-10. This has significant advantages compared with the current mainstream refrigerant-free cooling technologies (semiconductor cooling COP of about 0.3-0.6, magnetic cooling COP of about 2-4, and electric card cooling COP of about 2-5). Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the low-grade heat energy recovery refrigeration and power generation integrated system provided in the embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the shape memory material actuator used in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the system in direct thermal energy-driven cooling mode provided in this embodiment of the invention. Figure 4 This is a schematic diagram illustrating the working principle of the system in the heat recovery power generation and energy storage mode provided in this embodiment of the invention; Figure 5 This is a schematic diagram illustrating the working principle of the system in the energy storage and cooling mode provided in this embodiment of the invention. Detailed Implementation

[0022] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] This invention addresses the shortcomings of existing low-grade thermal energy utilization systems, such as limited functionality, inability to resolve spatiotemporal supply-demand mismatch, lack of multi-condition adaptive capability, and inability to achieve closed-loop self-powering. It provides an integrated system and method for low-grade thermal energy recovery, refrigeration, and power generation based on shape memory materials. By integrating a thermal-mechanical energy conversion unit, an elastic-thermal refrigeration unit, and a power generation, storage, and drive unit, and configuring a mode-switching mechanism to flexibly switch between three operating modes, this invention achieves efficient cascade utilization of low-grade thermal energy and closed-loop self-powering.

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Please refer to Figure 1 The diagram shows the overall structure of the low-grade heat energy recovery refrigeration and power generation integrated system provided in this embodiment. The system includes a heat energy to mechanical energy conversion unit 1, an elastic-thermal refrigeration unit 2, a power generation, energy storage and drive unit 3, a mode switching mechanism 4, and a system control module 5.

[0026] The thermal-mechanical energy conversion unit 1 includes a low-grade heat source 11, a room-temperature cold source 12, a first water pump 13, a heat exchange pipe 14, and a shape memory material actuator 15. The low-grade heat source can be industrial wastewater below 100℃, engine cooling water, geothermal tailwater, solar low-temperature hot water, etc.; the room-temperature cold source can be tap water, cooling tower return water, environmental cooling water, or surface water. The shape memory material actuator 15 is connected to the low-grade heat source 11 and the room-temperature cold source 12 via the heat exchange pipe 14. The first water pump 13 is installed on the heat exchange pipe 14 and is used to control the alternating flow of the heat transfer fluid (in this embodiment, water) between the low-grade heat source 11, the room-temperature cold source 12, and the shape memory material actuator 15.

[0027] Please refer to Figure 2 The diagram shows a detailed structural schematic of a shape memory material actuator 15. The shape memory material actuator 15 includes a first shape memory material 151, a piston-cylinder structure 152, a first heat exchange channel 153, and a first transmission mechanism 154. The first shape memory material 151 can be a shape memory alloy or a shape memory polymer. Taking a shape memory alloy as an example, through component proportioning and heat treatment processes, its austenitic phase transformation end temperature is modulated to slightly lower than the target low-grade heat source temperature, and its martensitic phase transformation end temperature is modulated to lower than the room temperature cold source temperature, ensuring that it can completely transform during heating to output mechanical work and completely return to its initial state during cooling. The first shape memory material 151 is nested within the piston-cylinder structure 152, with one end connected to the piston and the other end fixed to the cylinder. The first heat exchange channel 153 is disposed within the cylinder wall for the flow of heat transfer fluid. The first transmission mechanism 154 is connected to the piston and is used to convert the reciprocating deformation of the first shape memory material 151 into reciprocating linear motion output. For example, the first shape memory material 151 can adopt a shape memory alloy spring structure, which is nested in the piston-cylinder structure 152. Compared with the straight column or tube structure, it can greatly amplify the displacement range of phase transformation deformation and improve the mechanical power output efficiency. For large deformation demand scenarios, shape memory polymer structures such as natural rubber tubes can also be used.

[0028] Please continue reading. Figure 1The elastic-thermal cooling unit 2 includes a shape memory material cooler 21, a second water pump 22, a hot-end heat dissipation circuit 23, a cold-end cooling circuit 24, a hot-end radiator 26, and a cold-end radiator 27. The shape memory material cooler 21 has a second heat exchange channel inside, and the hot-end heat dissipation circuit 23 and the cold-end cooling circuit 24 are respectively connected to the second heat exchange channel. The second water pump 22 is installed on the hot-end heat dissipation circuit 23 and the cold-end cooling circuit 24 to drive the circulation of the heat transfer fluid. The hot-end radiator 26 is connected to the hot-end heat dissipation circuit 23 to release the heat generated during the cooling process into the environment; the cold-end radiator 27 is connected to the cold-end cooling circuit 24 to deliver the generated cooling capacity to the space to be cooled, such as an air-conditioned room in a building or a refrigerated transport vehicle.

[0029] The shape memory material cooler 21 includes a second shape memory material, which can be a shape memory alloy or a shape memory polymer. Taking a shape memory alloy as an example, through the composition ratio and heat treatment process, the austenitic phase transformation end temperature is modulated to be lower than the room temperature to ensure that the material maintains a stable austenitic phase at room temperature and has excellent elasto-thermal effect. Alloy components with large latent heat of phase transformation, long fatigue life and small phase transformation hysteresis are preferentially selected to improve cooling efficiency and cycle stability.

[0030] The shape memory material cooler 21 also includes a second transmission mechanism (not shown) for applying an axial load to or removing the load on the second shape memory material.

[0031] The power generation, energy storage, and drive unit 3 includes an electromagnetic induction power generation device 31, a rectifier and voltage regulator module 32, an energy storage battery 33, and a drive motor 34. The electromagnetic induction power generation device 31 is selectively mechanically coupled to the shape memory material actuator 15; the rectifier and voltage regulator module 32 is electrically connected to the electromagnetic induction power generation device 31; the energy storage battery 33 is electrically connected to the rectifier and voltage regulator module 32; and the drive motor 34 is electrically connected to the energy storage battery 33 and is selectively mechanically coupled to the shape memory material cooler 21.

[0032] The mode switching mechanism 4 includes a first clutch 41, a second clutch 42, and a third clutch 43. The first clutch 41 is located on the transmission path between the shape memory material actuator 15 and the shape memory material cooler 21; the second clutch 42 is located on the transmission path between the shape memory material actuator 15 and the electromagnetic induction power generation device 31; and the third clutch 43 is located on the transmission path between the drive motor 34 and the shape memory material cooler 21. In this embodiment, the first clutch 41, the second clutch 42, and the third clutch 43 are all electromagnetic clutches, and their engagement and disengagement are controlled by the system control module 5.

[0033] This embodiment also provides three working modes of the above system, which can be automatically switched according to heat source supply, cooling demand and battery power.

[0034] Mode 1: Direct-drive thermal energy cooling mode (basic operation mode) Applicable scenarios: Scenarios with stable supply of low-grade heat sources and continuous cooling needs (such as air conditioning in industrial waste heat production workshops, building cooling using geothermal resources, and cold chain logistics for vehicles and ships with continuously running engines).

[0035] Please refer to Figure 3 The diagram illustrates the working principle of the system in this mode. The system control module 5 controls the engagement of the first clutch 41, mechanically coupling the shape memory material actuator 15 with the shape memory material cooler 21, while simultaneously controlling the disengagement of the second clutch 42 and the third clutch 43.

[0036] After the system starts, the first water pump 13 introduces hot water from the low-grade heat source 11 into the first heat exchange channel 153 of the shape memory material actuator 15. When the temperature of the first shape memory material 151 rises to its characteristic transition temperature threshold, it spontaneously returns to its preset initial shape, producing macroscopic deformation (such as the contraction or elongation of a spring structure, the direction of deformation can be preset by the molding process), which drives the piston to move, outputs mechanical work through the first transmission mechanism 154, and drives the shape memory material cooler 21 to complete the loading action.

[0037] During the loading process, the second shape memory material inside the shape memory material cooler 21 undergoes a stress-induced phase transition, releasing latent heat of phase transition and causing the temperature to rise. At this time, the system control module 5 activates the hot-end heat dissipation circuit 23, which drives the heat transfer fluid through the second heat exchange channel of the shape memory material cooler 21 via the second water pump 22, transferring the heat to the hot-end radiator 26 and releasing it into the environment.

[0038] After the shape memory material cooler 21 has finished dissipating heat, the system control module 5 switches the flow direction of the first water pump 13, and introduces water from the ambient temperature cold source 12 into the first heat exchange channel 153 of the shape memory material actuator 15. The first shape memory material 151 cools down to below the characteristic transition temperature threshold, undergoes a reverse phase change, restores its original shape, drives the piston back to its original position, and thus drives the shape memory material cooler 21 to complete the unloading action.

[0039] During the unloading process, the second shape memory material inside the shape memory material cooler 21 undergoes a reverse phase change, absorbing the latent heat of the phase change, and its temperature drops significantly to about 5℃-10℃. At this time, the system control module 5 starts the cold end cooling circuit 24, which drives the heat transfer fluid through the second heat exchange channel of the shape memory material cooler 21 via the second water pump 22, delivering the cooling capacity to the cold end radiator 27 to cool the space to be cooled.

[0040] Repeating the above cycle, the shape memory material actuator 15 reciprocates at a certain frequency, continuously driving the shape memory material cooler 21 to complete the loading-unloading cycle and achieve continuous cooling output. During this process, the first water pump 13, the second water pump 22, the hot end radiator 26, and the cold end radiator 27 are all powered by the energy storage battery 33.

[0041] Mode 2: Heat recovery power generation and energy storage mode Applicable scenarios: Scenarios with no cooling demand, low cooling demand, or excess supply of low-grade heat sources (such as factories shutting down at night, excess solar heat during the day, and low cooling load periods).

[0042] Please refer to Figure 4 The diagram illustrates the working principle of the system in heat recovery power generation and energy storage mode. When the system control module 5 detects that the temperature of the low-grade heat source 11 is higher than the set threshold, the heat source flow is sufficient, but the cooling demand load is low, or the power of the energy storage battery 33 is lower than the set lower limit, the system switches to mode two operation.

[0043] In mode two, the system control module 5 controls the second clutch 42 to engage, so that the shape memory material actuator 15 is mechanically coupled to the electromagnetic induction power generation device 31, while controlling the first clutch 41 and the third clutch 43 to disengage.

[0044] The first water pump 13 alternately pumps hot water from the low-grade heat source 11 and water from the ambient temperature cold source 12 into the first heat exchange channel 153 of the shape memory material actuator 15, driving the first shape memory material 151 to complete a reciprocating phase change cycle and continuously output mechanical work at a frequency of approximately 0.3 Hz. The mechanical work output by the shape memory material actuator 15 drives the electromagnetic induction power generation device 31 to operate, converting mechanical energy into alternating current electrical energy.

[0045] Alternating current (AC) power is rectified, filtered, and regulated by the rectifier and voltage regulator module 32, then converted into direct current (DC) power and stored in the energy storage battery 33. The stored energy in the energy storage battery 33 is preferentially supplied to the first water pump 13, the second water pump 22, the system control module 5, and other auxiliary equipment within the system, achieving a self-powered closed-loop operation. Excess energy can be output to external electrical appliances, such as lighting equipment and monitoring systems.

[0046] Mode 3: Energy Storage and Cooling Mode Applicable scenarios: When the supply of low-grade heat sources is insufficient or interrupted, or when the cooling demand increases significantly and the direct-drive cooling capacity of heat energy cannot meet the demand (such as intermittent emissions of waste heat from factories, no solar heat at night, peak cooling load periods, etc.).

[0047] Please refer to Figure 5The diagram illustrates the working principle of the system in energy storage and supplementary cooling mode. When the system control module 5 detects that the temperature of the low-grade heat source 11 is lower than the set threshold, or the heat source flow is interrupted, or the cooling demand load increases significantly, causing the direct-drive cooling capacity to be insufficient to meet the demand, the system switches to mode three operation.

[0048] In mode three, the system control module 5 controls the third clutch 43 to engage, so that the drive motor 34 is mechanically coupled to the shape memory material cooler 21, while controlling the first clutch 41 to disengage, cutting off the connection between the shape memory material cooler 21 and the shape memory material actuator 15.

[0049] The energy storage battery 33 supplies power to the drive motor 34, which in turn drives the shape memory material cooler 21 at a set frequency to complete a continuous loading-unloading reciprocating cycle. During loading, the shape memory material cooler 21 releases heat through the hot-end heat dissipation circuit 23, and during unloading, it absorbs heat through the cold-end cooling circuit 24, continuously generating a cooling effect. The cold-end cooling circuit 24 directs the generated cooling energy to the space to be cooled, ensuring the continuity and sufficiency of cooling, and effectively solving the problem of cooling continuity when the supply of low-grade heat energy is interrupted.

[0050] By flexibly switching between the three modes described above, the system in this embodiment achieves tiered and efficient utilization of low-grade thermal energy: the first-drive mode is used for cooling, which has the highest energy efficiency; excess thermal energy is transferred to the power generation and storage system in mode two; and when the heat source is insufficient, energy storage in mode three is used to supplement cooling and ensure continuous cooling. All auxiliary equipment, such as the first water pump 13, the second water pump 22, and the system control module 5, are driven by the system's own generated electricity, requiring no external power grid input, thus achieving true off-grid independent operation.

[0051] In summary, this invention, through the integrated design of a thermal-mechanical energy conversion unit 1, an elastic-thermal cooling unit 2, and a power generation, energy storage, and drive unit 3, combined with a mode switching mechanism, enables flexible switching between three operating modes, and has at least the following technical advantages: (1) This invention constructs an integrated system for the entire chain of "low-grade thermal energy - mechanical energy - cooling / electrical energy" based on a single shape memory material system. Compared with traditional technologies, this invention uses a set of thermal energy-mechanical energy conversion units (shape memory material actuator 15) to simultaneously connect to the thermo-thermal cooling unit 2 and the power generation, energy storage and drive unit 3, realizing the three core functions of efficient low-grade thermal energy recovery, continuous cooling, and power generation and energy storage within a single system. This integrated architecture avoids the multi-level conversion chain of "thermal energy → electrical energy → mechanical energy → cooling" or "thermal energy → mechanical energy → electrical energy → mechanical energy → cooling" in traditional technologies, significantly reducing energy loss in intermediate links and greatly improving the comprehensive utilization efficiency and scenario adaptability of low-grade thermal energy.

[0052] (2) This invention innovatively designs three operating modes that can be automatically / manually switched: direct-drive cooling, heat recovery power generation and storage, and energy storage supplementary cooling, giving the system high flexibility and adaptability. When the heat source is sufficient and the cooling demand is high (mode 1), the heat energy directly drives the cooling, resulting in the shortest energy conversion link and the highest efficiency. When the heat source is excessive or the cooling demand is low (mode 2), the excess heat energy is converted into electrical energy for storage, realizing time-shifted energy utilization. When the heat source is interrupted or the cooling demand is high (mode 3), the stored electrical energy is released to drive the cooling, ensuring the continuity of cooling. This multi-mode collaborative mechanism fundamentally solves the contradiction between the intermittency and volatility of low-grade heat energy supply and the continuity and stability of cooling demand, enabling the system to maintain efficient and stable operation under various complex operating conditions. It significantly improves the robustness and adaptability of the system.

[0053] (3) This invention achieves closed-loop self-powered operation of the system through the integrated design of power generation, energy storage, and drive unit 3. During operation in mode two, the mechanical energy generated by the shape memory material actuator 15 is converted into electrical energy through the electromagnetic induction power generation device 31, and then stored in the energy storage battery 33 after rectification and voltage regulation. The energy storage battery 33 prioritizes powering all auxiliary equipment within the system, including the first water pump 13, the second water pump 22, the system control module 5, sensors, valves, etc. This means that the system can operate independently without connecting to an external power grid, making it particularly suitable for remote areas, mobile platforms (ships, vehicles), off-grid buildings, and other scenarios. This energy self-sufficiency significantly expands the system's application scope and greatly reduces dependence on external infrastructure.

[0054] (4) This invention uses shape memory material as the core functional material. The entire system operates in a solid state and does not use any synthetic refrigerants such as hydrofluorocarbons (HFCs) or chlorofluorocarbons (CFCs), resulting in a zero global warming potential (GWP). Simultaneously, the system has no high-pressure operating components (the high-pressure side pressure of traditional compression refrigeration systems can reach 1.5-2.5 MPa) and no flammable or explosive organic working fluids (traditional circulating systems commonly use flammable working fluids such as isobutane and R245fa), significantly improving operational safety. Furthermore, shape memory material has excellent fatigue life (high-quality nickel-titanium alloys can withstand millions of cycles), resulting in low system maintenance costs and high reliability.

[0055] (5) By selecting shape memory materials with different phase transition temperatures and combining them with appropriate tempering treatment, this invention can be adapted to low-grade heat sources with a wide temperature range below 100℃. Whether it is waste heat from factory cooling water (usually 40-80℃), waste heat from boiler flue gas (usually 60-150℃, which can be reduced to below 100℃ by heat exchange in the industrial field), or heat from chemical reactions, or geothermal energy (low-temperature geothermal energy, usually 50-90℃), solar water heating (usually 40-80℃), or even waste heat from engine cooling water (usually 70-95℃) in the renewable energy field, this system can efficiently recover and utilize them. This wide adaptability gives this invention huge market potential and application value.

[0056] (6) The elastothermal cooling technology used in this invention is based on the solid phase change thermal effect of shape memory materials. The theoretical cooling coefficient can reach 5-10, which has significant advantages compared with the current mainstream refrigerant-free cooling technology (semiconductor cooling COP about 0.3-0.6, magnetic cooling COP about 2-4, and electric card cooling COP about 2-5).

[0057] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "front," "rear," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-grade heat energy recovery refrigeration and power generation integrated system, characterized in that, include: A thermal-mechanical energy conversion unit (1) is used to convert low-grade thermal energy into reciprocating mechanical work. It includes a low-grade heat source (11), a room-temperature cold source (12), a first water pump (13), a heat exchange pipe (14), and a shape memory material actuator (15). The shape memory material actuator (15) is provided with a first heat exchange channel inside. It is connected to the low-grade heat source (11) and the room-temperature cold source (12) through the heat exchange pipe (14). The first water pump (13) is set on the heat exchange pipe (14) and is used to control the alternating flow of heat transfer fluid between the low-grade heat source (11), the room-temperature cold source (12), and the shape memory material actuator (15). The elastic-thermal cooling unit (2) is used to generate a cooling effect by utilizing mechanical energy. It includes a shape memory material cooler (21), a second water pump (22), a hot end heat dissipation circuit (23), and a cold end cooling circuit (24). The shape memory material cooler (21) is provided with a second heat exchange channel inside. The hot end heat dissipation circuit (23) and the cold end cooling circuit (24) are respectively connected to the second heat exchange channel. The second water pump (22) is installed on the hot end heat dissipation circuit (23) and the cold end cooling circuit (24). The power generation, energy storage and drive unit (3) is used to convert mechanical energy into electrical energy for storage and to convert electrical energy into mechanical energy for output when needed. It includes an electromagnetic induction power generation device (31), a rectifier and voltage regulator module (32), an energy storage battery (33), and a drive motor (34). The electromagnetic induction power generation device (31) is selectively mechanically coupled to the shape memory material actuator (15). The rectifier and voltage regulator module (32) is electrically connected to the electromagnetic induction power generation device (31). The energy storage battery (33) is electrically connected to the rectifier and voltage regulator module (32). The drive motor (34) is electrically connected to the energy storage battery (33) and is selectively mechanically coupled to the shape memory material cooler (21). The mode switching mechanism (4) is used to achieve selective mechanical coupling and disconnection between the shape memory material actuator (15) and the shape memory material cooler (21), between the shape memory material actuator (15) and the electromagnetic induction power generation device (31), and between the drive motor (34) and the shape memory material cooler (21); The system control module (5) is used to control the operating status and mode switching of each actuator.

2. The low-grade heat energy recovery refrigeration and power generation integrated system according to claim 1, characterized in that, The shape memory material actuator (15) includes: The first shape memory material (151) is made of shape memory alloy or shape memory polymer; The piston-cylinder structure (152) has the first shape memory material (151) nested inside the piston-cylinder structure (152), with one end connected to the piston and the other end fixed to the cylinder. The first heat exchange channel (153) is disposed inside the cylinder wall or around the first shape memory material (151) for heat transfer fluid to flow through; The first transmission mechanism (154) is connected to the piston and is used to convert the reciprocating deformation of the first shape memory material (151) into reciprocating linear motion or rotational motion output.

3. The low-grade heat energy recovery refrigeration and power generation integrated system according to claim 1, characterized in that, The shape memory material cooler (21) includes: The second shape memory material uses shape memory alloys or shape memory polymers; The second transmission mechanism is used to apply an axial load or remove the load from the second shape memory material; The second heat exchange channel is disposed around the second shape memory material for the heat transfer fluid to flow through.

4. The low-grade heat energy recovery refrigeration and power generation integrated system according to claim 1, characterized in that, The mode switching mechanism (4) includes: The first clutch (41) is disposed on the transmission path between the shape memory material actuator (15) and the shape memory material cooler (21); The second clutch (42) is located on the transmission path between the shape memory material actuator (15) and the electromagnetic induction power generation device (31); The third clutch (43) is located on the transmission path between the drive motor (34) and the shape memory material cooler (21); The first clutch (41), the second clutch (42), and the third clutch (43) are one of the following: electromagnetic clutch, mechanical clutch, or hydraulic clutch.

5. The low-grade heat energy recovery refrigeration and power generation integrated system according to claim 1, characterized in that, The elastic-thermal cooling unit (2) further includes: The hot end radiator (26) is connected to the hot end heat dissipation circuit (23) and is used to release the heat generated during the cooling process to the environment or external heat users. The cold end heat sink (27) is connected to the cold end refrigeration circuit (24) and is used to deliver the generated cold energy to the space to be refrigerated; The first water pump (13), the second water pump (22), the hot end radiator (26), and the cold end radiator (27) are all electrically connected to the energy storage battery (33).

6. The working method of the low-grade heat energy recovery refrigeration and power generation integrated system according to claim 5, characterized in that, Includes three switchable working modes: Mode 1: Direct-drive thermal cooling mode When the supply of low-grade heat source is stable and there is a cooling demand, the mode switching mechanism (4) is controlled to mechanically couple the shape memory material actuator (15) with the shape memory material cooler (21) and disconnect the connection between the shape memory material actuator (15) and the electromagnetic induction power generation device (31). Start the first water pump (13) to introduce hot water from the low-grade heat source into the first heat exchange channel of the shape memory material actuator (15). After the temperature of the shape memory material in the shape memory material actuator (15) rises to its characteristic transformation temperature threshold, it spontaneously returns to its preset initial shape, generating macroscopic deformation. The mechanical work is output through the first transmission mechanism to drive the shape memory material cooler (21) to complete the loading action. The shape memory material cooler (21) undergoes a stress-induced phase transition during loading, releasing latent heat of phase transition and increasing temperature; The hot end heat dissipation circuit (23) is activated, and the heat transfer fluid is driven by the second water pump (22) to flow through the second heat exchange channel of the shape memory material cooler (21) to transfer heat to the hot end heat sink (26) for release; After the shape memory material cooler (21) has finished dissipating heat, the first water pump (13) is switched to introduce room temperature cold source water into the first heat exchange channel of the shape memory material actuator (15). The shape memory material actuator (15) is cooled down to below the characteristic transition temperature threshold and undergoes a reverse phase change to restore its original state, thereby driving the shape memory material cooler (21) to complete the unloading action. The shape memory material cooler (21) undergoes a reverse phase change during unloading, absorbing the latent heat of the phase change and reducing its temperature. The cold end refrigeration circuit (24) is started, and the heat transfer fluid is driven by the second water pump (22) to flow through the second heat exchange channel of the shape memory material refrigerator (21) to deliver the cold energy to the cold end radiator (27) to cool the space to be cooled; Repeat the above steps to achieve continuous cooling output; Mode 2: Heat recovery power generation and energy storage mode When there is no cooling demand, low cooling demand, or excessive supply of low-grade heat source, control the mode switching mechanism (4) to mechanically couple the shape memory material actuator (15) with the electromagnetic induction power generation device (31), and disconnect the connection between the shape memory material actuator (15) and the shape memory material cooler (21). Start the first water pump (13) and alternately pass hot water from the low-grade heat source and cold water from the room temperature into the first heat exchange channel of the shape memory material actuator (15) to drive the shape memory material actuator (15) to complete the reciprocating phase change cycle and continuously output mechanical work; The mechanical work output by the shape memory material actuator (15) drives the electromagnetic induction power generation device (31) to operate, converting mechanical energy into alternating current energy. The AC power is rectified, filtered and regulated by the rectifier and voltage regulator module (32) and converted into DC power, which is then stored in the energy storage battery (33). The electrical energy stored in the energy storage battery (33) is preferentially supplied to the first water pump (13), the second water pump (22), the system control module (5) and other auxiliary equipment in the system, so as to realize the self-powered closed-loop operation of the system. Mode 3: Energy Storage and Cooling Mode When the supply of low-grade heat source is insufficient, interrupted, or the cooling demand increases significantly, resulting in the direct-drive cooling capacity of heat energy being unable to meet the demand, the mode switching mechanism (4) is controlled to make the drive motor (34) mechanically coupled with the shape memory material cooler (21), and at the same time disconnect the connection between the shape memory material cooler (21) and the shape memory material actuator (15). The energy storage battery (33) supplies power to the drive motor (34), and the drive motor (34) drives the shape memory material cooler (21) to complete a continuous loading-unloading reciprocating cycle; The shape memory material cooler (21) releases heat during loading and absorbs heat during unloading. Through the alternating switching of the hot end heat dissipation circuit (23) and the cold end cooling circuit (24), it continuously generates a cooling effect. The cold end refrigeration circuit (24) outputs the generated cooling energy to the space to be refrigerated, ensuring the continuity and sufficiency of refrigeration.

7. The working method according to claim 6, characterized in that, The low-grade heat source (11) is industrial waste hot water, geothermal water, engine cooling water, solar hot water or boiler flue gas waste heat, and the temperature of the low-grade heat source is below 100°C.

8. The working method according to claim 6, characterized in that, The ambient temperature cold source (12) is tap water, cooling tower return water, ambient cooling water or surface water.

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