Low-temperature waste heat recovery power generation system

Abstract

This invention provides a low-temperature waste heat recovery power generation system, which includes at least: a first heat source supply unit, comprising a solar water heater, a cold water tank connected to the inlet of the solar water heater, and a hot water tank connected to the outlet of the solar water heater; a second heat source supply unit, connected to the first heat source supply unit, and including a low-temperature waste heat source receiving device and a heat exchanger connected to the low-temperature waste heat source receiving device; and a power generation unit, connected to the first heat source supply unit and the second heat source supply unit, and including a heating device, a power generation device, a cooling device, and a pressurizing device, wherein the heating device, the power generation device, the cooling device, and the pressurizing device are sequentially connected to form an organic Rankine cycle structure.

Description

Technical Field

[0001] This invention relates to waste gas treatment systems, and more particularly to a low-temperature waste heat recovery power generation system. Prior Technology

[0002] A significant proportion of energy use in industry and transportation generates waste heat. Waste heat can be roughly categorized into three types based on its temperature range: high temperature (>600℃), medium temperature (200~600℃), and low temperature (<200℃), with low-temperature waste heat accounting for approximately 70% of industrial waste heat. Low-temperature waste heat is commonly found in industrial processes, commercial buildings, and power generation facilities, such as cooling water, exhaust gases, or other emitted hot fluids. Due to its low temperature, low-temperature waste heat is usually difficult to recover and reuse directly, and therefore is often directly emitted, causing direct thermal pollution or indirect environmental concerns related to gaseous emissions.

[0003] The sources of low-temperature waste heat can be mainly divided into the following categories:

[0004] 1. Industrial processes: Cooling water, waste gas, etc. released during the manufacturing process of industries such as chemical, oil refining and steel, or hot steam and heat emissions during the cooling stage of food processing.

[0005] 2. Commercial buildings: Heat released from air conditioning systems and ventilation equipment, or heat emitted from kitchen equipment in the catering industry.

[0006] 3. Power generation facilities: Cooling water in combined heat and power (CHP) systems, or waste heat that is not effectively utilized in thermal and nuclear power generation processes.

[0007] Due to the enormous total amount of low-temperature waste heat and its potential for reuse, it has attracted increasing attention in research and application. However, the recovery of low-temperature waste heat often faces the following challenges:

[0008] 1. Low thermal energy quality: Low-temperature waste heat has low energy density and is difficult to convert into a usable form efficiently.

[0009] 2. High dispersion: Low-temperature waste heat sources are often scattered in different locations, making centralized recovery difficult.

[0010] 3. Economic issues: The initial investment cost of developing a recycling system is high, while the waste heat itself has limited value and a long economic recovery period.

[0011] Common methods for treating and utilizing low-temperature waste heat include heat recovery technology, thermoelectric conversion technology, thermal energy storage technology, and indirect utilization technology. Heat recovery technology primarily uses waste heat to heat other fluids, thereby recovering some heat energy. For example, in industrial processes, heat exchangers are used to transfer waste heat to cooling water or steam systems. Alternatively, absorption cooling can be used to convert low-temperature waste heat into cold energy for air conditioning and refrigeration. Thermoelectric conversion technology uses thermoelectric materials to directly convert low-temperature heat energy into electrical energy, but its efficiency is limited by material properties. Another option is the Organic Rankine Cycle (ORC), which evaporates organic working fluids (such as Freon or propane) at low temperatures to drive a turbine for power generation. However, using only low-temperature waste heat as the heat source for an ORC power generation system is insufficient. Thermal energy storage technology involves storing waste heat in phase change materials for later use, such as heating buildings or supplying domestic hot water, or using materials with high specific heat capacity (such as water or rock) to store low-temperature thermal energy for peak demand. Indirect utilization of low-temperature waste heat involves applying it to agriculture or fisheries, such as heating greenhouses or heating water bodies in aquaculture to promote crop growth or fish farming; it can also be combined with centralized heating and decentralized waste heat recovery to establish a low-temperature waste heat transmission and distribution network to supply heat to surrounding communities.

[0012] To promote the development of cryogenic waste heat recovery technology, governments and institutions worldwide are providing subsidies, tax incentives, and policy support; simultaneously, energy efficiency-related laws and standards are driving companies to optimize waste heat utilization. Therefore, although cryogenic waste heat recovery faces technical and economic challenges, it offers significant environmental and energy-saving benefits. With advancements in materials science and energy technology, the potential of cryogenic waste heat utilization will be further explored, providing crucial support for achieving energy efficiency and carbon neutrality goals. Summary of the Invention

[0013] In view of this, the authors have proposed a low-temperature waste heat recovery power generation system after careful research. This system combines renewable energy and low-temperature waste heat with an organic Rankine cycle generator to regenerate and utilize the low-temperature waste heat.

[0014] In other words, the present invention can provide a low-temperature waste heat recovery power generation system, which includes at least: a first heat source supply unit, which includes a solar water heater, a cold water tank connected to the inlet end of the solar water heater, and a hot water tank connected to the outlet end of the solar water heater; a second heat source supply unit, which is connected to the first heat source supply unit and includes a low-temperature waste heat source receiving device and a heat exchanger connected to the low-temperature waste heat receiving device; and a power generation unit, which is connected to the first heat source supply unit and the second heat source supply unit and includes a heating device, a power generation device, a cooling device, and a pressurizing device, wherein the heating device, the power generation device, the cooling device, and the pressurizing device are sequentially connected to form an organic Rankine cycle structure.

[0015] According to one embodiment of the present invention, the pressurizing device pressurizes an organic working fluid to a specific pressure and then delivers it to the heating device; the heating device receives the second hot fluid and exchanges heat with the organic working fluid flowing through the heating device, vaporizing the organic working fluid and heating it into a high-temperature and high-pressure gas; the vaporized organic working fluid is then delivered to the power generation device, while the second hot fluid, cooled by heat exchange, is returned to the cold water tank as the first cold water.

[0016] According to one embodiment of the present invention, the working fluid is selected from any one of trichlorotrifluoroethane, dichlorofluoroethane, trichlorofluoromethane, dichlorotrifluoroethane, dichlorotrifluoromethane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane, isohexane, hexane, methanol, ethanol, acetone, pentane, and isopentane.

[0017] According to one embodiment of the present invention, the power generation device includes an expander and a generator, wherein the thermal energy and pressure of the vaporized organic working fluid from the heating device can be converted into the mechanical energy of the expander, thereby driving the generator to generate electricity.

[0018] According to one embodiment of the present invention, in the first heat source supply unit, the solar water heater receives first cold water from the cold water tank, heats it to 60~75°C, and then transmits it to the hot water tank as first hot water.

[0019] According to one embodiment of the present invention, in the first heat source supply unit, the heat exchanger has a hot-side pipe and a cold-side pipe. The inlet end of the hot-side pipe is connected to the low-temperature waste heat source receiving device, and the inlet end of the cold-side pipe is connected to the outlet end of the hot water tank. The low-temperature waste heat source and the first hot water exchange heat in the heat exchanger, so that the temperature of the first hot water is raised to above 80°C and then discharged from the outlet end of the cold-side pipe as a second hot fluid and transported to the power generation unit.

[0020] According to one embodiment of the present invention, the temperature of the low-temperature waste heat source is between 100°C and 230°C.

[0021] According to one embodiment of the present invention, the second heat fluid is hot water at 80~99°C or steam at 100°C or above.

[0022] According to one embodiment of the present invention, the second heat source supply unit further includes a waste heat discharge device, which is connected to the outlet end of the hot side pipeline of the heat exchanger.

[0023] According to one embodiment of the present invention, the first heat source supply unit further includes a solar cell, which is electrically connected to the solar water heater.

[0024] According to one embodiment of the present invention, the solar cell is a silicon-based semiconductor cell, a CdTe thin-film cell, a CIGS thin-film cell, a dye-sensitized thin-film cell, or an organic material cell.

[0025] According to one embodiment of the present invention, the power generation unit further includes an energy storage device, which is electrically connected to the power generation device for storing the electrical energy generated by the power generation device. Simple Explanation of the Diagram

[0026] Figure 1 is a system architecture diagram showing the low-temperature waste heat recovery power generation system in the first embodiment of the present invention. Figure 2 is a system architecture diagram showing the low-temperature waste heat recovery power generation system in the second embodiment of the present invention. Implementation

[0027] In the following, various applicable examples of the present invention relating to low-temperature waste heat recovery power generation systems and technologies are listed and described in detail with reference to the accompanying drawings; however, the present invention is by no means limited to the listed embodiments, drawings or detailed descriptions.

[0028] Furthermore, those skilled in the art should understand that the listed embodiments and accompanying drawings are for reference and illustration only and are not intended to limit the invention. Any modifications or alterations that can be easily implemented based on these descriptions are also considered to be within the spirit and intent of the invention and are included in the scope of the patent application of this invention.

[0029] Furthermore, the directional terms mentioned in the following embodiments, such as "up," "down," "left," "right," "front," and "back," are only for reference to the directions shown in the accompanying illustrations. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention; moreover, in the following embodiments, the same or similar elements will be labeled with the same or similar element numbers.

[0030] First, please refer to Figure 1, which is a system architecture diagram showing the low-temperature waste heat recovery power generation system in the first embodiment of the present invention. The low-temperature waste heat recovery power generation system 1 includes a first heat source supply unit 10, a second heat source supply unit 20, and a power generation unit 30.

[0031] As shown in Figure 1, the first heat source supply unit 10 includes a solar water heater 101, a cold water tank 102, and a hot water tank 103. The cold water tank 102 and the hot water tank 103 are respectively connected to the inlet and outlet of the solar water heater 101. The solar water heater 101 absorbs the radiation energy from the sun and uses it to heat the water. It can receive the first cold water C1 from the cold water tank 102, heat it to 60~75°C, and then send it to the hot water tank 103 as the first hot water H1.

[0032] Furthermore, the second heat source supply unit 20 includes a low-temperature waste heat source receiving device 201, a heat exchanger 202 connected to the low-temperature waste heat source receiving device 201, and a waste heat discharge device 203. The low-temperature waste heat source receiving device 201 is used to receive low-temperature waste heat source W1 from the factory. The low-temperature waste heat source W1 can be from process waste steam, process hot water, post-process exhaust mixture, flue gas, hot air, engine exhaust, or water jacket hot water. It can be stored in the low-temperature waste heat source receiving device 201 in liquid or gas form, and its temperature is generally between 100°C and 230°C, preferably between 150°C and 230°C, and more preferably between 180°C and 230°C.

[0033] The heat exchanger 202 has a hot-side pipe and a cold-side pipe. The inlet of the hot-side pipe is connected to the low-temperature waste heat source receiving device 201, and the inlet of the cold-side pipe is connected to the outlet of the hot water tank 103. The low-temperature waste heat source W1 and the first hot water H1 exchange heat in the heat exchanger 202, causing the temperature of the first hot water H1 to rise to above 80°C and become a second hot fluid H2, which is discharged from the outlet of the cold-side pipe. The form of the second hot fluid H2 is not particularly limited. For example, the second hot fluid H2 can be hot water at 80~99°C or steam at 100°C or above. In addition, the waste heat discharge device 203 is connected to the outlet of the hot-side pipe of the heat exchanger 202. Therefore, the residual waste heat W2 obtained after the low-temperature waste heat source and the first hot water H1 are cooled down after heat exchange in the heat exchanger 202 can be discharged to the outside through the waste heat discharge device 203.

[0034] The power generation unit 30 includes a heating device 301, a power generation device 302, a cooling device 303, and a pressurizing device 304, which are connected in sequence to form an organic Rankine cycle structure.

[0035] In this embodiment, the heat source used by the power generation unit 30 is the second hot fluid H2 from the second heat source supply unit 20. The pressurizing device 304 pressurizes an organic working fluid to a specific pressure and then delivers it to the heating device 301. The heating device 301 receives the second hot fluid H2 and exchanges heat with the organic working fluid flowing through the heating device 301, vaporizing the organic working fluid and heating it into a high-temperature and high-pressure gas. The vaporized organic working fluid is then delivered to the power generation unit 302, while the second hot fluid H2, which has been cooled by heat exchange, is returned to the cold water tank 102 as the first cold water C1.

[0036] According to the technical concept of the present invention, the organic working fluid can be a refrigerant or a hydrocarbon. More specifically, the refrigerant can be trichlorotrifluoroethane, dichlorofluoroethane, trichlorofluoromethane, dichlorotrifluoroethane, dichlorotrifluoromethane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, or 1,1,1,3,3-pentafluorobutane, and the hydrocarbon can be isohexane, hexane, methanol, ethanol, acetone, pentane, or isopentane.

[0037] The power generation device 302 includes an expander and a generator (not shown). The thermal energy and pressure of the vaporized organic working fluid from the heating device 301 can be converted into the mechanical energy of the expander, thereby driving the generator to generate electricity. The expander can be an impeller expander, a scroll expander, etc., preferably a modified scroll compressor, and the power of the expander can be controlled by an expansion valve.

[0038] After the organic working fluid has finished working, it is discharged to the cooling device 303 for condensation. The cold source used by the cooling device 303 is generally cooling water, which can be seawater, river water, or water from a cooling tower. It can exchange heat with the organic working fluid after working, cool down the organic working fluid, and then send it to the heating device 301 for recycling.

[0039] According to the technical concept of the present invention, the heating device 301 and the cooling device 303 can be plate heat exchangers or shell-and-tube heat exchangers, respectively, without particular limitation.

[0040] The electrical energy E1 generated by the power generation unit 30 can be transmitted to an energy storage device (not shown) for storage and subsequent power application, or it can be used directly without going through the energy storage device.

[0041] Please also refer to Figure 2, which is a system architecture diagram showing the low-temperature waste heat recovery power generation system in the second embodiment of the present invention. The low-temperature waste heat recovery power generation system 1 is the same as that in the aforementioned embodiment 1, including a first heat source supply unit 10, a second heat source supply unit 20, and a power generation unit 30. The main difference is that the first heat source supply unit 10 further includes a solar cell 104.

[0042] The solar cell 104 is electrically connected to the solar water heater 101. During periods of ample sunshine, it can absorb sunlight and convert it into electrical energy for storage. During periods of insufficient sunshine, it can provide backup power to the solar water heater 101 for operation. Furthermore, the type of solar cell 104 can be a silicon-based semiconductor cell, a CdTe thin-film cell, a CIGS thin-film cell, a dye-sensitized thin-film cell, or an organic material cell, without particular limitation.

[0043] In the low-temperature waste heat recovery power generation system of the present invention, a plurality of pumps can be further installed in the pipeline to help fluid transport; the number and placement of these pumps are not particularly limited and can be configured according to process requirements.

[0044] After the low-temperature waste heat recovery power generation system of the present invention was put into operation, a performance analysis was performed. The relevant parameter conditions used by the heat exchanger 202 are shown in Table 1 below (the low-temperature waste heat source W1 is in the form of flue gas):

[0045] Table 1 name symbol unit Formula Explanation numerical values [Heat Exchanger]

[0202] [Thermal fluid] [(] [Low-temperature waste heat source] [W1)] [Heat Transfer Calculation] Hot fluid inlet temperature T1 ℃ Known 220 Hot fluid outlet temperature T2 ℃ settings 105 Low-temperature waste heat source W1 flow rate under standard conditions Vy Nm 3 / h 78000 Density of low-temperature waste heat source W1 under standard conditions ρy kg / Nm 3 1.295 Low-temperature waste heat source W1 quality My kg / h Vy*ρy 101010 Low-temperature waste heat source W1 average flue gas temperature Tpj ℃ (T1+T2) / 2 162.5 Low-temperature waste heat source W1 has a constant pressure specific heat capacity Cy kJ / (kg·℃) Refer to the flue gas characteristics table based on average flue temperature. 1.09 Low-temperature waste heat source W1 releases heat Qy kJ / h My*Cy*(T1-T2) 12616591 kcal / h 3013421 kW 3505 Heat loss on the W1 side of the low-temperature waste heat source qy % 3 Heat exchanger tubes transfer heat Qc kJ / h Qy*(1-qy / 100) 12238093 kcal / h 2923018 kW 3399 Low-temperature end heat loss qc % 2 Waste heat recovery heat △H Q kJ / h Qc*(1-qc / 100) 11993331 kcal / h 2864558 kW 3331 [Heat Exchanger]

[0202] [of] [Calculation of Heat for Cold Fluids] Design pressure Pe MPa 0.4 The inlet temperature of the first hot water flow H1 t1 ℃ assumed 75 Second hot fluid H2 outlet temperature t2 ℃ Design temperature 95 Average temperature t pj ℃ (t1+t2) / 2 85 Isobaric specific heat capacity C pj kJ / (kg·℃) By average temperature 4.2 Required cooling fluid volume M kg / h Q / (C pj*(t1-t2)) 142749 Circulating cooling fluid volume H1 / H2 D t / h Q / (ibq-igs) / 1000 143 △t1 ℃ T1-t2 125 △t2 ℃ T2-t1 30 ℃ △t1 / △t2 4.17 Logarithmic mean temperature difference △tm Logarithmic temperature difference formula selection 66.57 △t m1 ℃ (△t1-△t2) / ln(△t1 / △t2) 66.57 △t m2 ℃ (△t1+△t2) / 2 77.50 P (t2-t1) / (T1-t1) 0.14 R (T1-T2) / (t2-t1) 5.75 Logarithmic temperature difference correction factor Ψ For heat exchanger design to be economically reasonable, Ψ > 0.9 is required. 0.89 Heat transfer temperature difference △t ℃ △tm*Ψ 59.55 [Heat Exchanger]

[0202] [Used] [Media Properties] Density under standard conditions (thermal fluid) ρ h kg / m 3 Refer to the table based on the average flue gas temperature. 0.82375 Density under standard conditions (Cold fluid) ρ c kg / m3 Refer to the table based on the average temperature of the cold fluid. 968.592 Dynamic viscosity (thermal fluid) μh Pa·s Refer to the table based on the average flue gas temperature. 0.00002 Dynamic viscosity (Cold fluid) μ c Pa·s Refer to the table based on the average temperature of the cold fluid. 0.00033 thermal conductivity (thermal fluid) λ h W / (m·℃) Refer to the table based on the average flue gas temperature. 0.03680 thermal conductivity (Cold fluid) λ c W / (m·℃) Refer to the table based on the average temperature of the cold fluid. 0.67281 Prandtl number (thermal fluid) Pr h Refer to the table based on the average flue gas temperature. 0.67750 Prandtl number (Cold fluid) Pr c Refer to the table based on the average temperature of the cold fluid. 2.08122

[0046] Furthermore, the parameter conditions used by the power generation unit 30 are as follows: Average temperature of the first cold water stream C1: 50 ℃ Average flow rate of first cold water flow C1: 143 TPH Working fluid type: 1,1,1,3,3-pentafluoropropane (R245fa) Temperature of the working fluid entering the power generation unit 302: 95℃ Average flow rate of working fluid entering generator 302: 143 TPH Average inlet pressure of expander: 1.0 kg / cm² Average outlet pressure of expander: 1.0 kg / cm² Average cooling water temperature: 28~32℃ Average net power generation of the generating unit (ORC system): 170 kWe Average voltage of the generator unit (ORC system): 380Vac Average current of the generator unit (ORC system): 447A Average power factor (PF) of the generating unit (ORC system): 98

[0047] Based on the above data, the power generation efficiency calculation shows that the low-temperature waste heat recovery power generation system of the present invention has a utilization rate of over 50% for low-temperature waste heat sources and a power generation efficiency of over 15%.

[0048] The formula for calculating the utilization rate of low-temperature waste heat sources is as follows: The heat recovery of waste heat from low-temperature waste heat source W1 is ΔH (kJ / h) = average temperature of low-temperature waste heat source W1 (T1) * average flow rate of low-temperature waste heat source W1 (Vv) * density (ρy); The heat recovery capacity of the low-temperature waste heat source W1 is ΔH (kW / h) = kJ / h / 860; Utilization rate of low-temperature waste heat source (conversion of low-temperature waste heat source to hot water) = Heat recovery of waste heat source W1 by low-temperature waste heat source △H(Q) / (Specific heat at constant volume Cpj*(95-75)) / 1000.

[0049] The formula for calculating power generation efficiency is as follows: Rated power generation = Waste heat recovered from low-temperature waste heat source W1 ΔH (kW / h) * Power generation coefficient (0.0587) = 200KW; Rated net power generation = Rated power generation * (1 - 15% self-consumption) = 170KW.

[0050] As described above, the low-temperature waste heat recovery power generation system of this invention can effectively utilize the low-temperature waste heat generated during the treatment of process exhaust gases. By combining renewable energy with low-temperature waste heat, it provides the heat energy required for the organic Rankine cycle generator. This not only avoids the consumption of additional energy but also facilitates energy reuse, thereby improving the economic efficiency of exhaust gas treatment and achieving carbon reduction goals.

[0051] However, the above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the scope of the patent application and the description of the invention shall still fall within the scope of the patent of the present invention.

[0052] 1: Low-temperature waste heat recovery power generation system 10: First heat source supply unit 101: Solar water heater 102: Cold Water Tank 103: Hot water tank 104: Solar Cells 20: Second heat source supply unit 201: Low-temperature waste heat source receiving device 202: Heat Exchanger 203: Waste heat emission device 30: Power generation unit 301: Heating device 302: Power generation equipment 303: Cooling device 304: Pressurization device W1: Low-temperature waste heat W2: Residual waste heat H1: First hot water flow H2: Second thermal fluid C1: First cold water flow E1: Electrical energy

Claims

1. A low-temperature waste heat recovery power generation system, comprising at least: a first heat source supply unit, comprising a solar water heater, a cold water tank connected to the inlet end of the solar water heater, and a hot water tank connected to the outlet end of the solar water heater; a second heat source supply unit, connected to the first heat source supply unit, and comprising a low-temperature waste heat source receiving device for receiving low-temperature waste heat sources from industrial processes or commercial buildings, and a heat exchanger connected to the low-temperature waste heat source receiving device, wherein the low-temperature waste heat source is selected from process waste steam, process hot water, process exhaust mixture, flue gas, hot gas, engine exhaust, water jacket hot water, or any combination thereof, and the low-temperature waste heat source may be in liquid or gaseous form; A power generation unit includes a heating device, a power generation device, a cooling device, and a pressurizing device. The heating device, the power generation device, the cooling device, and the pressurizing device are sequentially connected to form an organic Rankine cycle structure. The heating device is connected to a first heat source supply unit and a second heat source supply unit. In the first heat source supply unit, the solar water heater receives first cold water from a cold water tank, heats it to 60-75°C, and then delivers it to the hot water tank as first hot water. In the second heat source supply unit, the heat exchanger has a hot-side pipe and a cold-side pipe. The inlet of the hot-side pipe is connected to a low-temperature waste heat source receiving device, and the inlet of the cold-side pipe is connected to the outlet of the hot water tank. The low-temperature waste heat source and the first hot water exchange heat in the heat exchanger, causing the temperature of the first hot water to rise to above 80°C, after which it is discharged from the outlet of the cold-side pipe as a second hot fluid and transported to the heating device of the power generation unit. The pressurizing device pressurizes an organic working fluid to a specific pressure and then delivers it to the heating device. The heating device receives the second hot fluid and causes the second hot fluid to exchange heat with the organic working fluid flowing through the heating device, vaporizing the organic working fluid and heating it into a high-temperature, high-pressure gas. The vaporized organic working fluid is then delivered to the power generation device, while the second hot fluid, cooled by heat exchange, is returned to the cold water tank as the first cold water flow. The utilization rate of the low-temperature waste heat source in the low-temperature waste heat recovery power generation system is over 50%, and the power generation efficiency of the low-temperature waste heat recovery power generation system can reach over 15%.

2. The low-temperature waste heat recovery power generation system as described in claim 1, wherein the working fluid is selected from any one of trichlorotrifluoroethane, dichloromonofluoroethane, trichlorofluoromethane, dichlorotrifluoroethane, dichlorotrifluoromethane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, isohexane, hexane, methanol, ethanol, acetone, pentane, and isopentane.

3. The low-temperature waste heat recovery power generation system as described in claim 1, wherein the power generation device includes an expander and a generator, and the thermal energy and pressure of the vaporized organic working fluid from the heating device can be converted into the mechanical energy of the expander, thereby driving the generator to generate electricity.

4. The low-temperature waste heat recovery power generation system as described in claim 1, wherein the temperature of the low-temperature waste heat source is between 150°C and 230°C.

5. The low-temperature waste heat recovery power generation system as described in claim 1, wherein the second heat fluid is hot water at 80~99°C or steam at 100°C or above.

6. The low-temperature waste heat recovery power generation system as described in claim 1, wherein the second heat source supply unit further includes a waste heat discharge device connected to the outlet end of the hot-side pipeline of the heat exchanger.

7. The low-temperature waste heat recovery power generation system as claimed in claim 1, wherein the first heat source supply unit further includes a solar cell electrically connected to the solar water heater.

8. The low-temperature waste heat recovery power generation system as described in claim 7, wherein the type of solar cell is a silicon-based semiconductor cell, a CdTe thin-film cell, a CIGS thin-film cell, a dye-sensitized thin-film cell, or an organic material cell.

9. The low-temperature waste heat recovery power generation system as claimed in claim 1, wherein the power generation unit further includes an energy storage device electrically connected to the power generation device for storing the electrical energy generated by the power generation device.

10. The cryogenic waste heat recovery power generation system as claimed in claim 1, wherein the expander is a modified scroll compressor or a scroll expander, and the power of the expander can be controlled via an expansion valve.

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