Middle-deep layer geothermal power generation and domestic hot water coupling combined supply system and working method thereof

Abstract

The invention discloses a medium-deep layer geothermal power generation coupling domestic hot water combined supply system and a working method thereof, and belongs to the technical field of comprehensive utilization of renewable energy sources, the system comprises a geothermal fluid extraction unit, a first-stage flash evaporation power generation unit, a second-stage flash evaporation power generation unit, a condensation unit, an organic Rankine cycle power generation unit and a multi-stage heat supply unit, through the multi-stage coupling mode of'flash evaporation + ORC + gradient heat supply ', 'temperature alignment and gradient utilization' of geothermal energy is achieved, the comprehensive utilization rate of energy is greatly increased, and the system has the functions of power generation and heat supply, is economical and environmentally friendly and is suitable for popularization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of comprehensive utilization of renewable energy, and particularly relates to a middle-deep geothermal power generation coupled with a domestic hot water cogeneration system and a working method thereof. BACKGROUND

[0002] Geothermal energy is a stable, reliable, clean and renewable energy. Middle-deep geothermal resources have high temperature and great utilization potential. At present, the utilization mode of middle-high temperature geothermal resources (usually higher than 150 DEG C) is mainly flash power generation, that is, part of the geothermal fluid is flashed into steam by pressure reduction to drive the steam turbine to generate power.

[0003] However, the existing geothermal flash power generation system has the following obvious defects: after flash power generation, the geothermal fluid still carries a large amount of medium-low temperature heat (usually between 80 DEG C and 150 DEG C), and this part of waste heat is often discarded or recharged by a cooling tower in a traditional power station, and cannot be effectively utilized, resulting in energy waste. At the same time, the traditional geothermal power station has a single design function, mainly aiming at power generation and grid connection, and cannot be combined with regional heating and other needs, and cannot realize the cascade and comprehensive utilization of energy, and the economic and social benefits can be further improved. In addition, if the cooling tower is used to discharge the waste heat into the atmosphere, it will cause thermal pollution and a large amount of water resource evaporation loss. Although direct recharging is environmentally friendly, it cannot maximize the value of energy.

[0004] Therefore, there is an urgent need for a system and method which can "eat dry and squeeze" geothermal energy, realize the integration of power generation and heating, and greatly improve the comprehensive utilization efficiency of geothermal resources. SUMMARY

[0005] In view of the above defects of the prior art, the purpose of the present application is to provide a middle-deep geothermal power generation coupled with a domestic hot water cogeneration system and a working method thereof and method, so as to solve the problems of low energy utilization rate and single function of the existing geothermal utilization system.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is: In a first aspect, the present application provides a middle-deep geothermal power generation coupled with a domestic hot water cogeneration system, which comprises a geothermal fluid extraction unit, a first-stage flash power generation unit, a second-stage flash power generation unit, a condensing unit, an organic Rankine cycle power generation unit and a multi-stage cascade heating unit, wherein: The high-temperature geothermal fluid outlet of the geothermal fluid extraction unit is connected to the inlet of the first-stage flash power generation unit, and the high-temperature liquid outlet of the first-stage flash power generation unit is connected to the inlet of the second-stage flash power generation unit; The exhaust steam outlet of the second-stage flash power generation unit is connected to the inlet of the condensing unit; The liquid outlets of the second-stage flash power generation unit and the condensing unit are both connected to the inlet of the organic Rankine cycle power generation unit; The geothermal tail water outlet of the organic Rankine cycle power generation unit is connected to a multi-stage cascade heat supply unit.

[0007] Preferably, the geothermal tail water outlet of the organic Rankine cycle power generation unit is connected to a thermal energy storage and dispatching unit, and the heat source outlet of the thermal energy storage and dispatching unit is connected to the heat source inlet of the multi-stage cascade heat supply unit.

[0008] Preferably, the primary flash evaporation power generation unit comprises a high-pressure flash separation device and a high-pressure steam turbine, wherein the high-temperature geothermal fluid outlet of the geothermal fluid extraction is connected to the inlet of the high-pressure flash separation device, the high-pressure saturated steam outlet of the high-pressure flash separation device is connected to the high-pressure steam turbine, the high-temperature liquid outlet of the high-pressure flash separation device is connected to the secondary flash evaporation power generation unit, and the exhaust steam outlet of the high-pressure steam turbine is connected to the secondary flash evaporation power generation unit.

[0009] Preferably, the secondary flash evaporation power generation unit comprises a low-pressure flash separation device and a low-pressure steam turbine, wherein the inlet of the low-pressure flash separation device is connected to the high-temperature liquid outlet of the high-pressure flash separation device, the low-pressure saturated steam outlet of the low-pressure flash separation device is connected to the low-pressure steam turbine, and the exhaust steam outlet of the low-pressure steam turbine is connected to the condensation unit. The high-pressure steam turbine and the low-pressure steam turbine are coaxially arranged and both drive the connected generator.

[0010] Preferably, the condensation unit comprises a first condenser, wherein the liquid outlet of the low-pressure flash separation device and the liquid outlet of the first condenser are both connected to the first condenser, and the outlet of the first condenser is connected to the organic Rankine cycle power generation unit.

[0011] Preferably, the organic Rankine cycle power generation unit comprises an evaporator, a working fluid pump, a turbine and a second condenser, wherein the liquid outlet of the first condenser is connected to the evaporator, the steam outlet of the evaporator is connected to the turbine, and the turbine drives the connected generator. The exhaust steam of the generator is connected to the second condenser, and the liquid outlet of the second condenser is connected to the evaporator through the working fluid pump.

[0012] Preferably, the multi-stage cascade heat supply unit comprises a primary heat supply unit, a secondary heat supply unit and a tertiary heat supply unit, wherein the heat source inlet of the primary heat supply unit is connected to the geothermal tail water outlet of the organic Rankine cycle power generation unit, the heat source outlet of the primary heat supply unit is connected to the heat source inlet of the secondary heat supply unit, the cold side inlet of the primary heat supply unit is connected to an external water source, and the cold side outlet of the primary heat supply unit is connected to a user heat supply water; the heat source outlet of the secondary heat supply unit is connected to the heat source inlet of the tertiary heat supply unit, the cold side of the secondary heat supply unit is connected to a heat supply user end, and the cold side of the tertiary heat supply unit is connected to a heat supply user end.

[0013] Preferably, the heat energy storage and distribution unit comprises a heat storage tank, wherein the geothermal tail water outlet of the organic Rankine power generation unit is connected to the heat storage tank; and the heat source outlet of the heat storage tank is connected to the heat user end.

[0014] In a second aspect, the application provides a working method of a medium-deep geothermal power generation coupled with a domestic hot water supply system, comprising the following steps: extracting high-temperature geothermal fluid from a geothermal production well; introducing the high-temperature geothermal fluid into a primary flash power generation unit for flash power generation, introducing the geothermal fluid after flash power generation into a secondary flash power generation unit for secondary flash power generation, and condensing the exhaust steam after flash power generation to form condensed liquid; mixing the condensed liquid and the geothermal fluid after secondary flash to enter an organic Rankine power generation unit for power generation; introducing the geothermal tail water after power generation into a multi-stage cascade heat supply unit to exchange heat with an external water source and a heat supply medium.

[0015] Preferably, the geothermal tail water after power generation enters the multi-stage cascade heat supply unit to exchange heat with the external water source and the heat supply medium, and the specific method is as follows: using the high-temperature section tail water to heat domestic hot water; using the medium-temperature section tail water to heat ground heating circulating water; using the low-temperature section tail water to heat radiator circulating water.

[0016] Compared with the prior art, the application has the following beneficial effects: The medium-deep geothermal power generation coupled with a domestic hot water supply system provided by the application adopts a three-stage cascade utilization mode of “flash + ORC + heat supply”. The flash power generation utilizes high-grade heat energy, the ORC power generation utilizes medium-low grade waste heat, and finally the entire residual heat of the exhaust steam and waste water is used for domestic hot water, almost completely utilizing the heat of the geothermal fluid, and the comprehensive energy efficiency can reach more than 80%, which is much higher than that of the traditional single power generation mode, realizing efficient cascade utilization of energy; at the same time, the system can not only output stable green power, but also provide stable domestic hot water supply, widening the income source (both selling electricity and selling heat), significantly enhancing the economic competitiveness of the geothermal project, and being particularly suitable for being built in the periphery of a town to realize power and heat supply, improving the economy and functionality; in addition, the system is a closed cycle, and the final tail water is recharged into the underground, avoiding heat pollution and water resource consumption, protecting the geothermal reservoir pressure, and realizing sustainable development of geothermal resources. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a structural schematic diagram of the medium-deep geothermal power generation coupled with a domestic hot water supply system according to the application; 1, medium-depth geothermal production well; 2, high-pressure flash separator; 3, high-pressure steam turbine; 4, low-pressure flash separator; 5, low-pressure steam turbine; 6, generator; 7, first condenser; 8, evaporator; 9, working medium pump; 10, turbine; 11, condenser; 12, domestic water heater; 13, first plate heat exchanger; 14, second plate heat exchanger; 15, third plate heat exchanger; 16, indoor radiator; 17, floor heating; 18, user end; 19, heat storage tank; 20, recharging pump; 21, water pumping pump; 22, geothermal recharging well. DETAILED DESCRIPTION

[0018] In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0019] It is to be understood that the terminology "includes", "has", "holds", "contains" and / or "comprising", when used in this specification and in the following claims, indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] It is also to be understood that the terminology "and / or" when used in this specification and in the following claims, refers to at least one of the items, or any combination of one or more of the items, and includes all possible combinations of one or more of the items.

[0021] As used in this specification and in the claims, the term "if" can be interpreted as meaning "when", or "once", or "in response to a determination", or "in response to detecting", as appropriate, depending on the context. Similarly, the phrase "if determined", or "if detected [the described condition or event]" can be interpreted as meaning "once determined", or "in response to a determination", or "once detected [the described condition or event]", or "in response to detecting [the described condition or event]", as appropriate, depending on the context.

[0022] In addition, in the description of the application and in the following claims, the terms "first", "second", "third", etc. are only used to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0023] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0024] Example 1 like Figure 1 As shown in the figure, this embodiment provides a medium-deep geothermal power generation coupled with domestic hot water supply system, including a geothermal fluid extraction unit, a primary flash evaporation power generation unit, a secondary flash evaporation power generation unit, a condensation unit, an organic Rankine cycle power generation unit, a multi-stage cascade heating unit, a thermal energy storage and distribution unit, and a tailwater reinjection unit, wherein: The high-temperature geothermal fluid outlet of the geothermal fluid extraction unit is connected to the inlet of the first-stage flash evaporation unit, and the high-temperature liquid outlet of the first-stage flash evaporation unit is connected to the inlet of the second-stage flash evaporation unit. The exhaust steam outlet of the secondary flash evaporation unit is connected to the inlet of the condensation unit; The liquid outlets of both the secondary flash evaporation unit and the condensation unit are connected to the inlet of the organic Rankine cycle power generation unit. The geothermal tailwater outlet of the organic Rankine cycle power generation unit is connected to a multi-stage cascade heating unit and a thermal energy storage and distribution unit, respectively. The low-temperature fluid outlet of the multi-stage cascade heating unit is connected to the tailwater reinjection unit.

[0025] The heat source outlet of the thermal energy storage and distribution unit is connected to the heat source inlet of the multi-stage cascade heating unit.

[0026] Example 2 Based on Example 1, this example provides a medium-deep geothermal power generation coupled with domestic hot water supply system. The geothermal fluid extraction unit includes a water pump 22, which is used to continuously extract high-temperature geothermal fluid from the medium-deep geothermal production well 1.

[0027] The first-stage flash evaporation electrostatic unit includes a high-pressure flash separator 2 and a high-pressure steam turbine 3. The outlet of the high-temperature geothermal fluid extracted by the geothermal fluid is connected to the inlet of the high-pressure flash separator 2, the high-pressure saturated steam outlet of the high-pressure flash separator 2 is connected to the high-pressure steam turbine 3, and the high-temperature liquid outlet of the high-pressure flash separator 2 is connected to the second-stage flash evaporation electrostatic unit.

[0028] The secondary flash power generation unit comprises a low-pressure flash separator 4 and a low-pressure steam turbine 5, wherein the high-temperature liquid outlet of the low-pressure flash separator 4 is connected to the high-temperature liquid outlet of the high-pressure flash separator 2, the low-pressure saturated steam outlet of the low-pressure flash separator 4 is connected to the low-pressure steam turbine 5, and the exhaust steam outlet of the low-pressure steam turbine 5 is connected to the condensing unit.

[0029] The high-pressure steam turbine 3 and the low-pressure steam turbine 5 are coaxially arranged and are drivingly connected to the generator 6.

[0030] The exhaust steam outlet of the high-pressure steam turbine 3 is connected to the inlet of the low-pressure steam turbine 5.

[0031] The condensing unit comprises a first condenser 7, wherein the liquid outlet of the low-pressure flash separator 4 and the liquid outlet of the first condenser 7 are both connected to the first condenser 7, and the outlet of the first condenser 7 is connected to the organic Rankine cycle power generation unit.

[0032] The organic Rankine cycle power generation unit comprises an evaporator 8, a working medium pump 9, a turbine 10 and a second condenser 11, wherein the liquid outlet of the first condenser 7 is connected to the evaporator 8, the steam outlet of the evaporator 8 is connected to the turbine 10, and the turbine 10 is drivingly connected to the generator 6.

[0033] The exhaust steam of the generator 6 is connected to the second condenser 11, and the liquid outlet of the second condenser 11 is connected to the evaporator 8 through the working medium pump 9.

[0034] The multi-stage cascade heat supply unit comprises a first heat supply unit, a second heat supply unit and a third heat supply unit, wherein the geothermal tail water outlet of the organic Rankine power generation unit is connected to the heat source inlet of the first heat supply unit, the heat source outlet of the first heat supply unit is connected to the heat source inlet of the second heat supply unit, the cold side inlet of the first heat supply unit is connected to an external water source, and the cold side outlet of the first heat supply unit is connected to a user heat supply water.

[0035] The heat source outlet of the second heat supply unit is connected to the heat source inlet of the third heat supply unit, and the cold side of the second heat supply unit is connected to a heat supply user end.

[0036] The cold side of the third heat supply unit is connected to a heat supply user end.

[0037] The heat energy storage and allocation unit comprises a heat storage tank 19, wherein the geothermal tail water outlet of the organic Rankine power generation unit is connected to the heat storage tank 19, and the heat source outlet of the heat storage tank 19 is connected to a heat supply user end.

[0038] The tail water recharging unit comprises a recharging pump 20, and the tail water of the third heat supply unit is connected to a recharging well 22 through the recharging pump 20.

[0039] Embodiment 3 Based on the embodiment 1, the embodiment provides a middle-deep geothermal power generation coupled with domestic hot water supply system, the first heat supply unit is a first plate heat exchanger 13.

[0040] The second heat supply unit is a second plate heat exchanger 14.

[0041] The third heat supply unit is a third plate heat exchanger 15.

[0042] Embodiment 4 The embodiment provides a working method of a middle-deep geothermal power generation coupled with domestic hot water supply system, and the working method comprises the following steps. The water pump 22 continuously extracts high-temperature geothermal fluid (temperature is about 160-200 DEG C) from the middle-deep geothermal production well 1. The high-temperature geothermal fluid is used as the primary energy of the whole system.

[0043] The extracted high-temperature geothermal fluid is first sent to the high-pressure flash separator 2. Under the action of pressure reduction, part of the fluid is instantaneously flashed into high-pressure saturated steam, and the remaining unvaporized liquid remains at the bottom of the separator due to its large density.

[0044] The high-temperature liquid flowing out of the bottom of the high-pressure flash separator 2 then enters the low-pressure flash separator 4 for secondary pressure reduction and flashing, to generate a low-pressure saturated steam. The high-pressure steam generated first enters the high-pressure turbine 3 to expand and do work; the low-pressure steam generated second enters the low-pressure turbine 5 to expand and do work.

[0045] The high-pressure turbine 3 and the low-pressure turbine 5 are usually coaxially arranged to drive a generator 6 to rotate, thereby generating electric energy.

[0046] The low-pressure exhaust steam discharged from the low-pressure turbine 5 enters the condenser 7, and is condensed into liquid water after releasing the remaining heat to the cooling medium (such as cooling water or air).

[0047] The geothermal fluid (about 90-120 DEG C) with a relatively high temperature discharged from the bottom of the low-pressure flash separator 4 and from the condenser 7 is collected and pumped into the organic Rankine power generation unit, specifically: The high-temperature geothermal fluid first enters the evaporator 8, and transfers heat to the circulating organic working medium (such as pentane, R245fa, etc.) as a heat source, so that the organic working medium is evaporated into high-pressure organic steam. The organic working medium steam then drives the turbine 10 to expand and do work. The turbine 10 can drive the generator 6 coaxially with the main turbine, or drive another generator to generate additional electric energy.

[0048] The exhaust steam generated by the high-pressure steam turbine 3 is mixed with the low-pressure steam generated by the low-pressure flash separator 4, and enters the low-pressure steam turbine 5 for further expansion and work; the organic working medium exhaust steam after work is condensed into liquid in the condenser 11, and is pumped back to the evaporator 8 by the working medium pump 9, thus completing the organic Rankine cycle.

[0049] After the above power generation link, the temperature of the geothermal fluid has been greatly reduced, but it still contains abundant low-grade heat energy, which can be used for heating. The system realizes multi-stage cascade utilization of heat energy through three-stage plate heat exchangers: The geothermal tail water (relatively highest temperature) flowing out of the evaporator 8 first enters the condenser 7 and exchanges heat with the chilled water in the condenser 7, and the chilled water flows into the domestic water heater 12 and exchanges heat with domestic hot water. When the user needs to use domestic hot water, when the indoor user has heating demand, the domestic hot water flows out of the domestic water heater 12. The chilled water that has heated the domestic hot water first enters the first plate heat exchanger 13, and its heat is used to heat the circulating water of the indoor radiator.

[0050] The chilled water with reduced temperature after one-stage heat exchange then enters the second plate heat exchanger 14, and its heat is used to heat the circulating water to the floor heating 17. The floor heating system as a low-temperature radiant heating terminal is very suitable for utilizing this grade of heat energy.

[0051] The chilled water with further reduced temperature after two-stage heat exchange finally enters the third plate heat exchanger 15, and its remaining heat is used to heat the circulating water to the indoor radiator 16 (such as a heating pipe), providing convection heating for the indoor space.

[0052] The heat storage tank 19 plays the role of a "heat bank" in the system. It can be connected in parallel or in series with each heat exchange circuit. During the low demand period of heating, the excess heat energy can be stored in the heat storage tank 19; during the peak demand period of heating, the stored heat energy can be released to supplement the system heating, thereby realizing the cross-time and space allocation of heat energy and greatly improving the flexibility and energy utilization rate of the system.

[0053] After multi-stage power generation and cascade heat exchange, the temperature of the geothermal fluid is reduced to near ambient temperature (for example, below 30°C). Finally, the low-temperature tail water is all re-injected into the underground thermal reservoir through the re-injection well 22 by the re-injection pump 20.

[0054] This avoids heat pollution and waste of water resources, and on the other hand, maintains the pressure balance of the underground reservoir, ensuring the sustainable development of geothermal resources.

[0055] In conclusion, the application realizes the extreme comprehensive utilization of the medium-deep geothermal energy by the innovative process of "two-stage flash power generation + ORC waste heat power generation + three-stage cascade heat supply + heat storage allocation", integrates power generation, domestic hot water, floor heating and traditional radiator heating, and significantly improves the energy conversion efficiency and project economic benefits.

[0056] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A system for coupling a medium-deep geothermal power generation with a domestic hot water supply system, characterized in that, The geothermal fluid extraction unit, the primary flash power generation unit, the secondary flash power generation unit, the condensation unit, the organic Rankine cycle power generation unit and the multi-stage cascade heat supply unit, wherein: The high-temperature geothermal fluid outlet of the geothermal fluid extraction unit is connected to the inlet of the primary flash power generation unit, and the high-temperature liquid outlet of the primary flash power generation unit is connected to the inlet of the secondary flash power generation unit; The exhaust steam outlet of the secondary flash power generation unit is connected to the inlet of the condensation unit; The liquid outlets of the secondary flash power generation unit and the condensation unit are both connected to the inlet of the organic Rankine cycle power generation unit; The geothermal tail water outlet of the organic Rankine cycle power generation unit is connected to the multi-stage cascade heat supply unit.

2. The system according to claim 1, wherein, The geothermal tail water outlet of the organic Rankine cycle power generation unit is connected to the heat energy storage and distribution unit, and the heat source outlet of the heat energy storage and distribution unit is connected to the heat source inlet of the multi-stage cascade heat supply unit.

3. The system according to claim 1, wherein, The primary flash power generation unit comprises a high-pressure flash separator and a high-pressure steam turbine, wherein the high-temperature geothermal fluid outlet of the geothermal fluid extraction unit is connected to the inlet of the high-pressure flash separator, the high-pressure saturated steam outlet of the high-pressure flash separator is connected to the high-pressure steam turbine, and the high-temperature liquid outlet of the high-pressure flash separator is connected to the secondary flash power generation unit; and the exhaust steam outlet of the high-pressure steam turbine is connected to the secondary flash power generation unit.

4. The system according to claim 3, wherein, The secondary flash power generation unit comprises a low-pressure flash separator and a low-pressure steam turbine, wherein the inlet of the low-pressure flash separator is connected to the high-temperature liquid outlet of the high-pressure flash separator, the low-pressure saturated steam outlet of the low-pressure flash separator is connected to the low-pressure steam turbine, and the exhaust steam outlet of the low-pressure steam turbine is connected to the condensation unit; The high-pressure steam turbine and the low-pressure steam turbine are coaxially arranged and both drive the connected generator.

5. The system according to claim 1, wherein, The condensation unit comprises a first condenser, wherein the liquid outlets of the low-pressure flash separator and the first condenser are both connected to the first condenser, and the outlet of the first condenser is connected to the organic Rankine cycle power generation unit.

6. The system according to claim 1, wherein, The organic Rankine cycle power generation unit comprises an evaporator, a working medium pump, a turbine and a second condenser, wherein the liquid outlet of the first condenser is connected to the evaporator, the steam outlet of the evaporator is connected to the turbine, and the turbine drives the connected generator; The exhaust steam of the generator is connected to the second condenser, and the liquid outlet of the second condenser is connected to the evaporator through the working medium pump.

7. The system according to claim 1, wherein the system is characterized by, The multi-stage cascade heat supply unit comprises a primary heat supply unit, a secondary heat supply unit and a tertiary heat supply unit, wherein the heat source inlet of the primary heat supply unit is connected to the geothermal tail water outlet of the organic Rankine cycle power generation unit, the heat source outlet of the primary heat supply unit is connected to the heat source inlet of the secondary heat supply unit; the cold side inlet of the primary heat supply unit is connected to an external water source, and the cold side outlet of the primary heat supply unit is connected to a user heat supply water; the heat source outlet of the secondary heat supply unit is connected to the heat source inlet of the tertiary heat supply unit, and the cold side of the secondary heat supply unit is connected to a heat supply user end; and the cold side of the tertiary heat supply unit is connected to a heat supply user end.

8. The system according to claim 1, wherein, The heat energy storage and distribution unit comprises a heat storage tank, wherein the heat storage tank is connected to the geothermal tail water outlet of the organic Rankine cycle power generation unit; and the heat source outlet of the heat storage tank is connected to a heat supply user end.

9. A method for operating a medium-deep geothermal power generation coupled with a domestic hot water supply system, characterized in that, high-temperature geothermal fluid is extracted from a geothermal production well; the high-temperature geothermal fluid is introduced into a primary flash power generation unit for flash power generation, the flashed geothermal fluid is introduced into a secondary flash power generation unit for further flash power generation, and the flashed geothermal fluid is condensed to form condensed liquid; the condensed liquid and the secondary flashed geothermal fluid are mixed and introduced into an organic Rankine power generation unit for power generation; the generated geothermal tail water is introduced into a multi-stage cascade heat supply unit for heat exchange with an external water source and a heat supply medium.

10. The method according to claim 9, wherein the method is characterized by, The generated geothermal tail water is introduced into a multi-stage cascade heat supply unit for heat exchange with an external water source and a heat supply medium, and the specific method is: using high-temperature section tail water to heat domestic hot water; using medium-temperature section tail water to heat ground heating circulating water; using low-temperature section tail water to heat radiator circulating water.

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