Low-temperature driven geothermal coupled two-stage compression heat pump heating system and method

Abstract

This invention provides a low-temperature driven geothermal coupled two-stage compression heat pump heating system and method, comprising a low-temperature Rankine cycle power system, a two-stage compression heat pump system, a plate heat exchanger, a zero-stage network supply and return water system, and a primary network supply and return water system. The system uses waste heat from the zero-stage network return water to drive an organic Rankine cycle, providing power to the system. This reduces the zero-stage network return water temperature, widening the temperature difference between the supply and return water, thus reducing the zero-stage network flow rate and the power consumption of the heating network circulating water pump. The heat pump recovers waste heat from the cold end and geothermal energy in stages to heat the primary network supply water at the plate heat exchanger outlet, which is then heated by the zero-stage network supply water, further widening the temperature difference between the primary network supply and return water, and reducing the primary network circulation flow rate and the power consumption of the circulating water pump. Applying this system and method can increase the temperature difference between the supply and return water of the zero and primary networks in long-distance heating transmission networks, thereby reducing the heating network circulation flow rate, saving power consumption of the circulating water pump, improving heating network transmission efficiency, reducing heating costs, and achieving a highly efficient, energy-saving, and carbon-reducing long-distance heating method.

Description

Technical Field

[0001] This invention belongs to the field of long-distance heating technology, and relates to a low-temperature driven geothermal coupled two-stage compression heat pump heating system and method. Background Technology

[0002] With the steady increase in urbanization rates in recent years, urban boundaries have been expanding, and the outward expansion of urban fringe areas has not only promoted economic prosperity but also placed higher demands on urban infrastructure. At the same time, facing the severe challenges of global climate change, the steady progress towards carbon peaking and carbon neutrality has become an important strategic direction for national development. Against this backdrop, northern regions, especially those that have long relied on thermal power plants as their main source of centralized heating, are undergoing a profound transformation.

[0003] To adapt to stricter environmental requirements and promote the optimization and upgrading of the energy structure, many existing centralized heating sources—thermal power plants—have begun to be relocated from urban centers or densely populated areas to more distant locations on the outskirts of cities. This adjustment aims to reduce pollution emissions, improve air quality, and also create more space for sustainable urban development. However, this change has also brought a series of technical challenges, the most significant of which is how to achieve long-distance heating efficiently, economically, and environmentally friendly.

[0004] Currently, long-distance heating faces several problems, primarily high operating power consumption, significant heat loss, and high investment and construction costs for pipeline networks due to long transmission distances. Heating costs are the main factor limiting the development of long-distance heating technology. Currently, influenced by coal prices and electricity spot market policies, the heating units operating under these conditions experience excessively high shared costs, even leading to cost inversions, thus restricting the development of the heating industry. In long-distance pipeline heating, transmission costs account for approximately 30-40% of the total heating cost. Furthermore, the pressure drop caused by large flow rates and long distances results in excessively high power consumption for the circulating water pumps in the heating network.

[0005] If the circulating water volume of the heating network can be reduced, the power consumption of the water pumps can be lowered, which can significantly reduce the cost of long-distance heating, increase the profit margin of heating, popularize long-distance heating technology, and solve the heating dilemma under the current urban development and energy policy background. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a low-temperature driven geothermal coupled two-stage compression heat pump heating system and method, which is used to increase the supply and return water temperature difference between the zero-stage network and the primary network in a long-distance heating pipeline, thereby reducing the circulating water flow rate of the heating network and reducing the power consumption of the circulating water pump. At the same time, it utilizes geothermal energy to participate in heating, thereby reducing heating costs and indirectly reducing the carbon emissions from the heating system.

[0007] This invention is achieved through the following technical solution:

[0008] A low-temperature driven geothermal coupled two-stage compression heat pump heating system includes,

[0009] Low-temperature Rankine cycle power system, two-stage compression heat pump system, plate heat exchanger, zero-stage network supply and return water system and primary network supply and return water system;

[0010] The low-temperature Rankine cycle power system includes a first compressor, a first low-temperature evaporator, a power unit, and a first condenser connected in sequence; the two-stage compression heat pump system includes a second low-temperature evaporator, a low-pressure stage compressor, a high-pressure stage compressor, and a second condenser.

[0011] The circulating water outlet of the first low-temperature evaporator is connected to the return water side of the zero-level network supply and return water system.

[0012] The circulating water inlet of the first low-temperature evaporator is connected to the plate heat exchanger; the plate heat exchanger is connected to the supply side of the zero-level network supply and return water system respectively.

[0013] The return water side of the primary network water supply and return system is connected to the supply water side of the primary network water supply and return system in sequence through a plate heat exchanger and a second condenser.

[0014] The initial heat exchange of the zero-level network supply and return water system and the primary network supply and return water system is carried out in a plate heat exchanger;

[0015] The closed water side of the first condenser is connected to the closed water side of the second low-temperature evaporator;

[0016] The first compressor, the power unit, the low-pressure stage compressor, and the high-pressure stage compressor are connected by a power transmission connection.

[0017] Preferably, the two-stage compression heat pump system further includes buried heat exchange pipes and an intermediate heat exchanger;

[0018] The working fluid side outlet of the second condenser is connected to the inlet of the intermediate heat exchanger, and the outlet of the intermediate heat exchanger is connected in sequence to the working fluid side inlet of the buried heat exchange pipe and the low-temperature evaporator.

[0019] The working fluid side outlet and the buried heat exchange pipe outlet of the low-temperature evaporator are connected in sequence to the inlets of the low-pressure stage compressor and the high-pressure stage compressor.

[0020] The outlet of the high-pressure stage compressor is connected to the working fluid side inlet of the second condenser.

[0021] Preferably, a first pressure-reducing valve is installed on one of the pipelines between the working fluid side outlet of the second condenser and the intermediate heat exchanger.

[0022] Preferably, a second pressure-reducing valve is installed on the pipeline between the intermediate heat exchanger and the low-temperature evaporator.

[0023] Preferably, a closed-loop water pump is provided between the first condenser and the low-temperature evaporator.

[0024] Preferably, the first compressor, the power unit, the low-pressure stage compressor, and the high-pressure stage compressor are connected by a coupling.

[0025] Preferably, the zero-level network water supply and return system is a pipeline network between the heat source and the pressure reducing station.

[0026] Preferably, the primary water supply and return system is the pipeline network between the pressure reducing station and the heat exchange station.

[0027] Preferably, the internal circulating working fluid of the low-temperature Rankine cycle power system is an organic compound.

[0028] A method for operating a low-temperature driven geothermal coupled two-stage compression heat pump heating system, comprising:

[0029] The zero-level network supply water exchanges heat with the primary network return water in a plate heat exchanger. After cooling, the zero-level network return water enters the low-temperature evaporator to provide a heat source for the low-temperature Rankine cycle power system. The low-temperature Rankine cycle power system drives the two-stage compression heat pump system through the heat source to transfer heat to the second condenser. After being heated by the zero-level network supply water in the plate heat exchanger, the primary network return water is further heated by the second condenser before being supplied to the heat exchange station.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] This invention provides a low-temperature driven geothermal coupled two-stage compression heat pump heating system and method, applicable to long-distance heating transmission networks. It utilizes waste heat from the zero-stage network supply water to drive a low-temperature organic Rankine cycle. The system employs a coaxial coupling between the power cycle compressor, the power unit, and the two-stage compressors of the two-stage compression heat pump, allowing the organic Rankine cycle power to directly supply power to the three compressors. Geothermal energy and waste heat from the Rankine cycle's cold end serve as the two-stage low-temperature heat sources for the heat pump. The system uses waste heat from the zero-stage network return water to drive the organic Rankine cycle, providing system power. This lowers the zero-stage network return water temperature, increasing the supply and return water temperature difference, reducing the zero-stage network flow rate and the power consumption of the heating network circulating water pump. The heat pump recovers waste heat from the cold end and geothermal energy in stages, then heats the plate heat exchanger outlet, which is then heated by the zero-stage network supply water to the first-stage network supply water, further increasing the first-stage network supply and return water temperature difference and reducing the first-stage network circulation flow rate and the power consumption of the circulating water pump. By applying this system and method, the temperature difference between the supply and return water of the zero and primary networks can be increased in long-distance heating transmission pipelines, thereby reducing the circulation flow of the heating network, saving the power consumption of the circulating water pump, improving the transmission efficiency of the heating network, reducing heating costs, and realizing a long-distance heating method that is highly efficient, energy-saving, and reduces carbon emissions.

[0032] Furthermore, this invention uses the outlet of the heat pump-heated plate heat exchanger to supply water to the primary network, thereby increasing the supply water temperature of the primary network. It also uses the return water from the zero-level network to drive a low-temperature organic Rankine cycle, thereby reducing the return water temperature of the zero-level network, increasing the temperature difference between the supply and return water of the zero and primary networks, reducing the circulating water flow rate of the two-stage heat network, reducing the power consumption of the circulating water pump, and reducing the cost of heat transfer.

[0033] Furthermore, this invention uses an organic Rankine cycle driven by the waste heat of the zero-stage network return water to drive the compressor of a two-stage compression heat pump to do work, while simultaneously driving the compressor of the main circulation, thereby realizing the direct transfer of mechanical energy, avoiding the loss caused by energy form conversion, and improving energy utilization efficiency.

[0034] Furthermore, this invention uses the waste heat from the cold end of an organic Rankine cycle as a low-temperature heat source for a two-stage compression heat pump, thereby improving the efficiency of waste heat utilization.

[0035] Furthermore, this invention uses geothermal energy as the intermediate heat source for a two-stage heat pump, adding a cost-free renewable energy source to the system, reducing heating costs and carbon emissions, while reducing the temperature difference between high and low temperature heat sources, utilizing two-stage compression to reduce power consumption, improve the heat pump COP, reduce heat pump power consumption, and improve energy utilization efficiency. Attached Figure Description

[0036] Figure 1 A schematic diagram of a low-temperature driven, geothermal coupled, two-stage compression heat pump heating system.

[0037] In the diagram: 1-First compressor; 2-First low-temperature evaporator; 3-Power unit; 4-First condenser; 5-Closed-loop water pump; 6-Second low-temperature evaporator; 7-Low-pressure stage compressor; 8-High-pressure stage compressor; 9-Second condenser; 10-First pressure reducing valve; 11-Buried heat exchange pipe; 12-Intermediate heat exchanger; 13-Second pressure reducing valve; 15-Plate heat exchanger. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] This invention provides a low-temperature driven geothermal coupled two-stage compression heat pump heating system. The system heats the outlet of a plate heat exchanger via a heat pump to supply water to the primary network, increasing the primary network supply water temperature. The return water from the zero-stage network drives a low-temperature organic Rankine cycle, lowering the zero-stage network return water temperature. This increases the temperature difference between the primary and zero-stage network supply and return water, reducing the circulating water flow rate of both heating networks, lowering the power consumption of the circulating water pump, and reducing heat transfer costs. The organic Rankine cycle, driven by the waste heat from the zero-stage network return water, drives the compressor of the two-stage compression heat pump, simultaneously driving the compressor of the main circulation, achieving direct transfer of mechanical energy, avoiding losses caused by energy conversion, and improving energy utilization efficiency. The waste heat from the cold end of the organic Rankine cycle serves as a low-temperature heat source for the two-stage compression heat pump, improving waste heat utilization efficiency.

[0041] like Figure 1 As shown, it includes a low-temperature Rankine cycle power system, a two-stage compression heat pump system, a plate heat exchanger 15, a zero-stage network supply and return water system, and a primary network supply and return water system; the low-temperature Rankine cycle power system includes a first compressor 1, a first low-temperature evaporator 2, a power unit 3, and a first condenser 4 connected in sequence; the two-stage compression heat pump system includes a second low-temperature evaporator 6, a low-pressure stage compressor 7, a high-pressure stage compressor 8, and a second condenser 9;

[0042] The circulating water outlet of the first low-temperature evaporator 2 is connected to the return water side of the zero-level network supply and return water system.

[0043] The circulating water inlet of the first low-temperature evaporator 2 is connected to the plate heat exchanger 15; the plate heat exchanger 15 is connected to the water supply side of the zero-level network supply and return water system respectively.

[0044] The return water side of the primary network water supply and return system is connected to the supply water side of the primary network water supply and return system in sequence through plate heat exchanger 15 and second condenser 9.

[0045] The initial heat exchange of the zero-level network supply and return water system and the primary network supply and return water system is carried out in the plate heat exchanger 15; the initial heat exchange between the zero-level network and the primary network is carried out in the plate heat exchanger 15. The zero-level network pipeline comes from the heat source and passes through the plate heat exchanger 15 and the waste heat evaporator 2 in sequence, and is sent back to the heat source. The primary network comes from the heat exchange station and passes through the plate heat exchanger 15 and the condenser 9 in sequence, and is sent back to the heat exchange station.

[0046] The closed water side of the first condenser 4 is connected to the closed water side of the second low-temperature evaporator 6;

[0047] The first compressor 1, the power unit 3, the low-pressure stage compressor 7 and the high-pressure stage compressor 8 are connected by a power transmission connection.

[0048] The two-stage compression heat pump system also includes a buried heat exchange pipe 11 and an intermediate heat exchanger 12;

[0049] The working fluid side outlet of the second condenser 9 is connected to the inlet of the intermediate heat exchanger 12, and the outlet of the intermediate heat exchanger 12 is connected in sequence to the working fluid side inlet of the buried heat exchange pipe 11 and the low-temperature evaporator 6.

[0050] The working fluid side outlet of the low-temperature evaporator 6 and the outlet of the buried heat exchange pipe 11 are connected in sequence to the inlets of the low-pressure stage compressor 7 and the high-pressure stage compressor 8.

[0051] The outlet of the high-pressure stage compressor 8 is connected to the working fluid side inlet of the second condenser 9.

[0052] A first pressure reducing valve 10 is installed on a pipeline between the working fluid side outlet of the second condenser 9 and the intermediate heat exchanger 12. Geothermal energy is used as the intermediate heat source for the two-stage heat pump. This adds a cost-free renewable energy source to the system, reduces heating costs and carbon emissions, reduces the temperature difference between high and low temperature heat sources, reduces power consumption by using two-stage compression, improves the COP of the heat pump, reduces the power consumption of the heat pump, and improves energy utilization efficiency.

[0053] A second pressure-reducing valve 13 is installed on the pipeline between the intermediate heat exchanger 12 and the low-temperature evaporator 6.

[0054] A closed-loop water pump 5 is installed between the first condenser 4 and the low-temperature evaporator 6. The closed-loop water pump 5 provides power for the closed-loop water circulating between the condenser 4 and the low-temperature evaporator 6.

[0055] The first compressor 1, the power unit 3, the low-pressure stage compressor 7, and the high-pressure stage compressor 8 are connected by a coupling.

[0056] In long-distance heating networks, pressure-reducing stations are generally installed. This system and method are generally applied to pressure-reducing stations. The network between the heat source and the pressure-reducing station is called the zero-level network, and the network between the pressure-reducing station and the heat exchange station is called the primary network. The zero-level network supply and return water system is the network between the heat source and the pressure-reducing station. The primary network supply and return water system is the network between the pressure-reducing station and the heat exchange station. The internal circulating working fluid of the low-temperature Rankine cycle power system is an organic compound.

[0057] The operation method of a low-temperature driven geothermal coupled two-stage compression heat pump heating system includes,

[0058] The zero-level network water supply exchanges heat with the primary network return water in the plate heat exchanger 15. After cooling, the zero-level network return water enters the low-temperature evaporator 2 to provide a heat source for the low-temperature Rankine cycle power system. The low-temperature Rankine cycle power system drives the two-stage compression heat pump system through the heat source to transfer heat to the second condenser 9. After being heated by the zero-level network water supply in the plate heat exchanger 15, the primary network return water is further heated by the second condenser 9 before being supplied to the heat exchange station.

[0059] The specific process is as follows:

[0060] During system operation, the zero-level network supply water exchanges heat with the primary network return water in plate heat exchanger 15. The cooled zero-level network supply water enters the first low-temperature evaporator 2 to provide a heat source for the organic Rankine cycle working fluid, and then is sent back to the first station of the heating network. The primary network return water is heated by the zero-level network supply water in plate heat exchanger 15, and then further heated by the second condenser 9 of the heat pump before being supplied to the heat exchange station. The organic working fluid heated and evaporated in the low-temperature evaporator 2 enters the power unit 3 to expand and do work, driving the coaxial first compressor 1, low-pressure stage compressor 7, and high-pressure stage compressor 8 to operate. The outlet organic working fluid is condensed in the first condenser 4 and then enters the compressor 1 for pressurization before being sent back to the low-temperature evaporator 2 to complete the organic Rankine cycle. The closed-loop water is pumped by the closed-loop water pump 5. The working fluid, which provides power for circulation, enters the first condenser 4 to absorb waste heat from the exhaust steam and rise in temperature. It then enters the second low-temperature evaporator 6 as a low-temperature heat source for the heat pump to extract waste heat. The circulation is completed by the closed-loop water pump 5. The working fluid that condenses and releases heat in the second condenser 9 is divided into two paths. One path expands through the first pressure-reducing valve 10 and enters the intermediate heat exchanger 12, where it absorbs heat from the other working fluid and enters the buried heat exchange pipe 11 to extract underground heat energy. The other path cools down through the intermediate heat exchanger 12 and expands through the second pressure-reducing valve 13. It then enters the second low-temperature evaporator 6 to absorb waste heat from the closed-loop water and evaporate. After being compressed by the low-pressure stage compressor 7, it mixes with the working fluid at the outlet of the buried heat exchange pipe 11. The mixture then enters the high-pressure stage compressor 8 for compression and enters the second condenser 9 to complete the circulation.

[0061] It should be noted that the terms "first," "second," "low temperature," "high temperature," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0062] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be in a centered component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may also be in a centered component. When a component is said to be "set to" another component, it can be directly set on the other component or it may also be in a centered component.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A geothermal coupled two-stage compression heat pump heating system driven at low temperature, characterized in that, Comprising, The low-temperature Rankine cycle power system, the double-stage compression heat pump system, the plate heat exchanger (15), the zero-stage network water supply and return system and the first-stage network water supply and return system; The low-temperature Rankine cycle power system comprises a first compressor (1), a first low-temperature evaporator (2), a power machine (3) and a first condenser (4) connected in sequence; the double-stage compression heat pump system comprises a second low-temperature evaporator (6), a low-pressure stage compressor (7), a high-pressure stage compressor (8) and a second condenser (9); The outlet of the circulating water side of the first low-temperature evaporator (2) is connected with the return water side of the zero-stage network water supply and return system; The inlet of the circulating water side of the first low-temperature evaporator (2) is connected with the plate heat exchanger (15); the plate heat exchanger (15) is connected with the water supply side of the zero-stage network water supply and return system respectively; The return water side of the first-stage network water supply and return system is connected with the water supply side of the first-stage network water supply and return system through the plate heat exchanger (15) and the second condenser (9) in sequence; The preliminary heat exchange of the zero-stage network water supply and return system and the first-stage network water supply and return system is carried out in the plate heat exchanger (15); The closed water side of the first condenser (4) is connected with the closed water side of the second low-temperature evaporator (6); The first compressor (1), the power machine (3), the low-pressure stage compressor (7) and the high-pressure stage compressor (8) are connected in power transmission; The double-stage compression heat pump system further comprises a buried heat exchange pipe (11) and an intermediate heat exchanger (12); The outlet of the working medium side of the second condenser (9) is connected with the inlet of the intermediate heat exchanger (12); the outlet of the intermediate heat exchanger (12) is connected with the inlet of the second low-temperature evaporator (6) through the buried heat exchange pipe (11) in sequence; The outlet of the working medium side of the second low-temperature evaporator (6) and the outlet of the buried heat exchange pipe (11) are connected with the inlet of the low-pressure stage compressor (7) and the high-pressure stage compressor (8) in sequence; The outlet of the high-pressure stage compressor (8) is connected with the inlet of the working medium side of the second condenser (9); The first compressor (1), the power machine (3), the low-pressure stage compressor (7) and the high-pressure stage compressor (8) are connected through a shaft coupling.

2. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, A first pressure reducing valve (10) is arranged on a pipe between the outlet of the working medium side of the second condenser (9) and the intermediate heat exchanger (12).

3. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, A second pressure reducing valve (13) is arranged on a pipe between the intermediate heat exchanger (12) and the second low-temperature evaporator (6).

4. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, A closed water pump (5) is arranged between the first condenser (4) and the second low-temperature evaporator (6).

5. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, The zero-stage network water supply and return system is a pipe network between a heat source and a pressure isolation station.

6. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, The first-stage network water supply and return system is a pipe network between the pressure isolation station and a heat exchange station.

7. The low-temperature driven geothermal coupled two-stage compression heat pump heating system according to claim 1, characterized in that, The internal circulating working medium of the low-temperature Rankine cycle power system is an organic matter.

8. A method of operating a low-temperature driven geothermal coupled two-stage compression heat pump heating system according to any of claims 1-7, characterized in that, Comprising, The zero-stage network supply water exchanges heat with the first-stage network return water in the plate heat exchanger (15), and the cooled zero-stage network return water enters the first low-temperature evaporator (2) to provide a heat source for the low-temperature Rankine cycle power system. The low-temperature Rankine cycle power system drives the work of the two-stage compression heat pump system through the heat source, and the heat is transferred to the second condenser (9). The first-stage network return water is heated by the zero-stage network supply water in the plate heat exchanger (15), and then is further heated by the second condenser (9) and supplied to the heat exchange station.

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