Ground source heat pump and aquifer energy storage coupled cold and heat source system and regulation method thereof

Abstract

This invention discloses a ground-source heat pump coupled with aquifer energy storage and its control method, relating to the field of renewable energy technology. It solves the technical problem of low efficiency in ground-source heat pump systems caused by geothermal imbalance. The key technical point is that during cooling operation, the aquifer energy storage system is prioritized for direct cooling, with the remaining capacity handled by the ground-source heat pump system. During heating operation, the heat pump unit and the aquifer energy storage system provide combined heating. Simultaneously, within safe limits, the pumping water flow rate is increased to create effective seepage in the aquifer between the pumping and injection wells, enhancing heat exchange between the buried pipe network and the surrounding seeping soil and rock. This application, by combining a shallow ground-source heat pump with an aquifer energy storage system, effectively balances building load demand and geothermal energy supply, achieving efficient cross-seasonal geothermal energy building applications.

Description

Technical Field

[0001] This application relates to the field of renewable energy technology, and in particular to a cold and heat source system coupled with aquifer energy storage and its control method. Background Technology

[0002] As a renewable energy technology for heating and cooling, ground source heat pump systems are environmentally friendly and sustainable, and have great development potential in the market.

[0003] Ground source heat pump systems use the soil as a low-temperature heat source. During project design and application, the thermal balance of the soil must be considered; otherwise, it will lead to an accumulation of underground energy, affecting unit operation. Within the calculation period, the total annual heat release and absorption of the ground source heat pump buried pipe system should be basically balanced, with the ratio preferably between 0.8 and 1.25.

[0004] In my country's hot-summer, cold-winter regions, and for buildings primarily used for cooling, the cooling and heating loads and durations far exceed the heating loads and durations. This long-term imbalance between cooling and heating on the ground source side leads to a "heat accumulation" phenomenon, causing the performance of the ground source heat pump system to gradually decline, and eventually rendering it unusable. Blindly adding auxiliary systems to alleviate the heat imbalance problem will inevitably increase the initial investment, operating costs, and control complexity of the system.

[0005] To address the thermal imbalance problem in ground source heat pump systems caused by imbalances in building heating and cooling loads, seasonal energy storage can be used, one approach being underground aquifer energy storage systems. Aquifer energy storage systems offer lower costs, higher storage capacity, and cooling / heating efficiency between 68% and 87%. Low-temperature aquifer energy storage systems typically operate at water temperatures not exceeding 25°C, allowing for free cooling and resulting in higher energy efficiency. However, aquifer energy storage systems also suffer from thermal imbalance, leading to a gradual expansion of thermal breakthroughs between pumping and injection wells, ultimately degrading system performance. Summary of the Invention

[0006] This application provides a cold and heat source system coupled with aquifer energy storage and its control method. The technical purpose is to solve the problem of the decline in the coefficient of performance of ground source heat pumps or even shutdown caused by the thermal imbalance of the ground source heat pump system.

[0007] The above-mentioned technical objectives of this application are achieved through the following technical solutions:

[0008] A ground source heat pump coupled with aquifer energy storage cold and heat source system includes a cold well, a hot well, a buried pipe, a cold well-side circulation pump, a cold well-side circulation pump bypass valve, a plate heat exchanger, a plate heat exchanger-side bypass valve, a hot well-side circulation pump, a hot well-side circulation pump bypass valve, a valve from the heat exchanger to the heat pump unit, a valve from the heat exchanger to the terminal coil, a buried pipe-side circulation pump, a buried pipe-side valve, a heat pump unit, and terminal coils;

[0009] The cold well side circulation pump and the cold well side circulation pump bypass valve are connected in parallel; the plate heat exchanger and the plate heat exchanger side bypass valve are connected in parallel; the hot well side circulation pump and the hot well side circulation pump bypass valve are connected in parallel.

[0010] The cold well is connected in sequence to the cold well side circulation pump, plate heat exchanger, heat exchanger to heat pump unit valve and heat pump unit to terminal coil; or in sequence to the cold well side circulation pump, heat exchanger to terminal coil valve and terminal coil.

[0011] The hot well is connected in sequence to the hot well side circulation pump, plate heat exchanger, heat exchanger to the heat pump unit valve, and the heat pump unit to the terminal coil.

[0012] The buried pipe is connected to the terminal coil in sequence through a buried pipe side circulation pump, a buried pipe side valve, and a heat pump unit.

[0013] In cooling operation, when the cooling load of the cold wells can fully meet the required cooling capacity, the entire building cooling load is provided by the cold wells. When the cooling load of the cold wells is insufficient but the total cooling capacity is sufficient, the building cooling load is primarily provided by the cold wells, with underground pipes providing supplementary cooling. When the cooling load of the cold wells is insufficient and the cooling capacity is exhausted, the building cooling load is provided by the underground pipes. In heating operation, when the building's heat load demand is low, the required heat is provided by the heat wells. When the building's heat load is high, the required heat is provided by a combination of heat wells and underground pipes.

[0014] A control method for a cold and heat source system based on the above-mentioned coupling of ground source heat pump and aquifer energy storage, wherein in the cooling operation, the cold well, which acts as a pumping well, directly supplies the cooling capacity required for the cooling load to the terminal coils through a plate heat exchanger. When the cold well cannot meet the cooling capacity required for the cooling load, the surplus cooling capacity is supplied to the terminal coils through a heat pump unit via a buried pipe. If the cooling capacity in the cold well, which acts as a pumping well, is exhausted, the terminal coils are supplied solely through a heat pump unit via a buried pipe.

[0015] During heating operation, when the heat load demand is low, the heat required for the heat load is supplied to the terminal coils through plate heat exchangers and heat pump units using the hot wells that serve as reinjection wells; when the heat load demand is high, the heat is supplied to the terminal coils by a combination of plate heat exchangers and buried pipes, and the surplus heat is supplied to the terminal coils through the buried pipes and heat pump units.

[0016] The beneficial effects of this application are as follows:

[0017] (1) This application solves the technical problem of low efficiency of ground source heat pump system caused by thermal imbalance of soil and rock, and can effectively alleviate the thermal imbalance problem of ground source heat pump and aquifer energy storage system.

[0018] (2) In the cooling operation, this application prioritizes the use of the cooling capacity of the cold well in the aquifer energy storage system to obtain free cooling of the aquifer energy storage system, providing an auxiliary cold source for the ground source heat pump system which is mainly for cooling, and reducing the heat accumulation near the buried pipe in the ground source heat pump system.

[0019] (3) In the heating operation, this application prioritizes the use of heat from the thermal wells in the aquifer energy storage system. If the building heat load is large, the required heat load is provided by the thermal wells and the ground source heat pump system in combination, thereby reducing operating costs.

[0020] (4) When the cold well or hot well cannot meet the building’s required cooling or heating load and the ground source heat pump system needs to be turned on, this application strengthens the heat transfer of the buried pipe by increasing the pumping water flow rate, forming an effective seepage between the hot well and the cold well to improve the heat exchange performance of the buried pipe between the wells and improve the system’s operating efficiency.

[0021] (5) The system described in this application can realize the synergistic effect of system energy supply and energy storage, with high flexibility and multiple control methods to meet the different cooling and heating load balance requirements of the system mainly for cooling.

[0022] (6) The system described in this application can be applied not only to the initial design but also to the energy-saving renovation of existing systems; by adding pumping wells on both sides of the existing buried pipe ground source heat pump system, the heat accumulation around the buried pipe of the existing system can be alleviated, thereby improving the system performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the cold and heat source system coupled with the ground source heat pump and aquifer energy storage described in this application;

[0024] In the diagram: 1-Cold well, 2-Hot well, 3-Buried pipe, 4-Cold well side circulation pump, 5-Cold well side circulation pump bypass valve, 6-Plate heat exchanger, 7-Plate heat exchanger side bypass valve, 8-Hot well side circulation pump, 9-Hot well side circulation pump bypass valve, 10-Valve from heat exchanger to heat pump unit, 11-Valve from heat exchanger to terminal coil, 12-Buried pipe side circulation pump, 13-Buried pipe side valve, 14-Heat pump unit, 15-Terminal coil. Detailed Implementation

[0025] The technical solution of this application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other, and the described embodiments are merely some, not all, of the embodiments of this invention.

[0026] like Figure 1 As shown, the ground source heat pump coupled with aquifer energy storage cold and heat source system described in this application includes a cold well 1, a hot well 2, a buried pipe 3, a cold well-side circulation pump 4, a cold well-side circulation pump bypass valve 5, a plate heat exchanger 6, a plate heat exchanger-side bypass valve 7, a hot well-side circulation pump 8, a hot well-side circulation pump bypass valve 9, a valve from the heat exchanger to the heat pump unit 10, a valve from the heat exchanger to the terminal coil 11, a buried pipe-side circulation pump 12, a buried pipe-side valve 13, a heat pump unit 14, and a terminal coil 15.

[0027] The cold well side circulation pump 4 is connected in parallel with the cold well side circulation pump bypass valve 5; the plate heat exchanger 6 is connected in parallel with the plate heat exchanger side bypass valve 7; and the hot well side circulation pump 8 is connected in parallel with the hot well side circulation pump bypass valve 9.

[0028] The cold well 1 is connected to the terminal coil 15 in sequence via the cold well side circulation pump 4, plate heat exchanger 6, heat exchanger to heat pump unit valve 10 and heat pump unit 14; or in sequence via the cold well side circulation pump 4, heat exchanger to terminal coil valve 11 and terminal coil 15.

[0029] The hot well 2 is connected to the terminal coil 15 in sequence through the hot well side circulation pump 8, plate heat exchanger 6, heat exchanger to heat pump unit valve 10, and heat pump unit 14.

[0030] The underground pipe 3 is connected to the terminal coil 15 in sequence through the underground pipe side circulation pump 12, the underground pipe side valve 13 and the heat pump unit 14.

[0031] During the summer cooling season, cold water drawn from cold well 1 by the cold well side circulation pump 4 exchanges heat with the terminal coil 15 via plate heat exchanger 6. The resulting high-temperature cooling water releases heat into the soil through hot well 2, thus achieving energy storage in hot well 2. Low-temperature cooling water seeps back to cold well 1 through the soil and rock layer for the next cycle.

[0032] During the winter heating season, cold water drawn from hot well 2 by hot well side circulation pump 8 exchanges heat with heat pump unit 14 via plate heat exchanger 6. The resulting low-temperature chilled water releases its cooling capacity into the soil through cold well 1, thus achieving energy storage in cold well 1. High-temperature chilled water seeps back to hot well 2 through the soil and rock layer for the next cycle.

[0033] When the cold / heat stored in the cold well / hot well cannot meet the building's required cooling / heating load, the ground source heat pump circulation system needs to be activated to provide additional cooling / heat.

[0034] Under cooling conditions and when the cooling load of cold well 1 fully meets the required cooling capacity, the cold well-side circulating pump 4, the valve 11 from the heat exchanger to the terminal coil, and the bypass valve 9 of the hot well-side circulating pump are open. The cold well-side circulating pump bypass valve 5, the plate heat exchanger-side bypass valve 7, the hot well-side circulating pump 8, the buried pipe-side circulating pump 12, the buried pipe-side valve 13, and the valve 10 from the heat exchanger to the heat pump unit are closed. The cooling capacity of cold well 1 is supplied to the terminal coil 15 sequentially through the cold well-side circulating pump 4, the plate heat exchanger 6, and the valve 11 from the heat exchanger to the terminal coil. Simultaneously, cold water from cold well 1 is drawn to hot well 2 through the cold well-side circulating pump 4, the plate heat exchanger 6, and the bypass valve 9 of the hot well-side circulating pump, where it exchanges heat with the plate heat exchanger 6. In this case, all the cooling capacity required for the building's cooling load is provided by cold well 1.

[0035] Under cooling conditions, when the cooling load of the cold well does not meet the required cooling capacity but the cooling capacity is sufficient, the following valves are opened: cold well-side circulation pump 4, hot well-side circulation pump bypass valve 9, buried pipe-side circulation pump 12, buried pipe-side valve 13, and heat exchanger-to-heat pump unit valve 10. Meanwhile, cold well-side circulation pump bypass valve 5, plate heat exchanger-side bypass valve 7, hot well-side circulation pump 8, and heat exchanger-to-terminal coil valve 11 are closed. The cooling capacity of cold well 1 is supplied to terminal coil 15 sequentially through cold well-side circulation pump 4, plate heat exchanger 6, heat exchanger-to-heat pump unit valve 10, and heat pump unit 14. Similarly, the cooling capacity of buried pipe 3 is supplied to terminal coil 15 sequentially through buried pipe-side circulation pump 12, buried pipe-side valve 13, and heat pump unit 14. Simultaneously, cold water from cold well 1 is pumped to hot well 2 through cold well-side circulation pump 4, plate heat exchanger 6, and hot well-side circulation pump bypass valve 9, where it exchanges heat with plate heat exchanger 6. In this case, the cooling capacity required for the building's cooling load is mainly provided by the cold well 1, and if it is insufficient, the underground pipe 3 will provide auxiliary cooling capacity.

[0036] Under cooling conditions, when the cooling load of the cold well is insufficient to meet the required cooling capacity and the cooling capacity is exhausted, the following valves are closed: cold well-side circulation pump 4, hot well-side circulation pump bypass valve 9, heat exchanger-to-heat pump unit valve 10, and heat exchanger-to-terminal coil valve 11. Meanwhile, cold well-side circulation pump bypass valve 5, plate heat exchanger-side bypass valve 7, hot well-side circulation pump 8, buried pipe-side circulation pump 12, and buried pipe-side valve 13 are opened. The buried pipe 3 supplies cooling capacity to the terminal coil 15 sequentially through the buried pipe-side circulation pump 12, buried pipe-side valve 13, and heat pump unit 14. Seepage occurs between cold well 1 and hot well 2 through the cold well-side circulation pump bypass valve 5, plate heat exchanger-side bypass valve 7, and hot well-side circulation pump 8. In this case, the required cooling capacity for the building's cooling load is provided by the buried pipe 3.

[0037] Under heating conditions and when the building's heat load demand is low, the following valves are closed: cold well side circulation pump 4, plate heat exchanger side bypass valve 7, hot well side circulation pump bypass valve 9, heat exchanger to terminal coil valve 11, buried pipe side circulation pump 12, and buried pipe side valve 13. Meanwhile, cold well side circulation pump bypass valve 5, hot well side circulation pump 8, and heat exchanger to heat pump unit valve 10 are open. Heat from hot well 2 is sequentially supplied to terminal coil 15 via hot well side circulation pump 8, plate heat exchanger 6, heat exchanger to heat pump unit valve 10, and heat pump unit 14. Simultaneously, hot water from hot well 2 is drawn from hot well 2 to cold well 1 via hot well side circulation pump 8, plate heat exchanger 6, and side circulation pump bypass valve 5, where it exchanges heat with plate heat exchanger 6. In this case, the heat required for the building's heat load is provided by hot well 2.

[0038] When the building's heat load demand is high during heating operation, the cold well-side circulation pump 4, the heat exchanger-to-terminal coil valve 11, the hot well-side circulation pump bypass valve 9, and the plate heat exchanger-side bypass valve 7 are closed. Meanwhile, the cold well-side circulation pump bypass valve 5, the hot well-side circulation pump 8, the heat exchanger-to-heat pump unit valve 10, the buried pipe-side circulation pump 12, and the buried pipe-side valve 13 are opened. Heat from the hot well 2 is sequentially supplied to the terminal coil 15 via the hot well-side circulation pump 8, the plate heat exchanger 6, the heat exchanger-to-heat pump unit valve 10, and the heat pump unit 14. Similarly, heat from the buried pipe 3 is sequentially supplied to the terminal coil 15 via the buried pipe-side circulation pump 12, the buried pipe-side valve 13, and the heat pump unit 14. Simultaneously, hot water from the hot well 2 is drawn to the cold well 1 via the hot well-side circulation pump 8, the plate heat exchanger 6, and the cold well-side circulation pump bypass valve 5, where it exchanges heat with the plate heat exchanger 6. In this case, the heat required for the building's heat load is provided jointly by the heat well 2 and the underground pipe 3.

[0039] In a specific implementation example, during project planning and design, the selection and quantity of buried pipe 3 are primarily based on the heat load required. The selection and quantity of cold well 1 and hot well 2 are based on the difference between the building's required cooling capacity and the cooling capacity provided by the buried pipe under design conditions. During cooling operation, cold well 1, acting as a pumping well, initially provides cooling. If this is insufficient, the remaining cooling capacity is provided by buried pipe 3. If the cooling capacity in cold well 1 is exhausted, the cold well-side circulation pump 4 is shut off, and the bypass valve 5, the plate heat exchanger-side bypass valve 7, and the heat source-side circulation pump 8 are opened. In this case, buried pipe 3 provides cooling independently. During heating operation, hot well 2, acting as a reinjection well, is prioritized for heating. If this is insufficient, hot well 2 and buried pipe 3 provide combined heating.

[0040] As a specific embodiment, when the cold and heat source system is first run, it first runs in the summer combined cooling operation mode. When the cold well's cooling capacity is exhausted, it switches to the high-flow enhanced heat transfer operation mode and the subsequent combined heating operation mode. In the next cycle, the positions of the cold well and the hot well are swapped.

[0041] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A cold and heat source system of coupling of a ground source heat pump and an aquifer energy storage, characterized in that, Includes cold well (1), hot well (2), buried pipe (3), cold well side circulation pump (4), cold well side circulation pump bypass valve (5), plate heat exchanger (6), plate heat exchanger side bypass valve (7), hot well side circulation pump (8), hot well side circulation pump bypass valve (9), heat exchanger to heat pump unit valve (10), heat exchanger to terminal coil valve (11), buried pipe side circulation pump (12), buried pipe side valve (13), heat pump unit (14) and terminal coil (15); The cold well side circulation pump (4) is connected in parallel with the cold well side circulation pump bypass valve (5); the plate heat exchanger (6) is connected in parallel with the plate heat exchanger side bypass valve (7); the hot well side circulation pump (8) is connected in parallel with the hot well side circulation pump bypass valve (9); The cold well (1) is connected to the terminal coil (15) in sequence via the cold well side circulation pump (4), plate heat exchanger (6), heat exchanger to heat pump unit valve (10) and heat pump unit (14); or in sequence via the cold well side circulation pump (4), heat exchanger to terminal coil valve (11) and terminal coil (15). The hot well (2) is connected to the terminal coil (15) in sequence through the hot well side circulation pump (8), plate heat exchanger (6), heat exchanger to heat pump unit valve (10) and heat pump unit (14); The buried pipe (3) is connected to the terminal coil (15) in sequence through the buried pipe side circulation pump (12), the buried pipe side valve (13) and the heat pump unit (14); When the cooling load of the cold well (1) fully meets the required cooling capacity, the cooling capacity of the cold well (1) is supplied to the terminal coil (15) through the cold well side circulation pump (4), plate heat exchanger (6) and heat exchanger to terminal coil valve (11) in sequence; at the same time, the cold water of the cold well (1) is pumped to the hot well (2) through the cold well side circulation pump (4), plate heat exchanger (6) and hot well side circulation pump bypass valve (9) to exchange heat with the plate heat exchanger (6); When the cooling load of the cold well is insufficient and the cooling capacity is sufficient, the cooling capacity of the cold well (1) is supplied to the terminal coil (15) in sequence through the cold well side circulation pump (4), plate heat exchanger (6), heat exchanger to heat pump unit valve (10) and heat pump unit (14); the underground pipe (3) supplies the cooling capacity of the terminal coil (15) in sequence through the underground pipe side circulation pump (12), underground pipe side valve (13) and heat pump unit (14); at the same time, the cold water of the cold well (1) is pumped to the hot well (2) through the cold well side circulation pump (4), plate heat exchanger (6) and hot well side circulation pump bypass valve (9) to exchange heat with the plate heat exchanger (6); When the cooling load of the cold well is insufficient to meet the required cooling capacity and the cooling capacity is exhausted, the buried pipe (3) supplies the cooling capacity to the terminal coil (15) in sequence through the buried pipe side circulation pump (12), the buried pipe side valve (13) and the heat pump unit (14); the cold well (1) and the hot well (2) form seepage through the cold well side circulation pump bypass valve (5), the plate heat exchanger side bypass valve (7) and the hot well side circulation pump (8); When the building's heat load demand is small, the heat from the hot well (2) is supplied to the terminal coil (15) through the hot well side circulation pump (8), plate heat exchanger (6), heat exchanger to heat pump unit valve (10) and heat pump unit (14) in sequence; at the same time, the hot water from the hot well (2) is drawn to the cold well (1) through the hot well side circulation pump (8), plate heat exchanger (6) and cold well side circulation pump bypass valve (5) to exchange heat with the plate heat exchanger (6); When the building heat load demand is large under heating conditions, the heat from the hot well (2) is supplied to the terminal coil (15) in sequence through the hot well side circulation pump (8), plate heat exchanger (6), heat exchanger to heat pump unit valve (10) and heat pump unit (14); the buried pipe (3) supplies the heat to the terminal coil (15) in sequence through the buried pipe side circulation pump (12), buried pipe side valve (13) and heat pump unit (14); at the same time, the hot water from the hot well (2) is drawn to the cold well (1) through the hot well side circulation pump (8), plate heat exchanger (6) and cold well side circulation pump bypass valve (5) to exchange heat with the plate heat exchanger (6); When the cold and heat source system is first put into operation, it will first run in the summer combined cooling operation mode. When the cold well is exhausted, it will switch to the high flow enhanced heat transfer operation mode and then the combined heating operation mode. In the next cycle, the positions of the cold well and the hot well will be swapped.

2. The cold heat source system according to claim 1, wherein The selection and quantity of the underground pipe (3) are designed based on the heat required by the heat load. The selection and quantity of the cold well (1) and the hot well (2) are designed based on the difference between the cooling capacity required by the building cooling load and the cooling capacity required by the underground pipe (3) under the design conditions.

3. A method for regulating a cold and heat source system based on the coupling of a ground source heat pump with an aquifer energy storage according to any one of claims 1-2, characterized in that, During cooling operation, the cold well (1), which acts as a pumping well, directly supplies the cooling capacity required for the cooling load to the terminal coil (15) through the plate heat exchanger (6). When the cold well (1) cannot meet the cooling capacity required for the cooling load, the remaining cooling capacity is supplied to the terminal coil (15) through the heat pump unit (14) via the buried pipe (3). If the cooling capacity in the cold well (1), which acts as a pumping well, is exhausted, the terminal coil (15) is supplied solely by the buried pipe (3) through the heat pump unit (14). During heating operation, when the heat load demand is small, the heat required for the heat load is supplied to the terminal coil (15) through the plate heat exchanger (6) and the heat pump unit (14) using the hot well (2) which serves as a reinjection well. When the heat load demand is large, the plate heat exchanger (6) and the buried pipe (3) jointly supply heat to the terminal coil (15), and the surplus heat is supplied to the terminal coil (15) through the heat pump unit (14) via the buried pipe (3).

4. The method of claim 3, wherein the step of regulating comprises the step of: When the cooling load of the cold well (1) fully meets the required cooling capacity, the cold well side circulation pump (4), the heat exchanger to terminal coil valve (11) and the hot well side circulation pump bypass valve (9) are opened, and the cold well side circulation pump bypass valve (5), the plate heat exchanger side bypass valve (7), the hot well side circulation pump (8), the buried pipe side circulation pump (12), the buried pipe side valve (13) and the heat exchanger to heat pump unit valve (10) are closed. ​ 5. The method of claim 3, wherein the step of regulating comprises the step of: When the cooling load of the cold well does not meet the required cooling capacity and the cooling capacity is sufficient, the cold well side circulation pump (4), the hot well side circulation pump bypass valve (9), the buried pipe side circulation pump (12), the buried pipe side valve (13) and the heat exchanger to heat pump unit valve (10) are opened, and the cold well side circulation pump bypass valve (5), the plate heat exchanger side bypass valve (7), the hot well side circulation pump (8) and the heat exchanger to terminal coil valve (11) are closed. ​ 6. The method of modulation of claim 3, wherein, When the cooling load of the cold well does not meet the required cooling capacity and the cooling capacity is exhausted, the cold well side circulation pump (4), the hot well side circulation pump bypass valve (9), the heat exchanger to heat pump unit valve (10) and the heat exchanger to terminal coil valve (11) are closed, and the cold well side circulation pump bypass valve (5), the plate heat exchanger side bypass valve (7), the hot well side circulation pump (8), the buried pipe side circulation pump (12) and the buried pipe side valve (13) are opened.

7. The method of claim 3, wherein the step of regulating comprises the step of: When the building's heat load demand is low and the cold well side circulation pump (4), plate heat exchanger side bypass valve (7), hot well side circulation pump bypass valve (9), heat exchanger to terminal coil valve (11), buried pipe side circulation pump (12) and buried pipe side valve (13) are closed, while the cold well side circulation pump bypass valve (5), hot well side circulation pump (8) and heat exchanger to heat pump unit valve (10) are opened. ​ 8. The method of claim 3, wherein the step of regulating comprises the step of: When the building heat load demand is large during the heating operation, the cold well side circulation pump (4), the heat exchanger to terminal coil valve (11), the hot well side circulation pump bypass valve (9) and the plate heat exchanger side bypass valve (7) are closed, and the cold well side circulation pump bypass valve (5), the hot well side circulation pump (8), the heat exchanger to heat pump unit valve (10), the underground pipe side circulation pump (12) and the underground pipe side valve (13) are opened. ​

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