Ground Source Heat Pump System Research Articles

Evaluating tidal impact on ground source heat exchanger performance under fluctuating groundwater levels

Coastal regions undergo dynamic changes due to tidal forces, posing distinct challenges for groundwater management and utilization of ground source heat pump (GSHP) systems. This study examines the impact of tidal fluctuations on groundwater levels and the performance of ground heat exchangers (GHEs), specifically focusing on the suitability of horizontal directional drilling (HDD) technology in high-tidal zones. Itoman City in Okinawa Prefecture, Southern Japan, serves as an ideal location for this study due to its complex coastal hydrogeological conditions and increasing interest in renewable energy solutions. Employing a comprehensive approach involving field experiments, FEFLOW software simulations, and model validation, we aim to elucidate the intricate relationship between tidal dynamics, groundwater behavior, and GHE performance. Furthermore, our investigation assesses the effectiveness of HDD-GHEs installed in highly tidal-affected zones to determine the optimal installation depth for this type of GHE in coastal regions. According to our research, the layer at a depth of 30 m is most affected by tidal influence and fluctuations in groundwater levels in coastal regions. This layer is the most suitable for installing horizontal HDD-GHEs, with an average heat exchange rate of about 89 W/m. This rate is approximately four and two times higher than the depths above and below this layer, respectively, due to groundwater saturation and flow in the formation. Furthermore, we noticed that the heat exchange rate increases from the top to the bottom of this layer, but the extent of this increase diminishes as the depth increases. This is because deeper depths are less affected by tidal fluctuations in groundwater levels.

Effects by geothermal gradient on thermal response tests for boreholes

A thermal response test (TRT) on a borehole provides information needed in the design of ground heat exchangers for ground source heat pump systems. Conventional analysis of TRT data sets uses the late-time period to estimate the ground thermal conductivity and the effective borehole resistance. During this quasi-steady-state period, the transient average fluid temperature has a logarithmic linear trend, which is consistent with conventional heat transfer models that assume a uniform undisturbed ground temperature. As the depth of the borehole increases the undisturbed ground temperature increases with depth following the geothermal gradient. This paper focuses on how the geothermal gradient affects a TRT. As the geothermal gradient increases, the required time to reach the conventional logarithmic linear trend may increase beyond any practical testing duration in coaxial boreholes. Then, conventional analysis methods based on a quasi-steady-state period incorrectly estimate the ground thermal conductivity. The magnitude of this effect is controlled through a dimensionless parameter |qratio|, which includes the geothermal gradient and other test parameters. In place of conventional models, a transient model that includes the geothermal gradient and fluid thermal storage can estimate the ground thermal conductivity and local borehole resistance within the typical TRT testing duration.

Comparative Analysis of Influencing Factors on Heat Extraction Performance of Multi-Type Shallow Borehole Heat Exchangers

In this paper, the influence of design parameters and geological parameters on the heat extraction capacity of common coaxial type, single U-type, and double U-type borehole heat exchangers(BHEs) in shallow ground source heat pump system is analyzed, and the heat extraction performance of different types of BHEs is further compared. The results show that with the increase in borehole depth and ground temperature gradient, the outlet temperature of the three types increases at the end of the heating season, and the single U-type BHE increases most significantly. The increase in inlet flow rate will decrease the outlet temperature of the three BHEs, and the U-type is the most obvious decrease. The increase in inlet temperature will reduce the temperature difference between inlet and outlet of the three types BHEs. Given the same design parameters, coaxial-type BHE obtains the maximum heat.

Operating characteristics of photovoltaic/thermal–ground source heat pump system in cold regions

To investigate the operating performance of photovoltaic thermal integrated heat pumps in terms of the effects of the control strategy and the component parameters, this paper considers an office building in Zhengzhou city as the research object. A photovoltaic/thermal integrated ground source heat pump system model is established using TRNSYS software. Using this model, a system is developed with four operating modes based on temperature differences and seasonal control. The soil temperature, the unit energy consumption, and the solar energy guarantee rate are used as indicators to study the soil’s thermal balance and the energy consumption characteristics of the model system in the four operating modes. The effects of the control strategy design and the photovoltaic/thermal collector area on the system performance are analyzed, and the annual cost method is used to evaluate the system’s economy. The research results indicate that the tank heating mode’s closing temperature increased from 47 °C to 49 °C, the system energy consumption and power generation were reduced by 1.86 % and 1.24 %, respectively, and the instances of unsatisfied demand for domestic hot water were reduced by 19.05 %. The soil temperature increased gradually with increasing photovoltaic/thermal collector area, but the rate of this increase slowed down at larger areas; when the area increased from 50 m2 to 100 m2, the soil temperature increased by 16.6 %, but when the area increased from 200 m2 to 250 m2, the temperature then only increased by 10.6 %. In addition, there is a specific photovoltaic/thermal collector area that can maintain the soil temperature in equilibrium. When compared with a solar-assisted ground source heat pump heating system, the photovoltaic/thermal integrated ground source heat pump heating system can save 63.2 % in terms of operating costs and can reduce the annual cost by 60.9 % over a 10-year period. The research results show that the law of the photovoltaic/collector area affects the soil heat balance, and also provide data support for promotion of photovoltaic/thermal integrated ground source heat pump systems from both performance and economic perspectives.

Evaluation and machine learning prediction on thermal performance of energy walls in underground spaces as part of ground source heat pump systems

Energy walls (i.e. wall heat exchangers) exhibit more complex thermal performance than do energy piles and borehole heat exchangers in ground source heat pump systems, due to their individual geometry. This study conducted field tests of energy wall thermal performance to analyze the influence and interaction of the pipe burial depth, flow rate, heating load, and operation mode. To evaluate the energy wall thermal performance in multiple dimensions, three novel evaluation indices (energy utilization ratio, thermal saturation, and effectiveness) were defined. A thermal performance SVR prediction model of an energy wall was established based on 227 field-measured samples. The heat exchange power, energy utilization ratio, and effectiveness of the ground side pipe are approximately 15%, 8% and 64% greater than those of the excavated side pipe, respectively. Considering the interaction between the flow rate and heating load, blindly increasing the heating load is not the most effective way to improve the thermal performance. The influences of heating loads and operation modes on heat exchange power differs from that on the energy utility ratio and both side’s thermal saturations, indicating that there is a complex interaction between the heating loads and operation modes. The cross-verification and prediction results show that the optimized thermal performance of the SVR model exhibited satisfactory generalizability and prediction performance.

Feasibility Study on the Optimal Design Method of Ground-Water Source Hybrid Heat Pump System Applied to Office Buildings

In order to reduce the energy consumption of buildings, a ground source heat pump (GSHP) system was introduced to reduce the building energy consumption. However, general GSHP systems are not as popular as photovoltaic and thermal systems owing to soil imbalances and performance degradation during long-term operation. To solve this problem, we propose a ground-water source hybrid heat pump (GWHP) system. GWHP systems can simultaneously use ground and water sources to avoid soil imbalance and degradation. In this study, we proposed a GWHP system and investigated its feasibility as a replacement for a GSHP system in terms of performance and heat source temperature. In addition, an optimal capacity design method for the GWHP system is presented to evaluate its economic feasibility. The performance and economic analysis show that the cooling and heating performance of the proposed GWHP was 15% and 3% better, respectively, compared to the existing GSHP system. Our results also showed that the proposed design method was approximately 5.3% less expensive than the existing GSHP systems. The GWHP system could be a suitable alternative to the GSHP system, as confirmed by both the energy simulation and cost analysis.

Perfection of an Energy-Economic and Environmental Parameters of the Ground Source Heat Pump Systems with Preventing Freezing of the Soil around Ground Pipes

This article is devoted to the methods for perfection of energy, economic factors, environ-mental factors and work modes of the ground source heat pump systems with the account of climate conditions. The purpose of the work is to predict and prevent freezing of the soil during long term of exploitation of the low-power and high-power ground source heat pump systems for justifying rational conditions of implementation GSHP in Ukraine and South-East Regions of Europe. This goal is achieved by solving the following problems: determining the energy-economic and environmental factors based on considering the work modes of the ground source heat pumps; evaluation of the operating efficiency of ground source heat pump systems based on minimizing fuel consumption and green-house gas emissions; perfection of solutions enable implementation of ground source heat pumps friendly to the environment and justifying rational conditions of implementation the ground source heat pumps for residential sector. The important results of the work are the obtained and analyzed data on the influence of energy and economic factors both environmental criteria on the work modes and scheme-constructive solutions of ground source heat pumps. Modeling of heat exchange processes in the soil around the soil tube shows that in order to avoid freezing of the soil, the minimum permissible specific number of vertical tubes should be at least 0.12–0.15 pieces/m2 of heated area. The significance of the results consists in the possibility of using the results of numerical simulation for preventing freezing of the soil around ground pipes of the ground source heat pump systems.

Comparison of different strategies for operating a solar-assisted ground-source CO2 heat pump system for space and water heating

This study quantifies and compares operational strategies as applied on a solar-assisted ground-source trans-critical CO2 heat pump (CO2 SAGSHP) system for simultaneous space and water heating, optimized on an hourly basis over the course of a week. Four (4) boundary conditions, representing spring, summer, autumn, and winter, were considered. To enable the use of a dynamic model for optimization simulations, the use of a previously developed surrogate Artificial Neural Network (ANN) model of a Modelica CO2 heat pump model was evaluated for use in this study. The simulation results from the system model that applies the surrogate ANN model demonstrated strong alignment with those generated by the full Modelica model, yielding low root mean square errors and mean absolute percentage errors. Furthermore, it accelerated the speed of results generation for a single forward run by 6–15 times, depending on the boundary conditions. It can be inferred from the results of the optimization runs that when warm climate conditions dominate, implementation of the on/off operation with thermal energy storage (TES) should be prioritized, given that it could potentially yield greater operational cost benefits (12% to 58 % cost reduction) compared to hourly discharge pressure optimization (0.5 to 1.5 % cost reduction). Conversely, when colder seasons are longer, optimizing the CO2 heat pump's discharge pressure becomes more practical (6.5 % to 6.9 % cost reduction) than on/off operation, particularly when only a small TES is installed (1.2 % to 2.6 % cost reduction). The optimization of the mass flow rate of the supply side working fluid of a CO2 SAGSHP system exhibited minimal benefit, except notably in the summer where it generated an even better cost reduction than controlling the discharge pressure. This shows the practicality of this strategy for conditions where relatively high solar irradiation and relatively low heat demand are concurrently expected. In general, weekly reductions in operational costs were more substantial when both the discharge pressure and the on/off operation of the CO2 heat pump were concurrently optimized, especially when using a larger TES tank. Hence, both should be applied if there are no practical or cost limitations that restrict their implementation. While previous studies on CO2 heat pumps primarily emphasized efficiency optimization via discharge pressure control, this study shows that comparable or greater operational cost reductions can also be achieved from other strategies, depending on the boundary conditions.

Performance prediction of a ground source heat pump system using denoised long short-term memory neural network optimised by fast non-dominated sorting genetic algorithm-II

The ground source heat pump (GSHP) is a commonly employed technique that utilises geothermal resources to heat or cool buildings, offering an advantageous alternative for reducing conventional energy consumption. Considering that the output energy of GSHP system is a critical criterion for evaluating the geothermal energy extraction, this study proposes an improved long short-term memory (LSTM) model for predicting the energy output of geothermal heat exchangers (GHE) EGHE-PT and the electrical energy consumption EEC-PT of a GSHP system. The model is trained and validated using a comprehensive real-time monitoring dataset gathered over a four-year period from a three-story residential house situated in Cleveland, Ohio, USA. To process the raw data, the wavelet denoising method is employed, while the fast non-dominated sorting genetic algorithm-II (NSGA-II) is employed to automatically determine the optimal hyperparameters for the LSTM model. Comparative analyses with alternative prediction models demonstrate the superior performance of the Denoised-LSTM-NSGA-II model. The results indicate that the Denoised-LSTM-NSGA-II model yields reasonable prediction for the two performance indicators: EGHE-PT and EEC-PT (with the R2 of 0.91 and 0.89, respectively). Further examination reveals that outdoor temperature holds a significantly high importance rank within the Denoised-LSTM-NSGA-II model. This implies that the proposed method can achieve an acceptable level of accuracy by only utilising weather data from the preceding 5 days. The aforementioned findings present a potentially cost-effective approach for predicting the performance of GSHP system based on limited monitoring data.

Assessment of Environmental Impacts of Thermal Caisson Geothermal Systems

This paper investigates the total environmental impacts of a thermal caisson (TC) system by implementing a life cycle assessment methodology. The total environmental impacts consider the comprehensive effect on the environment across two life cycle stages: manufacturing and operation. A comparison between the TC results and two different HVAC systems, including air-conditioning/furnace and conventional ground-source heat pump (GSHP) systems, was made by adopting the ReCiPe 2016 methodology. This study reveals that the operation phase is the predominant contributor to environmental impacts across systems, mainly due to its extended duration. Specifically, the operational impacts of GSHPs are substantial, accounting for approximately 87% of total environmental impacts. A TC GSHP system demonstrates a notable environmental advantage, achieving a 79% reduction in total environmental impact when compared to traditional AC/furnace systems. This represents a 21% improvement over conventional GSHP systems. Despite this substantial reduction in total environmental impact, the TC GSHP system shows an almost 5% increase in the resource availability damage category relative to the conventional GSHP, which is attributed to its higher material consumption. These results highlight the TC GSHP system’s superior efficiency in reducing environmental impacts and its potential as a more sustainable alternative in residential heating and cooling applications.

Field test of a ground-source heat pump system and numerical investigation on advanced control strategies

Ground source heat pump (GSHP) systems have been widely studied for space heating in recent years. Aiming at reducing the power consumption of GSHP, this study focuses on leveraging advanced load-predictive control strategies to minimize unnecessary power consumption in circulating pumps under variable load operation. Taking a GSHP system in an office building as a typical case, a field test was conducted and the heating performance in 2023 was obtained. By comparing measured data with the rated performance, the limitations of the existing control strategy were identified. To investigate the energy-saving potential of new control strategies, a transient GSHP simulation model was developed in TRNSYS. Based on the experimentally validated model, two load-predictive control strategies were numerically studied. By modulating the flow rate and supply water temperature, the two advanced control strategies can achieve energy-saving of 9.9% and 11.0%, respectively.

Influence of Geology, Hydrogeology, and Climate on Ground Source Heat Pump Distribution in Slovenia and Selected European Countries

Shallow geothermal energy (SGE) is a renewable energy that could contribute to the decarbonatization of the heating and cooling sector. SGE is predominantly harnessed through ground source heat pump (GSHP) systems. The choice of which type of GSHP system depends on various factors. Understanding these factors is crucial for optimizing the efficiency of GSHP systems and fostering their implementation. In this paper, we have analysed the spatial distribution of GSHPs in Slovenia. We identified 1073 groundwater and 1122 ground-coupled heat pump systems with a total heat pump capacity of almost 30 MW. We quantitatively assessed the influence of geological, hydrogeological, and climate conditions on their spatial distribution. Using the χ2 test and information value method, we identified hydrogeological conditions as the most influential factor for the GSHP systems’ spatial distribution. We also performed the spatial analysis of geological and hydrogeological data in 22 European countries, including Slovenia. We collected the reported numbers of installed GSHP units in 2020 and were able to distinguish the shares of groundwater and ground-coupled heat pump systems for 12 of these countries. The analysis showed that ground-coupled heat pumps predominate in most countries, even if the natural conditions are favourable for groundwater heat pumps.

Effectiveness of phase change materials and their properties on the performance of geothermal and foundation-based energy systems: A review

As buildings contribute notably to emissions of greenhouse gases, it is important to move towards building heating and cooling systems with good sustainability attributes and efficiencies, such as ground-source heat pumps (GSHPs). In this review, an integrated picture of the effect of utilizing phase change material (PCMs) having various physical properties on the performance of GSHPs and foundation-based geothermal systems is presented. Two major questions are addressed in this paper: how effective is a PCM for enhancing the performance of both conventional GSHP systems and foundation-based geothermal energy systems? The results show that PCMs can be effective at enhancing performance for conventional GSHP and foundation-based geothermal energy systems by, on average, 17% and 36%, respectively. However, the degree of PCM effectiveness depends on some parameters such as its physical characteristics (thermal conductivity, latent heat, phase change temperature) and design considerations (ground loop configuration, depth, etc.) among other factors. The results also show that, in general, the greater the PCM thermal conductivity, the higher the effectiveness of the PCM. Furthermore, by adding composites such as expanded graphite to the PCM, the thermal conductivity of a PCM increases more than 250% which can potentially improve the performance of geothermal systems. More research is warranted to maximize the system performance improvements by enhancing the PCM.

Enhancing ground source heat pump system design optimization: A stochastic model incorporating transient geological factors and decision variables

In this study, a cost minimization model of a ground source heat pump (GSHP) was performed to obtain its best design configurations based on system reliability. To implement a high-fidelity optimization, the uncertainties of decision parameters and geological parameters' distributions were considered. The GSHP's lifespan costs were functionalized based on an analytical borehole heat transfer model. Multiple constraints were established to serve as reliability goals to ensure a turbulent ground pipe flow without extreme temperature variations. The ground thermal conductivity, groundwater velocity, and unit price of electricity were considered as three random variables. Their dynamic characteristics were incorporated by assigning different increasing rates to the average magnitudes of them. Additionally, their transient fluctuations were accommodated by integrating probabilistic uncertainties into the optimization process, all of which followed normal distributions. The results demonstrated that the time-dependent characteristics of these uncertain variables could significantly affect the system investment of GSHP by reducing the total costs by 20.7% and 21.1% when the increasing rates of groundwater velocity and ground thermal conductivity reach 5% and 4% respectively. The study also provided optimized design variables under an 85% confidence level in various predicted scenarios, considering a wide range of dynamic geological parameters and energy costs.

Thermal performance and energy flow analysis of a PV/T coupled ground source heat pump system

Ground source heat pump (GSHP) system in cold regions will lead to a decrease in soil source temperature over the years after a long period of operation, and if no timely measures are taken, the system performance will get worse and worse, and even face the risk of shut down. The PV/T (photovoltaic/thermal) is an integrated energy supply system that can both improve the efficiency of solar energy utilization and weaken the soil temperature imbalance. In this paper, the thermal performance and year-round energy flow of the system are analyzed by the simulation model, and the effects of different soil thermal storage control strategies on the thermal storage performance in the transition season are explored. The results show that the coefficient of performance of the heat pump unit can reach 3.99 and 3.96 in the heating and cooling periods. The soil temperature only increases by 0.09 °C and 0.11 °C compared with the initial temperature after five and ten years of long-term system operation, respectively. In addition, after a comprehensive comparison of the thermal storage performance of different control strategies in the transition season, this study found that the temperature difference control strategy was superior to the time control strategy. Ultimately, the annual energy supply of the simulation system produces an additional 391.8 kWh of electricity in addition to meeting the energy demand for cooling, heating and power supply of the building, which realizes the zero-energy operation of the building.

Parametric analysis and potential evaluation of an all-day radiative sky cooling radiator-assisted ground source heat pump system

Practical utilization of radiative sky cooling (RSC) in an active way to produce cold water breaks the cooling limitation of 150 W/m2 for passive RSC but requires thoughtful system design. Therefore, this study proposes a novel radiative sky cooling radiator (RSCR)-assisted ground source heat pump (RGSHP) system to maximize the cooling potential of using RSCR and GSHP. The RGSHP can take full advantage of the ground’s thermostability to improve the cooling performance of the RSCR. Based on this developed hybrid system, the effects of designing parameters, weather conditions, and spectral properties of coatings on the performances of radiative cooling have been comprehensively investigated. The results show that a larger water flow rate is conducive to cooling power production of RSCR, but a smaller flow rate is beneficial to the COP improvement of the whole system. Moreover, compared with the ideal RSCR (iRSCR), the practical RSCR (pRSCR) shows comparable cooling performances due to the higher convective cooling performances, with an considerable annual average COP which is only 0.8 % smaller than the iRSCR-assisted GSHP system. Due to less heat rejected into the ground by RGSHP, the borehole wall temperature shows smaller values than stand-alone GSHP. For a ten-year simulation, the RGSHP system can reduce borehole wall temperature by 10.2 %. Moreover, using the RGSHP can also achieve cooling storage in the ground during the non-cooling seasons, and thus the RGSHP outperforms the GSHP by 13.2 % regarding the cooling season average COP.

A predictive model of long-term performance assessment of Ground Source Heat Pump (GSHP) systems in Japanese regions

This study predicts the long-term performance of ground source heat pump (GSHP) systems in different climatic regions of Japan. The research model calculates the dynamic heat load of a typical Japanese building in various cities using their meteorological data, considering different schedules for heating and cooling seasons. The model aims to analyze the performance degradation of the GSHP system after 15 years of operation due to the imbalanced heating and cooling loads. Additionally, it compares ground temperature changes, coefficient of performance (COP) variations, and annual operation times based on different thermal imbalance ratios (TIR) for the case studies. The results demonstrate that TIR serves as an appropriate factor for comprehensively evaluating system aspects, including GHE length, ground temperature, and COP degradation, across various climates. It was found that ground temperatures increased by a maximum of up to 4 °C in cooling-dominated regions due to higher thermal imbalance accumulative loads, while it decreased to around 1 °C in heating-dominated regions. The model also revealed that the COP decreased in the dominant operation for each case study due to induced thermal imbalance and soil temperature change. The thermal imbalance caused the system cooling COP decreased by 0.015/year in the worst case (Okinawa City) and 0.006/year in average for other cases.

Impact of rainfall on the thermal performance of geothermal permeable pavement systems

Geothermal permeable pavement (GPP) systems are a nascent type of energy geo-structures. GPP combine ground-source heat pump (GSHP) systems with permeable pavements to enable the additional functionality of heating and cooling, through energy harvesting using roads alongside existing drainage controls. GPP thermal performance is relatively unknown, hence, this research focuses on the development of a detailed 3D finite element (FE) model that considers local thermal non-equilibrium (LTNE) for exploring the influence of rainfall infiltration on the thermal performance of GPPs. The 3D numerical model was successfully validated and was used to evaluate the short-term thermal response of GPPs during rainfall events in both cooling (summer) and heating (winter) demand conditions. Furthermore, the diurnal rainfall effects and the influence of raindrop temperature and rainfall duration on GPPs were also examined. Results show that rainfall can have significant impacts on the thermal performance of GPPs and the raindrop temperature is an important parameter in yield predictions. Compared to no-rainfall events, the GSHP system fluid temperature during rainfall can differ by up to 19% when in the cooling operation model (air conditioning) and 63% in heating mode. These results indicate the significantly better performance of GPPs than impervious geothermal pavements, depending on the climatic conditions and end-use.

Optimization of double layered horizontal directional drilled ground heat exchangers by water injection into the borehole

Ground Heat Exchangers (GHEs) drilled using Horizontal Directional Drilling (HDD) technology have been proven to be a cost-efficient way of installing ground source heat pump systems (GSHP). They can also be installed in places where conventional horizontal ground heat exchanger (HGHE) would not be possible e.g., due to lack of land.In this research, a double layered horizontal borehole was installed as a GHE in Saga City, Japan. The two holes had a diameter of 114.3 mm and a length of 59 m and 56 m, respectively, while reaching depths of 5 m and 9.5 m. A polyethylene pipe with an outer diameter of 60 mm was inserted as a borehole heat exchanger (BHE). In March 2022, a two days thermal response test (TRT) showed the influence of rainfall on the system. A numerical model developed in FEFLOW based on the GHE dimension and the region's geology was validated using the measured temperatures of the heat medium at the return point and outlet of the GHE during the TRT. The validated model was then used to carry out sensitivity analysis examining different conditions of water injection into the borehole. The result of the sensitivity analysis showed that water injection into the borehole can improve the performance of the system and reduce the temperature change of the heat medium. Varying the injection rate can improve performance to a certain degree and the injection point has a strong influence on the performance. The injection temperature was also found to play a role in the performance, but even high temperatures in the case of heating showed significant improvement. Lastly, the influence of permeability was investigated and showed that impermeable layers are more favorable for injection compared to permeable layers.

Research on the influence of underground seepage on regional heat accumulation of ground source heat pump heat exchanger

During the long-term operation of the ground source heat pump system, the temperature imbalance of the rock and soil around the heat exchanger results in the deterioration of the performance of the ground source heat pump system. Through previous projects, it has been found that in the area of underground seepage speed, it is helpful to alleviate the heat or cold accumulation of rock and soil mass around the ground source heat pump system. Based on this, two test sites in Zhangqiu District, Jinan City, Shandong Province, were selected to conduct pumping and irrigation tests to change the underground seepage velocity, determine the flow velocity through isotopic tracer tests, obtain soil thermal physical parameters and simulate heat accumulation through thermal response tests, and establish long-term numerical simulation through Opengeosys to synthesize the conclusion that the seepage velocity increases. The more efficiently the temperature of the rock and soil mass is restored to the initial condition, the more efficiently the heat exchange performance of the buried pipe heat exchanger and the surrounding rock and soil mass is maintained, and the efficient operation of the ground source heat pump system in winter and summer is ensured.