Solar Ground Source Heat Research Articles

Research on multi-objective optimization configuration of solar ground source heat pump system using data-driven approach

Under the premise of ensuring the stable operation of solar coupled ground source heat pump systems (SGSHPs), optimizing the configuration to improve the thermal performance of the system and reduce the cost of the system area key measures to promote the popularization of such systems in cold regions. The SGSHPs models of three different operation modes are established in this paper, taking office buildings in the Shenyang area as an example and basing on the TRNSYS platform. The ground temperature imbalance rate and the total energy consumption of the system after thirty years of operation in different modes are compared and analyzed. The parallel transition season thermal storage mode with better energy saving potential is selected as the main research object, and six main design parameters are determined through sensitivity analysis, which are the number of buried pipe boreholes, solar collector area, thermal storage start temperature difference, thermal storage stop temperature difference, collector start temperature difference, and collector stop temperature difference. The 1000 groups of systems with different parameter combinations are simulated, and 1000 sample data are generated as a database.The multiple outputs support vector regression (MSVR) network was trained and validated using the sample database, and the particle swarm optimization (PSO) algorithm was used to optimize the hyper-parameters in the MSVR network, and the trained PSO-MSVR network could correlate the design variable parameters and performance parameters of SGSHPs. Finally, a multi-objective optimization model of the SGSHPs was established using a genetic algorithm, and the Pareto solution set for the optimization of the system configuration was obtained with the objectives of thermodynamic performance and economy of the system, and the optimal solution was obtained by using technique for order preference by similarity to ideal solution (TOPSIS) decision-making. Compared with the pre-optimization design of the heat balance method, the annual cost (AC) is reduced by 17.733%, and the system COP (COPsys) and winter solar direct supply ratio (fsolar) are improved by 29.174% and 163.78%, respectively. The data-driven optimization method proposed in this paper has a significant advantage in obtaining the optimized configuration parameters of the SGSHPs system with multi-objective optimization.

Capacity matching and optimization of solar-ground source heat pump coupling systems

Capacity matching and optimization of solar-ground source heat pump coupling systems

Thermal performance of solar ground source heat pump system for rural buildings in Chinese cold zone

In response to China's national policy of “achieving carbon peak by 2030 and carbon neutrality by 2060″, and to promote the heating system of rural buildings in China's severe cold zone. Two heating schemes of the GSHP (Ground Source Heat Pump) system and the SGSHP (Solar Ground Source Heat Pump) system are designed and simulated for a single rural residential building in Harbin city. The results present that the outlet temperature of buried pipe in SGSHP system is 13.86 % higher than that in GSHP system, and coefficient of performance (COP) correspondingly increases 9.2 %. There is a better comprehensive performance for the SGSHP system in cold climates. The standard coal consumption of SGSHP system is about 72.35 % less than that of biomass boiler system, showing a greater energy efficiency. Compared to the local conventional biomass boiler system, the dynamic cost payback period of the SGSHP system amounts to 11 years, while yielding a net present value (NPV) of 10,800 CNY throughout the project's life cycle. The emissions of CO2, SO2, and dust are reduced by 2617.13 kg, 19.38 kg, and 14.535 kg respectively. The results indicate a great overall performance of the SGSHP system for residential heating in the cold climate zone. This research offers an energy efficient and eco-friendly alternative for the space heating of Chinese rural buildings in cold climates.

Simulation study on the system performance of solar-ground source heat pump using return water of the district heating network as supplementary heating

In order to mitigate the extreme climate change and improve the utilization of renewable resources, a solar-ground source heat pump system using return water of the district heating network as supplementary heating(SGSHP-DHNSH)has been proposed. This system compared with parallel and series connections of solar assist ground source heat pump systems for simulation and analysis. The results indicate that the SGSHP-DHNSH system raises the evaporation temperature, demonstrates a high rate of renewable energy utilization, and efficiently stores heat within the buried pipes. Notably, the soil temperature in the SGSHP-DHNSH system experiences only a 0.16 °C decrease, which represents reductions of 8 % and 9.8 % compared to the series and parallel systems, respectively. Furthermore, the system COP demonstrates a commendable improvement of 20 % and 13.7 %, the evaporator inlet temperature is higher than the series and parallel systems by 6.7 °C and 5.3 °C, respectively. Moreover, the total energy consumption throughout the heating season stands at 63 MW h, reflecting a substantial 24 % and 19 % reduction in comparison to the series and parallel systems, respectively. The SGSHP-DHNSH system plays a crucial role in improving the utilization rate of renewable resources and alleviating the soil heat imbalance caused by ground source heat pump operation.

Techno-economic and environmental study of a hybrid solar ground source heat pumps for a heating-dominated community in a cold climate; a case study in Toronto

Employing ground source heat pumps (GSHP) in heating-dominated areas presents challenges, including load imbalance and decreased efficiency. This study examines using solar energy to prevent soil thermal depletion in cold climates by comparing two systems. The first system (HPPV) uses geothermal heat pumps, borehole thermal energy storage, and photovoltaic modules. The second system (ST-HPPV) adds solar thermal collectors to reduce soil thermal depletion over long-term operation. Both systems supply hot or chilled water to the community's fan-coil systems via a short-term storage tank and heat exchanger. Their energy performance, greenhouse gas emissions, and costs were compared with a conventional fossil-fueled system (natural gas boiler and absorption chiller). Results showed the ST-HPPV system outperformed the HPPV system by 15 % in the seasonal coefficient of performance in heating mode after 20 years. However, solar thermal collectors did not benefit the cooling mode due to the community's load characteristics. Cost analysis revealed the HPPV system is more cost effective and reliable due to lower operating and carbon costs. The findings recommend the ST-HPPV system for communities where the annual heating load is 75 % or more of the cooling load.

Study on optimization of winter operation characteristics of solar-ground source heat pump in Shanghai

The operational characteristics of the combined solar-ground source heat pump system (referred to as SGSHPS) are influenced by local solar resources, climate characteristics, and operating modes. This paper aims to study the operational characteristics of SGSHPS in Shanghai under different operation modes, providing a reference for engineering applications of SGSHPS.Three operation modes were selected for this study: operation of the soil source heat pump, tandem operation mode 1, and tandem operation mode 2. The tandem operation mode 1 represents the heat pump source-side outlet fluid passing first through the buried pipe and then through the thermal storage tank, The tandem operation mode 2 represents the heat pump source-side outlet fluid passing first through the thermal storage tank and then through the buried pipe. The highest system COP was experimentally measured for tandem mode 1. TRNSYS software was used to construct the three oeration modes and obtain parameters such as unit COP, system COP, and buried pipe heat exchange.By comparing and analyzing the winter typical january month average system COP values obtained from experiments and simulations for each operation mode, The maximum error between the experimentally derived conclusions and the simulated conclusions is 9.9 %. The winter typical month january average system COP for the operation of the soil source heat pump was 3.26, while for tandem mode 1 it was 3.5, and for tandem mode 2 it was 3.44. Tandem mode 1 exhibited a 7 % higher system COP compared to the operation of the soil source heat pump, and a 1.7 % higher system COP compared to tandem mode 2. This indicates that the tandem operation of the solar-ground source heat pump is more energy-efficient than the operation of the soil source heat pump system. Therefore, tandem mode 1 is considered the optimal operating mode for SGSHPS in Shanghai during winter.

Analysis of the soil heat balance of a solar-ground source absorption heat pump with the soil-based energy storage in the transition season

In order to solve the problem of the soil heat imbalance due to the year-round operation of the solar-ground source heat pump in regions with the large gap between cooling and heating loads, this paper proposes to collect and store solar energy in the soil in the transition season. Based on the heating and cooling design of a solar-ground source double effect LiBr–H2O absorption heat pump for an office building, the heat pump system considering the solar energy stored in the soil has been built on TRNSYS platform. The long-term operating simulation has been conducted. The soil-based energy storage effect has been evaluated with taking the soil heat balance as the objective. The necessity of using the soil-based energy storage in the transition season has been discussed based on dynamic performance analysis results. The results show that the average soil temperature in the single heating condition rises to 16.49 °C, which is stable around 15 °C in the double cooling and heating condition after 10-years operation. The soil heat imbalance rates under two conditions are 18.32% and 11.64%, respectively. It can be seen that soil heat imbalance can be solved by the soil-based energy storage in the transition season.

Multi-objective optimization of an absorption solar-ground source heat pump considering the environmental and economic performance

ABSTRACT Solar heat pump has attracted more and more attention. This paper aims to improve the performance of an absorption solar-ground source heat pump (ASGSHP) through multi-objective optimization. Firstly, a double-effect absorption heat pump module is developed and a simulation model of the ASGSHP is established on TRNSYS platform. Secondly, considering both the economy and the environmental protection, the equivalent uniform annual cost (EUAC) and the environmental impact load (EIL) are taken as two objective functions. The non-dominated sorting genetic algorithm with elite strategy (NSGA-II) is applied to optimize the environmental and economic performance of the ASGSHP by TRNSYS and MATLAB joint. Pareto front of the multi-objective optimization of the ASGSHP system is obtained. Thirdly, using the TOPSIS decision-making method, the best optimization values for three optimization variables including the solar collector area, the storage tank volume and the setting temperature of the auxiliary heater are obtained. The optimization rate of the environmental impact load and the equivalent uniform annual cost of the optimal point selected by the TOPSIS decision-making method is 10.9% and 3.4%, respectively. The research results can provide the basic data and theoretical guidance for the further development and utilization of the solar-ground source heat pump.

Study on performance of solar energy interseasonal heat storage ground source heat pump system in cold region

In order to solve the problem of soil heat imbalance caused by winter heat load much higher than summer cooling load in severe cold areas of China, TRNSYS simulation software was used to analyze the performance of solar energy interseasonal regenerative ground source heat pump system in a hospital in Baotou City. The results show that COP and EER of the two heat pump units have little difference on a typical day, and the heating and cooling effect of the heat pump is relatively stable. Within ten years of operation of the inter-seasonal heat storage system, the soil temperature increased from 10℃ to 10.68℃, and the soil temperature of the solar-ground source heat pump composite system decreased to 5.62℃. At this time, the COP of interseasonal heat storage model was 3.25, up 2.2% year-on-year. It can be concluded that the solar energy cross-season heat storage mode can effectively alleviate the soil heat imbalance and improve the heat performance coefficient of the heat pump.

Performance of a solar ground source heat pump used for energy supply of a separated building

In order to achieve the carbon peak and carbon neutrality strategy in China, A SAGSHP (solar-assisted ground source heat pump) system is developed and four partition operation schemes of quarterly multi-mode switching buried pipe were designed in this research. Four types of buried pipe interconnection were schemed including central type, N type, H type, diagonal type, and the field tests were conducted. The system performance, soil heat balance, economic characteristics of the SAGSHP system were analyzed and compared with the ASHP&CFB (Air source heat pump & Coal-fired boiler) system. The results show that the energy supply by the SAGSHP system can meet the heating, cooling and domestic hot water needs of separated buildings after adopting the partitioned multi-mode switching operation scheme. Meanwhile, the system's heat loss is decreased, soil heat balance is well maintained, and the system flexibility is improved. The graded use of solar and soil energy is well realized. The COPs of SAGSHP system in heating period and cooling period were 3.62 and 5.76 respectively under the control of the central zoning operation scheme of buried pipes. Solar energy can provide 49.97 % of the total heat supply of the system. Compared with the ASHP&CFB system, the SAGSHP system can save 9.84 t of standard coal after operating 13 years, and the equivalent reductions of CO2, SO2, and dust are 26.568 t, 0.1968 t, and 0.1476 t, respectively. The system economy is the most sensitive to the project's initial cost whereas the least sensitive to electricity prices. The research in this paper provides a feasible alternative for the energy supply of separated office buildings in Chinese the severely cold regions of China.

Analysis of the operation performance of a hybrid solar ground-source heat pump system

The operational performance of a hybrid solar ground source heat pump (HSGSHP) system built at the Hebei University of Technology and composed of a ground source heat pump (GSHP) system and a solar-assisted ground source heat pump (SAGSHP) system is investigated in this work. For the GSHP system, the coefficient of performance (COP) of heat pump unit and system of the GSHP system varies from 4.59 to 5.07 and 3.87 to 4.28, respectively, in the cooling seasons from 2012 to 2016. During the heating season, the COP of heat pump unit and system of the GSHP system varies from 4.59 to 5.07 and 3.87 to 4.28, respectively. The annual COP of heat pump unit and system of the GSHP system increases from 3.19 to 4.18 and 3.03 to 3.63, respectively. For the SAGSHP system, solar space heating can improve performance by nearly 79.0%. For the HSGSHP system, increasing the proportion of the heat supply of the SAGSHP system within a certain range can effectively improve the COP of the HSGSHP system in the heating season. The results show that solar space heating can improve the performance of the HSGSHP system by nearly 25.8%.

Energy Saving Control of Integrated Energy Multi-Energy Complementary Coupling Space Heating System Based on Fuzzy Theory

Because the traditional solar-ground source heat pump heating system uses temperature difference controllers to control most, it causes the problem of large energy consumption of the equipment. In order to improve such problems, the complexity of the space heating control system is considered comprehensively, and the fuzzy strategy is used to improve the previous control system. TRNSYS was used to build a heating system simulation model, MATLAB was used to build a solar heating system fuzzy controller model, and the two models were coupled to jointly simulate the internal temperature change and energy consumption of the space under the same environmental conditions and different controllers. Experiments show that under the design conditions, the solar collector is greatly affected by the light, the temperature of the hot water storage tank is controlled between 58°C and 65°C. Using the traditional temperature difference controller, the system COP (Coefficient Of Performance) is low and the energy consumption is large, and the economic benefits are not high; the use of the fuzzy controller can increase the system COP by 6.1%, reduce the energy consumption by 22.85%, and save 8.71 yuan in the daily economic benefits of the system.

Thermal behavior of a combi-storage in a solar-ground source heat pump system for a single-family house

Experimental investigations on thermal behavior of a combined solar and ground source heat pump (SGHP) system for a single-family house are presented. The SGHP system was installed at the Lyngby campus of Technical University of Denmark. Detailed experiments were carried out on the system in 2019 under real weather conditions covering domestic hot water (DHW) consumption and space heating (SH) demand. Depending on the contributions of the energy inputs to the combi-storage, five typical daily operation modes are classified. The focus of the investigations is on the dynamic thermal behaviors of the heat storage under different operating conditions. When the combi-storage was primarily heated by solar energy, the inlet stratifier in the storage performed well, ensuring thermal stratification and a good utilization of solar energy. Water temperature in the storage reached up to about 68℃ at the end of the solar heating process. When the combi-storage was primarily heated by the ground heat, the water temperature near the outlet for SH was kept at a temperature range from 26℃ to 31℃ in the heating process to ensure the outlet temperature level of SH, and the water temperature near the outlet for DHW was in the temperature range 47℃∼51℃ in DHW volume. When there was no heat input to the combi-storage, the pre-stored heat can meet the daily heating demand, and the number of days on this mode was up to 9.4% of the total experimental days. The paper gives valuable inputs for researchers and engineers who plan to integrate the combi-storage in a renewable heating system with solar collectors and ground source heat pumps.

Study on solar-ground source heat pump and combined heating system in severe cold area

This paper studies the operation strategy and economy of solar-ground source heat pump gas heating system in severe cold region. Two operation modes of the system are introduced: series operation and parallel operation, and the two operation modes are simulated. This paper compares and analyses the heat exchange of the ground pipe, the change of the water temperature at the inlet and outlet of the ground pipe heat exchanger, the heating efficiency coefficient cop and the refrigeration efficiency coefficient EER of the heat pump unit during the five-year operation of the combined heating system, and studies the change of the soil temperature, Finally, the economic analysis is made from the initial investment cost and operation cost of two different heating schemes. The results show that the maximum heat transfer efficiency of the parallel system is 2.5 times that of the serial system, and the total heat transfer between the parallel system and the heat network is 83.2 % higher than that of the serial system. The inlet and outlet water temperature of the buried pipe decreased under both operation modes. After five years of operation, although the operation cost of the parallel combined heating system is higher than that of the serial combined heating system, the parallel combined heating system has more advantages than the serial combined heating system in terms of the overall heating effect of the system and the influence degree of the system on soil temperature.

Absorption solar-ground source heat pump: Life cycle environmental profile and comparisons

The developing and utilizing of the renewable energy in the field of the building air conditioning is one of the effective environmental protection ways. This paper conducts the comprehensive environmental impact assessment of an absorption solar-ground source heat pump(ASGSHP) and a vapor compression ground source heat pump(VGSHP) using the life cycle assessment (LCA) method. The three stages in the whole life cycle, i.e., the manufacturing, transportation/installation and operation phase of these two systems which meet the cooling demand of an office building in Beijing are analyzed, respectively. The comprehensive environmental assessment indexes including the pollutant emissions, the global warming potential(GWP), the acidification potential (AP), the dust potential and the environmental impact load(EIL) in the whole life cycle of the two systems are calculated and compared with each other. The environmental impact load, GWP, AP and the dust potential of the ASGSHP can be reduced by 42.20 %, 38.66 %, 45.73 %, 42.71 % compared with the VGSHP, respectively. The research results can provide the basic data and theoretical guidance for the further development and utilization of the GSHP system.

Designing and Optimizing Heat Storage of a Solar-Assisted Ground Source Heat Pump System in China

The cold accumulation problem can lead to performance degradation of heat pumps. This paper presents the design and optimization of a solar-assisted storage system to solve this issue. A ground source heat pump (GSHP) project was established using the transient system simulation program (TRNSYS) based on a ground heat exchange theoretical model, which was validated by a previously established experiment in Beijing. The Beijing, Harbin, and Zhengzhou regions were used in numerical simulations to represent three typical cities where buildings require space heating (a cold region, a severe cold region, and a hot summer and cold winter region, respectively). System performance was simulated over periods of ten years. The simulation results showed that the imbalance efficiencies in the Beijing, Harbin, and Zhengzhou regions are 55%, 79%, and 38%, respectively. The annual average soil temperature decreases 7.3°C, 11.0°C, and 5.3°C during ten years of conventional GSHP operation in the Beijing, Harbin, and Zhengzhou regions, respectively. Because of the soil temperature decrease, the minimum heating coefficient of performance (COP) values decrease by 23%, 46%, and 11% over the ten years for GSHP operation in these three regions, respectively. Moreover, the simulation data show that the soil temperature would still be decreasing if based on the previous solar energy area calculation method. Design parameters such as the solar collector size are optimized for the building load and average soil temperature in various cold regions. Long-term operation will test the matching rate of the compensation system with the conventional GSHP system. After the system is optimized, the solar collector area increases of 20% in the Beijing region, 25% in the Harbin region, and 15% in the Zhengzhou region could help to maintain the annual average soil temperature balance. The optimized system could maintain a higher annual average COP because of the steady soil temperature. It provides a method for the design of a solar collector area which needs to be determined in the seasonal heat storage solar ground source heat pump system.

Performance analysis of solar assisted ground coupled heat pump system in Latvia

Today, with the increased popularity and availability of renewable energy sources the question of ensuring a proper household heating, that is energy, is not as complicated as it used to be. Users are embracing the environmental sustainability stand and are turning to heat pumps and solar panels as means of providing heat for their homes. The geothermal heat pump and solar thermal panels energy efficiency rates coupled make these the perfect choice for those, who are concerned about the impact they make on the environment-aspiring to zero emission buildings. The combined system of solar thermal panels and ground source heat pump for heating capacity 13 kW will be developed. The main novelty is the investigation of a new type of a solar thermal accumulation tank. Hypothetically this solar assisted ground coupled heat pump system should reach COP rate 4 and reduce electricity demand consumption by 40%. To find out the truth of proposed thesis, the research will be carried out. Both simulation and real-life object data analysis will be performed. As a result, the potential of such a system in northern latitudes will be determined.

Experimental performance evaluation and parametric study of a solar-ground source heat pump system operated in heating modes

The dual heat source coupling modes of solar-ground source heat pump system (SGSHPS) directly determine its operation characteristics. In this paper, the thermal performance of a SGSHPS operated in different dual heat source coupling modes were studied experimentally. The unit COP, solar collecting efficiency and inlet and outlet temperatures of GHE were tested for various modes. The results show that for the combination operation mode, solar and ground heat source are dynamically coupled by the water tank and plate heat exchanger, and the average unit COP and collecting efficiency are 3.61 and 51.5%, respectively. For the water tank heat storage mode, the inlet water temperature of evaporator in the daytime stop mode of GSHP is 1.85 °C higher than daytime operation mode of GSHP, and the average unit COP and collecting efficiency are respectively 3.43 and 34.8%, 3.91and 34.9% for the daytime stop mode of GSHP and daytime operation mode of GSHP. For the ground heat storage mode, the ground temperature can be improved effectively for ground continuous heat storage mode and the outlet temperature of GHE can be increased significantly for ground intermittent heat storage mode. The average unit COP and collecting efficiency are 3.65 and 47.9%, 3.8 and 41.5% for the ground intermittent and continuous heat storage mode, respectively. A TRNSYS dynamical simulation model of the SGSHPS was established to explore the influences of key parameters on the system performance. The results indicate that the collector area and GHE number have evident influences on the system efficiency, but the impact of water tank volume is very small. The suitable collector area and GHE number are found to be 80 m2 and 9, respectively, and the water tank volume should be set as small as possible with the permission of actual conditions.

Design and optimization of a hybrid solar ground source heat pump with seasonal regeneration

This study describes an optimization method for the design and operation of a hybrid solar ground source heat pump. The system studied consists of solar thermal collectors, borehole heat exchanger (BHE), a heat pump, natural gas boiler and a stratified daily storage tank. The method uses a single-objective optimization for operation nested within a multi-objective optimization of the design parameters that minimizes the total annual costs and CO2 emissions. The methodology focuses on modelling the thermal behavior of BHEs, operational system constraints and seasonal effects of solar regeneration within an optimization framework.

Optimization design and compare of different solar-ground source heat pump system of office building in cold regions

This paper presents two different operation modes of Solar-Ground Source Heat Pump System (SGSHP(S)). With the simulation tool TRNSYS, two different SGSHP system models were built to taking simulation. After making analysis and compare of different simulation results, series operation mode was believed to be better than parallel in the target building.