Solar Assisted Ground Source Heat Research Articles

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.

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 Study of a Hybrid Solar-Assisted Ground-Source Heat Pump System Used for Building Heating and Hot Water Demands

Performance Study of a Hybrid Solar-Assisted Ground-Source Heat Pump System Used for Building Heating and Hot Water Demands

Comparison of different configurations of a solar-assisted ground-source CO2 heat pump system for space and water heating using Taguchi-Grey Relational analysis

This work deals with the comparison of different optimized configurations of solar-assisted ground-source CO2 heat pump systems using the Taguchi method and Grey Relational Analysis (GRA) when used for simultaneous space and water heating in cold coastal climate conditions. The configurations studied include: (1) the solar collectors (SCs) and borehole heat exchangers (BHEs) connected in series, with the working fluid flowing to the SCs first; (2) the SCs and BHEs connected in series, with the fluid flowing to the BHEs first; and (3) the SCs and BHEs connected in parallel to the heat pump. Eight parameters were considered for optimizing the systems’ design, including the BHE length, BHE spacing, BHE number, SC area, BHE-SC mass flow rate, space heating return temperature, heat pump discharge pressure, and heat pump’s outlet temperature. The seasonal performance factor (SPF), levelized cost of heating (LCOH), and the estimated maximum annual ground temperature change (GTC) were chosen as performance indicators to evaluate system performance. The system model was developed using Modelica and 27 simulation runs for every configuration were implemented according to the L27 (93) Taguchi orthogonal array. Single objective optimizations were first performed using the Taguchi method to determine the parameter combinations that would optimize the SPF, LCOH, and GTC, separately. After that, multi-objective optimization was performed using Taguchi-GRA to determine the control factor combination that would give the optimal overall performance when all output variables are considered simultaneously and given equal importance. When the performance indicators were considered separately, simulations show that configuration 2 gave the best SPF (4.025), configuration 3 gave the best LCOH (0.124 USD/kWh), and configuration 1 gave the best GTC (100.257%), respectively. Analysis of variance (ANOVA) showed that the SPF is most sensitive to the heat pump’s discharge pressure and outlet temperature; the LCOH to the BHE length, BHE number, and SC area; and the GTC to all the BHE and SC sizing variables. Multi-objective optimization showed that configuration 1 performs the best, giving a grey relational grade of 0.6875, which is equivalent to an SPF of 3.267, and LCOH of 0.155 USD/kWh, and GTC of 100.021%. BHE length was found to be the most influential parameter to overall performance, irrespective of the configuration.

Ground and solar assisted heat pump systems for space heating and cooling applications in the northern region of India – A study on energy and CO2 saving potential

In the recent past, energy demand of India has increased multifold as a fast-growing developing country, due to progressive expansion of industrial and building sectors. The demand for devices that provide both cooling and heating has increased in both commercial and residential buildings. However, nearly two-thirds of electricity generation in India is obtained from fossil fuel sources such as coal, oil and gas. Hence any attempt to save electricity consumption by the conventional space heating/cooling devices will benefit the country to meet other electricity demands and will indirectly aid for reduction in CO2 emission. Ground source heat pumps (GSHP) and solar assisted GSHP are sustainable systems that consume less electricity compared to conventional devices. They can achieve cooling and heating more efficiently by exploiting the temperature difference between the deep ground and ambient during winter and summer. In this research work, a detailed analysis has been made to assess the scope for the use of GSHP and Solar Assisted Ground Source Heat Pump (SAGSHP) systems for space cooling and heating applications in ten cities located in northern region of India. Calculations on the saving of electricity and reduction in CO2 emission has been carried out by comparing SAGSHP with conventional devices such as electric heater, solar coupled heat pump system for space heating. Air-conditioners are compared with GSHP for space cooling. Implementation of SAGSHP and GSHP technologies for space heating and cooling applications will result in the saving of 151.77 GW of electricity for space heating in ten cities and 88.39 GW of electricity for space cooling in six cities respectively with forthright reduction in CO2 emission of 123.83 million ton and 144.2 million ton. For 1.5-ton capacity heating load of SAGSHP and cooling load of GSHP, the payback period is estimated as 6.8 and 4.5 years respectively.

System optimization and mode modification of the solar assisted ground source heat pump system for primary schools in northern rural areas of China

With the increasing application of geothermal and solar energy in northern regions of China, it has become one of the main clean heating technologies for rural primary schools. However, the mismatch in equipment capacity has led to poor operating effect and economic efficiency of such systems. This paper puts forward experimental and analysis on a solar assisted ground source heat pump system in a primary school in Beijing's Daxing District. And then, to address the above issues, a TRNSYS model is established and verified to optimize the system strategy and form during 15 years period. What’ more, the main factors affecting solar collector selection are screened by sensitivity analysis. And through the step-by-step regression analysis, the collector selection correction model based on the coefficient Km is obtained. The results show that the temperature difference of the optimized collector control is 10 °C/1°C, and that of the supplementary heat is 20 °C/1°C. The applicable scenarios of the two system forms are different, and the energy efficiency of the system operation is increased by 23% and 23.4% respectively. In addition, the revised model ensures the balance of soil temperature for 15 years of operation under the condition of considering multiple elements, which provides a reference for the matching and selection of equipment for the same type of project in the future.

Performance analysis and multi-objective optimization of solar assisted ground-source heat pump heating system

ABSTRACT Heating through a solar assisted ground-source heat pump system is an efficient method, and optimizing its parameters can significantly improve its energy efficiency. However, the research on the impact of the start-stop temperature difference of the heat collection cycle on the system is currently limited. To address this issue, this study aims to develop a SAGSHP system model located in Tianjin using TRNSYS software, investigate the effect of parameters such as the start-stop temperature difference on the system performance, and guide the optimization process. The optimization parameters include the collector’s area, the water tank’s volume, and temperature difference during the heat collection cycle. The NSGA-II algorithm is applied to perform multi-objective optimization to enhance the system’s energy efficiency and economy. Furthermore, a sensitivity analysis is conducted to study each variable’s impact on the optimization results. The variation in temperature between the start and stop of the collection cycle has a significant impact on the system’s performance, as revealed by the study. The optimal operation scheme lies within the boundary range of parameter settings. The optimization leads to a decrease of 8.63% in the system’s annual operating cost and a reduction of 1555 kWh in the annual power consumption. The relationship between the area of the collector and the temperature difference during heat collection startup is expressed as 0.034°C/m2, and the ratio to the tank volume is 1.33°C/m3. The degree of influence of optimization parameters on optimization results is ranked as V i>A i>T s>T e.

Optimized design and integration of energy storage in Solar-Assisted Ground-Source Heat Pump systems

The integrated use of multiple renewable energy sources to increase the efficiency of heat pump systems, such as in Solar Assisted Geothermal Heat Pumps (SAGHP), may lead to significant benefits in terms of increased efficiency and overall system performance especially in extreme climate contexts, but requires careful integrated optimization of the different system components. In particular, thermal storages take a fundamental role in optimizing the integration of renewable energy sources and the system operation. This work investigates the potential design optimization of a SAGHP system in a mountain site by exploring many different alternatives to optimize the mutual relationship between the solar field, the geothermal field and the water thermal storages. This is done through an original simulation-based multi-objective optimization framework considering energy efficiency and economic feasibility, which allows appraising the impact of the different design alternatives on the overall system performance and on the dynamics of the different system components. Results identify a set of optimized system configurations that optimize the integrated exploitation of the different thermal sources showing a potential increase of the overall system performance leading to 34% lower global cost compared to the initial design. High robustness of the optimal design solutions is reported with respect to the current context of high economic uncertainty.

Performance analysis of a novel solar assisted ground source heat pump water heating system with graded thermal energy storage

The solar assisted ground source heat pump system (SAGSHP) is recognized as an efficient, clean and economical renewable energy technology for hot water supply. However, in SAGSHP systems with an all-day hot water supply, the solar collectors can only heat the water tank with intense solar radiation, which wastes moderate and weak solar resources. In addition, as the SAGSHP system draws heat from the soil for a long time, the soil temperature around the borehole decreases, causing the performance of the GSHP to deteriorate. To solve the above problems, a SAGSHP system with graded thermal energy storage (SAGSHP-GTES) was proposed. This paper investigated the performance and feasibility of the SAGSHP-GTES system, using a case study of hot water supply in a campus dormitory in Changsha, China. Firstly, the drawbacks of solar energy utilization in the conventional SAGSHP system were analyzed. Then, the SAGSHP-GTES system was modeled by TRNSYS, and its operational performance was evaluated and compared with the conventional SAGSHP system. Finally, the feasibility and performance of the SAGSHP-GTES system in different climate zones of China were analyzed. The results showed that the conventional SAGSHP system had a poor solar energy utilization efficiency, with an average thermal efficiency of the SC (ηSC) of only around 19.4%. The long period of operation caused the soil temperature to drop from 18.1 °C to 2.78 °C, which led to a decrease in system efficiency and an increase in electricity consumption. By controlling the heat collection of the SC and the graded utilization of solar energy in the SAGSHP-GTES system, a high ηSC of around 42.7% was obtained, which improved the system efficiency while eliminating the problem of soil temperature drop. After 15 years of operation, the soil temperature increased from 18.1 °C to 19.9 °C, which led to an increase in the coefficient of performance of the system (COPsys) from 3.77 kW/kW to 3.84 kW/kW and COPGSHP from 3.45 kW/kW to 3.5 kW/kW, and a reduction in electricity consumption from 51,746 kWh to 50,735 kWh. In addition, the conventional SAGSHP system was not feasible in severe cold zones (Harbin) and cold zones (Beijing) of China, where soil temperatures fell below 0 °C and freezing of the circulating fluid occurred, while the SAGSHP-GTES system showed excellent performance in all climatic zones of China and is a feasible and efficient technology for hot water supply.

Multi-objective optimization of solar-assisted ground-source heat pumps for minimizing life-cycle cost and climate performance in heating-dominated regions

The use of solar-assisted ground-source heat pumps (SGSHPs) with serial and parallel configurations can reduce the energy consumption compared with conventional ground-source heat pumps (GSHPs). However, the environmental and economic issues associated with SGSHPs, which involve high initial costs and CO2 emissions, remain major barriers to their application. Therefore, SGSHPs should be carefully designed considering both the economic and environmental circumstances to guarantee their competitiveness over GSHPs. In this study, multi-objective optimization of SGSHPs with serial and parallel configurations was conducted to minimize the life-cycle cost (LCC) and climate performance (LCCP). Based on the estimated energy consumption using Transient System Simulation Tool (TRNSYS), the design parameters and refrigerants of the SGSHPs were optimized using an artificial neural network and multi-objective genetic algorithm in the four heating-dominated regions. The optimized SGSHP with a parallel configuration exhibited lower LCC and LCCP by up to 7% and 10%, respectively, compared to that with a serial configuration. Furthermore, as building insulation technology improves, the optimal system size decreases. In addition, R134a is the best option for minimizing LCC owing to its high performance, whereas R1234yf is the best option for minimizing LCCP in Helsinki and Stockholm, showing up to a 37% reduction in LCCP.

Solar harvest: Enhancing carbon sequestration and energy efficiency in solar greenhouses with PVT and GSHP systems

It is universally acknowledged that climate change brings widespread attention to solar greenhouse plant carbon sequestration. Suitable technologies in solar greenhouses were, are, and will be play a leading role in this vital transition. The primary aim of this research is to examine the energy efficiency and carbon sequestration potential of a solar-assisted ground-source heat pump (SAGSHP) heating system. This hybrid system, which integrates a horizontal ground-source heat pump (GSHP) system with PVT and heat storage, can efficiently fulfill the heating demands of a greenhouse and function as a positive energy building. Four plants include cucumber, tomato, cowpea, and lettuce were selected to compare the carbon absorption effects. Results show that the hybrid system outperforms conventional systems, with a coefficient of performance (COP) of 6.71 during peak hours and PVT efficiency over 57.88%, which effectively meet the heat load of the greenhouse and keep the indoor heat comfortable. In addition, for the carbon sequestration potential of four plants, tomato exhibited the highest photosynthetic carbon sequestration of 3522 kgCO2·m−2. Cowpea showed the strongest daily carbon sequestration capacity at 26.86 gCO2m−2d−1 and better economic income. Through the application of this enhanced solar greenhouse, people can enhance the utilization of solar energy, establish flexible interaction between energy and information flow, and make a promising option for sustainable building design.

Numerical investigation of using a field of shallow boreholes with latent heat storage and solar injection in cold climates

Modeling heat transfer within a field of boreholes (borefield) is essential to correctly assess the long-term performance of a solar-assisted ground source heat pump, which uses the ground to store the injected solar thermal heat. A novel model was developed that uses a hybrid approach, combining a numerical thermal resistance and capacitance model for the borehole with an analytical g-function for the ground. The developed model has the capability to simulate the long-term performance of a borefield with the phase change that is occurring in the water content of the grout. The model is used to assess the benefit of phase change within a saturated sand mixture, acting as filling material in the borehole and thermal energy storage for solar heat injected in the ground. The injected solar heat compensates the ground thermal load imbalance caused by substantially higher heating demand than cooling demand in cold climate regions. Through long-term hourly simulations, results show that water content in the borehole helps keep the temperature constant at the vicinity of the borehole, particularly during peak hours, and that solar injection permits the design of a more compact borefield by concentrating the stored heat in the vicinity of the boreholes.

Performance Analysis of Solar Assisted Ground Source Heat Pump to Supply Heating Load and Domestic Hot Water

Algeria’s geographical location offers several advantages related to the extensive use of renewable energy sources such as solar and geothermal. Owing to the vast Algerian territory, the need for isolated areas to be supplied with energy by autonomous systems using sustainable energy. In this study, we propose a hybrid renewable energy system to provide heating systems for residential buildings and domestic hot water (DHW). Four different solar-assisted ground source heat pump (SAGSHP) combinations are being studied, with the aim of satisfying the energy needs of a building located in Batna, Algeria. The TRNSYS software allowed us to study the different effects of the parameters on their performance. It turned out that a 7.7 kW ground source heat pump system combined with flat solar collectors is a feasible choice that satisfies our objective. The extreme annual average values of the heat pump coefficient of performance (COP) obtained are 3.48 and 4.55. In the system, with recharging the borehole, the net energy extracted from the ground is decreased by 30.4% compared to the reference case (GSHP). This can reduce the ground thermal imbalance problem, which positively affects the stability of the operational system.

Advances in coupled use of renewable energy sources for performance enhancement of vapour compression heat pump: A systematic review of applications to buildings

Vapour compression heat pump provides efficient cooling and heating through the use of various renewable energy sources and plays a significant role in the energy conservation of modern buildings. Its performance enhancement gains increasing attention under the background of conventional energy and environmental crisis. Since the efficiency of a heat pump cycle is closely related to its thermal source condition, a stable high-temperature heat source or low-temperature cold source could benefit its heating or cooling efficiency a lot. Following this improvement strategy, significant progress has been made over the past years on the use of different renewable energy sources as coupled thermal sources of heat pumps. However, a specialised review that summarises relevant studies remains to be published. This paper aims at presenting operating mechanisms, characteristics, benefits, and limitations of different energy source coupling methods for heat pump performance enhancement towards its building application. The most concerning research on solar-assisted air source heat pumps, solar-assisted ground source heat pumps, and air-ground dual source heat pumps is emphasised. The existing thermal source coupling attempts under other renewable energy fields, such as waste heat, biomass, and water sources, are also summarised. Recommendations for further research and marketisation of such technologies are made based on detailed performance characterisation and comparison. The review is expected to benefit researchers in heat pumps and relevant applied energy fields to understand the challenges and opportunities in thermal source coupling technology and to promote its research and application development.

Energy Performance Evaluation of a Solar PVT Thermal Energy Storage System Based on Small Size Borefield

In this study, a PVT-based solar-assisted ground source heat pump (SAGSHP) system with a small size borefield as the long-term heat storage component was energetically evaluated. The mathematical model of the system was formulated in TRNSYS and three cities with distinctive climates were chosen: Athens (Greece); Melbourne (Australia); and Ottawa (Canada). The parametric analyses were carried out for 10 years by varying the number of the PVT collectors and the size of the earth energy bank (EEB). The evaluation of the systems was made via two energy indicators, and the heat flow across the EEB was analyzed. The under-consideration system was found capable of establishing self-sufficiency as regards the energy consumption (renewable power fraction RPF > 1) for all locations. Namely, for Athens, any system with more than four PVT collectors, and for Melbourne, any system with more than eight PVTs was found with an RPF higher than 1, regardless of the EEB size. For Ottawa, self-sufficiency can be achieved with PVT arrays larger than 12 collectors for small EEBs, and with eight collectors for larger EEBs. The storage capacity was found to be an important parameter for the energy performance of the system. In particular, it was determined that, as the storage capacity enlarges the RPF and the seasonal performance factor (SPF) of the system improves, mainly due to the reduction of the electricity consumed by the heat pump and the auxiliary heating. Moreover, a larger storage capacity facilitates solar heat production by enlarging the available heat storage volume and by maintaining the EEB at relatively low temperatures.

CO2 emissions and energy performance analysis of ground-source and solar-assisted ground-source heat pumps using low-GWP refrigerants

The energy consumption and CO2 emissions of heat pump systems can be reduced effectively by adopting an appropriate alternative refrigerant. However, investigation on alternative refrigerants for ground-source heat pump (GSHP) and solar-assisted ground-source heat pump (SGSHP) systems is limited although these systems still use conventional refrigerants. In this study, the life cycle climate performance (LCCP) and primary energy consumption (PEC) for GSHP and SGSHP systems using conventional and alternative refrigerants are compared to those for conventional boiler systems. Experiments are conducted to investigate the heating performance of selected refrigerants. For regions with low CO2 emission conversion factor for electricity (μCO2.elec), GSHP systems using R1234yf are the most suitable considering the LCCP, owing to its low GWP and high performance. However, SGSHP systems using R134a with a large system size are preferred in regions with high μCO2.elec, because system efficiency takes the priority in reducing the LCCP. For PEC, SGSHP systems using R134a are recommended owing to its high efficiency. However, in regions where oil or natural gas is used dominantly, either the system size of SGSHPs should be increased or the primary energy conversion factor of electricity should be reduced to guarantee the benefits of PEC reduction of SGSHP systems.

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.

Techno-economic approach for optimum solar assisted ground source heat pump integration in buildings

Two-step approach for optimum solar assisted ground source heat pump integration in buildings is proposed. At the first step energy targeting based on dynamic pinch analysis allows to target the energy and optimum equipment size according to buildings’ dynamic demands, and as a result, several energy efficient daily design candidates are extracted. At the second step of the proposed approach, a final design working for the whole year is selected among all the candidates by computing the total annual cost (TAC). A special algorithm is proposed to compute the yearly average energy and capital cost penalty for complementary hot/cold utilities in order to adapt the daily designs to the overall year design. As an objective function, TAC is defined for a 20-year lifetime design. Moreover, the TAC of several daily optimum designs (DOD) based on different scenarios are investigated for a multifamily test building. In the context of Canadian market, it is illustrated that the choice of the overall year integration design depends mainly on the electricity cost. For example, with Quebec electricity cost (i.e., 0.073 CAD/kWh), the DOD of September is optimal for the whole year, where there is no need for vertical ground heat exchangers. However, if Canadian average electricity cost (i.e., 0.147 CAD/kWh) is considered, the DOD of March is optimal for the whole year, with a vertical ground heat exchanger depth of 200 m. The DOD of September and March can reduce building’s annual electricity consumption by 55.9% and 79.2%, respectively.

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%.

Simulation and analysis of three, solar assisted, ground source heat pump systems

The use of Ground Source Heat Pump (GSHP) systems is promising in reducing the energy consumption in the households and services sector, which accounts for almost 40% of the total energy consumption in Europe and in Northern America. There is an increasing interest in combining such earth energy systems with solar energy. In this study, three Solar Assisted Ground Source Heat Pump configurations comprised of Flat-Plate (FPC), Photovoltaic (PV) and hybrid Photovoltaic/Thermal (PV/T) collectors are investigated aiming at upgrading an existing GSHP system installed in a university building complex at in Volos, Greece. These systems were simulated with the dynamic system simulation tool TRNSYS and were assessed on energy performance and on an economic and an environmental basis. Results of the analysis showed that the PV system is the best option due to its substantial energy savings and to the lower cost compared to the PV/T system.