Assisted Ground Source Heat Pump Research Articles

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.

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.

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.

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.

Optimization of combined cooling, heating, and power systems for rural scenario based on a two-layer optimization model

In the process of rural urbanization, the burden of energy and carbon emissions has increased. To alleviate these problems, this study proposes a combined cooling, heating, and power with a photovoltaic/thermally assisted ground source heat pump system to meet the load demand of rural users. A two-layer optimization model is constructed with the goal of optimal economy. The upper layer is a capacity allocation model simulated with MATLAB software and solved with an accelerated particle swarm optimization algorithm to obtain the optimal equipment parameters. The optimization variables are constrained by the operation strategy of the lower layer. The lower layer is the operation optimization model. The operation model is established on the TRNSYS platform, and the operation strategy is formulated. The charging and discharging time of its energy storage device is constrained by the local time-of-use electricity price system. Taking a rural house nearby Huaihe river in Huainan, China as an example, a combined cooling, heating, and power system is designed. And an annual simulation of the system is conducted and optimized based on the local parameters. The optimization results show that the economy and performance of the optimized system are improved. During the heating period, the average COP of the optimized system increased from 4.94 to 6.59, and its energy saving rate reached 7.18%. The operating income increased by 862.93 CNY and 2866.87 CNY, respectively, compared with the non-optimized system and the separate production system. And the optimized PV/T waste heat utilization system can provide 3254.70 kWh of heat. The utilization rate of waste heat reaches 72.26%, which realizes the full utilization of renewable energy.

Integrated operation of PV assisted ground source heat pump and air source heat pump system: Performance analysis and economic optimization

The ground source heat pump (GSHP) system is widely recognized as an efficient, clean and economical renewable energy technology for buildings, and can be utilized for building cooling, heating and hot water supply. In the hot summer and cold winter zones of China, however, the total thermal load (heating load and hot water load) of GSHP systems is greater than the cooling load, which may cause a significant soil temperature drop and GSHP performance deterioration. To solve the above problems, a photovoltaic (PV) assisted GSHP and air source heat pump system (PVGSHP-ASHP) was proposed. This paper investigated the performance and feasibility of the PVGSHP-ASHP system, using a case campus building in Changsha city, China. The PVGSHP-ASHP system was firstly established by TRNSYS, and then, its operational performance was evaluated and compared with the PV assisted GSHP (PVGSHP) system and the PV assisted GSHP and electric heater (PVGSHP-EH) system. Finally, the economic optimization of the integrated operation of the PVGSHP-ASHP system was carried out with the combined simulation of TRNSYS and GenOpt. The results showed that for the PVGSHP system, the soil temperature reduced from 18.1 °C to 11.8 °C after 15 years of operation, which caused a decrease in the annual coefficient of performance of the GSHP (COPGSHP) and an increase in the annual electricity consumption. Although the PVGSHP-EH system can solve the load imbalance problem, its annual lifecycle cost (ALCC) increased by 39.3 % due to the low efficiency of the EH. The PVGSHP-ASHP system can solve the appeal problem with high annual COPGSHP and COPsys values of 3.49 kW/kW and 4.69 kW/kW, respectively, and only 71,700 kWh of the annual electricity consumption, while its ALCC was the lowest at 99,223 CNY, which was 8.1 % lower than the PVGSHP system. After optimization, the ALCC of the PVGSHP-ASHP system reached the minimized value of 91,158 CNY, with a reduction of 8.1 %. These findings can provide new ways to solve the load mismatch problem of GSHP systems while enhancing the system efficiency in the hot summer and cold winter zones 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.

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.

Energy targeting approach for optimum solar assisted ground source heat pump integration in buildings

Application of solar assisted ground source heat pumps (SAGSHP) in buildings have been increased in recent years. However, a systematic approach for integrating the optimum SAGSHP system in buildings in order to meet the space heating/cooling and the domestic hot water loads is still missing. A novel dynamic targeting approach is proposed. It can predict and guarantee the maximum possible direct and indirect heat recovery in a given building by introducing an interconnected network of heat exchangers (including ground heat exchanger) + energy storage (both electric and thermal energies) + heat pump (HP) + solar photovoltaic (PV) panels based on the real-time hot and cold composite curves (CCs). The main novelty of this approach consists in the fact that the dynamic building's loads and the time variation of renewable and waste sources of energies are included into the targeting procedure. The approach is applied to a multifamily test building, where the solar irradiance and building's heating and cooling demands are taken into account. In addition to the maximum heat recovery, the proposed approach computes the minimum area of the solar photovoltaic panels, the minimum volume of TES, and the minimum capacity of the electric energy storage for each representative day.

Performance analysis of a solar thermal system coupled with a ground source heat pump in Nordic conditions

The main objective of this work is to investigate the energy and exergy performance of a solar assisted ground source heat pump for a school building designed according to Norwegian passive house standard. The system is designed in such a way that the solar collector prioritizes to provide heat to the hot water tank and whenever there is excess heat from the solar collector it can be used to charge the ground borehole. A detailed thermodynamic analysis of the system has been carried out in Engineering Equation Solver (EES). Isobutane (R600a), propane (R290), ammonia (R717) and solstice (R1234ze(E)) have been investigated as working fluid for the heat pump. The result revealed that the solar collector and the different working media have affected both the COP and the exergy of the system. Moreover, the mass flow rate of the brine and the length of the borehole affect the performance of the system.

Energy, economic and emission assessment of a solar assisted shallow earth borehole field heat pump system for domestic space heating in a north European climate

The performance of a solar assisted ground source heat pump (SAGSHP) system was evaluated and compared with a conventional gas boiler system using simulation, for a central England location. The earth energy bank was the long-term heat store element of the system and consisted of a very shallow field (1.5 m deep) of borehole heat exchangers (BHE). The mathematical model of the system was formulated, and parametric analyses were carried out by varying the number of BHEs and their spacing. The energy performance was expressed using four energy metrics, while its economy and CO2e emissions were compared with a natural gas boiler (NGB) system via the life cycle cost method and the fractional CO2e savings, respectively. The system can be energy self-sufficient by installing 40 BHEs at 1.25 m spacing or with 32 BHEs at 1.5 m spacing. The NGB system appears more economic than the SAGSHP system, due to low natural gas prices, the high price of the imported electricity, the low price of the exported electricity and the higher capital cost of the SAGSHP system. However, the SAGSHP system was found to have net negative carbon emissions, in contrast to the high positive emissions of the NGB system.

Performance analysis of photovoltaic-thermal road assisted ground source heat pump system during non-heating season

Photovoltaic-thermal road as solar collector is a promising technology. To expand the application of photovoltaic-thermal road, a novel energy system which integrated photovoltaic-thermal road with ground source heat pump system is proposed. Focus on this system, a dynamic mathematical model during non-heating season is established and validated, and it is used to explore the system performances under two operation modes: heat collection loop and heat storage loop operate simultaneously in mode 1 while they operate independently in mode 2. Furthermore, effects of setting temperature difference in both heat collection loop and heat storage loop on system performance are investigated. It is indicated that system performance in mode 1 is better than that in mode 2. As setting temperature difference in both heat collection loop and heat storage loop are increased, the thermal energy storage, electric power generation and energy consumption are decreased. And influence of setting temperature difference on thermal energy storage is greater than that on electricity generation. The overall efficiency under mode 1 and mode 2 are 27.12–36.96% and 18.78–26.36% respectively. Considering both energy generation and energy consumption, the optimal values of setting temperature difference in heat collection loop and heat storage loop are 2 °C and 10 °C under mode 1, and that are 2 °C and 4 °C under mode 2, respectively.

Multi-criteria optimization for a residential horizontal ground heat exchanger

Ground source heat pumps (GSHP) are the most efficient heat pump systems currently in use for residential sector today. Although these systems outperform all other heat pump systems when considering the energy source, the installation costs represent an ongoing issue. For the market to increase in this area, multi-criteria optimization for the ground heat exchanger (GHE) is the main research topic today. The main objective of this study is to search ways to optimize the horizontal ground heat exchanger focusing on two distinct viewpoints: physical and energetic optimization. To achieve this goal, the entropy generation number and the coefficient of performance based on several configuration are studied. Using the Pareto optimal set obtained from two objectives provides useful information about the design optimization. In comparison with traditional single objective optimization, multi-criteria optimization avoids cost increase when regarding only the performance or performance decrease when regarding only the cost. The results indicate that the use of a cheaper heat source such as solar panels to mitigate the energy needed for peak loads during the heating and cooling systems can reduce the horizontal ground heat exchanger size and therefore the installation cost. A hybrid solar assisted ground source heat pump system, using more than one renewable energy source, shows a much higher flexibility for residential purposes than a heat pump system that uses only one renewable energy source.

10-year simulation of photovoltaic-thermal road assisted ground source heat pump system for accommodation building heating in expressway service area

The photovoltaic-thermal (PVT)-ground source heat pump (GSHP) system has been proved to have great potential in improving building energy efficiency, but ordinary PVT collector requires a large installation area and limits the popularization of PVT. In this paper, a novel solar energy collector, called photovoltaic-thermal road (PVTR), is proposed to replace the traditional PVT collector, and a novel energy system that is PVTR-GSHP system is proposed. In order to study the system performance, taking a typical expressway service accommodation building in Beijing as an example, a 10-year simulation is carried out to analyze the heating operation characteristics of the proposed system. Moreover, the effects of the PVTR area, the length and layout of ground heat exchanger (GHE) on the system performance are also discussed. Results show that, when the length of GHE is 5000 m, and the number of boreholes is 25 and the borehole depth is 100 m, the minimum area of PVTR satisfying the soil heat balance and meeting the system power consumption are 187.2 m2 and 216 m2, respectively. When the PVTR area is 216 m2, the minimum GHE length satisfying the soil heat balance is 4000 m. Finally, to realize system zero energy consumption and soil heat balance, the best combination of GHE length and PVTR area is 4000 m and 216 m2 under the cases of this paper. And in this case, the average COPHP and COPsys in ten years are 5.59 and 2.31 respectively.

Energy and economic evaluation of a solar assisted ground source heat pump system for a north Mediterranean city

In this study, a PVT based solar assisted ground source heat pump (SAGSHP) system was investigated regarding its energy performance and cost-effectiveness for the city of Thessaloniki (Greece). The SAGSHP system was set to cover the space heating and domestic hot water needs for a low-rise dwelling. A mathematic model formulated in TRNSYS was used with the aim to carry out parametric analysis by varying the number of the PVTs. It is worth noting that, two of the most important components of the employed model, the PVT collector and the geothermal heat exchanger, have already been validated via experimental data. Simulations were conducted and through the results seven energy metrics were estimated, with the objective to examine the system’s energy performance from various perspectives. The SAGSHP system with 16 PVTs was found capable to covering 73% of the heating load and to generate 1.22 times more electricity than that consumed by the system. The electricity yield of PVTs was not affected throughout the parametric analysis, and the maximum specific productivity was estimated at 301.5 kWhe PVT−1 per year. The results suggest that a SAGSHP system equipped with about 14 PVTs can reach energy self-sufficiency. As regards the economics of the SAGSHP system, this was compared with a natural gas boiler system via two methods, the life cycle cost (LCC) and the life cycle savings (LCS). A sensitivity analysis with major economic parameters of the systems was carried out. It was found that the cost-effectiveness of the SAGSHP system is influenced mainly by its capital cost and by the price of the natural gas. Systems equipped with less than 12 PVTs can be cost-competitive by subsiding from 8% up to 42% of their capital cost. Also, system with more than 12 collectors were found of more benefit than the smaller ones, in the case where feed-in-tariff schemes are applied, or the bank loan’s interest rate is low. It can be concluded that, the proposed system can be an attractive monetary solution for covering the heating load in comparable dwellings with a similar climate to Thessaloniki.

Energy performance indexes for solar assisted ground source heat pump systems with photovoltaic-thermal collectors

Applications with photovoltaic thermal collectors (PVTs) are becoming popular due to their capability of cogenerating heat and power from the same surface. Solar assisted ground source heat pump (SAGSHP) systems are considered a potential solution for utilization of PVTs. Up to now, the seasonal performance factor (SPF) has been used by most of the existing literature to evaluate the energy performance of the PVT based SAGSHP systems. However, the PVTs coproduce heat and power, and the SPF omits the generated electricity and overlooks the influence of the system on the collectors’ electrical efficiency. Driven by the limitation of the SPF to illustrate the overall system’s energy performance, this study introduces a new improved energy performance metric. The study was carried out by varying the size of the PVT array and via the results six energy indexes were evaluated. The parametric analysis was conducted by a validated model formulated in TRNSYS. Based on the results, the renewable power fraction (RPF) was found as the most suitable index to assess the performance of PVT-SAGSHP system. A 7% reduction was estimated in the PVTs’ electricity generation, by choosing the higher SPF instead the higher RPF. The proposed RPF index overcomes restrictions of doing calculations with both electricity and heat at the same equation. Thus, the RPF is considered capable of indicating the overall energy performance of the systems, without limitations. Finally, the proposed metric (RPF) can be used to study the energy performance of any solar system equipped with PVTs.

A dynamic analysis of a SAGSHP system coupled to solar thermal collectors and photovoltaic-thermal panels under different climate conditions

The use of multi-source energy systems is a promising technical solution for the reduction of greenhouse gases emissions and, at the meantime, for enhancing the exploitation of renewable energy sources.The present paper analyses a Solar Assisted Ground Source Heat Pump system and tries to fill the gap in the literature, where a direct comparison between the consolidated solar thermal technology and the emerging and widely discussed photovoltaic thermal technology is missing. Indeed, the two different devices for the exploitation of solar energy have been analysed through dynamic simulations carried out in TRNSYS environment. Through this approach, it is possible to investigate and predict in detail the thermal and electrical behaviour of the energy system, composed by a water-to-water heat pump, which withdraws from two thermal reservoirs that are connected to a solar loop, composed either of solar thermal collectors or of photovoltaic thermal panels and to a ground loop.The heat pump is used to provide space cooling and space heating to a residential building, through fan coil terminal units or radiant floor system. Furthermore, the heat pump system assists the solar field in the production of domestic hot water.This study looks at the development of a flexible system able to work in different operating conditions. The model’s boundary conditions can be changed for simulating a variety of case studies as the weather condition, the building load and the domestic hot water profile can be easily changed, together with specific components’ parameters. The control strategy makes it possible to vary the setpoint temperatures for simulating different operating conditions and management choices. In this way, the user can easily adapt the model functions to a specific plant system.The operating conditions of the two systems layouts have been compared and the energy performances evaluated for three case studies characterised by the weather conditions of the European cities of Berlin (mild-cold climate), Venice (mild climate) and Barcelona (mild-warm climate), and the corresponding thermal load profile of a two-storey building with a useful floor area of 170 m2.The study shows the possibility to directly exploit the solar energy for the domestic hot water production and as a heat source for the heat pump. The results from the comparison between the two systems’ configurations, with photovoltaic thermal panels and with solar thermal collectors, prove that there is the possibility to obtain a relevant improvement in the efficiency of the heat pump using photovoltaic thermal panels. The investigated multi-source energy system, moreover, allows an optimal employment of the available renewable heat sources and could easily be applied to case studies characterized by different boundary conditions.

A study on the viability of an on-site combined heat- and power supply system with and without electricity storage for office building

The building sector in the European Union accounts for over 40% of the final energy use, where the usage of non-residential buildings may be up to 40% higher than the residential sector. Improving building energy efficiency across all categories of buildings is one key goal of the European energy policies, made prominent by the Climate and Energy package, Energy Performance of Building Directive and Energy Efficiency Directive. In this study, the profitability of an on-site combined heat and power supply system for an office building is investigated. A reference model utilizing solely district heating was constructed and used for validation purposes. Then, a photovoltaic assisted ground source heat pump model was developed and investigated with and without electrical storage to reveal the most cost-effective investment scenario in cold climate regions. The reference model was validated using consumption data provided by the facility owner, after which an investigation of the energy saving potential along with the economic viability of adapting a new heat- and power supply system was conducted. It was concluded that a ground source heat pump in combination with a standalone rooftop photovoltaic system, was successful in satisfying thermal requirements while lowering the building specific energy demand compared to utilizing a district heating system. The photovoltaic assisted ground source heat pump system including a battery bank is the most profitable when incentives are granted, a higher self-consumption of 93.1% is achieved with a battery capacity of 38.4 kWh.