Dual Source Heat Pump System Research Articles

Experimental study of dual-source heat pump coupled with water-cooled photovoltaic/thermal system

This paper presents a study on an innovative solar-air dual heat source heat pump coupled with a water-cooled photovoltaic/thermal system. The research investigated the real-time operation of solar electrical and thermal efficiency, as well as the coefficient of performance Field experimental platform construction and experimental testing were conducted. The experimental results show that when running the system in composite mode, the average electrical efficiency in the two phases was 16.79% and 18.33%, while the average collector efficiency reached 42.72% and 98.94%, respectively. Under typical autumn working conditions, the heat pump’s coefficient of performance with the fans off and on was 4.37 and 4.73 respectively on sunny days, and under cloudy day conditions, it reached 3.76 and 4.20 respectively. With the fans on, the average collector efficiency on a cloudy day increased by 3.34% compared with that without the fans, and the total average collector efficiency reached 310.5%. Compared with conventional single water-cooled photovoltaic/thermal systems or solar-assisted heat pump systems, the combination of these two systems, with the addition of both fins and fans which increased the heat transfer performance of the system and improved the stability and economy of the system’s operation, providing data to support the feasibility of a water-cooled photovoltaic/thermal coupled dual-source heat pump system.

Energy, economic and environmental analysis of a photovoltaic-thermal integrated dual-source heat pump system under a system coefficient of performance − based switching strategy

The photovoltaic-thermal integrated dual-source heat pump system can offer performance improvement by addressing the limitations of a single heat pump system, which not only improves energy efficiency and system performance but also reduces pollutant emissions. However, the operational performance of the system is significantly affected by different switching strategies between two heat sources, which has not been given adequate attention from researchers. Therefore, this study introduced a system coefficient of performance − based switching strategy, which can alternate between air-source heat pump and solar water heat pump modes to make full use of air and solar energy, to optimize the operation of the photovoltaic-thermal integrated dual-source heat pump system and compare with the conventional water temperature of the heat storage tank − based switching strategy. A TRNSYS model of the system was developed and validated, and the simulated results demonstrated the better performance of system coefficient of performance − based switching strategy in energy, economic and environmental perspectives. The average photoelectric and photothermal conversion efficiency under system coefficient of performance − based switching strategy were higher than those under water temperature of the heat storage tank − based switching strategy by 1.1 % and 4.0 %, respectively, with average modified coefficient of performance of 7.43 and 6.55. Furthermore, the system not only achieved savings of 5.63 % in annual electrical cost and 5.33 % in yearly operational cost but also reduced standard coal by 19.25 kg and total pollutant emissions by 242.55 kg per year under system coefficient of performance − based switching strategy, compared to water temperature of the heat storage tank − based switching strategy.

Performance analysis on the heating performance of CPV/T-air dual source heat pump system with finned microchannels heat exchanger

Solar-assisted heat pump technology is a clean building energy conserving technique with high efficiency, but it often has limitations such as large evaporator cover area and significant susceptibility to weather conditions, preventing it from being widely used. In this paper, a concentrated photovoltaic/thermal-air dual source heat pump system integrated with finned microchannel heat exchanger (CPV/T-FMC-SAHP) is proposed to solve these problems. A mathematical model for the CPV/T-FMC-SAHP system is developed, and sensitivity analysis of different environmental parameters on system performance is conducted by numerical simulation. Performance comparisons are made under dual-source and solar heating modes to explore the optimal operating conditions. The results suggest that changes in ambient temperature have a relatively minor impact, primarily attributed to the limited surface area of the evaporator. On the other hand, increased irradiance, facilitated by the concentrator, significantly improves the system's performance. In the case of solar irradiation at 600 W/m2 and an ambient temperature of 13 °C, the system's heating capacity is 1747.38 W, with a COP reaching 5.31. In comparison, the COP of existing solar-assisted heat pump systems under this condition are about 4.5, so there is an improvement of about 18 %. Furthermore, activating the air blower on the weather with bad irradiation but relatively warm can further increase the system's heating capacity. To sum up, the CPV/T-FMC-SAHP system exhibits a substantial improvement in performance and high level of integration compared to traditional solar-assisted heat pumps. Therefore, this system can provide ideas for improving the performance of heat pumps in the case of limited space. It is not only meaningful in the field of building energy conserving, but also conducive to addressing global energy challenges.

Thermodynamic and economic analyses of modified ejector enhanced solar-air composite dual-source heat pump system in residential buildings

This research utilizes an ejector enhanced solar-air composite dual-source heat pump (EDHP) system for water heating in residential buildings. The main advantage of the EDHP system is the use of an ejector and dual-heat source to efficiently utilize solar energy, thereby enhancing heating performance. This ejector operates by utilizing a refrigerant stream from the solar collector line with higher pressure to elevate the suction pressure of the compressor. This feature enables the EDHP system to maintain stable heating performance even in adverse weather scenarios with low temperatures or limited solar radiation. Thermodynamic modeling using energetic and exergetic analysis methods is employed to theoretically evaluate the conventional air-source heat pump and EDHP systems. The energy analysis of the EDHP system using R134a refrigerant has shown significant improvements in both heating coefficient of performance (COP) and exergy performance (ECOP). Under specific conditions, such as an ambient temperature of −5 °C and an irradiance level of 250 W∙m2, and utilizing a 20 m2 PVT (Photovoltaic and Thermal) collector for a heating supply of 5 kW, the EDHP system exhibits a 23.64 % increase in COP and a 25.83 % increase in ECOP. Furthermore, when the electricity generated by the PV system is incorporated into the EDHP system, the demand for electricity from the grid can be reduced by up to 51.96 % under the same conditions. In the Beijing area and considering the current energy price system, the heating operating cost of the EDHP system is 0.206 Yuan/kWh. Compared to a standard air-source heat pump system, the payback period for EDHP system ranges approximately from 10 to 12 years, taking into account an annual heating period of 5 months. Among the alternative refrigerants to R134a in the EDHP system, R152a is found to be the most suitable. It shows COP improvements of 24.92 %–30.0 % and ECOP improvements of 24.89 %–29.96 %. This innovative approach opens up new possibilities for the application of heat pump technology under adverse weather conditions in residential and commercial buildings.

Energy and exergy analysis of a novel dual-source heat pump system with integrated phase change energy storage

In order to improve the application of renewable energy in cold regions and overcome the drawback of the low performance of traditional air source heat pumps (ASHP) in a low temperature environment, a novel type of dual-source heat pump system is proposed, which includes a heat pump, photovoltaic–thermal (PVT) modules, an air heat exchanger, and phase-change energy storage equipment. In response to different outdoor environmental parameters, the heat pump can use the PVT, ambient air, or solidification latent heat of water in the ice tank as the heat source. This study focuses on analyzing the applicability of this novel system in residential buildings. Firstly, the thermodynamic performance of the system under typical operating conditions is experimentally analyzed, proving that the system can effectively utilize solar energy under low solar irradiation. Then, the operational strategy of the system is optimized with the optimization goal of system exergy efficiency. Finally, the continuous operation performance of the system in winter is simulated and analyzed. The results show that the utilization ratio of solar energy reaches 2/3 in winter. Compared with the traditional ASHP system, the energy-saving rate of the novel system is 73.6 %, which can reduce the carbon emissions by 69 %. These results provide technical guidance for the application of the novel system in residential buildings in cold regions.

Solar-Air Source Heat Pump Water Heater for Scorching Climatic Condition: Energy, Exergy, Economic and Enviroeconomic (4E) Exploration for Sustainable Future

As solar-powered air source heat pump is an emerging water heating technique in scorching climatic conditions, it is necessary to explore their performance in terms of energy, exergy, economic, and environeconomic (4E) perspective. Henceforth, current research experimentally investigates and reports on 4E of Direct Expansion Solar-Air Source Heat Pump water heater for hot regions. A heat pump with a dual source evaporator is proposed in two working modes: solar air source mode and air source mode. The impact of ambient conditions on the thermal performance, such as power consumption, evaporator and condenser capacity, heating time, coefficient of performance, and exergy efficiency of the heat pump water heating system in both the working modes, was experimentally investigated. Results depict the coefficient of performance of the proposed heat pump system in solar air source mode and air source mode in the range of 2.37-5.05 and 2.26-4.21, respectively. On average, the system heating time in solar air source mode is 16.5% shorter than in air source mode. Based on the simulation results, compared to a conventional standard electric heating system, the payback period and lifetime carbon-dioxide mitigation savings cost of the proposed dual-source heat pump system are about 616 days and $179866, respectively.

Yearly photoelectric/thermal and economic performance comparison between CPV and FPV dual-source heat pump systems in different regions

Traditional flat PV heat pumps has low irradiation density, large PV area, and the PV evaporators are always fixed, causing large area occupation and lots of irradiation missing, which limit the application and system efficiency. To solve the problems, a novel concentrated PV-air dual-source heat pump system (CPV-DSHP) was proposed in the previous paper, but the annual performance and economic comparison with flat PV-DSHP (FPV-DSHP) are still blank, which are extremely concerning to researchers. Besides, the paper also fills related content about the impact of irradiation composition on the system performance and economics, as well as the irradiation comparison on tracking CPV and fixed FPV surface. From the calculation of the validated model, it's found that the CPV-DSHP system could capture 6098 MJ and 2213 MJ more solar energy, and produce 282.21 kWh and 100.16 kWh more electricity in Garze and Hefei in a year. The annual concentration efficiency is 82.73 % in Garze where direct irradiation accounts for 68.89 %, which is only 73.15 % in Hefei with 39.84 %.The COPPVT is annually lifted by 0.40 in Garze. Although the two systems could both get payback in 5∼6 years, the CPV-DSHP only shows economic advantages in places with good direct irradiation conditions like Garze.

Eco-economic performance and application potential of a novel dual-source heat pump heating system

Decarbonization of building heating is the key to carbon neutrality. Heat pumps have great potential to replace non-renewable heating devices, thus creating economic and renewable heating systems. To overcome the application challenges of conventional heat pumps (HP), a novel dual-source heat pump (DSHP) heating system and corresponding model are proposed and validated in this paper. Simulated by the validated experiment-based model, the performance of the DSHP heating system is numerically investigated by comparing with different systems in various regions. The results show that the DSHP system has higher seasonal performance factors and near-zero defrosting costs when compared to the conventional HP heating system in different regions, resulting in 1.88%–21.53% reductions in annual heating bills and carbon emissions. Compared to the gas boiler heating system, the DSHP system can achieve 20.64%–54.36% of annual heating bill savings and 14.39%–86.09% of annual carbon reductions in selected regions. The investigation of heating characteristics and eco-economic performance of the DSHP system in different regions provided important guiding significance for the DSHP in global application, and thus contributes to achieving bill-saving and low-carbon heating and sustainable development.

Performance improvement and comparison analysis of the hybrid concentrated dual-source heat pump system regarding proper throttling process

In this paper, a high-efficient and three-dimensional compact heat pump system integrated with the concentrated photovoltaic plus fins (CPV/fin-SAHP) is constructed and built. Smaller space occupation and higher energy utilization are realized. The mathematical model is completed and validated by experimental data. By changing the throttling device and adjusting the mass flow rate, the system performance is improved. From the results, the exergy efficiency, heating capacity, total output, COPPVT, and COPth of the CPV/fin-SAHP system are increased by 7.92%, 13.2%, 11.01%, 4.73%, and 7.12%. Moreover, compared with traditional single-source heat pumps, the CPV/fin-SAHP achieved the highest total output and COPPVT, showing great competitivity and potential. Then two-dimensional environmental variable coordinates are established to explore the compound impact of different ambient factors, and the capacities of the three systems with adjusted opening degrees are also comparatively analyzed. In general, wind speed and ambient temperature have greater impacts on the finned structure system, while the irradiance is dramatically affecting the PV-SAHP system. The compact CPV/fin-SAHP system is less dependent on a single ambient element, showing satisfied performance under various operating ambient and presenting the most potential in comprehensive ability.

Multi-objective optimization of a photovoltaic thermal curtain wall assisted dual-source heat pump system

To address the limitations of single renewable energy applications in cold regions, a novel photovoltaic thermal curtain wall assisted dual-source (air and ground source) heat pump system is proposed. The performance of the system was investigated using numerical simulations and experimental tests. Furthermore, a multi-objective optimization based on the non-dominated sorting genetic algorithm was employed to achieve the optimal design of the hybrid renewable system for a nearly zero-energy building in Shenyang, China. The energy consumption, life cycle cost, and photovoltaic power generation of the system were considered as objective functions. A sensitivity analysis was performed to study the effect of the design variables on the objective functions. The results showed that the seasonal coefficient of performance (COP) of the unit and the proposed system were 3.30 and 2.80, which are increases of 6 % and 5 %, respectively, compared with the dual-source heat pump system. According to the Pareto front obtained, life cycle cost is negatively correlated with energy consumption and positively correlated with photovoltaic power generation. When the area of the photovoltaic thermal curtain wall increased from 0 to 15 m2, the energy consumption and life cycle cost were reduced by 253 kWh and 1118 CNY, respectively.

Dynamic modelling of a dual-source heat pump system through a Simulink tool

In this paper, the performance of a reversible Dual-Source Heat Pump (DSHP) system, able to exploit renewable energy from, alternatively, air and ground sources, is evaluated by using Matlab-Simulink. The actual source exploited depends on a simple control strategy on the basis of the current external air temperature. Yearly dynamic simulations have been carried out by coupling the DSHP to a detached residential building located in Bologna, in which heating and cooling loads are strongly unbalanced, and coupled to a Borehole Heat Exchangers (BHEs) field. Different case studies have been analysed in which the length of the borefield has been modified. The obtained results show that an optimal switching temperature can be determined to maximise the Annual Performance Factor (APF) for a fixed BHE field length. Additionally, it has been demonstrated that DSHPs can be very useful in order to reduce the total required length of the borehole heat exchangers and, consequently, the associated costs, and to solve the problems linked to the ground temperature drift, which can be originated by the presence of an undersized borefield and/or by unbalanced building loads. As a consequence, DSHPs can be suggested for the retrofitting of traditional ground-coupled heat pump systems in presence of undersized BHEs.

Energy Analysis and Cost-Effective Design Solutions for a Dual-Source Heat Pump System in Representative Climates in Europe

Ground-source heat pumps are an efficient technology for heating and cooling in buildings. However, the main limitation of their widespread application is the borehole heat exchanger’s (BHE) high investment cost. Hybridizing GSHP systems may overcome this limitation. This research work analyzes the long-term energy performance of a dual-source heat pump (DSHP) system, which uses the air or the ground as external heat/sink sources, in three representative European climates. First, a BHE cost-effective design solution is proposed for each climatology; then, a complete energy analysis is carried out, and the optimal source control parameters that best enhance the system performance in each climate are determined with the use of a complete dynamic model of the DSHP system developed in TRNSYS. Simulations were carried out for a 25-year operation period. Results show that the DSHP maintains the efficiency during the simulated period, with deviations lower than 1.7% in all cases. Finally, the source control optimization method results in only slight efficiency gains (<0.35%) but with a stronger effect on the ground/air use ratio (up to 25% use of air in cold climates), reducing the thermal imbalance of the ground and leading to a consequent BHE size length and cost reduction.

Numerical modeling and parametric study of a dual purpose underground thermal battery

Integrating thermal energy storage with building energy systems can enable flexible building electric demands at buildings to help mitigate the mismatch between electricity supply and demand. A novel building heating and cooling system that integrates a dual-source heat pump with hybrid thermal storage named dual-purpose underground thermal battery (DPUTB) has been developed for reshaping building electric demands. The proposed DPUTB integrated geothermal heat pump system is an original innovation that enables Grid-interactive Energy Efficient buildings. This paper focuses on the study of the novel DPUTB. The DPUTB works as both a thermal storage tank (an inner tank) and a ground heat exchanger (an outer tank separated from the inner tank by the insulation material). High fidelity and computationally effective models are needed to predict the performance of the novel DPUTB. This study has developed a simplified dynamic model for the DPUTB according to heat transfer and energy conservation principles and validated it by using experimental data obtained from testing a small-scale DPUTB apparatus. A parametric study was conducted to identify a design that can achieve the target thermal storage performance of load shift and energy efficiency. The parametric study results show that the inner tank shell thermal conductivity and the phase change material's melting point are the two most influencing factors on the performance of the DPUTB. One single full-size DPUTB with the identified design could provide 1-ton cooling (3.51 kW) with the supply temperature lower than 11 °C for 4 hours in summer after being fully charged in 8 hours. The inner tank filled with phase change material is for cooling thermal storage as a latent tank in the design. However, its capacity can be as high as 60 MJ as a sensible water tank for heating storage in winter. In the future study, the DPUTB model will be incorporated into the dual-source heat pump system for evaluating the overall system performance of demand side management in the long term.

Energy Analysis and Techno-Economic Assessment of a Novel Dual-Source Heat Pump System in Different Climates in Europe

Energy Analysis and Techno-Economic Assessment of a Novel Dual-Source Heat Pump System in Different Climates in Europe

Data on the environmental performance analysis of a dual-source heat pump system.

This data article reports supplementary input and output data related to the research article “Environmental performance analysis of a dual-source heat pump system” on the life cycle assessment evaluation of an heat pump prototype, able to use alternatively the air and the ground as external heat sources. Primarily, the present article shows the life cycle inventory input data of the system under study and of the conventional air and ground heat pump systems, which were used for comparison. Secondly, complete numerical results are exposed, which are showed only graphically and in an aggregated form in the main article. Data include normalised and unaggregated environmental impacts of each investigated life cycle phase. The article also reports the complete results of the sensitivity analysis conducted using different assumptions on the energy mix and on the energy use.

Energy Analysis of a Dual-Source Heat Pump Coupled with Phase Change Materials

Installation costs of ground heat exchangers (GHEs) make the technology based on ground-coupled heat pumps (GCHPs) less competitive than air source heat pumps for space heating and cooling in mild climates. A smart solution is the dual source heat pump (DSHP) which switches between the air and ground to reduce frosting issues and save the system against extreme temperatures affecting air-mode. This work analyses the coupling of DSHP with a flat-panel (FP) horizontal GHE (HGHE) and a mixture of sand and phase change materials (PCMs). From numerical simulations and considering the energy demand of a real building in Northern Italy, different combinations of heat pumps (HPs) and trench backfill material were compared. The results show that PCMs always improve the performance of the systems, allowing a further reduction of the size of the geothermal facility. Annual average heat flux at FP is four times higher when coupled with the DSHP system, due to the lower exploitation. Furthermore, the enhanced dual systems are able to perform well during extreme weather conditions for which a sole air source heat pump (ASHP) system would be unable either to work or perform efficiently. Thus, the DSHP and HGHE with PCMs are robust and resilient alternatives for air conditioning.

Environmental performance analysis of a dual-source heat pump system

Using all phases of a life cycle assessment (LCA), this paper analyses the environmental impact of a dual-source heat pump (DSHP) system that uses either the air or the ground as external heat sources. Data on the production were provided by the manufacturer of the heat pump prototype. The use phase was considered by evaluating the seasonal and annual energy performance of the system, using dynamic simulations. The system maintenance and end-of-life were modelled in accordance with the current regulations and statistical data in this sector. The Ecoinvent database was used as a reference for background data. The ReCiPe, CED and IPCC 100a impact methods were used to assess the environmental impact categories. The results were compared with those of conventional air and ground source heat pump systems. A sensitivity study on the influence of the energy in the use phase was carried out in terms of a variation in energy use and for different energy mixes, including photovoltaic energy. The results demonstrated the environmental validity of the technology in comparison with the two conventional heat pumps used for residential applications in different conditions. The results could be used by heat pump manufacturers to improve the design and performance of their products, by designers in the selection of thermal technologies, and by researchers involved in the study of similar emerging renewable energy technologies.

Energetic and economic optimization of the yearly performance of three different solar assisted heat pump systems using a mixed integer linear programming algorithm

This paper presents a yearly energetic and economic assessment of three different solar assisted heat pump concepts integrated with electrical and thermal storages and applied to a single-family house. The three heat pump-based systems are (i) a conventional air-to-water heat pump plus photovoltaic solar modules, (ii) a water-to-water heat pump coupled to hybrid photovoltaic-thermal solar modules and (iii) a dual source heat pump integrated with hybrid photovoltaic-thermal solar modules. The energetic and economic analysis is performed using physically-based models of each component for different numbers of solar modules and sizes of the electric storage. The maximum economic saving of these highly integrated systems is determined through an optimization algorithm based on the mixed integer linear programming technique. The results show that the dual source heat pump system with the largest battery size is the system that achieves the highest energetic performance, i.e. 77% primary energy saving with respect to traditional boiler-based system, whereas the lowest operating cost and the highest economic saving are obtained using the conventional air-to-water heat pump without any electric storage since it achieves 31% economic saving compared with the baseline system.

Comparative analysis of solar-air dual source heat pump system with different heat source configurations

The concept of solar-air dual source heat pump has been proposed to overcome the limitations of single source heat pump system. In this paper, a comparative investigation is presented among three types of solar-air dual source heat pump with different heat source configurations: solar-air series source heat pump (SA-SHP), solar-air parallel source heat pump (SA-PHP) and air-solar series source heat pump (AS-SHP). The impact of environmental parameters has been discussed, and the optimal working condition for each system has been identified. The results indicate that SA-SHP is suitable for working under the environment with low solar irradiation, AS-SHP shows the best performance under the condition with low ambient temperature and high solar irradiation, and SA-PHP can achieve the optimal state at high ambient temperature or high solar irradiation. The dynamic performance of SA-SHP, SA-PHP and AS-SHP in the daytime has been compared. The dynamic behavior of each system is significantly different. The COP of SA-PHP is the highest ranging from 4.50 to 4.58, followed by AS-SHP ranging from 4.39 to 4.50, and the COP of SA-SHP is the lowest ranging from 4.33 to 4.41. Moreover, the annual performance and economic feasibility for each system in different climatic regions are evaluated.

Design and performance simulation of a novel hybrid PV/T-air dual source heat pump system based on a three-fluid heat exchanger

To pursue an environmentally friendly and efficient heating solution, a novel hybrid PV/T-air dual source heat pump based on a three-fluid heat exchanger was proposed. In the heating season, the system can absorb energy from solar and air simultaneously; in the non-heating season, the PV modules can be cooled actively or passively by heat pipe. The system was designed to provide heating and electricity for a rural single-family house in Beijing, and a mathematical model was developed. The results indicated that: (1) compared to a conventional air-source heat pump, the energy consumption of this system throughout the heating season was reduced by 13.1%; (2) for electricity generation, compared to a conventional PV panel, the electrical energy output increased by 14.7%. Additionally, the proposed integrated system has the advantages of a compact structure, standardized production, easy maintenance, and no risk of freezing.