Solar Assisted Heat Pump System Research Articles

A comparative investigation of solar-assisted heat pumps with solar thermal collectors for a hot water supply system

The concept of a hybrid solar collector was newly proposed, which has a solar thermal receiver part and air-source receiver part that can operate as a fin-tube exchanger with fans when there is no solar radiation. This is the distinguishing feature of the hybrid solar collector. The solar-assisted heat pump system applying the hybrid solar collectors was also introduced. To analyze the proposed solar-assisted heat pump system, a simple thermodynamic model considering the electric power consumption for fans and circulation pumps was developed. The model results for the air-source heat gain were validated from the corresponding experimental data with the maximum error of 8.8%. Based on the parametric study, the increase of the collector area and the absorption coefficient led to the enhancement of the system performance of the solar-assisted heat pump with hybrid solar collectors. In addition, a comparative investigation was carried out for three different indirect solar-assisted heat pumps. Regarding of annual operation hour, the serial-type solar-assisted heat pump was worst at 3509 h over a year. On the other hand, the solar-assisted heat pump with hybrid solar collectors had the superior performance of 7036 h. If the efficiency of the hybrid solar collector was as superior as the conventional flat plate solar collector, the system COP of the suggested solar-assisted heat pump system in the winter season could be improved by 5.1% compared with that of the parallel-type solar-assisted heat pump system. Consequently, it clearly showed the feasibility of the suggested solar-assisted heat pump system as a standalone system for hot water supply due to the merits of significantly extending the annual operation hour, the simple system configuration, and the economic aspect with lower capital cost.

Energy, exergy and exergoeconomic analysis of solar-assisted vertical ground source heat pump system for heating season

The purpose of this study is to evaluate the experimental performance of a solar assisted vertical ground source heat pump system (VGSHP) for the winter climatic conditions of Mardin, which is in the South-Eastern Anatolia region of Turkey. For this aim, an experimental analysis was performed on solar assisted VGSHP system, which was designed to meet the heating needs of an experimental room, during the heating season (10.01.2013/03.31.2014). The experimentally obtained results were used to calculate energy, exergy and exergoeconomic analyses of the system and its components. The energy efficiency, exergy efficiency and exergoeconomic factors of the entire system were 67.36 %, 27.40 % and 60.51 %, respectively. In this study, the system was proposed for disseminating the use of alternative technologies supported by renewable energy systems and it has been tested for the first time in Mardin to meet its heating needs with convectional systems. The experimental results showed that the proposed solar assisted VGSHP system can be used for residential heating in Mardin and similar regions. As a result, it has been detected that the system is very effective in both reducing energy consumption and decreasing emissions of green-house gases.

Experimental study on the heat gain of water in hybrid solar collector integrated with fin-and-tube heat exchanger with respect to air and water flow rate

Solar assisted heat pump system is the system using solar thermal energy that can lead to the improvement of performance of heat pump by transferring solar thermal energy obtained from solar collector to evaporator of the heat pump for evaporation of refrigerant. In traditional system, solar collector can get a thermal energy only from solar radiation. So, the collector is hard to be used when the solar radiation is not enough such as cloudy day or night even though these collector take up much space. Thus the hybrid solar collector that has fin- and-tube heat exchanger have been developed for getting a thermal energy from not only solar radiation but also ambient air. Due to the fin-and-tube heat exchanger, this collector can get a thermal energy from ambient air for heating chilled water by evaporation of refrigerant in heat pump system. At this time, heat gain of water from ambient air by the collector needs to be confirmed before combining with real heat pump system. Thus, in this study, heat gain of water in the hybrid solar collector was investigated experimentally with respect to air and water flow rate on the various temperature difference between inlet air and water. As a results, heat gain of water was shown maximum value of 900W and it was increased with increment of air and water flow rate. Also, heat gain of water was changed linearly with increment or decrement of temperature difference between inlet air and water on the specific air and water flow rate. Furthermore, relationship between heat gain of water and operating conditions was also confirmed that can be used for decision of collector area and heat pump capacity for designing solar assisted heat pump integrated with this collector.

Multi-objective optimization of a solar-assisted heat pump for swimming pool heating using genetic algorithm

A proper assessment of heating systems for swimming pools should evaluate the compromise between comfort level and the willingness to pay for it. The present work presents a multi-objective optimization of indirect solar assisted heat pump systems for outdoor swimming pool heating. Four different configurations are reported; (air-to-water heat pump and three solar assisted heat pumps, air-to-water, water-to-water and a dual-source); and evaluated in six different locations (three location in Chile: Antofagasta, Santiago, and Concepción; and three locations in Brazil: Brazilia, São Paulo, and Florianópolis). The methodology approach configures two objectives optimization, the minimization of the Annualized Life Cycle Cost (ALCC) and the maximization of the comfort level offered by the swimming pool. The optimization scheme consists of using a combination of tools: the energy-savings potential of i-SAHP are evaluated using the TRNSYS software in combination with GenOpt; and the economic modeling and optimization are performed in the MATLAB environment, using an approximation model and variant of NSGA-II genetic algorithm for building the Pareto frontiers. The optimization results demonstrate that solar-assisted configurations present significant improvements in performance for almost all locations, reaching the same levels of comfort at lower ALCCs when compared with the ASHP configuration.

Exergy analysis of direct-expansion solar-assisted heat pumps working with R22 and R433A

In this paper, the exergy performance of direct-expansion solar-assisted heat pump systems working with R22 and R433A (mixture of R290 and R1270, 70:30 by mass) was experimentally assessed. The experiments were carried out under the metrological conditions of Calicut in India. (Longitude and latitude of location are $$75.78 ^{\circ }\hbox {E}$$ and $$11.25^{\circ }\hbox {N}$$ , respectively.) The artificial neural network model was developed for simulating the performance of a direct-expansion solar-assisted heat pump system to have realistic performance comparison. The experimental data observed during the year 2016 were used for training and testing the performance of network. The results showed that the network predicted exergy performance of a direct-expansion solar-assisted heat pump was found to be closer to the experimental results with a maximum fraction of absolute variance, minimum root-mean-square values and coefficient of variance. The system exergy destruction of R22 and R433A was found to be 1.36 and 1.25 kW, respectively. Moreover, R433A is identified as an energy-efficient and environmental-friendly alternative to phase out R22 in solar-assisted heat pump systems.

Experimental studies of a variable capacity direct-expansion solar-assisted heat pump water heater in autumn and winter conditions

A variable capacity direct-expansion solar-assisted heat pump (DX-SAHP) system was studied experimentally under the meteorological condition of Qingdao located in the East China area. It was mainly made up of a solar collector/evaporator, a variable-frequency rotary-type hermetic compressor, a micro-channel condenser, and an electronic expansion valve. A series of experiments were carried out, in order to evaluate the performance of the DX-SAHP system during the autumn and winter period, including the system coefficient of performance (COP), the electric power to the compressor, the evaporating and condensing pressures, and the discharge temperature of the compressor. Experimental results showed that for the base case considered in this study, under the sunny and overcast day conditions in the autumn, the average COP was higher than 4.0 and 3.0, respectively. Even in the extreme weather of the winter conditions, the average COP was also higher than 2.5. In general, with the increase of water temperature, the compressor speed increased gradually, and the corresponding electric power of the compressor increased sharply. The condensing pressure also increases, as does the discharge temperature of the compressor, while the evaporating pressure remains a relatively low level with smaller variations.

Experimental performance analysis of a direct-expansion solar-assisted heat pump water heater with R134a in summer

A direct-expansion solar-assisted heat pump (DX-SAHP) system for domestic hot water supply was built and tested, which mainly consisted of a bare flat-plate collector/evaporator with a surface area of 2.1 m2, a variable-frequency rotary-type hermetic compressor, a hot water tank with the volume of 0.2 m3 surrounded by a micro-channel condenser, and an electronic expansion valve. A series of experiments were carried out to test the system performance under typical summer weather conditions in Qingdao, China. The effects of various parameters, including solar radiation intensity of 258–634 W·m−2, ambient temperature of 28–34 °C, compressor speed of 2500–6000 rpm and final water temperature of 50–60.3 °C, on the system performance are analyzed. Experimental results show that the system coefficient of performance(COP) could be enhanced with the increase of the solar radiation intensity or the ambient temperature, and with the decrease of the compressor speed or the final water temperature.

Performance studies of R433A in a direct expansion solar-assisted heat pump

ABSTRACTEnergy assessment of a simple direct expansion solar-assisted heat pump system has been experimentally assessed with R433A as a possible alternative to R22. An artificial neural network integrated genetic algorithm model was developed to assess the performance system. The data obtained from the experimentation at different ambient conditions are used as the training data for the ANN network. The back propagation learning mechanism with variants Lavenberg-Maguardt with 20 neurons in the hidden layer were used in modelling of ANN. The values obtained from the analysis using ANN are optimised further by integrating the ANN procedure with GA. The results indicated that R433A has 6.4% and 1% lower instantaneous compressor power consumption and heating capacity compared to R22. Energy performance ratio of R433A was found to be about 5.67% higher compared to R22. The results confirmed that R433A can be used as a possible alternative to R22 DX-SAHP systems.

Model predictive control for a solar assisted ground source heat pump system

There has been an increased interest in cost and energy efficiency for heating, ventilation, and air conditioning systems for buildings since these are responsible for between 25% and 40% of total building energy demand. Solar assisted ground source heat pump systems which combine solar and geothermal energy are gaining attention due to their higher efficiency and greater functional diversity when compared with conventional systems. This paper presents a mixed integer linear programming approach to minimize the operational cost of a solar assisted ground source heat pump system, considering time-of-use electricity price (peak, off peak). Two types of system configurations are investigated in order to examine the effect of thermal storage in the system. Two different objectives are explored: minimizing electricity consumption and operational cost. The results indicate that the system having integrated thermal storage leads to improved peak shaving, which reduces the need for expensive peak electricity production for the grid, and has a reduction of operating cost by 7.8% when it is optimized for minimal cost.

A novel type solar assisted heat pump using a low GWP refrigerant (R-1233zd(E)) with the flexible solar collector

Low GWP refrigerants have been extensively paid attention to solve the environmental problems. Meanwhile, the integration of systems such as a solar assisted heat pump has been also developed consistently to compensate shortcomings of individual systems and enhance the efficiency of the system. In this study, the performance of the novel type solar assisted heat pump system using a low GWP refrigerant (R-1233zd(E)) with the flexible solar collector is investigated by experiments. R-1233zd(E) is a low GWP refrigerant with GWP lower than 7.0. The performance of solar assisted heat pump system using R-1233zd(E) is firstly compared with that using R-134a. From the study, it is found that the flexible solar collector shows the average efficiency of 40% irrespective of the weather conditions. In addition, high performance of the solar assisted heat pump using R-1233zd(E) is obtained by controlling the mass flow rate and heat source temperature. Finally, although the heat capacity of the solar assisted heat pump using R-1233zd(E) is lower than that with R-134a at same conditions, COP of the system using R-1233zd(E) shows a higher value due to low power consumption rate compared to that using R-134a.

Experimental study of solar assisted ground source heat pump system during space heating operation from morning to evening

Experimental investigation of solar assisted ground source heat pump system has been carried out to understand performance variation during space heating for continuous eight hours operation from morning to evening for Indian winter climatic conditions. Heat extraction rate from solar collector and ground exchanger were monitored from 9 AM to 5 PM on hourly basis by measuring the inlet and outlet temperatures of heat transfer fluids. A detailed thermodynamic energy balance carried out on hourly basis indicates maximum heat loss is observed at 12 noon at which maximum heat extraction from solar collector and ground heat exchanger was obtained. Maximum COP of the SAGSHP system is observed at 12 noon for all the three mass flow rates, however, the COP decreases up to 3 % with increase in severity of winter due to increase in heat loss. About 44 % increase in mass flow rate of heat carrying fluids has enhanced the heat extraction rate up to 18 %, resulting in about 3 % increase in room temperature. The SAGSHP system was able to maintain the room temperature at about 20 to 21 °C when the ambient temperature was at about 12 °C.

Exergetic-Economic analysis and optimization of solar assisted heat pump using Multi-objective Genetic Algorithm

This study proposes the use of two-stage heat pump systems (SAHPs) for high temperature applications, 105°C. This system integrates solar thermal collectors and heat pumps into a hybrid system to meet the 400 kW heating load. The aim of this research is providing a method to deliver heat with sustainable energy resource, than to improve the performance of the system which is indicated by low exergy destruction. The model creation, performance evaluation and the optimization of solar assisted heat pump system are discussed in this paper. This system used R1234ze (E) as working fluid. A genetic algorithm is employed to optimize operation condition of the system. To ensure that the optimal solution obtained from the proposed method is an optimum condition, three constraints are selected, including evaporation temperatures, condensing temperatures and compressor temperatures while exergy destruction and total cost as the objective functions. The result showed that the system has an optimum condition at evaporating temperature of 317 K, Flash Tank temperature of 353.6 K and condensing temperature of 380.4 K with exergy destruction of 70.21 kW and total cost of 63,441 US$.

Control strategy and experimental analysis of a direct-expansion solar-assisted heat pump water heater with R134a

A direct-expansion solar-assisted heat pump (DX-SAHP) system was designed and built in Qingdao China, which was used to supply domestic hot water. The system mainly consisted of a bare solar collector/evaporator with area of 1.56 m2, a rotary-type hermetic compressor with rated power of 400 W, an electronic expansion valve (EEV) and a micro-channel aluminum flat tube condenser with single surface area of 0.435 m2 surrounding a 0.195 m3 water tank. The system was charged with 800 g of R134a. Based on the degree of superheat at the outlet of the solar collector/evaporator, a control strategy for the system was developed and tested over a wide range of operating conditions, which proved that it could regulate the degree of superheat in range of 5–10 °C effectively. Then the thermal performance of the system was experimentally studied under various operating conditions. Experimental results showed that for most of the time in 2016, when the 0.195 m3 water was heated to the temperature between 55 °C and 60 °C, the coefficient of performance (COP) of the prototype device was higher than 3.0. As the solar radiation intensity or ambient temperature increased, the COP of the system increased, and the heating time decreased.

Numerical simulation and experimental validation of a solar-assisted heat pump system for heating residential water

This paper presents a model for numerical simulation with a distributed parameter for a solar assisted heat pump. The model of evaporator and condenser are based on equations of continuity, momentum and energy conservation. Compressor and expansion valves are modeled using semi-empirical models based on data presented in its respective datasheets. This model provides spatial and temporal profiles of temperature, pressure, enthalpy, mass flow and density of the refrigerant. Model validation is achieved by comparing simulation results and experimental data. These comparison shows good results for the model in transient and steady state. Final section presents the conclusions obtained from the comparison between the simulation data and the experimental data, some aspects to be corrected in the simulation for the reduction of time required and some mechanical modifications for the presented prototype.

Environmental performance of a solar assisted hybrid power gas heat pump based on life cycle assessment

Energy crisis and environment damage are the two worldwide urgent problems and building energy plays an important role in the energy and environment field. To reduce heating and cooling energy consumption in buildings, a novel solar assisted hybrid power gas heat pump system is proposed. The novel system runs in five working conditions and applies solar energy combined with battery pack to guarantee the engine always works in its economic zones. Because of the complexity of photovoltaic panels in environment effect, the life cycle assessment method is introduced to evaluate the whole system’s energy and environment effect. According to different photovoltaic ratios, simulation shows that the application of solar panels achieves a significant improvement in energy consumption while also causes a large mount in environment damage. At last the environmental payback time is put forward and the best environment payback time for the photovoltaic hybrid power gas heat pump system is 13.4 years at a photovoltaic ratio of 40%.

Corrigendum to “Effects of latent heat storage and controls on stability and performance of a solar assisted heat pump system for domestic hot water production” [Solar Energy 150 (2017) 394–407

Corrigendum to “Effects of latent heat storage and controls on stability and performance of a solar assisted heat pump system for domestic hot water production” [Solar Energy 150 (2017) 394–407

Indirect expansion solar assisted heat pump system for hot water production with latent heat storage and applicable control strategy

Integration of renewable energy with energy conversion application for hot water production is a significant technology to be studied for industrial, commercial and residential proposes. It has been further enhanced since the international energy agency (IEA) puts effort to standardize such kind of technology. In this paper, a novel study has been carried out experimentally to control an indirect solar assisted heat pump (IDX-SAHP) system integrated with a latent heat storage (PCM) tank. The PCM heat exchanger tank was designed specially and controlled automatically which allowed storing excess energy during the day and releasing it when needed. In addition, a system control strategy has been purposely designed and implemented in a Building Management System (BMS) to ensure the stable and reliable system operations. The experimental results show that the PCM heat exchanger tank installation has a significant effect on the system operation stability and can improve the COP of the IDX-SAHP system at different weather conditions and a specified hot water load profile.

Solar assisted heat pump with ice storage for a 19’000 m2 retrofitted multi-family building complex

This paper concerns the evaluation of a 500 kW solar assisted heat pump system with combined ice storage installed on “La Cigale”, a 19’000 m2 retrofitted multi-family building complex situated in Geneva. The presented results are based on a detailed monitoring campaign, covering a full year of operation, in real use conditions. After presenting the system concept, the system performance is analyzed by way of a detailed Sankey diagram (heat and electricity flows between the various production units, heat storages, and demand units), along with specific analysis of the diverse sub-systems. As a complement to the monitoring results, we present a simulation tool that was specifically developed for this type of application, and its validation against monitoring data, in terms of annual values and monthly profiles of the diverse energy flows.

Life cycle assessment optimization of hybrid power gas heat pump integrated with photovoltaic

Building energy consumption accounts for a large proportion in the total social energy consumption and solar energy plays an important role in the building renewable energy system. A novel hybrid power gas heat pump system integrated with photovoltaic is put forward in this paper. An optimization design based on life cycle assessment for the solar assisted hybrid power gas heat pump system (SHPGHP) is proposed in consideration of three main environmental impact factors: human health, ecosystem quality and resources. The normalized environmental impact for the system during the whole life cycle is chosen as the objective to minimize the life cycle environmental impact. The influence of main independent decision variables is employed including the photovoltaic ratio, transmission ratio and mixing degree. Results show that the optimal photovoltaic ratio is 0.4. The system's environmental impact potential increases with the increase of transmission ratio and decreases with the increase of mixing degree.

Development of a new dynamic test procedure for the laboratory characterization of a whole heating and cooling system

The performance of heating and cooling systems are affected by their dynamic operating conditions. Asa consequence, a sound evaluation of system performance should be done through a dynamic test procedure. However, the complexity, the cost, and the time for such type of experimentation are obstacles to the diffusion of this test method.A new whole system test procedure was developed to reduce its potential failure. The test method considers the emulation of system components that cannot be installed in the laboratory, while the selection of short-yet-significant test sequence is performed classifying the days of the year with clustering analysis.The procedure was applied to a solar-assisted heat pump system in four different European climates. The seasonal performance figures are extrapolated from the test results and compared with the numerical simulations of the entire heating and cooling system. In all test cases the seasonal performance factors are lower than the simulated ones by approximately 10%. The results obtained with dynamic tests confirm the necessity of their implementation, since they provide useful information to improve the system layout and control. In this way, the manufacturers can introduce more efficient products into the market.