Solar Air Source Research Articles

Simulation and performance analysis of combined parallel solar thermal and ground or air source heat pump systems

The combination of solar thermal (ST) systems and heat pumps (HP) is a promising hybrid heating system concept for efficient energy supply of buildings. In this work, a simulation study on the performance of combined ST and HP systems and a comparison with systems without ST collectors for different types of buildings and climates is presented. With regard to the dominating market-available systems, the evaluation is limited on systems with parallel integration of ST collectors. For a better transparency of the results, the simulation models and the main model parameterization are explained in detail. The results of the simulations show that the performance of HP systems can significantly be increased by adding a ST system. The relative increase of the performance decreases with increasing space heating demand of the building and is lower for climates with low ambient temperatures. In contrast, in most cases the absolute electricity savings increase with increasing space heating demand and are higher for systems with air source HPs. The seasonal performance factor (SPF) of parallel solar thermal and ground source heat pump (SGSHP-P) systems is between 0.5–1.1 (Strasbourg) and 1.0–2.0 (Helsinki) higher than the SPF of parallel solar thermal and air source heat pump (SASHP-P) systems with the same ST collector area. Hence, the difference between the performance of SASHP-P and SGSHP-P systems increases with increasing heat load and decreasing ambient temperatures of the location. However, in case of moderate climates like Strasbourg, SASHP-P systems can achieve the same or even higher values of SPF than ground source heat pump (GSHP) systems without ST collectors. Especially for buildings with low energy demand for space heating, the SPF is higher (up to 78.5% with a collector area of 25m2) and the systems can compete with each other. In a nutshell, in particular if the investment costs of a borehole heat exchanger and a ST system are similar or if there is no possibility to use a GSHP system with borehole heat exchanger, using a SASHP-P system may be a useful opportunity for a heating system concept with high energy performance and low electricity demand.

Energy and exergy analysis of solar integrated air source heat pump for radiant floor heating without water

The solar integrated air source heat pump (SIASHP) with R407c for radiant floor heating without water (RFHW) is proposed and investigated. The first generation of prototype of SIASHP RFHW system developed is suitable for marketization at the present. On the basis of experiment room in Taiyuan, the energy and exergy analysis of SIASHP RFHW system are implemented, compared with the same type of conventional air source heat pump (ASHP). On the condition of −9.9°C outdoor calculated dry-bulb temperature for space heating in winter, Taiyuan and a 130W/m2 solar irradiance, the 76.8% exergy efficiency of SIASHP is 7.9% higher than the 71.1% exergy efficiency of ASHP. The 2.55 COP of SIASHP is 5.8% higher than the 2.41 COP of ASHP. From 9:00 to 21:00, the 2.89kWh power consumption of SIASHP is 7.4% lower than the 3.12kWh of ASHP. The 52.7% process quality number of SIASHP is higher than the 51.4% of ASHP. The SIASHP RFHW system with no water pipe exposed to outdoor environment is safe and convenient for the narrow and vertical outdoor installation space of high-rise building users to meet their individual demand of space heating.

The Study on the Performance of Solar Photovoltaic and Air Source Heat Pump Composite Building Energy Supply System

A new type solar photovoltaic and air source heat pump composite building energy supply system was designed for the purpose of saving energy. The system can realize a variety of functions needed for building, including the annual power supply, heating in winter, as well as cooling in summer. 1HP rotor compressor is used in the heat pump system, and the other parts of the heat pump match the 1HP heat pump. In this paper, the operation mode of PV/T and dual heat source heat pump operating at the same time in winter was experimental studies and the performance of the system was analyzed. Results shows that in the environmental conditions of the average temperature of 4.3℃and the average irradiance of 644 W/m2, the maximum of generating efficiency reaches 15.3%, and the maximum of generated power reaches 827W, and the average generating efficiency is 12.1%, and the average of heat-collecting efficiency is 38.8%, and the average of comprehensive efficiency of PV/T system is 50.9%, and instantaneous COP of the heat pump changes from 2.3 to 3.0, and the average COP is 2.6.

Experiment Study on Heating Performance of Solar-Air Source Heat Pump Unit

Ambient temperature has a great impact on heating performance of air source heat pump. Outdoor fin-tube heat exchanger of air source heat pump usually frost on low temperature conditions, which results low operation efficiency and further deterioration. A solar-air heat pump unit was established and outdoor fin-tube heat exchanger of air source heat pump is used jointly by the refrigerant and solar hot water. Running parameters such as outlet temperature of refrigerant, heat capacity and COP of air source heat pumps of composite heat pump units were tested respectively under the standard working conditions and low temperature conditions. The results showed that the performance of solar-heat pump is significantly improved, compared with the single air source heat pump. The effect is more obvious with increasing of the temperature of the solar hot water temperature. Under standard working conditions (ambient temperature 7℃), the unit heat capacity reached 60.9kW、62.9kW和64.5 kW，increased13.4%、17.1%、20.1% respectively and the coefficient of performance also increased 13.9%、17.4%、20% respectively. Under low temperature conditions (ambient temperature -5℃), the unit heat capacity increased16%, 23.3% and 27.6% respectively, up to 49.52kW、52.67kW、54.5kW，and COP also increased 31.2%、38.6%、45.5% with different solar hot water temperature 20°C, 25°C and 30 °C.

Experimental study on performance of a solar-air source heat pump system in severe external conditions and switchover of different functions

A phase change material (PCM) based solar-assisted air source heat pump (PCM-SAHP) composed of an air source heat pump (ASHP), a PCM unit, and a solar thermal collector is proposed. In this work, the system performance is experimentally tested in the severe external conditions, and the effect of switchover of different functions on the system stability is examined as well. The results indicate that a great improvement in both the system efficiency and heating/cooling capacity in the severely external conditions is achieved by the application of the PCM unit in the SAHP cycle. The outdoor air temperature throughout a whole day-night cycle has a significant effect on the system cooling performance. In contrast, the solar-heated hot water temperature, rather than the ambient temperature, exerts a great influence on the system heating performance. In order to maximize the system capacity and efficiency, how to match the capacity of the PCM unit and the compressor is crucial. In addition, the effect of switchover of different functions on the system stability is unapparent. Finally, the compatibility of the PCM unit with the SAHP system is concluded based on kinds of individual approach.

Analysis of system improvements in solar thermal and air source heat pump combisystems

A solar thermal and heat pump combisystem is one of many system alternatives on the market for supplying domestic hot water (DHW) and space heating (SH) in dwellings. In this study a reference solar thermal and air source heat pump combisystem was defined and modelled based on products available on the market. Based on the results of an extensive literature survey, several system variations were investigated to show the influence of heat pump cycle, thermal storage and system integration on the use of electricity for two houses in the climates of Zurich and Carcassonne. A singular economic cash flow analysis was carried out and the “additional investment limit” of each system variation was determined for a range of economic boundary conditions. This is the maximum extra investment cost for the system variant compared to the reference system that will give a break even result for a 10year period. The results show that variations in electricity price affects the additional investment limit far more than the other economic parameters. Several of the variants show potential for achieving a cost benefit, but the potential varies a lot depending on load and climate boundary conditions. For all variants, the biggest difference in electricity savings was found for Zurich rather than in Carcassonne, which is explained by the larger heating load. However, in three cases the largest savings were for the SFH45 house despite the fact that the annual electricity use of the system is much lower than that for the SFH100 house, 3581kWh/year compared to 8340kWh/year. This was attributed to the fact that, in these cases, the operating level of the space heating circuit played a significant role, the SFH45 house being supplied with a 35/30°C heating system while the SFH100 was supplied with a 55/45°C heating system.

Experimental study on the operating characteristics of a novel photovoltaic/thermal integrated dual-source heat pump water heating system

This paper proposed a novel solar photovoltaic/thermal (PV/T) integrated dual-source heat pump (DSHP) water heating system. This system used the circulating water in solar photovoltaic thermal system and air source to provide domestic hot water for domestic usage, and meanwhile decreased the cooling water temperature for the PV/T panel to improve the electrical conversion efficiency. An experimental PV/T integrated DSHP unit was established in Shanghai to examine its performance. The influences of the inlet temperature of the evaporator and the hot water temperature under water–water mode and the influence of the outdoor temperature under air–water mode on the system performance were studied. Energy analysis was conducted between water–water mode and air–water mode. The cooling effect and photovoltaic efficiency of the PV/T panel were evaluated. The results showed that when water side evaporator was used, the PV/T panel operating temperature can be decreased up to 45 °C, and the electrical conversion efficiency yielded a surplus of 10.3%.

Reliability verification of a solar–air source heat pump system with PCM energy storage in operating strategy transition

In the recent decade, with solar energy assisted heat pump systems have increasingly developed. In the previous studies, a hybrid air source heat pump (ASHP) system was proposed, which coupled with latent heat thermal energy storage (LHTES) and solar thermal collector, for operating in various types of configurations. This paper describes the approach and principle for organizing the hybrid system in detail. Thereafter, a phase change material (PCM) based solar–air source heat pump (PCM-SAHP) prototype was set-up and implemented under variant testing conditions. Experimental results demonstrate that the PCM-SAHP system presented remarkable advantages on correcting the mismatch between supply and demand of thermal energy and electricity. Further, when the ambient temperature was higher than 38 °C, cooling COP of the hybrid system enhanced by 17%, compared with that of ASHP system under same surroundings. During the days that outdoor air temperature was below −10 °C, heating COP of the PCM-SAHP system rose by 65% comparing with that of ASHP system. In additional, switching operating strategies during system running will scarcely result in the violent or continuous fluctuations on the operating parameters. Therefore, the efficiency of the PCM-SAHP systems can be improved with capacity lapse avoiding, and exhaust controlling as well.

Direct use of solar energy as heat source for a heat pump in comparison to a conventional parallel solar air heat pump system

In this paper different combinations of solar energy and heat pump systems are compared and investigated through transient system simulations. The focus is on a small capacity heat pump (HP) with a heating capacity rate of 5.36kW. The building (single family house 140m2) which are considered in this paper have a space heating demand of about 45kWh/m2a. Based on a conventional air source HP and a parallel solar air source HP system, serial solutions for the combination of solar-HP systems are defined and analysed. For the consideration and evaluation of different systems through transient system simulations, a semi-physical HP-model is used, which offers the possibility to use two evaporators in series. With a combined parallel solar air source HP system the system performance (SPFSystem=3.65) can be increased significantly compared to a conventional air source HP system (SPFSystem=2.55). Unglazed selectively coated absorbers as source for the HP offer the advantage, that the collector can be used as an air heat exchanger. If solar radiation is available, higher temperatures at the evaporator of the HP can be achieved, compared to a conventional air source HP system. By the integration of unglazed solar absorbers as source for the HP the HP performance can be increased significantly (SPFHP increases from 3.25 up to 3.55 compared to a conventional air source HP).

Feasibility Study about Solar Energy-Air Source Heat Pump System in Cold Region Rural Residential Applications

This paper proposes a solar-air compound source heat pump system, for the rural residential area of Hebei and independent villas. The system can realize heating in winter and refrigerating in summer, and demand of heat water. This paper simulates and analyzes the winter heating situation of this system. The entire heating season, heat collecting efficiency of the solar collector is 0.45 in average, and solar guarantee rate is 46%. Solar-air compound source heat pump system average COP is 4.5 in the heating season, increased by 26% than the air source heat pump system run separately , and the fluctuation range is small. Throughout the heating season, the contribution of solar collectors is 59%, the contribution of air source heat pump is 41%.

The Heating Coefficient Experimental Analysis of Solar Water-Assisted Low Temperature Air Source Heat Pump System

In winter,Many families use air source heat pump because of the low evaporation temperature of the system, resulting in lower heating efficiency of system. To solve this problem, the low temperature solar assisted hot water was added to the project which is on the basis of air source heat pump, and the system has been tested. After analysis of the collection efficiency of solar collectors at low temperatures and comparative analysis of the temperature cycle, pressure, energy consumption of the low-temperature solar-assisted systems and air source heat pump system, the optimal collector temperature and law of heat pump refrigerant cycle changes of the system were obtained. Theoretically, comparative analysis of low temperature air source heat pumps and solar hot water secondary air source heat pump compression ratio and COP. It gives the key parameters affecting the compression ratio and COP, pointing out ways to improve the heat pump COP. Finally, a key measure to improve the thermal performance of the unit system is proposed, to provide a reference for future practical applications and research. Foreword Air source heat pump in ambient air contains rich low grade solar potential as a source of heat, it has inexhaustible characteristics [1] . The main reason for restricting the use of air source heat pump in northern area of our country is when the outdoor air temperature is low in winter, the outdoor coil frost severe heating efficiency air source heat pump is greatly reduced. Martinez suggested experimental study on the application of solar radiant floor heating systems , solar water temperature is 50-60°C, low efficiency, especially when overcast snow lower system efficiency [2] .In view of the outdoor coil frosting problem, direct expansion solar assisted heat pump water heater system using the proposed by Li Yuwu, from a certain extent alleviated the problem of heat in winter for coil winter fros, improving the heating coefficient and improved the operating characteristics of the unit. However, this system requires the direct absorption of heat in air tube, and the specific heat of air is small, difficult to heat storage, illumination by solar radiation impact, unstable system operation [3]. Based on the above issues, for the low-level office building , the new rural residential , this study presents low temperature solar auxiliary air source heat pump system , the device uses low-temperature solar hot water heat pump system as low , both full use of solar energy , but also eliminates the original system frost problems and improve the efficiency of solar collectors and heat set to improve the evaporation temperature of the evaporator , thereby increasing the compression ratio of the heat pump unit .

Performance analysis of a novel dual-nozzle ejector enhanced cycle for solar assisted air-source heat pump systems

In this study, a novel dual-nozzle ejector enhanced vapor-compression cycle (DEVC) for solar assisted air-source heat pump systems is proposed. In DEVC, the use of the dual-nozzle ejector for recovering the expansion losses is a very promising approach to improve the cycle performance. A mathematical model of the DEVC is developed to predict its performance under specified operating conditions. The simulation results indicate that for the range of given operating conditions, the coefficient of performance (COP) and the volumetric heating capacity of the novel cycle using refrigerant R410A are theoretically improved by 4.60–34.03% and 7.81–51.95% over conventional ejector enhanced vapor-compression cycle (CEVC), respectively. The results imply that the solar-air source heat pump systems could take advantage of the best features of the DEVC. The potential use of DEVC therefore deserves further experimental validation. It is expected that this new cycle will be beneficial to developing dual-source coupled heat pump applications.

Sludge Drying by Virtue of the Solar Energy and Reclaimed Water Heat Pump with Double High-Temperature Heat Source

Sludge is the solid waste that generated during the sewage treatment process, because of high moisture content limits the final disposal and utilization. In this paper that solar and reclaimed water as heating heat source, It's not easy to design a new drying procedure that solar energy and reclaimed water heat pump with double high-temperature heat source, the system could make full use of respective advantages which of the solar energy, the hot of reclaimed water and heat pump. It would enhance the dehydration ratio, and high efficiency, lower energy consumption, sludge of moisture content (MC) decreased greatly; have created favorable conditions for the reuse. Technology what solar energy, air and reclaimed water heat pump with double high-temperature heat source were used to deal with sludge, the solar energy and air source heat pump were the main heating source. When the heat was insufficient, reclaimed water heat pump was turned on as energy supplementary. The dry air (70°C) was pumped into drying room continually; the moisture content (MC) of sewage was shrunk from 75% to 40% after drying.

Experimental Research on Performance Optimization of Solar-Air Source Heat Pump Water Heater

A practical indirect expansion solar-air source heat pump water heater (IESASHPWH) is used as the measured object. Several feasible performance optimization schemes are proposed in this paper through the fundamental performance and theoretical analysis of the system structure. Then several tests are conducted to test feasibility of the schemes and effect of performance optimization of the schemes through simulating different temperature and climate conditions.

A simulation study on the operating performance of a solar–air source heat pump water heater

A simulation study on the operating performance of a new type of solar–air source heat pump water heater (SAS-HPWH) has been presented. The SAS-HPWH used a specially designed flat-plate heat collector/evaporator with spiral-finned tubes to obtain energy from both solar irradiation and ambient air for hot water heating. Using the meteorological data in Nanjing, China, the simulation results based on 150 L water heating capacity showed that such a SAS-HPWH can heat water up to 55 °C efficiently under various weather conditions all year around. In this simulation study, the influences of solar radiation, ambient temperature and compressor capacity on the performance of the SAS-HPWH were analyzed. In order to improve the overall operating performance, the use of a variable-capacity compressor has been proposed.

97/03095 Exergetic evaluation of gas turbine cogeneration systems for district heating and cooling

Solar assisted air source heat pump shows great potential as a promising energy-saving heating technology, which integrates solar collector and air source heat pump. It is widely considered for supplying hot water, space heating and/or space cooling in the domestic sector. The performance of solar assisted air source heat pumps can be evaluated in system level by parameters such as coefficient of performance, seasonal performance factor, energy consumption, solar fraction as well as initial and operating costs, and in component level by parameters such as efficiencies of solar collection and thermal energy storage. Their performances are affected by many factors such as system configuration, components size, working fluid, working conditions and weather conditions. This paper presents a comprehensive review on the recent advances in solar assisted air source heat pump for the domestic sector in terms of system configuration, solar collectors, thermal energy storage, defrosting method and the perspective areas of further investigations. The results of this review confirm that research is still required to improve the performance of such a combined system and reduce initial cost compared with existing heating systems based on hydrocarbon combustion. The information presented in this paper is beneficial to the researchers, small and medium-sized enterprises suppling renewable energy system technologies, heating engineers and service workers, energy policy and decision makers, environmental activists and communities.