Review of solar assisted heat pump drying systems for agricultural and marine products

Combining solar energy and heat pump technology is a very attractive concept. It is able to eliminate some difficulties and disadvantages of using solar dryer systems or solely using heat pump drying separately. Solar assisted heat pump drying systems have been studied and applied since the last decades in order to increase the quality of products where low temperature and well-controlled drying conditions are needed. This paper reviewed studies on the advances in solar heat pump drying systems. Results and observation from the studies of solar assisted heat pump dryer systems indicated that for heat sensitive materials; improved quality control, reduced energy consumption, high coefficient of performance and high thermal efficiency of the dryer were achieved. The way forward and future directions in R&D in this field are further research regarding theoretical and experimental analysis as well as for the replacement of conventional solar dryer or heat pump dryer with solar assisted heat pump drying systems and solar assisted chemical and ground source heat pump dryers which should present energy efficient applications of the technologies.     

太阳能-空气源热泵联合干燥系统设计及干燥枸杞的实验研究

为缩短枸杞干燥时间,提高干制枸杞的质量,减少能源消耗,本文提出了一种新型太阳能–空气源热泵联合干燥系统。该系统主要由太阳能集热器和空气源热泵机组等设备组成,可以实现太阳能单独干燥、热泵单独干燥和太阳能–空气源热泵联合干燥三种工作模式。本文根据枸杞的干燥特性,分段设定最佳的干燥温度,进行了热泵单独运行和太阳能–热泵联合运行两种工作模式下干燥枸杞的对比实验。结果表明,干燥50 kg枸杞,太阳能–热泵联合运行比热泵单独运行节省了2.9 kW?h电能,若同时除去系统本身的耗能,节省的电能占热泵单独运行耗电量的29.5%。同时,与太阳能单独干燥相比,太阳能–热泵联合干燥具有较高的除湿能耗比,两者最大差值为0.71 kg/(kW?h)。本文提出的太阳能–热泵联合干燥系统具有提高干燥产品的品质、缩短干燥时间和节约干燥成本等优点,适宜推广。     

A solar assisted heat pump drying system for grain in-store drying

For grain in-store drying, a solar assisted drying process has been developed, which consists of a set including a solar-assisted heat pump, a ventilation system, a grain stirrer, etc. In this way, low power consumption, short cycle time and water content uniformity can be achieved in comparison with the conventional method. A solar-assisted heat pump drying system has been designed and manufactured for a practical granary, and the energy consumption performance of the unit is analyzed. The analysis result shows that the solar fraction of the unit is higher than 20%, the coefficient of performance about system (COPS) is 5.19, and the specific moisture extraction rate (SMER) can reach 3.05 kg/kWh.     

A solar assisted heat pump drying system for grain in-store drying

For grain in-store drying, a solar assisted drying process has been developed, which consists of a set including a solar-assisted heat pump, a ventilation system, a grain stirrer, etc. In this way, low power consumption, short cycle time and water content uniformity can be achieved in comparison with the conventional method. A solar-assisted heat pump drying system has been designed and manufactured for a practical granary, and the energy consumption performance of the unit is analyzed. The analysis result shows that the solar fraction of the unit is higher than 20%, the coefficient of performance about system (COP_S) is 5.19, and the specific moisture extraction rate (SMER) can reach 3.05 kg/kWh.     

Solar heat pump drying and water heating in the tropics

In this study, the performance of a solar assisted heat pump dryer and water heater has been investigated. A simulation program has been developed. The predicted results are compared with those obtained from experiments under the meteorological conditions of Singapore. A coefficient of performance (COP) value of 7.0 for a compressor speed of 1800 rpm was observed. Maximum collector efficiencies of 0.86 and 0.7 have been found for evaporator–collector and air collector, respectively. A value of the specific moisture extraction rate (SMER) of 0.65 has been obtained for a load of 20 kg and a compressor speed of 1200 rpm. Results suggest that the total drying time of the product decreases with the increase in drying potential. Drying potential is directly proportional to the air flow rate, drying air temperature and inversely proportional to the air relative humidity. Three important parameters that affect the system performance are solar radiation, compressor speed and the total load placed in the drying chamber. Both SMER and COP decrease with increase in compressor speed.     

Performance analysis of a heat pump assisted drying system

The paper describes a simulation model developed to predict the performance of drying systems assisted by vapour-compression heat pumps. The heat is used to preheat the air stream before it enters the drying chamber. Energy consumption is thus reduced, as the heat pump is capable of delivering more energy as heat than it in fact consumes as input work. Ambient air provides the heat source. A computer program, based on simplified modelling of components (compressor, heat exchangers and drying chamber) has been developed. Results have been produced for a typical application, revealing that a considerable reduction in energy consumption can be obtained with the use of a heat pump. The effect of air flow rate on system performance is also studied.     

Heat pump assisted continuous drying part 1: Simulation model

The addition of a heat pump to a conventional hot air drying system can enhance the efficiency of drying. To investigate the performance of heat pump assisted continuous drying system a detailed simulation model has been developed. The system modelled consists of a vapour compression heat pump coupled to a continuous cross-flow dryer. The model takes account of detailed heat and mass transfer phenomena taking place in each component of the system and can be used to investigate many different system configurations.     

LiBr-H_2O太阳能吸收式热泵海参干燥系统应用分析

提出以LiBr-H2O为工质对的太阳能吸收式热泵海参干燥系统,介绍此系统的组成及工作流程。LiBr-H2O太阳能吸收式热泵应用于干燥过程可以降低能耗,绿色环保。对其应用前景进行分析,同时提出该系统在推广应用方面的限制因素,对太阳能吸收式热泵海参干燥装置设计及推广具有参考价值。     

Development of advanced solar assisted drying systems

The Solar Energy Research Group in the Universiti Kebangsaan Malaysia has been set-up more than two decades ago. One of the activities is in the field of solar thermal process, particularly in development of solar assisted drying systems. Solar drying systems technical development can proceed in two directions. Firstly simple, low power, short life, and comparatively low efficiency-drying system. Secondly, the development of high efficiency, high power, long life expensive solar drying system. The group has developed four solar assisted drying systems namely (a) the V-groove solar collector, (b) the double-pass solar collector with integrated storage system, (c) the solar assisted dehumidification system for medicinal herbs and (d) the photovoltaic thermal (PVT) collector system. The common problems associated with the intermittent nature of solar radiation and the low intensities of solar radiation in solar thermal systems can be remedied using these types of solar drying systems. These drying systems have the advantages of heat storage, auxiliary energy source, integrated structure control system and can be use for a wide range of agricultural produce.     

太阳能热泵低温地板辐射供暖系统的研究与展望

太阳能热泵低温地板辐射采暖系统是以太阳能热泵为热源,以地板辐射采暖系统为末端装置的新型供暖系统.本文综述了太阳能热泵在国内外的研究与应用,并阐述了太阳能热泵低温地板辐射供暖系统的工作原理及在国内的研究现状.分析了该系统的特点,结果表明该系统是一种舒适、经济和节能的理想供热系统.本文还探讨了该系统在当前的应用中尚待解决的问题.     

A comparative study of solar assisted heat pump systems for canadian locations

The feasibility of solar assisted heat pump systems for space heating and domestic hot water preheating in Canada is examined by simulating the performance of these systems on a computer using the program WATSUN. Simulations are carried out using meteorological data for seven representative Canadian cities, two different building types, and six types of system configurations. For the solar assisted heat pump system, twenty year life cycle cost comparisons are made with two reference systems, namely a conventional resistance heating system and an air-to-air heat pump system, based on current economic parameters and projected escalation scenarios for electricity rates.Results of the study show that the solar assisted heat pump systems conserve significant amounts of energy over resistance heating and heat pump systems. On the life cycle unit cost basis, solar assisted heat pump systems costs are relatively insensitive to location, but the dependence on building types is substantial with multiplex dwellings showing the least cost. Liquid based dual source solar assisted heat pump systems are found to be cost effective over resistance heating (but not over an air-to-air heat pump system) at some of the locations for multiplex units. They are not cost effective for single family dwellings at the present time.     

Thermal Performance Simulation of a Heat Pump Assisted Solar Desalination System for Kazakhstan Climatic Conditions

ABSTRACT

A numerical model has been proposed in this research work for predicting the energy performance of a heat pump assisted regenerative solar still using phase change heat storage materials such as paraffin wax and hydrate salt. The numerical model is based on energy and mass balance. The performance was simulated for Fort Sherchenko town in Kazakhstan. The performance comparison between the conventional solar still and heat pump assisted regenerative solar still with and without phase change materials are presented. Moreover, the influence of two different phase change materials on thermal performance of a heat pump assisted regenerative solar still are described. The numerical simulation results showed that heat pump assisted regenerative solar still is more energy efficient and produces better productivity when compared to the conventional simple solar still. The use of hydrate salt phase change heat storage material was found to be a good option for enhancing the performance of a heat pump assisted regenerative solar still.     

太阳能热泵供热水系统的实验研究

在青岛地区建立一套太阳能热泵实验系统，此系统可以完成冬季太阳能热泵供暖(启动热泵)和非采暖季太阳能直接供热水实验。进行了太阳能热泵冬季供暖的实验研究，测得热泵机组的平均供热系数COP＝2．71。     

Performance analysis of solar-assisted chemical heat-pump dryer

A solar-assisted chemical heat-pump dryer has been designed, fabricated and tested. The performance of the system has been studied under the meteorological conditions of Malaysia. The system consists of four main components: solar collector (evacuated tubes type), storage tank, solid-gas chemical heat pump unit and dryer chamber. A solid-gas chemical heat pump unit consists of reactor, condenser and evaporator. The reaction used in this study (CaCl2-NH₃). A simulation has been developed, and the predicted results are compared with those obtained from experiments. The maximum efficiency for evacuated tubes solar collector of 80% has been predicted against the maximum experiment of 74%. The maximum values of solar fraction from the simulation and experiment are 0.795 and 0.713, respectively, whereas the coefficient of performance of chemical heat pump (COP^h) maximum values 2.2 and 2 are obtained from simulation and experiments, respectively. The results show that any reduction of energy at condenser as a result of the decrease in solar radiation will decrease the coefficient of performance of chemical heat pump as well as decrease the efficiency of drying.     

太阳能热泵供热系统实验台的设计及误差分析

开发新能源和节能是寻找能源出路的两大途径,太阳能热泵系统以其显著的节能性和环保性具有广阔的发展前景。介绍了太阳能热泵供热实验台集热器、蓄热器等设备的设计,分析了集热器集热效率的测试误差,指出太阳能热泵供热实验台测试数据准确、可靠,为太阳能热泵供热系统的设计、安装和运行提供了有价值的参考依据。     

太阳能辅助地源热泵联合供暖(制冷)运行模式分析

太阳能和地源热泵联合供暖系统以其良好的节能和环保特性,近年来得到国内外众多学者和研究机构的广泛关注。总结了国内外地源热泵和太阳能集热器联合供暖（制冷）技术的发展现状和最新研究动态,介绍了太阳能辅助地源热泵联合供暖（制冷）的技术和特点,指出太阳能辅助地源热泵供暖（制冷）技术具有较好的发展前景。     

太阳能冷热暖三联供热泵系统的研究

在分析太阳能利用与热泵技术发展背景的基础上,介绍一种新型的太阳能冷热暖三联供热泵系统,并指出各工作模式及其之间的转换,最后阐述了该系统的技术特点以及其应用前景。     

Analysis of solar desalination system using heat pump

This paper investigates a pilot desalination system which consists of a direct expansion solar assisted heat pump (DXSAHP) coupled to a single-effect evaporator unit. The working fluid used is R134a and distillate is obtained via falling film evaporation and flashing in the unit. Experiments have been conducted in both day and night meteorological conditions in Singapore and the effects of solar irradiation and compressor speed have been studied against the system performance. From the experiments, the Performance Ratio (PR) obtained ranges from 0.43 to 0.88, the average Coefficient of Performance (COP) was 8 and the highest distillate production recorded was 1.38 kg/h.     

太阳能辅助地源热泵供热的可行性研究

通过对邯郸地区太阳能资源分布规律的分析,从技术性、经济性方面对太阳能辅助地源热泵供热与单纯的地源热泵供热进行比较。结果表明:太阳能辅助地源热泵供热的综合性能优于单纯地源热泵供热。因此,在邯郸地区,太阳能辅助地源热泵供热是完全可行的。     

Theoretical thermal performance analysis of two solar‐assisted heat‐pump systems

The thermal performance of two different schemes of solar‐assisted heat‐pump systems has been theoretically studied. In first scheme, the evaporator of the heat pump is taken directly as the solar collecting plate and always maintained at the ambient temperature. As there is no heat loss from the collecting plate, the thermal efficiency of the collector is high and equals the solar absorptivity of the collecting plate. As suggested, the heat‐pump evaporator of the second scheme is placed in a novel fresh water solar pond/tank with high efficiency. Since the evaporator operates at a relatively high temperature, the COP of the heat pump can be increased. The calculated results show that the COP of a solar‐assisted heat pump using the second scheme is considerably higher than that of the first scheme. Copyright © 1999 John Wiley & Sons, Ltd.