الفهرس 
Introduction
solar radiationOnly 14 pages are availabe for public view
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Abstract
Two identical solar panels were functioned to investigate the effect of mass flow rate of water, orientation and tilt angle, and water inlet temperature on solar panel thermal performance. Solar panel thermal performance was found to be directly proportional to mass flow rate of operating fluid and inversely proportional to water inlet temperature. The obtained results evidently showed that, the appropriate mass flow rates of water according to the incoming solar radiation and the temperature difference between the absorber surface and water inlet, are 12 l/min for January and February, 18 l/min for March, and 24 l/min for April and May. The solar panel which was tilted and orientated to track the rays of the sun from sunrise to sunset was on average 20.98% more efficient than a stationary nontracking solar panel. The two different heat distributing systems were used to compare whether the two heating systems differed significantly in the heat energy supplied and transferred to the microclimate of greenhouses. The heat distributing system using parallel flow system was on average 6.45% more efficient than the other system (series flow system). The temperature of the crop leaves during heating process should be higher than the dew point temperature, in order to prevent condensation and thus reduce the risk of fungal diseases. An experiment was executed to utilize solar energy stored in the storage tank in heating the microclimate of two greenhouses for a hot pepper crop. The solar energy system provided the following proportion of the total energy consumed in February, March, April, and May, respectively 74.82%, 70.88%, 77.25%, and 82.53%.To maximize solar panel thermal performance throughout the year, panels should be adjusted continuously for orientation and tilt angle to track the sun?s rays from sunrise to sunset. The mass flow rate of operating fluid must be adjusted according to the intensity of solar radiation, water temperature in the storage tank and water temperature required for the utilization of the stored energy. A microcomputer could be employed to control all these parameters including the water inlet temperature. Further research is required to develop such a control system.