Finding the optimal tilt angle of evacuated tube solar collectors and their correlation with latitude

Solar water heater is the most employed solar energy system. This system is in utmost efficiency if it is installed in optimal slope and direction''s and this subject depends as different parameters such as geographical location. This study examines the way of attaining optimum slope and direction for evacuated solar collector and their relation to geographical location of their installation. As examining this type of Evacuated Solar Collector in different geographical locations and during the year is difficult for example because of environmental conditions¡ changing amount of radiation and etc. At the begging of the study evacuated solar collector has been examined in fixed day and in a fixed geographical location in different slope and direction and then. After comparing the result are assuring from the behavior of these evacuated solar collector¡ with the help of related controlling formulas. Evacuated solar collector has been examined during the whole year. The results of this study demonstrated that Hay and Davies''s Anisotropic Sky models efficiently describe thermal behavior of evacuated solar collector. This model demonstrated that the optimum annual and seasons slope is related to the latitude of installation place and for evacuated solar collector¡ optimum annual slope is equal to the latitude.