Solar energy availability at Tehran: Performance of different types of solar collectors

In this report, the optimum tilt of the solar collectors in Tehran is computed through a computer program. The annual optimum tilt of the collector is found to be 30°. The summer and winter optimum tilts are found to be 0° and 50°, respectively. Based on these optimum tilts, the annual performance of different types of solar collectors which have experimental efficiency curves is predicted. The variation of the performance of the collectors with the optimum tilts is found to be small. The difference between the outlet temperatures of these collectors is also found to be small. The effect of changing the incident angle from zero degrees is found to increase the efficiency of the flat-plate collectors and to reduce the efficiency of the evacuated collectors. In the coldest month of the year, the flat-plate collector can collect heat up to 70°C, while the tubular one can collect heat with temperature more than 90°C. In the other months, all the collectors collect heat with temperatures more than 90°C. The performance of a well-mixed storage tank used with one of the flat-plate collectors is annually predicted. For the initial storage tank temperature assumed at 20°C, the minimum and maximum temperatures are found approximately to equal 42°C and 93°C, respectively. The results show the high potential of the solar collectors in Tehran.