JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, cilt.27, ss.837-846, 2012 (SCI İndekslerine Giren Dergi)
The study is based upon the measured values of daily global and diffuse solar radiation on a horizontal surface which are taken in Izmir, Turkey. The optimum tilt angle of solar collector is determined between 0 degrees and 61 degrees and changed by the time period through the year. In winter (December, January, and February) the tilt should be 55,7 degrees, in spring (March, April, and May) 18,3 degrees, in summer (June, July, and August) 4,3 degrees, and in autumn (September, October, and November) 43 degrees. Annually, optimum tilt is found to be 30,3 degrees as a fixed tilt throughout the year. Also, these measured values are compared with other equations put forward for calculating the optimum tilt angles. Small deviations are observed between 2,87 degrees and 5,90 degrees. The equations that give a result higher then 3 degrees as a deviation are not suitable to calculate the optimum tilt angle. If solar collector is installed on the monthly optimum tilt angle, optimum azimuth angle (gamma) has to be 0 degrees for all months of the year. However, azimuth angle of the solar collector has to be (gamma=+/- 60 degrees) if the slope is chose (beta >= 60 degrees) in April. In addition, azimuth angle of the solar collector has to be (gamma=+/- 75 degrees) if the slope is chose (beta >= 40 degrees) in May and August, azimuth angle of the solar collector has to be (gamma=+/- 90 degrees) if the slope is chose (beta >= 30 degrees) in June and July, azimuth angle of the solar collector has to be (gamma=+/- 45 degrees) if the slope is chose (beta >= 70 degrees) in September.