Modeling the variation of optimum tilt angles for flat-plate solar collectors in Ifrane, Morocco

The conventional flat-plate solar collectors that are used in domestic solar water heating systems are often mounted at a fixed position from the horizontal, which makes them less efficient as they do not always face the sun. Adjusting the tilt angle seasonally ensures high energy collection efficiency through different seasons, especially winter, when the sun radiation is limited. The purpose of this study is to determine the variations in tilt angles for domestic solar collectors in order to maximize the amount of solar radiation captured. As an example of this for the Moroccan environment, the monthly optimum tilt angles in Ifrane were determined from the monthly average direct and diffuse radiations on horizontal surfaces, which were estimated based on the Liu and Jordan model [1, 2]. The results showed high tilt angles during winter (71° average tilt) and autumn (47° average tilt) and very low tilt angles during summer season (5° average tilt). Moreover, a significant increase was noticed in the estimated solar radiation on tilted surfaces as we change the tilt angle monthly, seasonally and bi-annually instead of leaving it mounted at a fixed position throughout the entire year. The study indicates that changing the tilt angle monthly would result in an increase of total radiation on the inclined surface by 14.5% during winter season and a yearly average increase of 10% compared to a fixed position. On the other hand, adjusting the tilt angle bi-annually would result in an increase of 12.5% during winter season and a yearly average increase of 7% in total radiation.