Document Type : Research Note
Authors
1
Dept. of Mechanical Engineering Shahid Bahonar U&zw
2
Dept. of Mechanical Engineering\r\nShahid Bahonar U&z
3
Dept. of Mechanical Engineering Kerman Graduat&zwnj
Abstract
For receiving maximum solar energy, the collectors surface should be perpendicular to the suns rays, and this can be accomplished when the solar trackers are used to follow the sun instantaneously. The main problem in this regard is, however, the high cost of this kind of tracker. So, instead of employing solar trackers, the angles of the collectors surface could be changed manually every day or month or season, in order to adjust the collector almost perpendicular to the suns rays. In this paper, the slope and surface azimuth angles of solar collectors are determined for maximum solar energy gain in six Iranian cities: Kerman, Yazd, Zahedan, Birjand, Shiraz and Tabas. The genetic algorithm is used in order to calculate optimum solar angles and maximum solar energy gain. The slope and surface azimuth angles are considered the two main variables of solar collectors, as well as the optimum variables, and the solar energy gain is considered as the cost function in the optimization process. The daily, monthly, seasonally, and yearly optimum angles are calculated employing different models. Note that the values of seasonally optimum angles are achieved by averaging the monthly optimum slope angles for that season and the value of yearly is achieved by averaging the monthly optimum slope angles in the whole year. The results show that the optimum azimuth angle is zero for maximum solar energy gain. It is noticed that the maximum solar energy gain in different days of a year is accomplished in different slope angles and it is not economical to use a solar tracker in order to change the angle each day. However, the solar energy gain computed using the daily and monthly optimum angles is almost the same. In other words, changing the angles of solar collectors each day using the solar trackers is not economical, but, changing the angles each month to gain more solar energy compared to fixed solar collectors is very useful. Furthermore, the results show that increasing the ground reflection coefficient increases the optimum slope angle considerably, but, however, it has little effect on maximum solar energy gain. The data of maximum solar energy gain are useful in order to determine the best location for constructing a solar power plant in southeast Iran. The results show that among the cities considered in this paper, Yazd has the most solar energy gain and is the best place for building a solar system.
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