International Review of Automatic Control (I.RE.A.CO.), Vol. 4, n. 6 November 2011 Manuscript received and revised December 2011, accepted November 2011 Design and Implementation of an Intelligent Solar Power Plant Based on Fuzzy Logic Elham Ataei 1 , Rouhollah Afshari 2 , Ebrahim Rahimpour 3 Abstract –Solar energy has been accepted as an alternative source of energy worldwide recently. Current researches and markets have shown that Solar Photovoltaic (PV) is the fastest growing and most promising form of renewable energy used in generating electricity. This paper presents an intelligent sun tracking system in which photo-resistors (sensors) are used to determine the direction of the sunlight along with wind sensors to specify the direction of the wind. Due to their high performance and low expense, these sensors have been preferred and used. An algorithm based on fuzzy logic is designed to implement the controlling system considering all the various meteorological conditions. The hardware structure of the system consists of an AVR microcontroller; hence the small size of the whole controlling system. The solar cell is used as the power supply of the controlling system. Finally, an intelligent solar power plant is implemented by means of the techniques mentioned above. Keywords: Solar Plant, Fuzzy Logic, AVR Microcontroller, Renewable Energy Nomenclature T V = vertical error T H = Horizontal Error V 0 = DC offset voltage VS =output voltage of the photo resistor sensors θ V and θ H = the angle of the sunlight with cell A/D = Analog to Digital Convertor dT H and dT V = error variation I. Introduction The sun’s energy travels to the earth in the form of electromagnetic radiation with a wide spectrum of frequencies. Solar energy is often expressed in watts per square meter (W/m2) or watt hours per square meter (Wh/m2). The amount of energy available from the sun outside the atmosphere of the Earth is approximately 1367 W/m2 [1]. However, the solar radiation reaching the Earth is less than this value. This is because of other energies entering the atmosphere, which lower the solar radiations, through scattering and absorption, down to about 1000 W/m2. Although the global irradiation on the surface of the Earth can be as high as 1000 W/m2, the available radiation is usually considerably lower than this maximum value due to the rotation of the Earth and different weather conditions. At any particular time, the available solar energy primarily depends upon how high the sun is in the sky and what the current cloud conditions are. The available amount of solar energy also depends upon the location. In general, the amount of usable solar energy is contingent upon the available solar energy, other weather conditions, the technology utilized, and the intended application. The science of using solar energy has exceedingly developed during last decade due to the harmful effects of fossil fuels [2]-[4]. This paper is going to concern itself specifically with photovoltaic cells and solar concentrating power plants. In less modern solar power plants, fixed cells are used to concentrate solar energies; however, the fixed conditions of the cells lead to the loss of some energy during the morning and evening each day which inevitably decreases the efficiency of such solar power plants. As previously studied and demonstrated, the photovoltaic cells are devices that convert sunlight to electricity and reach their maximum efficiency if the sun-tracking procedure is carried out sufficiently well [5]. Solar trackers are, traditionally, open loop systems but in order to increase the efficiency of such plants, closed loops ought to be considered. Some algorithms have been designed to implement the sun tracking system [6]. Among these algorithms, fuzzy logic is one of the best ones used to control such plants [7]. If a sunlight tracking system is used, the amount of energies absorbed will be much more than when fixed solar cells are employed. The efficiency of traditional fixed systems is about 8.1% which can increase up to 18.5% by using intelligent systems [8]. Not only does the designed power plant consist of a sun tracking system but also it is equipped with sensors determining both the direction and intensity of the wind so that under specific weather conditions, such as storms, the system will be able to handle maximum amounts of energy as well as keep its mechanical units safe. This paper aims to design and implement an intelligent solar power plant by means of tracking sunlight systems, through the data they provide as to the direction and strength of any given wind, based on fuzzy logic.