1.1. Concentrating and tracking system

With the intention of creating a practical and economical solar concentrator that can provide high- concentration sunlight, a parabolic dish that was developed to collect radio transmissions from cable television satellites in past has been converted into a highly reflective concentrator. The diameter of the parabolic dish is 1.2 meter and its focal length is 0.456 meter and the projected aperture area is about 1.1 square meters. As a reflecting surface we used reflecting film which is cheap and easy to buy locally.

It is well known that concentration necessarily leads to an unavoidable reduction of the angular aperture (acceptance angle) [6,7] of any collector system. Concentrators are thus limited to collecting only those rays coming from a narrow solid angle cone centre on the solar disc, i. e. mainly beam radiation. Therefore, whenever a system is intended to operate with an effective concentration ratio larger than 6 X [7], it must be provided with sun tracking to collect a reasonable fraction of this available beam radiation. Point-focus optics generally require that the concentrator track about two axes so that it is always pointed at the sun, and the focused light falls on the cell. From a mechanical standpoint, two-axis tracking is more complex than one-axis tracking; however, point focus systems are also capable of higher concentration ratio and hence lower cell cost.

A two axes sun tracking system will be applied to increase the solar system efficiency. As we know, the greater the accuracy in computing the sun position, the greater the margin of tolerance will be for other sources of error, such as optical and mechanical, that may arise within the concentrating system. Blanco et al. [8] reviewed the solar literature concerning determination of the sun position published in the last decades. In their paper, they introduced the new, more accurate and simpler algorithm that will be used here. Moreover, a programmable logic controller system will be designed and constructed.

The CPV receiver is composed of solar cells, electrical connections and vessel to provide liquid to cool the cells. The design concepts of the CPV receiver are given in Fig. 1. High performance photovoltaic cells will be used to make the system efficiency higher. Moreover, solar cells will be immersed in a dielectric liquid that will provide an effective cooling to the solar cells. The liquid enters the vessel with the temperature Tfi and leaves at the temperature Tfo. Heat from solar cells is

transferred to the liquid through convection and conduction. The size of the vessel will be changed with the solar modules to provide effective cooling.