A Novel Design Of Octagonal Line Focusing Solar Collector

Abstract

For solar-thermal applications principally two types of systems are used namely: flat plate collector and concentrating collector. The main limitation of flat plate solar collector is the maximum achievable temperature. Conversely, parabolic point focusing collector can give relatively higher temperature but it is very difficult and costly to manufacture exact parabolic shape. In this paper, the novel design of octagonal solar collector is presented. The reflector has been given a shape of frustum of octagonal pyramid with its base acting as aperture to capture the solar radiation. The reflector reflects most of the beam radiation and it is concentrated along a line where cylindrical vessel has been kept to absorb the energy. This energy is transferred to the fluid which can be used for different applications. The collector has been tested extensively. Temperature of around 100°C was achieved with water as working fluid. In order to measure the maximum achievable temperature, high boiling point fluid like castor oil has been used. With castor oil as working fluid temperature of around 130°C was achieved. The collector was tested without and with two types of cover namely glass cover and acrylic cover. 10 to 15°C higher temperature was achieved with glass or acrylic cover compared to without cover. It seems that the octagonal solar collector can become the cost-effective design compromise between flat plate collector and parabolic collector.