Comparative performance studies on flat plate and evacuated tube solar collectors for local climatic conditions

Abstract

Solar energy is free, environmentally clean, and therefore it is accepted as one of the most promising alternative energy sources. The effective use of solar energy is hindered by the intermittent nature of its availability, limiting its use and effectiveness in domestic and industrial applications especially in water heating. Conversion of solar energy into thermal energy is the easiest and most used method. The efficiency of solar thermal conversion is around 70% but solar electrical direct conversion system has an efficiency of only 17%. Solar water heating systems are mostly suited for its ease of operation newlineand simple maintenance. Many research papers revealed that the improvement on thermal newlineefficiency of solar water heating systems resulted in techniques to improve the convection heat transfer. Solar water heating systems are classified into two broad categories as passive and active systems. Passive techniques have been used to improve the convective heat transfer. Solar water heating systems with various heat transfer enhancement techniques include collector design, collector tilt angle, coating of pipes, fluid flow rate, thermal insulation, integrated collector storage, thermal energy storage, use of phase change materials and insertion of twisted tapes are explained in various research papers. newline newline