Investigations on Evacuated Tube Solar Collector as Thermic Fluid Heater

Abstract

Currently, the energy requirement is increasing due to industrial development and population growth all over the world. A large portion of energy demand is met by use of fossil fuels. The two pivotal challenges associated with these energy resources are environmental pollution and high cost. Continuous usage of fossil fuels causes climate change due to the emission of greenhouse gases such as CO2 which leads to global warming. Thus we need suitable alternative for fossil fuels which are not abundant and are limited source of energy. Solar energy is one of the most promising form of renewable energy. The simplest method to convert solar energy to thermal energy is by solar collectors with a conversion efficiency of about three to four times that of solar electrical direct conversion system. Presently evacuated tube solar collector is used in many countries worldwide to meet the heat requirements in low temperature range. In order to have better performance, a lot of research has been focused towards increasing the efficiency of the system by making many optical and thermal modifications. Thermal performance of the solar collector can be enhanced by reducing the thermal losses or by increasing the heat transfer rates between the absorber and working fluid. Numerous researchers have studied the thermal performance of the solar collector with various turbulators such as twisted tapes, wire coil, fins, porous configurations etc. in order to enhance the performance of the collector. Thus the challenge is to develop a solar collector which captures the solar radiation that leads to minimum heat losses and better overall performance. The main objective of the present work is to develop an evacuated glass tube based solar collector to heat thermic fluid up to 150°C. In order to achieve better performance, a new concentrating solar collector is developed which uses evacuated glass tube with a novel turbulator as the receiver and a parabolic reflector. The present research work investigates various thermal aspects of the so