Global advancement on experimental and thermal analysis of evacuated tube collector with and without heat pipe systems and possible applications

Sun is the prime source of energy. There are two types of technologies available for the harnessing of solar energy i.e. Solar Thermal and Solar photovoltaic. Solar thermal energy having a potential to provide the domestic and industrial energy demand for hot water, air heating, solar cooling, solar drying etc. Among multiple applications of solar energy, water heating, space heating, and cooling are consuming more energy. The energy consumption in production of hot water represents a large contribution of total building energy consumption. The Collector is the important aspect for efficient energy needs for these applications. Among all thermal collectors specifically for low/medium temperature applications, evacuated tube collector is found to have the best efficiency. This paper addresses the advancement, different types of evacuated tube collectors and its low/medium temperature applications. The use of heat pipe in evacuated tube has been studied by many researchers around the globe to overcome the lower performance issue in direct flow evacuated tube collector. This turns out to be one of the most important advancement in this area. Another, important advancements in this research have been found to be integration of phase change materials with evacuated tube collector which has the great impact on its performance. This makes the evacuated tube technology more efficient, reliable and user-friendly. This review covers the recent research areas of the direct flow and heat pipe evacuated tube collector with different applications and comprehensive knowledge of the theoretical analysis. This paper also provides financial advantages, classification with and without thermal energy storage, advantages and drawbacks of evacuated technology and future recommendation for future improvement and recent research trend have also incorporated in this manuscript for researchers and practice engineers.