Solar Thermal Engineering

Abstract

The increasing demands to energy, from one side, and the global warming crisis of the world, from other side, are the reasons for developing renewable energies [1]. Among all resources of renewable energies, solar energy is the unlimited resource which can be exploited all over the world. The prices for solar generation technologies continue to rapidly decrease; so that, in some cases, the cost is competitive with the fossil fuel costs [2]. The thermal conversion of solar energy is possible by different collectors including flat and concentrating collectors. For the purpose of reaching largescale energy conversion in both forms of electricity and thermal, the usage of different solar concentrating collectors would be a favorite selection [1]. Besides the application of solar flat and concentrating collectors, other kinds of energy conversion units have been focused by different researchers. For achieving wind and rotating turbines, solar chimneys would be a preferred option in the windless zones [3]. Also, for the purpose of supplying potable water, the solar stills have been developed in different types and designs [4].In the recent years, in case of the application of solar thermal systems, the usage of special materials has been paid attention for increasing the efficiency. For instance, using of nanofluids has been the subject of research by many researchers [5]. Nanofluids are capable to enhance the heat transfer coefficient of the working fluids, which are circulating through the absorber tubes of the solar thermal units. Also, the phase change materials (PCMs) are another materials which have found a special situation in the solar thermal systems. PCMs can store/release a large amount of heat during melting/solidification or gasification/liquefaction processes. Since the phase-transition enthalpy of PCMs is usually much higher than sensible heat, latent heat storage has much higher storage density than sensible heat storage [6]. So, this case will be another potential for the future studies in the field of solar thermal energy.Regarding the importance of solar energy as the main sustainable resource among all renewable resources, it was interesting to gather the research findings of this subject in a special issue. The issue covers all new research articles about solar radiation and solar thermal energy systems. The aim was focused on the thermal conversion aspect of solar energy. So, the conversion systems including flat collecting and concentrating systems were gathered in this issue. Besides the technical issues related to solar thermal energy, the economic and environmental subjects were of interest for review. So, the topics including solar radiation, potential and feasibility study, flat and evacuated tube collectors, trough and Fresnel collectors, solar Stirling systems, heliostat fields, solar chimney, solar desalination, nanofluid in solar thermal systems, green buildings, passive solar systems, solar biomimetic systems, optimization in solar thermal systems, economic aspects of solar power plant...

Performance study of low temperature air heated rock bed thermal energy storage system

“…In recent years, solar energy conversion technology has become more and more affordable, and in some circumstances, it is now competitive with the price of fossil fuels. Numerous collectors, including focussed and flat collectors, can be used to transform solar energy into heat 1 …”

“…Numerous collectors, including focussed and flat collectors, can be used to transform solar energy into heat. 1 Because solar energy is unpredictable, storage is necessary to guarantee a steady supply for the intended use. Systems for packed bed heat storage usually make use of inexpensive, readily available materials like silica sand or gravel.…”