Thermal Efficiency of Evacuated Tube Receivers in Steam Generation under Concentrated Solar Power.

Abstract

In this research the efficiency of evacuated tubes used in commercially available solar hot water systems under concentrated solar powe? has been estimated. The solar energy is readily available in nature, environmentally friendly, and therefore it is accepted as one of the most promising non-conventional energy sources to sustain the growing energy demand. Solar energy is captured by parabolic trough solar collector and an evacuated tube receiver is the most efficient and convenient collector among various kinds of solar collectors. Based on the available literature, it has been found that evacuated tube collectors have higher efficiency than the other type of collectors. An evacuated tube collector is also very efficient to be used at higher operating temperatures. The use of solar water heating systems with evacuated tube collectors has been experiencing a rapid growth in recent years around the world, but less attention has been paid to concentrated solar power, when compared with solar PV systems. In almost all of the parabolic trough systems, either double side open evacuated receiver tubes or non-evacuated receiver tubes are used. However, in this study, the researchers experiment on the feasibility of using a single side open evacuated tube in solar thermal hot water systems under concentrated solar power, and investigate its thermal efficiency. The parabolic trough system was exposed to sun for 20 minutes and the generated steam was condensed by a condenser and the mass of condensed distilled water was measured by a triple beam balance and the experiment was repeated 10 times. With reference to the standard solar irradiation/solar constant (about 1400 W /m2), the efficiency of the evacuated tube was estimated for each trial and it was found that the calculated average energy efficiency of the evacuated tube was found as ""' (18.5 ± 1.2)%. Nevertheless, there prevails a big scope for future researchers to experiment on required improvements to the system to enhance the level of efficiency.