Compound parabolic solar collector – Performance evaluation as per standard test method and actual field conditions for industrial process heat application in Indian context

Abstract

Industrial process heating has been identified as a potential field for solar thermal applications. In this paper, a comparative study was carried out on the performance of an individual solar collector under laboratory conditions and performance of the collector array under field condition. Compound Parabolic Concentrator (CPC) has been used as a solar collector for the application of boiler feed water preheating. The characterization of CPC has been done in liquid phase with water as a working fluid as per the standard, IS 16648 (Part-5):2017. The optical efficiency of the CPC is found to be 64.8% under standard test conditions. In the field, total 200 number of CPCs, each having 3 m2 area, were installed. The performance monitoring and evaluation of the actual installation was carried out over a period of 10 months. The system was designed to supply average 448,500 kWh- Thermal/year, saving the equivalent amount of fossil fuel. The comparative study of the performance of CPC collector under standard conditions and actual operating conditions in the field shows significant variation. The average variation in the performance was about 9% with a maximum variation of 14.7%. The major reasons behind the lower performance output than expected, attribute to the heat losses through the collector manifold and piping (3.9%), soiling of reflector and absorber of CPC (1.72%), uncertainties of instruments (1.49%) and other unaccounted losses like dislocation of the evacuated tubes from the original position, loss of vacuum through evacuated tubes, shadow effect, heat utilization pattern etc. (1.89%), which should be considered while designing the solar field to meet the required output.