Role of thermal energy storage for enhancing thermal performance of evacuated tube with compound parabolic concentrator collector

Evacuated tube (ET) solar collectors are utilized in all climatic conditions for harnessing solar energy. This work aims to investigate thermal performance of ET with compound parabolic concentrator collector, integrated to a multiple phase change material-based thermal energy storage (TES) system. The phase change material (PCM) have been selected depending on the degree of stratification in sensible heat storage configuration under constant heat load conditions. The charging experiments have been performed under three different TES configurations viz. sensible heat storage, three (Case 1) and five (Case 2) PCMs, using water as the heat transfer augmenting the energy storage by 41% than the sensible heat storage. A higher stratification number in Case 2 reveals the significance of multiple PCMs in improving the charging efficiency of TES system. Cascaded arrangement of PCMs facilitates the supply of HTF at lower temperature to the collector resulting with an increase in useful heat energy gained. The instantaneous thermal efficiency of collector with Case 2 is as high as 58%, storing 27 MJ d(-1). Use of ET-CPC and TES system with cascaded arrangement of PCMs finds potential application in water heating system.

Automated summary

This study investigates the thermal performance of evacuated tube solar collectors with compound parabolic concentrator collectors integrated to a thermal energy storage system based on phase change materials. Results show that selecting PCMs under constant heat load conditions can enhance energy storage efficiency.