Evaluation of a High Solar Fraction Collector System
Abstract
One of the most important goals on solar collector development is to increase the system’s solar fraction. The studied collector is formed by a compound parabolic reflector which decreases the collector optical efficiency during the summer period. Hence, it is possible to increase the collector area and thus, the annual solar fraction, without increasing the overproduction. Collector measurements were fed into a validated TRNSYS model which estimates the solar fraction of the concentrating system and also that of a traditional flat plate collector, both for domestic hot water production. The system design approach aims to maximise the collector area until an annual overproduction limit is reached. Then, the highest solar fraction achieved by both systems was determined. The results show that, at 50Û tilt, the concentrating system achieves 68% solar fraction using 17 m2 of collector area compared to 66% solar fraction and 7 m2 of a flat plate collector system. Thus, it is possible to install larger collector areas and achieve a higher solar fraction using the load adapted collector. However, the summer optical efficiency reduction was proved to be too abrupt. Consequently, the area increase is too big and the absorber surface of both systems becomes comparable making it difficult for the concentrating collector to compete with a conventional flat plate collector. However, if the reflector geometry is properly design, the load adapted collector can be a competitive solution in the market since it can be produced in a cheap way.