The effect of the non – uniform distribution of solar radiation on cylindrical absorbers of CPC type ICS solar water heaters

摘要

Integrated Collector Storage (ICS) solar water heaters are alternative devices to the well known Flat Plate Thermosiphonic Units (FPTU). They are cost effective solar devices as the absorbing surface and the water tank are combined together to the same unit. The use of cylindrical storage tank in combination with Compound Parabolic Concentrating (CPC) type reflectors results to non–uniform distribution of the absorbed solar radiation on the receiver. This effect can be used to increase the water temperature stratification inside the storage tank, shorting the time of quick heating of water during the daily operation of the ICS systems. In this paper the results of an analytically theoretical optical study along with a computational optical model are presented in order to determine the role of the reflector geometry on the optical performance of the ICS systems. In addition, experimental results of the daily operation of ICS systems indicated the water temperature stratification inside the storage tank, are presented, aiming to correlate this stratification to the distribution of the solar radiation. The results show that the water temperature increase and generally the thermal performance of the ICS systems can be boosted by the use of CPC reflector geometry.