Investigation of an innovative flat-plate integrated collector-storage solar water heater with latent heat storage

Abstract

A novel Integrated Collector Storage Solar Water Heater (ICSSWH) has been developed, in a variety of 3 sizes, and investigated at outdoor conditions, in the Greek climate. The devices consist of flat-plate collectors integrated with latent heat storage tanks at their back, filled with a Phase Change Material (PCM). A conventional paraffin wax PCM was applied, with a melting point of 53 °C. Two heat exchanger circuits, a closed loop collector-storage circuit for charging and an open loop (service water) for discharging process are immersed in the PCM tank. The heat charging and discharging processes of the storage tank are investigated, for various charging and discharging flow rates. The three device storage sizes have total volumes of 0.620, 0.808 and 1.148 m³, with corresponding solar collector areas of 1.51, 2.02 and 2.92 m². During discharging, the stored heat in the PCM is delivered to tap water. A minimum acceptable water temperature of 38 °C is considered, according to international standards. Under normal insolation conditions, daily stored heat of about 4.2, 6.2 and 9 kWh were measured for the three mentioned sizes, respectively. Of this amount, about 3, 4.8 and 7 kWh were transferred to tap water, respectively. The heat transferred to the storage tank was above 41 % of the daily incident solar energy on the collector plane, for all studied cases. The daily hot water production was measured up to 88.4 ℓ, 137 ℓ and 190 ℓ for each mentioned size. Details of the Heat Transfer Fluid (HTF) and tap water temperature profiles are also extracted and presented.