A simple method of characterising Solar Thermal Water Heating Systems (SWHS) and the prediction of thermal and economic performance of the SWHS

Abstract

This research is based on manipulating the Hottel-Whillier-Bliss equation to determine the performance characteristics FRԎα, FRUL and Us of the system by substituting mass flow m̊ in the collector based equation ; m̊cpΔTs = AcFRGT(Ԏα)n – FRUL(Ti-Ta) with 𝑑𝑇𝑑𝑡 in the collector- storage tank system equation; Mcp𝑑𝑇𝑠𝑑𝑡 = AcFRGt(Ԏα)n- (AcFRUL+UsAs)(Ts-Ta). This is an innovative and cost effect approach to achieve results that would otherwise require sophisticated equipment and gadgetry. Measurements of radiation, Gt and temperatures, Ts and Ta were taken and the optical and thermal parameters to construct a performance model were evaluated. The resultant model was tested on clear days by measuring actual storage tank temperatures and compared them with the predicted ones. The results showed that this novel method can be used to characterise solar water heating systems to get satisfactory if not excellent results. This information was further used to predict the performance of load simulated SWHS in Harare in any month of the year given meteorological information that is readily available.