Evaluating the performance of domestic solar thermal systems

The paper reports the findings of a two year case study into the performance of solar thermal hot water (STHW) systems installed on new build properties in South Yorkshire, UK. All properties were fitted with 12 No. flat-plate solar thermal panels, covering 4.67 m2 and designed to supply, on average, up to 1064 kiloWatt hours (kWh) of solar energy output per annum. The case study concentrates on properties with high occupancy levels: an arbitrary level of 87% was chosen which enabled ten properties to be considered. The results show that there is a significant difference in performance across the selected STHW systems and none of the systems achieved the design specification. The average gas energy displaced was only 5% with a solar fraction (including losses) of just 19%. However, the STHW systems (along with the installed photovoltaic systems) working to their full capacity have the potential of generating 29% of the average household energy demand per annum.