Experimental investigation of forced and wind assisted domestic solar hot water systems

Abstract

This paper investigates a proposal to replace the electrically operated pump of a forced circulation solar hot water system with a windmill-driven pump. A two-stage centrifugal pump driven by a vertical axis windmill with a Savonius type rotor is added to the fluid loop. Tests on the forced circulation system (FCS) mode, with two different pump speeds, driven by an electrically operated pump or in wind-assisted system (WAS) mode were carried out during January, April, July, and October 2009. Test results obtained on clear days are reported. A daily average thermal efficiency level of between 30 and 37 per cent was obtained in FCS mode and it was between 31 and 36 per cent in WAS mode. With higher wind velocities, higher collector flow rates and higher efficiencies are obtained. In general, the performance of a domestic hot water system operating in WAS mode is on a par with that obtained in FCS mode. The WAS mode is a viable alternative to FCS mode in remote areas where the supply of electricity is problematic.