Analysis of the thermal performance of a solar water heating system with flat plate collectors in a temperate climate

The thermal performance of a solar water heating system with 4 m ² flat plate collectors in Dublin, Ireland is presented in this paper. The experimental setup consisted of a commercially available forced circulation domestic scale system fitted with an automated sub-system that controlled hot water draw-offs and the operation of an auxiliary immersion heater. The system was tested over a year and the maximum recorded collector outlet fluid temperature was 70.4 C while the maximum water temperature at the bottom of the hot water tank was 59.9 C. The annual average daily energy collected was 19.6 MJ/d, energy delivered by the solar coil was 16.2 MJ/d, supply pipe loss was 3.2 MJ/d, solar fraction was 32.2%, collector efficiency was 45.6% and system efficiency was 37.8%. Supply pipe losses represented 16.4% of energy collected.