The performance of an evacuated tube solar hot water system in a domestic house throughout a year in a northern maritime climate (Dublin)

The performance of an evacuated tube solar hot water system, installed on a domestic house (occupied by 2 adults and 3 children) in Dublin, Ireland has been intensely monitored over the period of a year. Instrumentation to measure flows and temperature were installed throughout both the solar circuit and domestic hot water system, in addition to solar radiometers being installed on site to measure both global and diffuse radiation. The overall annual solar system efficiency at the installation angle of 29° to the horizontal was 63%. Heat losses from all aspects of the solar circuit and hot water system have also been quantified. The ongoing hot water usage pattern of the house occupants over the course of the year has been analysed as well as the changing attitudes to the use of hot water since the installation of the new solar system. This has shown some evidence that more hot water tends to be used on days where there has been more direct sunlight. Net present value calculations based on 5 years of operation however, have shown that the retrofit of such a system is not currently economically viable, although it has produced a carbon saving of approximately 1.1 tonnes CO2eq over its first 5 years of operation.