A UK-based assessment of hybrid PV and solar-thermal systems for domestic heating and power: System performance

The goal of this paper is to assess the suitability of hybrid PVT systems for the provision of electricity and hot water (space heating is not considered) in the UK domestic sector, with particular focus on a typical terraced house in London. A model is developed to estimate the performance of such a system. The model allows various design parameters of the PVT unit to be varied, so that their influence in the overall system performance can be studied. Two key parameters, specifically the covering factor of the solar collector with PV and the collector flow-rate, are considered. The emissions of the PVT system are compared with those incurred by a household that utilises a conventional energy provision arrangement. The results show that for the case of the UK (low solar irradiance and low ambient temperatures) a complete coverage of the solar collector with PV together with a low collector flow-rate are beneficial in allowing the system to achieve a high coverage of the total annual energy (heat and power) demand, while maximising the CO2 emissions savings. It is found that with a completely covered collector and a flow-rate of 20L/h, 51% of the total electricity demand and 36% of the total hot water demand over a year can be covered by a hybrid PVT system. The electricity demand coverage value is slightly higher than the PV-only system equivalent (49%). In addition, our emissions assessment indicates that a PVT system can save up to 16.0tonnes of CO2 over a lifetime of 20years, which is significantly (36%) higher than the 11.8tonnes of CO2 saved with a PV-only system. All investigated PVT configurations outperformed the PV-only system in terms of emissions. Therefore, it is concluded that hybrid PVT systems offer a notably improved proposition over PV-only systems.