This 4-bedroom detached house has been transformed by an extensive retrofit to improve its energy efficiency. Measures taken include external insulation provision of heat by a heat pump linked to a 500 litre thermal store. The heat pump extracts heat from 20 Powervolt collectors (combined PV and solar thermal panels) mounted on its south facing roof and stores it in the thermal store.
The efficiency of the heat pump is enhanced by utilising solar thermal energy extracted from the PVT collectors to achieve a relatively high COP (between 4 and 5) during daylight hours. With the thermal store the heat generated by the heat pump during the day is then used to the heat the house at night.
The PVT array also includes 3.80 kWp of photovoltaic capacity. To minimise the impact of shading from nearby trees a StecaGrid 2010+ has been used with 4 separate MPPT outputs, each supporting a string of 5 panels. The cooling effect of the heat pump on the fluid circulating through the solar thermal array can enhance the electrical output of the PV by up to 15%.
During peak solar irradiation the solar thermal array heats the thermal store directly, rather than via the heat pump, utilising dual solar coils. These direct heat firstly into the upper store until it is up to temperature and subsequently into the lower store.
The thermal store is also linked to a wood burning stove with a back boiler. This is used during the winter to generate additional heat.