The system consists of three core components:
How it works
An array of hybrid Photovoltaic Thermal (PV-T) panels, which collect both electrical and thermal energy, are installed in the roofline of the building. These are used to generate heat to warm the house and its hot water system, as well as provide electricity to run the system and for lighting.
The system utilises a patented energy storage method, the Earth Energy Bank (EEB). The heated fluid is pumped from the roof through a series of pipes underneath the house, warming the surrounding earth. This heat can then be drawn upon as required via a heat pump during the coldest weeks of the year.
A sophisticated controller manages the flow of energy within the system. Taking into account the outside and inside temperatures, the occupants’ desired temperature, the temperature of the domestic hot water and the temperature of the EEB, whilst monitoring the energy flow from the PVT panels, the system determines the best energy source to meet demand at least cost.
Day / night
In daytime mode the PV-T panels will collect light in the visible spectrum and heat in the infra-red spectrum. In the middle of England, the total energy reaching a single panel is about 2,000 KWH of which about 340 KWH (17%) in in the form of light producing electrical energy and about 1000 KWH (51%) in the form of heat producing thermal energy. These outputs exceed what can be expected from conventional PV and Solar Thermal panels because they are being kept cool from circulation from the heat store (EEB). The output from photovoltaic cells degrades as they get hot and solar thermal panels re-radiate some of their heat back into space and suffer from wind chill when they get hot.
This means that a PV-T panel will collect no less than 4 times the energy from the sun as a simple PV panel, when used in this way. That can provide enough thermal energy to produce space heating and hot water all year round as well as the electrical power to run the heat pump and all the other electrical devices associated with heating and lighting from a comparatively modest roof area.
In night-time mode these panels can do some even more remarkable things. They can act as heat absorbers whenever that air temperature is greater than the ground temperature in the heat store.
During the winter, when the panel temperature is less than that of the EEB, the panels will be omitted from the circulation and the energy taken only from the ground. As the energy stored in the EEB becomes depleted, so its temperature falls and that of the circulating fluid falls even further. Under these conditions, the cold fluid coming out of the heat pump is diverted to the PV-T array where thermal energy can be extracted from the air through both front and rear faces of the panels. Thermal insulation is omitted from the back face of the panels to maximise energy absorption. This significantly extends the life of the thermal store and the process can last continuously over several nights and days in mid-winter.