Design aim: groundhouse is zero carbon, producing more electricity than consumed, and makes a surplus of hot water
The main electrics are conventional. We put in a 2 way connection to the national grid and secured a beneficial feeder tariff from EDF the power company. There are no expensive batteries to buy in and maintain and our grid connection means we need no backup power supply.
We installed fourteen solar electric panels with a 2.3 kW capacity. and crucially also ‘designed down’ power consumption.
We approached the idea of being ‘off grid’with an open mind.
A physical wire connection to a power station means a relationship and a dependency and all the issues that go with centralised power. But that same wire connection enables us to pump power into the grid, changing the relationship (and bringing us a financial gain). If we had chosen to have no relationship with the power station, we would instead have chosen a relationship with another enterprise making very large, very expensive lead acid batteries. And since they need replacing every few years, we would have an ongoing relationship, an ongoing connection and dependency.
Solar Hot Water
If you have a large enough tank for storing hot water, this simple technology has the benefit of enabling you to easily store the suns energy from sunny days, and then use it when it’s cloudy, like a thermal battery. This is what we went for on the Groundhouse. We installed both a large tank for storage and a large roof collector to get plenty of solar hot water off the roof. We use this for both preheating our hotwater and for piped underfloor heating.
Key to our design is the large domestic solar hot water tank supplied by Akvaterm. At 1000 litres, the tank is five times bigger than a conventional tank, enabling us to store a serious amount of hot water during sunny days. This immense vessel is linked to the underfloor heating pipes. The system works automatically, and kicks in
The suns energy is taken off the roof and ‘injected’ into the large thermal mass of the floor and subfloor – a ‘solar boost’ that enhances the heating efficiency already achieved by the ‘glass and mass’ passive solar design.