Solar House, West Bridgford 2007

The Peveril Solar house is powered by sunshine, heated by sunshine! For power, it has the largest practical area of Photovoltaic roof panels for a single house (4 kW). For heating and HW, it has a Ground Source heat pump that gets heat from the ground under the house, warmed by solar heat on the black tarmac, and also gets direct heat from large solar Sunboxes on the south wall. A Sunpipe in the roof brings sunshine to the centre of the house.

It was built in 2006-7, as a developer house, so we were not able to influence the external design - apart from steepening the roof pitch to 40º. During the building, we were able to improve the internal layout, door positions etc, and have a say in the heating system, disabled elevator, kitchen, bathroom, lighting design, and other features. We needed a house with an elevator in it, and it was impossible to find an existing house with space for this. So adapting a house already under construction was perfect.

For our part, it was a chance to experiment with Eco Design ideas, within the limits of an already-designed house. So we went for a ground source heat pump with underfloor heating on both floors. Due to the tiny site and the bordering trees, we could not use pipes under the lawn, so we had to go to the cost of having two deep drilled boreholes. Over successive years, a ground source heat pump tends to chill the ground permanently. After two years occupation, we looked for ways to prevent this chilling effect - hence the design and building of the  Sunboxes for 'charging the earth'.

The idea of Charging the Earth is to recycle sunshine! The practical method is to have solar collectors on the wall in large glassy boxes whose sole purpose is to pump solar heat deep down into the ground. The building's heat pump gets much of this back immediately, finds a bit more during the evenings, and hopes for residual summer heat later in the winter. Our storage boreholes go 48 metres below the house, reaching directly to about 8,000 tons of clay and rock, with an infinite mass beyond that.
    The sunboxes are on target to put down 3,000 kWh of solar heat, annually. As the heatpump needs to pull 9,000 kWh up annually, we are sure that all of the solar heat is used in the house. How much electricity will it save annually? The first year of operation of the PV and Sunboxes have saved 2,450 kWh in a single year.  The heatpump's coefficient of performance is greatly improved, This is what we are quantifying in the next couple of years, with datalogger readings and daily tuning. Sunboxes will not actually raise the soil temperature, as there is just too much of it - the heat injection is equivalent to only 1 kW/hr, so this heat will prevent soil chilling, and will be reclaimed by the heatpump, daily.

The panels, sunboxes, plumbing and electrics are entirely invented and built by the house owner. This is, in effect a new and unique technology, so the Surya Sunbox system is being presented at the global conference of Sustainable Energy Technologies, Shanghai, August 2010.

What else? The house has good insulation specification in the walls, floor and roof, thermal-break windows, and energy efficient lighting throughout. It has a compact minimal surface area, and an airlock lobby at the entrance. The kitchen is optimised for disabled access, and has an Induction hob. Most of the appliances in the house are A-rated for energy efficiency.

Rainwater collection was intended, but due to the complexity of the borehole pipes and RW pipes in the driveway and 'eco-mutiny' by the builder, the underground rainwater tank was returned to the supplier. We now have 200 litres of waterbutt storage for all garden water needs.

Normal houses of this size consume about 25,000 kWh annually:- about 3,500 of electricity for lighting and appliances, and 21,500 of gas for cooking and heating, mostly emitted as CO2. As an 'all electric' house, supplemented by sunshine, we managed 2007 and 2008 on 8,500 kWh/annum, which is only a third. During 2009-10, we are on target to cut our total electricity import to about 6,200 kWhrs, all from renewable sources, and next year will be under 6000. Our roof will export over 3,000 kWhrs. The photovoltaic roof is linked to the internet. Energy use and energy generation are metered daily, and water use metered weekly, and the results are also published on the internet.

For more detailed information, a glossary and who installed what in this eco house click the links.
PV by EvoEnergy. Heatpump by Ice Energy.