Background

The Peveril Solar house is powered by sunshine, heated by sunshine! It has the largest practical area of Photovoltaic roof panels for a single house (4 kW), plus a Ground Source Heat Pump that gets its heat from two deep boreholes under the driveway. These are warmed by solar heat on the earth's surface and a proportion of its heat comes from the large solar Sunbox on the south wall, and from some Tubes on the roof. The house also has a Sunpipe in the centre, bringing sunshine into the centre of the house.

For those who don't know us, here is a bit of background on the project:

House with PV roof and
the mark 1 Sunboxes, from
March 2010 to July 2011
The house started life  in 2006-7 as a typical british developer-built house. I did not design it, and the plan was drawn by a plan-drawer, not an architect. We modified it during the construction process. It was window-head height when we found it being built (by the builder) so we were not able to influence the external design and planning - apart from steepening the roof pitch to 40ยบ.
   During the building, we were able to improve the internal layout, door positions etc, and have a say in the heating system, elevator, lighting, kitchen, bathroom and other features. We steepened the roof to make it easier to fit solar panels, and give more internal storage space. My wife 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 my 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 serious cost of having either one very deep (85m) or two deep (48m) drilled boreholes. We had the two because shallower holes can be drilled by landrover pulled trailers, whereas the very deep hole requires something the size of a furniture van! We are now very lucky that we have twin boreholes!
Environmental info for Nottingham (Gaisma website)
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 watering needs.
MVHR (Heat Recovery) was intended, but due to the same 'eco-mutiny' and the difficulty of inserting vertical ducts through the rooms with so many heating pipes in the floor, we had to drop that too. We have a mini-MVHR unit in the combined kitchen-dining, but this is on only during cooking times.
Sunrise and Sunsets (Gaisma website)
Sunpath diagram (Gaisma website)
What else? The house is 120 sqm plus small 9 sqm conservatory (facing north), has good insulation specification in the envelope:
  • Walls (Brick+100mm glassfibre filled cavity+Block) (U=0.25)
  • Floor (Beam and block floor above a cavity, 70mm Celotex, 70mm screed, 10mm tiles (U=0.20)
  • Roof 200mm loft insulation across middle section and 400mm loft insulation at long edges (U=0.1), 
  • Thermal-break double glazed windows, air volume of 285 cu.m
  • Energy efficient lighting throughout. 
  • It has a compact minimal surface area, and airlock lobbies at all entrances
  • Family who observe good energy saving lifestyle, e.g. showers not baths, turning lights off, turning heating off when going out, etc.
The all electric kitchen is optimised for disabled access, and has an Induction hob. I mentioned the hydraulic elevator earlier. Most of the appliances in the house are A-rated for energy efficiency. A very large unobstructed daylit loft is available for easy installation of tanks, ducts, cables and pipes.
  • The house has a PV roof of 3.96 kW facing ESE, and this generates an average of 3,250kWh per year (ranging from 3,050 to 3,450).
  • The PV roof reports its progress to a visual datalogger every 15 mins, and this can be seen on tinyurl.com/peveril-solar-roof
  • The house costs approx 3,200 kWh annually in electricity to heat and provide hot water, thanks to a reasonably good performance of the Heat pump. The PV roof generates enough electrical power to meet all of this requirement. So on heating, the house is Carbon Zero. Of this, the DHW costs approx 700 kWh / year. The efficiency of the GSHP has risen (thanks to Sunboxes) and we have achieved Carbon Neutral on heating AND hot water. Averaged Solar Fraction over 32 months from April 2010 to Nov 2012 is 120%. During 2011, the SF was 130% and during 2012, it has been 90%. In 2007,  8 and 9 the SF was only between 58-68% depending on weather.
  • Normal British houses of this size consume about 25-30,000 kWh annually:- about 3,500 kWh of electricity for lighting and appliances, and 21,500 kWh or more of gas for cooking, hot water and heating. 
  • We assume that our house and lifestyle uses about 3,300 kWh for cooking, power and lighting. (this takes into account incidental gains, such as solar gain, electrical appliances, occupants). With the help of conservation and the PV, this amount was cut to 2,000 kWh and remains consistently so, ever since.
  • As a well insulated all-electric house, but drawing kilowatts of heat from the boreholes, the Peveril Solar house managed Aug 2007-8 and Aug 2008-9 on 8,500 kWh/annum import in each year (with no PV operating). The largest heating requirement is ventilation heat loss as the house is well insulated.
  • Since the PV was fitted in October 2009, we estimate that of the PV we produce, we sell approx 35% and use 65% - a saving on our total bill in the first year of 2,400 kWh!
  • The GSHP's assumption is that of the 14,600 kWh needed annually by the house, approximately 9,800 kWh are being drawn from the earth, and 4,800 kWh are generated by operating the heatpump. That's an average efficiency ratio of about 3. In the last year, we managed to confine the GSHP annual consumption to less than 4,000 kWh, and in 2012, it is averaging about 2,700 kWh/annum. We hope to do better next year by putting 3,000 kWh down into the earth from our Sunboxes - but wonder how much of it will come back up - so far it seems that it all comes up.
  • We do have gas because the builder installed it even though we asked him not to (he had already paid deposit to the Gas board), so we have a small fire in the living room. In three years, it has only been turned on during very cold evenings for a short while, and our total of bills over 4 years is so far £6.50. 
Plan of Ground floor
Other Eco Ideas:
  • Light tube in centre of house brings bright daylight and sometimes sunlight into the upper landing. This doesn't save much electricity as the bulb inside is 3 watts, but its nice to have natural light.
  • Heat reclaim ventilation unit in kitchen - Never need to open window when cooking, because smells are cleared and humidity is balanced, for only 3 watts consumption - reduces annual ventilation heat loss.
  • Induction Hob in kitchen - energy saving and very much safer than a normal hob.
  • Bottle store under the stairs. This is a collection of 2-litre milk bottles that collect heat from the underfloor heating manifold in the day, and release it at night. 
  • Solar powered External security light and garage light. (more to follow)
  • Vegetable garden, to grow a small amount of our own food.
  • Tilting mirror reflector over kitchen window to boost heat gain in winter+equinox, and to provide solar shading in summer. 
  • Additional insulation in loft - 400mm - more was added after the house was completed.
Location: West Bridgford, Nottingham, England, UK

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