But the main thing I wanted to see what how their large solar PV array was working in practice. There are plenty of theoretical specs for such systems but this is a chance to see how it actually works out. They have a 13.6 square metre array on a third story roof. It’s facing south and carefully angled to the sun. The project was managed by Sustainable Energy Action Ltd and installed by Sundog Energy. It cost £12,000 and was completely funded by grants from the Energy Saving Trust, SW Electricity, EDF and the DTI Major PV Demonstration Programme. Quite a lot of other boxes were involved (notably inverters to turn the DC current into AC).
But the really interesting question was - of the theoretical 1.5 kW the system could produce what has it actually produced in the past two years? And the answer is 22,798 kWh between April 2003 and March 2005. That is 991 kWh a month or 11,898 kWh a year. This saving is worth around £700 a year, making the payback on investment 17 years -well withing the 25 years the PV system is due to last. Moreover, the payback in CO2 saved is around 5 tonnes a year.
The preliminary conclusions for Hedgerley are:
- it suggests the early figures I had for the size of panel to generate 1.5 kW were much too low
- Hedgerely doesn’t have the necessary roof area and is very shaded by trees
- We have the advantage of generating (and selling) renewable power back to the grid on the days that we are not there
- We should look next at the hot water version of solar.
Pictures above show the set-up.