Testing for PV

After the disappointments about finding a place for a turbine with enough wind, I’ve starting thinking about solar again. One way or another I am determined to start making our own electricity to balance out the amount used by the heat pump and all our media work.

I had thought that the roof was too shaded by the trees, but then I realised that the upper portion of the mansard was actually quite promising. So I’ve been doing some tests. First I put a small PV panel on the roof and made a series of measurements during the course of the day. I chose days before the leaves came on the trees and days afterwards – also sunny days and overcast days.

This was the position in mid May when all the leaves are on the trees. By 10.30 the mansard is almost clear of shadow from the trees on the East.

Then it’s clear all day – this is the picture at 3.0 in the afternoon:

By 4.30 the trees on the South-West are shading the other end.

In fact this afternoon shading can be reduced completely by trimming just two of the trees. So it looks pretty promising. The gables don’t have any effect on the top roof.

The other interesting finding was that, on the multimeter at least, there was little difference between sun and shade, and even little difference between full sun and a cloudy day. I must find out why this is – presumably it doesn’t apply to fully loaded systems.

Looking again at cost, PV is certainly expensive. But I’ve discovered that the grant for a charity is 50%. And, checking with EST, it seems that the charity has only to work in the building, not own it. The other thing is the rumour of prices always about to come down. Perhaps the best will be to get the first 1kW system up to prove things, and then add to it later with, hopefully, cheaper technology.