On Sat, 4 Mar 2006 17:15:44 -0000, "ashnook"
wrote:


I want to use something on a barn conversion we might move to. Add more
insulation etc. is not an option as no loft etc. exists. The boiler is oil
fired but no indirect to HW tank so all HW is electric, E7 at night and full
price during the day. I can get to the tank from the roof line so I was
thinking solar HW would be helpful here.

You would be better replacing the existing system with one which
included hot water provision off the boiler. Almost anything you do
to improve the efficiency or running cost of existing systems will be
more worthwhile than solar panels.

I thing self build for possibly £1k might be worthwhile if we assume we will
stay for 10 years. Once installed the running costs are very low and almost
free of energy price rises.

... or have I got me head in a dark place?

Mostly :-). The best you will get from a south facing correctly
angled collector is about 350kWh/year per m2 of installed collector.
In the winter months this drops to well under 500Wh a day. Most
practical installations are about 4m2. In the winter they can't
provide enough energy, in the summer you usually end up unable to use
all the energy collected as you simply don't use enough hot water.
Solar water heaters are most economically in places with large hot
water demands, such as schools and hospitals.

Typically you might save about GBP100 a year. However solar systems
are not as maintenance free as some suppliers and ecowarriors would
have you think and failures in the panels, which are obviously
subject to a lot of temperature cycling, is not uncommon. Certainly
the figure of 25 years useful life quoted by protagonists are not
supported by past experience anywhere in the world (unless you invoke
Triggers Broom).


--
Peter Parry.
http://www.wpp.ltd.uk/