In article ,
(Andrew Gabriel) wrote:

While on PV cells. Alternative, with high capital cost, is a normal wet UFH
system, fed from a large thermalstore/heat bank. Use roof PV cells to heat
dc immersion elements in the water store. The thermal store will "store
energy" for use in DHW and UFH.

Again, avoid conversion of sunlight to electricity. Most of
the Sun's energy is lost at that stage. Collect and use the
heat directly.

According to an opinion piece in New Scientist Shell and BP have
calculated that if you replaced all roofing materials with photovoltaics
at current efficiencies you would, even in cloudy UK, generate more
electricity than we currently use.

http://tinyurl.com/odgx

Though you will need to sign up to their free use period to see it
without a subscription.

Peter

--
Peter Ashby
School of Life Sciences, University of Dundee, Scotland
To assume that I speak for the University of Dundee is to be deluded.
Reverse the Spam and remove to email me.