"NickW" wrote in message
om...

Solar thermal however, I think should be exploited first as it seems
to yield the big numbers for something as simple as heating air.

Air heaters are very efficient. have one on the back wall of a conservatory
with the heat rising into the house, or loft and ducted down.

What is very efficient and economical, is a sun tracker focusing the sun via
lenses onto a heat exchanger and producing very hot water. These can also
produce steam and run a small steam or Stirling engine/generator. Even in
cloudy weather very hot useful water can be produced. Steam or Stirling
engines can be very small for high large torque. There is research in the
USA on sun trackers/heat generators for CHP applications, or cogen as the
Yanks say, and it appears more cost effective and efficient than most other
methods: PV cells, flat plate collectors, etc.



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