"N. Thornton" wrote in message
om...
"IMM" wrote in message
...
"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.

I like that approach too, tho its not problem free. I would go flat
plates /air first.

These can also
produce steam and run a small steam
or Stirling engine/generator.

They can but its very impractical and very inefficient.

The more sun in a brighter climate the better of course, but lenses have
been used that produce enough heat to make them more than feasible.

Even in
cloudy weather very hot useful water can be produced.

Partly cloudy yes, but qith full cloud youve got no way to concentrate
the diffuse sunlight.

That is so, but useful heat in part cloud conditions.

Steam or Stirling
engines can be very small for high large torque.

Steam is the true master of inefficiency and bulk.

Not these days. One double acting piston, the equivalent of a one stroke,
which is the equivalent of a V8 is very efficient, and small. Highly
efficient flash boilers containing no water, just water turned to steam
rather like a powerful instantaneous gas water heater, and burners have come
a along way too to improve efficiency.

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.

I'd be interested to see your refs then,
as figures I've always seen
or calculated would suggest its a real no-no.

There are also additional problems with any steam setup due to legal
issues with the high pressure boiler.

No boiler with stored water required. Instant flash boilers don't have very
high pressures. The technology has been around for 300 years. An internal
combustion engines has a series of explosions ignited by highly volatile
fuel (petrol), which is far more dangerous than a steam engine. As in the
internal combustion engines, electronics can make a steamer far more
efficient too.

Plus PV and hot air are far more
reliable.

PV? With all those inverters and batteries. You are joking of course? Hot
air is more reliable. A sun tracker focusing to make hot water is also very
reliable.


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