"Martin Angove" wrote in message
...
In message ,
"IMM" wrote:
"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.
Can I ask a couple of questions?
1: If suntrackers are so efficient, why is it that the only one at the
Centre for Alternative Technology is about 25 years old? Why haven't
they installed more? Is it perhaps that the reflectors are a waste of
time?
Lots have happened in 25 years. Do a Goggle on sun trackers. There are
some off the shelf versions from the USA.
2: Are you *sure* Stirling engines have high torque? The ones I've seen
certainly don't - they are very efficient, but only when operating high
speed/low torque.
Specifically steam engines have high torque at low speeds. Steam trucks,
which were built up to WW2, never had gear boxes the torque was so high.
The highest torque is at stall speed. A team engines does not idle; the old
steam trucks just opened up the steam and off she went at an amazing speed
for the time. The problem with steam engines is condensing the steam back
to water, otherwise the steam has to be released and water used at high
rates. Stirling's do not have that problem. So using steam and having a
guaranteed cool condenser, such as a large thermal store, may be feasible.
Seam engines are used in ships still with a guaranteed endless supply of
cool sea water to guarantee the steam turns back to water. The most
efficient steam engines are the marine variety , which have been made far
more efficient over the past 15 years or so. The cooling problem applies
also to Stirling's, which are used in French and Swedish submarines also
using cold seas water to cool. The engines are super quiet and virtually
vibration free.
R&D using sun trackers using Stirling's and steam engines, and focusing on a
metal water filled sphere to produce steam/hot water is going on. many keen
armatures using their own home built equipment have reported excellent
results.
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (
http://www.grisoft.com).
Version: 6.0.488 / Virus Database: 287 - Release Date: 05/06/2003