"Jim Thompson" wrote in message
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The efficiency of such a system FAR exceeds what will EVER be attained
with photo cells.

I won't take that without a bit of study. The solar cells take a scads of
energy to build, but once built run for a very long time without much
maintenance. The thermal system is mechanically more complex, requires a lot
more maintenance, is more sensitive to wind loading, and of course you are
running pretty cool so the thermal efficiency is not all that great. I would
think the solar trough is more like 20% and probably much closer to PV than
you allude. The very large focusing arrays can run a lot hotter, and may
then give you a bit better efficiency, but you are still not likely to make
much over 40% and even at that, if you add in the higher rates of "dead"
space that the big focusing arrays use, you may find the total percentage of
energy recovered per square mile to be under 20%. The cost per KWH recovered
is, I think, the killer here, and the increased maintenance adds a lot to
this cost for the thermal array.