Hi Chris
Your post to me included-
 CH> Were I worried about efficiency, I would have never considered steam.
 AC> In contrast, solar hot water collectors are simple and efficient.
 CH> With my plans of moving into the desert, hot water availablity just is 
not
 CH> my main concern. ;-) Now COOL water...
Ah, I learn geography at last. Other deserts have evening frosts!!
 CH> I need to make electricity, so I can run things like a "swamp cooler"
 CH> (evaporative air conditioning), my computer, water pumps, etc... so I 
an
 CH> live more comfortably.
If efficiency is of no interest and you want to make electricity, then you
will have to be very creative to figure a scheme that will score on
reliability, other than PV panels. In my head I am imagining a huge beam type
engine using inflatable bags or steel drums with elastic diaphragms instead
of traditional cylinders/ pistons, the power stroke being by the expansion of
low temp steam, and the return stroke being by partial vacuum induced by 
ater
spray or air draft cooling.
OK got your dream mode switched on? Imagine two rows of 45 gall drums stood
almost vertically. A long steel rocker shaft supported on sleeve bearings
at a height of ten feet. Cranks/ eccentrics connecting each drum diaphragm
to that horizontal rocker shaft.  Two or three stage cycle chain drive to
spin an alternator at say 500rpm.
Row "A" drums all heated lift their con rods sequentially and before the last
one reaches top dead centre, one or more of the "B" row drums is doing
likewise. The first of the "A" row drums will at that stage be cooled and
sucking the diaphragm in reverse.
Make it look like a V8 engine and an auto maker might provide some fun
capital $$!
The system could only work IF a very slow engine rpm was allowed, and if a
decent flow of cooling water spray could be delivered to the drums just 
efore
top dead centre. There might be no water loss and no exhaust valves required.
But there might have to be a cunning reversible control of the steam inlet.
Maybe the returning steam could be routed thru a reheater en route to the 
ext
drum to "fire" ie expand on a drive stroke.
The engine in theory is double acting ie a pressure stroke is followed by a
"vacuum" stroke.
I don't claim this as an invention, but probably read something in my teenage
days [1940s].  Cheers......ALEC
... I do most of my work sitting down; that's where I shine
--- PPoint 1.92
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