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Morris Dovey

DGG (in ) said:

| Not having kept up with the past history of this project, am I
| correct in assuming that this is to be used as a working fluid pump
| for a solar heating arrangement?

Actually, the project started out to be a desktop stirling engine -
then suffered considerable "scope creep".

I produce and (try to) sell passive solar heating panels; and so have
developed an interest in solar energy as a substitute for more
expensive energy sources. I haven't followed many of those interests
because of R&D costs. I have a particular fondness for mechanisms with
no moving parts to wear out and which can be made to exhibit "smart"
behaviors.

Anyway, once the little desktop engine was running, I wondered if it
could be made useful by growing it larger. The first application that
struck me as really suitable was the pumping application. I figured
that if I could produce a useful and inexpensive pump that used only
solar energy and never wore out - and could be easily reproduced by
ordinary folks, it could maybe offer some improvement to quality of
life for a lot of people.

It /could/ be used as a circulator pump as part of a solar heating
system. Since I'm looking for maximum impact, I decided to first take
aim at irrigation and village water supply applications - they're not
terribly demanding and would probably benefit the largest number of
people in the most significant manner.

One of the interesting characteristics of the stirling cycle is that
it is reversible - if, instead of putting heat in and getting work
out, you put work in then you'll see the engine work as a heat pump:
one side will get hot and the other cold (obviously, I'm one of the
"easily amused"). Once a full-sized pump is working, I plan to hook
two of these things together back-to-back and see if I can convince
the second engine to work as the heart of a solar refrigeration/air
conditioner. If I can manage that, people in remote areas without
electricity can have free (meaning "no operating cost") refrigeration;
and people in Arizona, New Mexico, and Texas can have similarly free
air conditioning whenever the sun shines.

Just these first two applications seemed to justify whatever effort is
necessary.

| And since you seem to have experience along these lines, an
| additional question. I have looked at the large solar water
| heating panels on a few homes, and have always felt that due to a
| reduction in exposed surface area (thermal loss) that a tracking
| parabolic reflector focused on a small cylindrical "boiler" would
| be more efficient than the large panel designs. Is this, in fact,
| the case? Or am I dreaming again - I haven't kept up with changes
| in this technology in 19 years.

I can give you a most definite "maybe". The collector is only one
component of a complete system. My rule of thumb is that large
temperature differentials relult in "lossy" (less inefficient) systems
unless the system really requires high temperatures. In general, you
want the most energy (heat) you can get with the lowest possible
temperature differential. It's _really_ important to not confuse heat
with temperature.

| My other quandary is, "How the heck do you find time and enthusiasm
| to pursue all of this stuff?"

I like people: enthusiasm is always a choice - I /make/ time for the
things I think worthwhile. Sometimes it's not easy.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto