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Solar-powered stirling engine project (corrected link) - Page 2

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Posted by Redigoogle on August 24, 2006, 3:07 pm
 

Morris Dovey wrote:

This is an interesting thread.
The Sterling Engine keeps cropping up here and there in my purview.
But, so far the only working models I here about are desktop units
or promising prototypes for which significant funding is required and
solicited.

Even  Dean Kamen has been promising us a Sterling Engine solar water
purification system, but the last I heard his solicitation for funds
from a United Nations departement was denied. Dean Kamen needs funding?

So, there must be some problem with the Sterling Engine. Otherwise, why
isn't it appearing in the current alternative energy vehicle
literature?

Comments appreciated.

Cliff


Posted by Jeff on August 24, 2006, 8:28 pm
 
Redigoogle wrote:


   I don't have a good link to it at the moment, but:

<URL: http://www.lanl.gov/mst/engine/  />

   If you look around you'll find something better.

Roughly the way those work is that in a standing acoustic wave, where
the air is compressed it is warmer, and where it is more rarified it is
cooler. The mechanics are that you insert heat at the compression point
and withdraw it at the rarification point. This is exactly a sterling
engine, although it took some time for that to be realized.

None of this is new, I think the concept is a century or so old.

   Jeff


Posted by Morris Dovey on August 24, 2006, 9:04 pm
 Redigoogle (in 1156432048.324318.310200@m79g2000cwm.googlegroups.com)
said:

| The Sterling Engine keeps cropping up here and there in my purview.
| But, so far the only working models I here about are desktop units
| or promising prototypes for which significant funding is required
| and solicited.

Brace yourself - I think I'm about to start construction of a larger
than desk top size version of what I put on my web page. I'm planning
to use 4" PVC pipe and fittings and I'm pretty sure that I can get the
job done on a poverty budget.

The challenge isn't to build a stirling engine - it's to build a
useful stirling engine into a system that constitutes a cost-effective
solution to some problem worth solving. The way you get there isn't by
looking for stirling cycle engines - it's by looking for and at
problems that might be best solved using stirling technology. :-)

| So, there must be some problem with the Sterling Engine. Otherwise,
| why isn't it appearing in the current alternative energy vehicle
| literature?
|
| Comments appreciated.

Well there /is/ a problem - the @#$%* stirling requires more noodling
than its high-pressure external combustion relative, the steam
engine - and it's not as cleanly self-contained as internal combustion
engines /and/ it's nowhere near as convenient as an electric motor
(when electricity is available).

OTOH, it seems a natural for inclusion into a number of solar
solutions to problems requiring mechanical energy in places where
there is no reliable or economical supply of fuel or electricity - but
where there _is_ an abundance of solar radiation at the appropriate
times.

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



Posted by Redigoogle on August 25, 2006, 3:37 pm
 Jeff,
Thanks for the gov link.

Morris Dovey wrote:

we'll be watching.


I have a perfect test site for your prototype. A remote island in Fiji
where self-sufficient power and desalination are a high priority. But,
this is precisely the reason the sterling engine crops up in all sorts
of scam investment schemes. It sounds so right.

Your suggestion of a "job done on a poverty budget" is refreshing.
Usually, promises are followed by "and here is how you can help fund
this revolutionary technology that will change the world".

Morris, I'll peruse your web site.
I trust you'll let us know how things go.

Cliff


Posted by Jeff on August 25, 2006, 5:08 pm
 Redigoogle wrote:

Some theory:

<URL:
http://www.lanl.gov/projects/thermoacoustics/Pubs/HEPSFinalDraftU.pdf  >

Note, that if I were doing this, I would scale this up to sonic
frequencies to make construction easier and less critical.

Lets say we have energy stored at 140F and a night time ambient of 60F.

That gives us about 18% theoretical efficiency. If you can get half of
that, you would have 2.6 KWH/therm.

  Something to think about, instead of dumping solar heat in the summer.
Not trivial to achieve.

   As far as the design, it seems to me that the weight of the water in
the rising column offsets that in the falling (hence little work). I
don't think you are going to get a lot of usefull work out of this.

   A cheap way to extract that as electrity could work similarly to
those flashlights you shake. A floating magnet in the water column with
a coil wrapped around the tube. You'd want a *strong* magnet, and you'd
want the magnet to pass completely through the coil.

Morris, what differences in water height and what frequency are you getting?

(My own thoughts lie closer to a pulsed turbine based system, roughly
based on solar chimneys)



Forget solar. Use something that extracts energy from the swells of the
tide. Perhaps Salter's Duck:

<URL: http://www.esru.strath.ac.uk/EandE/Web_sites/98-9/offshore/wave.htm  />

Or try tidal generation.

   Jeff



  But,


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