>I will very probably buy one of those since I have a wood stove and=20
>it is
> nice to use some sort of fan to circulate the air when it is really=20
> cold and
> the fire is stoked up first thing in the AM.
>
> And I will most likely try running it on solar power outside during=20
> the
> summer and may see if I can couple a little DC motor to it and light=20
> an LED.

I uggested some improvements to them :-)

The cold side doesn't seem to make good use of the fan draft from what=20
I could see. Hot/cold diffferential is a significant factor in power=20
output and efficiency. It's very likely that the cold side gets quite=20
hot with use.

The other aspect is harder to play with. It appears, and I may be=20
wrong, that it has no formal regenerator. If not then it's efficiency=20
will be much affected. (The regenerator is effectively a low pneumatic=20
resistance thermaal sink that traps heat/coolth as gas passes to and=20
fro to it. In an ideal case hot gas enetering comes out cold and cold=20
gas entering comes out hot with the energy to do this stored in the=20
regenerator matrix. Designing good ones is one of the major challenges=20
of a Strilin engine).

Many simple designs have informal regenerators formed by the sides of=20
the passageway from hot to cold. In this case they may use flow=20
directly up the sides of the diaplacer and in such cases the displacer=20
sides and the cylinder sides will act as a regenerator as best they=20
can.

> However, I don't believe it is producing anywhere near enough power=20
> to be
> useful as a generator. It needs 350=B0F to turn over and circulates=20
> 200-300
> cfm of air when operating. The unit is 13 inches tall and 10 inches=20
> wide.
> The fan has 5-blades, and is 10 inches in diameter. A unit warmed up=20
> on a
> 400=B0 surface will turn approximately 400 RPM.

Someone could easily enough work out the power from that information.=20
I'm not going to try as I know where my morning will go if I start=20
:-). Or an engineer could rig an electric motor with an equivalent fan=20
and simulate it :-). I'd guess at least a few watts, so a Luxeon LED=20
could probebly be driven.

Assuming the fan is efficient for the speed it runs at, a different=20
fan with similar air handling capacity should have roughly similar=20
power rating.

> Perhaps an array of them?

Or a properly designed Striling engine? :-)
Tens of watts should be easy enough in this application.


        RM

__________________________________



Aaagh

Fan Power
Fun. He makes some assumptions but the simplistic f=3Dma approach seems=20
good enough for rough results

        http://beale.best.vwh.net/measure/fan/fanspeed.html


Superb Nepal light from fires project.
Gas mantle from stove / thermoeletric / ...
No Stirling but excellent

        http://www.engr.colostate.edu/ewb/Docs/Modialogo%20Project.doc


High volume low speed "effciient modern fans"

        http://www.macro-air.com/principle/

--=20
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