Posted by mn_mn on May 9, 2009, 3:49 am
They are experimenting on solar towers, where air heated in
greenhouses by sun goes up km high tower with turbines in it to
generate electricity - so far results were disappointing. Has anyone
seen a turbine put in a wood fire chimney, or just at the vent hatch
of a normal greenhouse???
I know they use these to turn food on a spit, or in poland to blow hot
air around the house, , , , but can power usefully come from a fan
placed a few inches outside a chimney or vent hole???
Thank you, I am trying to find information on this.
Posted by Morris Dovey on May 9, 2009, 4:39 am
Hmm - I'd be interested in links to info on either of these applications.
In the context of a normal residential heating system's chimney,
probably not - there just isn't that much airflow.
DeSoto, Iowa USA
Posted by amdx on May 9, 2009, 9:57 pm
Here are a few,
Posted by Morris Dovey on May 9, 2009, 11:41 pm
These are interesting but probably not suitable for mounting on the OP's
residential chimney to turn food on a spit or blow hot air around the house.
I suspect that news:alt.energy.homepower might be a better forum in
which to ask about residential non-solar thermal applications.
DeSoto, Iowa USA
Posted by williamsdavid65 on May 10, 2009, 2:52 pm
Suppose the cross-sectional area of the chimney is 0.25 square
metres and the air in it moves upward at 4 metres per second.
Those figures are in the right ball-park for a residential chimney.
So, every second, 1 m^3 of air is accelerated upward to 4 m/s.
The density of air is about 1.5 kg/m^3. So the power that the fire
puts into moving the air up the chimney is 0.5 x 1.5 x 4^2 watts
(0.5mv^2), which comes to 12 watts. A turbine in the airflow could
recover only part of that, let's guess 5 watts. That could be enough
for some simple applications, but not for anything large.