Somewhere during my trips to Nova Scotia and New England I saw a small fan which was placed on the top of a woodburning stove. It was driven by the heat rising from the stove. As a result of the turning blades the warm air was pushed into the room. Does anyone know of such a thing, or did I imagine it?
NICK Aitken
Kingussie
Scotland
Replies
You can google "ecofan" and find a lot of places to buy one, maybe someone on your side of the pond has them. Here's one place: http://www.realgoods.com/shop/shop3.cfm/dp/302/ts/1064207
They're nice little fans. I've thought about getting one before, and I decided that a cheap little electric fan and the energy it uses in a lifetime would be quite a bit less money than an ecofan.
zak
thanks to all those who gave me info on these fans, I visit Seattle in a couple of weeks and will take the chance to look through the stores over there.
NICK
Yes you did see right. They are very popular here in Ontario Canada. See them in all the stores selling wood stoves. LOL say that last line quickly 3 times HA!Ha!
I saw some on EBAY a couple of days ago. They exist, but I don't know how well they work.
http://grantlogan.net/
Garrett Wade carries them http://www.garrettwade.com/shopping/product/detailmain.jsp?itemID=105749&itemType=PRODUCT&iMainCat=0&iSubCat=0&iProductID=105749
Nick, I suspect those fans are basically a "Stirling Engine". Named after their Scottish creator who lived in the 1800's.
IIRC the engine operated based on temperature differences. As the bottom plate heats up, it pushes the plate up, turning the fan blade. As the plate cools off, it settles back down and the process is repeated as it heats back up and rises again.
I have seen classroom Stirling Engine models that are designed to run off the heat from a cup of coffee, a cup of ice, or even from the heat from a human hand. The model would turn a small fan blade (about the size of a tongue depressor). IIRC, you had to spin it to get it started, but from there it would continue to spin while there was enough difference in temperature (between the steaming coffee and outside air, between the ice and outside air, or between the heat of your hand and the outside air).
A woodstove fan is a perfect application for a Stirling Engine.
jt8
"If a woman has to choose between catching a fly ball and saving an infant's life, she will choose to save the infant's life without even considering if there are men on base." -- Dave Barry
Here is one of the classroom models from the Edmund scientific site:
View Image
When the heat expands the air, the air pushes up on the piston. When the air cools, it contracts, pulling the piston down. This heating and cooling moves the piston, making the propeller turn. Made of metal parts with wood propeller.http://www.scientificsonline.com/product.asp_Q_pn_E_3082519
I'm not sure why, but every Stirling Engine I've seen seems expensive. I'm not sure WHY they're so expensive. $100+ for a wood stove fan. $100 for a classroom model.jt8
"If a woman has to choose between catching a fly ball and saving an infant's life, she will choose to save the infant's life without even considering if there are men on base." -- Dave Barry
Nick,
The manufacturer of the Ecofan warns users not to exceed a certain temperature. If your stovetop ever gets too hot -- like on a night when it's twenty below and the wind is howling -- guess what, you burn out the Ecofan and throw it away. I know because it happened to me. I concluded that the gizmos are too delicate for daily use on a real honest-to-goodness woodstove. Consider them expensive, amusing, short-lived toys.
I've seen heavier-duty ones on eBay from time to time. Don't know who retails them though.
jt8
"If a woman has to choose between catching a fly ball and saving an infant's life, she will choose to save the infant's life without even considering if there are men on base." -- Dave Barry
There's also this version from Lee Valley, though apparently they only carry them in winter:
http://www.leevalley.com/gifts/page.aspx?c=2&p=50246&cat=4,104,53221
It doesn't seem to be cheaper than other version folks have posted.
You can buy a lot of wood for $105 around here. Even more if you are only buying chainsaw gas and a chain file.
Yeah, other than "it looks cool" I am not sure of the use, and $105 isn't cool enough for me. Especially since I've got a fireplace for looks, (a fire on the weekend sometimes) not a stove for heat. Though the next poster points to benefits . . .
We purchased an Ecofan off the internet (look for the best price) at the beginning of last winter, a little pricey I agree , but we used gift money given to us around Christmas so I guess that's a little better.
Like the ad says its based on the Seebeck effect, I work with electrical engineers and they can explain it in detail, all I know is it has a little electric motor that runs from the power generated by the heat acting on one side of the electronic chip and the cold on the other. So far it has worked flawlessly, we use it to help push the humidity from the water pot on top of the stove, the 150 cfm can hardly be felt, but it does work. The trick is to put it on the back of the stove so it can always draw cool air across the chip, it should keep itself cool enough and hopefully not burn it up.
There is at least one model that has a bimetallic strip which will flex and lift the fan base off the conducting hot surface to help prevent overheating. The fan runs from what I believe is called the Peltier effect, and is a different principle than a Stirling engine.
It relys on the different electrical potential that exists at different temperatures. It's the reverse of the TECs (thermo-electric) picnic coolers that you plug into the cigarette lighter socket of your car - instead of putting heat in and getting voltage out, you put voltage in and get heat, or cold, depending on the polarity, out. Some heated/cooled car seats (I think the Lincoln LS for one) use this same principle.
The fans do work, but you won't get much more than a slight breeze from them, even at higher speeds. Bought one a while ago and returned it for that reason. Maybe this posting will save you that trouble.
Regards - Brian.
Edited 4/20/2006 11:52 pm ET by markls8
I do stand corrected - the fan does run off the Seebeck effect (heat in - voltage out). The Peltier effect is the opposite of that (voltage in = heat or cold out).
Seebeck, Peltier, Thompson, hard to keep track of these guys after all these years.
- B.
ps. They also will not work at all on a gas stove - the temperature of the surface is not as hot as a wood stove and the temperature gradient isn't great enough.
Edited 4/21/2006 12:07 am ET by markls8