Archive for Downsizer For an ethical approach to consumption
 


       Downsizer Forum Index -> Energy Efficiency and Construction/Major Projects
Rural Rambler

Heat powered stove fan

Best little thing i've bought in ages. They are in Aldi today. If you have a wood-burning stove then I recommend sticking one of these on top of it.
sean

Keep meaning to get one. Bit late in the evening for popping over to Aldi now.
Hairyloon

Keep meaning to get one. Bit late in the evening for popping over to Aldi now.

Don't leave it too long: they sell fast.

Anybody here tried making one? Is on my todo list...
dpack

i had a quick look at the power supply end , aldi will be cheaper than making a practical one.

ps heat gradient= leccy can be done a few ways that have no moving parts but there seems to be a gap in the tech between tiny(like a small fan or maybe slowly charging a phone battery ) and quite big or dangeroos (heat to power at factory scale or a just sub critical lump of plutonium and the cold darkness of deep space to power a long life exploration platform ).
gz

No power in a stove fan, just uses convection
Nick

Lots of power. Wink

And you’d never make one for close to the money needed to buy one.
Hairyloon

i had a quick look at the power supply end , aldi will be cheaper than making a practical one.

Nah, you can get a thermoelectric cell for a couple of quid, a motor for pennies and the rest of it is just bits of aluminium.
dpack

there are cells and cells. Wink Hairyloon

there are cells and cells. Wink
There are, but I don't think it is working hard.
dpack

not hard but it is very hot on one side Wink Hairyloon

not hard but it is very hot on one side Wink
How hot, do you know?

Thermal transfer depends on the design of the base, and it's blowing a stream of cooler air over it... shouldn't get that hot.
Nick

The thermometer on my stove reads 2-300C. Unsure how accurate it is. And the fan sits on that. I can get a much more accurate reading if you need one. Hairyloon

The thermometer on my stove reads 2-300C. Unsure how accurate it is. And the fan sits on that. I can get a much more accurate reading if you need one.
No, that's fine. Is just to get an idea. Do you get it up the high end often?
Nick

Yeah. I’ll recheck the figures next time it’s on. Mistress Rose

You would need to have all electronics and electrics well away from the heat source. I wouldn't expect domestic electronics to be useable above 125 C, or even lower. Temperature cycling is also the most stressful test for electronics, so repeat, keep them away from the heat source or they will fail quite quickly. We used to use that as a test when I was working in the industry, and short of keep turning things on and off, it was the best way to get them to fail. Hairyloon

Yeah. I’ll recheck the figures next time it’s on.
Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...
Hairyloon

You would need to have all electronics and electrics well away from the heat source. I wouldn't expect domestic electronics to be useable above 125 C, or even lower. Temperature cycling is also the most stressful test for electronics, so repeat, keep them away from the heat source or they will fail quite quickly. We used to use that as a test when I was working in the industry, and short of keep turning things on and off, it was the best way to get them to fail.

As far as I can tell, all it consists of is a thermoelectric cell and a motor, both of which are situated as far from the heat as they reasonably can be.
Nick

Yeah. I’ll recheck the figures next time it’s on.
Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...

I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.
Hairyloon

Yeah. I’ll recheck the figures next time it’s on.
Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...

I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.
Well if you're going to be like that about it, can you do me a thermal image of a fan in operation? Wink
Slim

I thought those fans used Stirling engines?

Edit: nevermind, quick google showed that most are thermoelectric but there are stirling engine options
Nick

Yeah. I’ll recheck the figures next time it’s on.
Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...

I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.
Well if you're going to be like that about it, can you do me a thermal image of a fan in operation? Wink

No.

But I can paint a thermal picture with numbers, if that helps.

Fire is on. Fan started turning when the cowl it sits on got to about 100. Base of the fan is that. Body of be fan, the rotating parts and the blades for heat transfer were about 45.

Fires running well now, on a reasonably low heat and the cowl is 180, fan base is around 145 and the other parts about 70.

All values in degrees C. Smile
Hairyloon

Thank you. Very helpful. Looks like the 150°C cells will probably cope, which is handy 'cos I have one here (somewhere).
I don't suppose you are able to measure the top of the stand? Effectively the hot side of the cell. I imagine it's a bit tricky to do so don't go to trouble, but I'm curious about the rate of heat transfer up the stem compared to the heat lost from the stem, if that makes sense.
Nick

I’ll try and remember next time it gets cold and I’m here. Hairyloon

As I said, don't go to trouble: is just curiosity now. Slim

Google must have remembered that I looked up stirling vs. thermoelectric stove fans. They've just suggested this scrapheap challenge DIY stove fan video to me (seems to be one of many out there): https://youtu.be/1u7POtVxtMI Hairyloon

Google must have remembered that I looked up stirling vs. thermoelectric stove fans. They've just suggested this scrapheap challenge DIY stove fan video to me (seems to be one of many out there): https://youtu.be/1u7POtVxtMI

I thought it was a really clever Stirling engine when I saw the chainsaw cylinder. Disappointed to find it was just being a cooling device. Sad

Did like his explanation of how the thermoelectric cell works. Very Happy
Slim

I was hoping he would use the pipe fitting that held the fan as a "chimney" with fan assist to draw air directly over the thermoelectric cell for better cooling the cool side. The fan still basically did that, I just wanted to see some extra flourishes I guess. Laughing

I also thought it was going to be stirling at first
dpack

a stirling that small might be a bit beyond scrapheap challenge.

scale matters when it comes to coefficients of friction, longevity of tolerences, etc etc.

my point is small and moving requires supergood engineering in general as well as in relation to energy harvest by mechanical means.
solid state stuff making leccy works well for small machines

pop a fan on the drive of a chainsaw and cut out most of the faff?
Laughing
Mistress Rose

I would agree with you Dpack. Having been fighting tolerances and coefficients of expansion most of my working life in microelectronics I understand the problem. dpack

rolex and t34 demonstrate the different approaches depending on scale. both are complex machines but one can be mended in a barn with a gas torch, half a dozen stout tools and a big hammer, the other needs a microscope, a cleanroom and a very steady hand. Hairyloon

a stirling that small might be a bit beyond scrapheap challenge.
I don't know. I've got one here where the transfer cylinder is made from a coke can, and the power cylinder is made from a milk bottle top.
It wouldn't work as a stove top fan because it's largely made of cardboard...
dpack

umm. i still recon a stirling to power a tiny fan is watchmaking

however i see no reason a stirling could not pull a kva (hp ) or two off a domestic woodburner giving more than enough power to drive any hvac fans required. add one of elon's battery packs and the lights n pooter work.

heat and power on a household scale from wood is an attractive option for some situations.

as a scrap heap challenge creating a practical woodburner x stirling hybrid seems plausible at the 5 to 10 kg of logs, ie heart of a house, size.

proof of concept should be fairly easy but making it work in a way that isn't extreme steam punk in the middle of the house might need a bit of thought .
a nice bonus is the "waste" heat is right where you might need some low temp heat.

30 odd years ago i came across a scandinavian system of wood fuel open fire with powered hvac and heat exchanger built into a whole house system. it was very good at warming a house efficiently on a few sticks.
adding in the power side (with an excess of leccy and still using all the heat) would be the next gen.
       Downsizer Forum Index -> Energy Efficiency and Construction/Major Projects
Page 1 of 1
Home Home Home Home Home