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Eco-Fan, doe's it work?


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#61 RLWP

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Posted 19 December 2008 - 10:26 AM

I'm so glad I don't have an eco-fan because I'd now be trying to work out an experiment to find out.

The problem is measuring and removing the wind-chill factor or blowing a gale that is equal to the stove-top's temperature.


Actually, I think it depends which way round it turns the fan. If it is the direction that the fan usually runs it will cool the stove (like it does when it is working), if it is in the other direction it will heat it.

Richard
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#62 John Orentas

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Posted 19 December 2008 - 11:33 AM

Those damn fans must hold some form of record for the number of posts they have generated and is there some form of relationship to value for money.. I have never understood why people don't simply make something utilising a computer fan, my mate made a very crude arrangement along these lines to test the principle, it worked a treat.

Bother! now I have done the same thing.
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#63 chris w

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Posted 19 December 2008 - 12:13 PM

So, having just done an extensive reading of a wikipedia page, the Seebeck-Peltier effect is how copper-constantan thermocouples work, but there are other material combinations as well.

Richard

As the Seebeck-Peltier effect is reversible, If you stand your eco-fan in a howling gale, will it cool your stove down or heat it up?

These Peltier junctions are the same things that are used in your warm/cool insulated picnic box. When you apply a voltage across the Peltier junction, one side cools and the other heats up so, depending which way you insert the 12v dc plug into the picnic box, the inside metal plate of the box will either get warmer or cooler, thus warming or cooling the food therein.

Most of these electronic effects in physics are reversible. ie; if you apply a voltage to the junction you get one hot side and one cold side. So if you instead do it the opposite way round and manually heat one side and cool the other, then you get a voltage out, which is what is used to drive the Eco-Fan's motor.

I measured the temperature difference on mine, needed to make the fan start to revolve, and its only 20degC.

Chris

Edited by chris w, 19 December 2008 - 06:28 PM.

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#64 RLWP

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Posted 19 December 2008 - 01:11 PM

These Peltier junctions are the same things that are used in your warm/cool insulated picnic box. When you apply a voltage across the Peltier junction, one side cools and the other heats up so, depending which way you insert the 12v dc plug into the picnic box, the inside metal plate of the box will either get warmer or cooler, thus warming or cooling the food therein.

Most of these electronic effects in physics are reversible. ie; if you apply a voltage to the junction you get one hot side and one cold side. So if you instead do it the opposite way round and manually heat one side and cool the other, then you get a voltage out, which is what is used to drive the Eco-Fan's motor.

I measured the temperature difference on mine, needed to make the fan start to revolve, and its only 30degC.

Chris


Hi Chris,

Any idea of the material combination/number of junctions in the peltier cell in one of these fans?

Richard
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#65 chris w

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Posted 19 December 2008 - 06:27 PM

Hi Chris,

Any idea of the material combination/number of junctions in the peltier cell in one of these fans?

Richard

I would imagine it's just one junction but I don't know the material used in the Eco-fan.

Chris
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#66 Pretty Funked Up

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Posted 19 December 2008 - 06:58 PM

If people are looking to build/make their own it might be prudent to just buy the Peltier module ready made.
I found this one for 18.95...
peltier module

Be interesting what people come up with :lol: and I'm sure theyll be cheaper modules out their.

I'd of also thought more junctions along with more heat would increase the power output enabling higher speeds or larger fans to improve air circulation

Edited by Pretty Funked Up, 19 December 2008 - 07:01 PM.

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#67 Keeping Up

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Posted 19 December 2008 - 07:09 PM

Any idea what is the actual power generation of the Peltier units (or consumption of the fan) in the Eco units?
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#68 Gibbo

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Posted 19 December 2008 - 07:20 PM

Any idea what is the actual power generation of the Peltier units (or consumption of the fan) in the Eco units?


As an educated guess I'd say somewhere between 100mW and 200mW

Gibbo

Hi Chris,

Any idea of the material combination/number of junctions in the peltier cell in one of these fans?

Richard


Almost certainly P-N type silicon junctions. Probably (but this is just a guess) 3 or 4 groups in series (thus giving a voltage of around 2.6 volts unloaded (0.65 volts per junction), each group consisting of several hundred, or possibly thousand, parallel junctions (big junctions can be made but they are less efficient so parallel small junctions are usually used).

Edited to add: The power per unit area is limited by the state of the art. The voltage can be chosen to be whatever is required. I suspect they will choose the voltage to match whatever reasonably efficient motors they can find at a sensible price.

Gibbo

Edited by Gibbo, 19 December 2008 - 07:22 PM.

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#69 RLWP

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Posted 19 December 2008 - 07:22 PM

As an educated guess I'd say somewhere between 100mW and 200mW

Gibbo



Almost certainly P-N type silicon junctions. Probably (but this is just a guess) 3 or 4 groups in series (thus giving a voltage of around 2.6 volts unloaded (0.65 volts per junction), each group consisting of several hundred, or possibly thousand, parallel junctions (big junctions can be made but they are less efficient so parallel small junctions are usually used).

Gibbo


Thanks Gibbo, that makes sense.

Richard

(I'm wondering how long it will be before Chris or Gibbo get a mulitmeter onto one of them)
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#70 Gibbo

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Posted 19 December 2008 - 07:25 PM

If people are looking to build/make their own it might be prudent to just buy the Peltier module ready made.
I found this one for 18.95...
peltier module

Be interesting what people come up with :lol: and I'm sure theyll be cheaper modules out their.

I'd of also thought more junctions along with more heat would increase the power output enabling higher speeds or larger fans to improve air circulation


Ok...... So...... a small electric motor (50 pence ebay) and a propellor, model shop, ebay, 50 pence. Aluminium heatsink for the top and aluminium base plate, painted black, ebay a few quid. Could be quite easy and cheap this.

Gibbo
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#71 RLWP

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Posted 19 December 2008 - 07:47 PM

This one is 320W for 12.95 : Clicky

and here's the datasheet: another clicky

Richard

Edited by RLWP, 19 December 2008 - 07:48 PM.

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#72 churchward

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Posted 19 December 2008 - 08:37 PM

Ok...... So...... a small electric motor (50 pence ebay) and a propellor, model shop, ebay, 50 pence. Aluminium heatsink for the top and aluminium base plate, painted black, ebay a few quid. Could be quite easy and cheap this.

Gibbo


It's a good idea isn't it. I quite fancy having a go at building my own. It'll make for a fun project.


This one is 320W for 12.95 : Clicky

and here's the datasheet: another clicky

Richard


Would that be OK though? The spec says a max temp of 138 deg which wouldn't be enough for the top of the fire I would have thought.
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#73 Gibbo

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Posted 19 December 2008 - 09:02 PM

This one is 320W for 12.95 : Clicky

and here's the datasheet: another clicky

Richard


I'm trying to work out a way to type "bullshit" interspersed with a cough.

If they could produce peltier elements at that rating for that money it would be the end of the world's energy crisis.

A quick fag packet calculation from the size of that unit and a typical boat multi fuel stove shows 100Kw of electrical power output from 1Kw of coal burning.

I think they have the decimal point in the wrong place, by about 6 positions. Or perhaps that is the maximum electrical input when running as a cooler?

Gibbo

This one is 320W for 12.95 : Clicky

and here's the datasheet: another clicky

Richard


Right I just checked the data sheet for that unit.

That's the mean between the heat transfer and the electrical input. Which is a slightly od way of rating one.

I reckon on top of a fire it might produce about 300mW

The problem is, how does one rate these things when they have so may uses?

Gibbo

It's a good idea isn't it. I quite fancy having a go at building my own. It'll make for a fun project.


I'm pretty sure you can make one for next to nothing (apart from the peltier element itself).

Gibbo
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#74 RLWP

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Posted 19 December 2008 - 09:50 PM

I'm trying to work out a way to type "bullshit" interspersed with a cough.



Right I just checked the data sheet for that unit.

That's the mean between the heat transfer and the electrical input. Which is a slightly od way of rating one.

I reckon on top of a fire it might produce about 300mW

The problem is, how does one rate these things when they have so may uses?



I'm pretty sure you can make one for next to nothing (apart from the peltier element itself).

Gibbo


The brief research I have done on these suggests you put them between the processor and heat sink in a PC, so the 320 Watts could mean anything. No way is it the electrical output if you hot it up.

Richard
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#75 Keeping Up

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Posted 19 December 2008 - 10:11 PM

Personally I feel tempted by the opposite approach using a similarly small, quiet, very low power motor running from 12v, driving a fan from behihnd the flue-pipe where the dog's tail won't keep knocking it over. After all, another 100mW or so won't drain the battery overnight.

Edited for tryping errrors again!

Edited by Keeping Up, 19 December 2008 - 10:11 PM.

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#76 Pretty Funked Up

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Posted 19 December 2008 - 10:51 PM

The brief research I have done on these suggests you put them between the processor and heat sink in a PC, so the 320 Watts could mean anything. No way is it the electrical output if you hot it up.
Richard


the 320w is probably its power consumption when at the max rated temperature which its states somewhere as 138degrees
Its intended to cool a chip.

Edited by Pretty Funked Up, 19 December 2008 - 10:54 PM.

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"If you cant fix it with duck tape®... You havent used enough."

I'm really worried about my parrot. He keeps saying, "I can't go on, I hate my life". My flat-mate's too selfish to notice, he's always crying.

NEVER TRUST ATOMS - THEY MAKE UP EVERYTHING!


#77 colin stone

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Posted 19 December 2008 - 11:15 PM

This looks much more fun - a stirling engine powered fan - http://www.gyroscope...t=WHISPERENGINE - but a bit more costly.
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#78 churchward

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Posted 19 December 2008 - 11:36 PM

This looks much more fun - a stirling engine powered fan - http://www.gyroscope...t=WHISPERENGINE - but a bit more costly.


That looks good! I wonder if they fitted one of those new Axiom props to it? :lol: :lol:
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#79 Pretty Funked Up

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Posted 20 December 2008 - 12:06 AM

This one really moves some air!!!! - not sure about the silent running though
Sterling power


And heres a nifty and robust looking eco fan
thermoelectric power
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"If you cant fix it with duck tape®... You havent used enough."

I'm really worried about my parrot. He keeps saying, "I can't go on, I hate my life". My flat-mate's too selfish to notice, he's always crying.

NEVER TRUST ATOMS - THEY MAKE UP EVERYTHING!


#80 Theo

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Posted 29 December 2008 - 06:06 PM

Eco-fans use the heat from a stove to drive the fan blades around.
Its just a circulatory thing.

They do work but only by spreading heat and reducing hot spots.


Well, sort of. They use the thermoelectric effect where if you have a circuit of dissimilar metals and the junctions are at different temperatures a voltage is produced. Connect lots of these together and you have what is called a thermopile. You need to keep the junctions at different temperatures which is the reason for the cooling fins on the top. The electric current produced drives a small electric motor.

Nick
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