Stove Fan - thermo electric generators

[Mitchellmoxo]

Hello,

 

i have a question regarding the thermoelectric generator inside stove fans. 

 

I am am in the process of fitting a back boiler to my squirrel and will need to add a circulation pump to the system. Not a problem however I was wondering if I could power this circulation pump (0.5A 12V) using the leads coming from the back of my stove fan and has anybody else done it? I have seen thermo electric generators on eBay cabable of producing 12v 6A so I don't see why not but I have not seen it mentioned before? 

 

the main benefits are obviously I am not drawing from the batteries and it will automatically power the circulation pump when the stove is on and turn it off when the stove cools down. 

 

Any thoughts ??

[MtB]

22 minutes ago, Mitchellmoxo said:

Hello,

 

i have a question regarding the thermoelectric generator inside stove fans. 

 

I am am in the process of fitting a back boiler to my squirrel and will need to add a circulation pump to the system. Not a problem however I was wondering if I could power this circulation pump (0.5A 12V) using the leads coming from the back of my stove fan and has anybody else done it? I have seen thermo electric generators on eBay cabable of producing 12v 6A so I don't see why not but I have not seen it mentioned before? 

 

the main benefits are obviously I am not drawing from the batteries and it will automatically power the circulation pump when the stove is on and turn it off when the stove cools down. 

 

Any thoughts ??

 

I very much doubt the Peltier cell in a stove fan is capable of delivering 0.5a at 12v. A good idea  in principle but I suspect you'd need a dozen or two of them. Googling and looking on ebay returns very little information about the voltage and current output. 

Bear in mind if you stick some to the stove side they only work if the other side of the cell is kept cool. How will you do that? 

[ditchcrawler]

The motor in my stove top fan is 3 volt

[Mitchellmoxo]

35 minutes ago, Mike the Boilerman said:

 

I very much doubt the Peltier cell in a stove fan is capable of delivering 0.5a at 12v. A good idea  in principle but I suspect you'd need a dozen or two of them. Googling and looking on ebay returns very little information about the voltage and current output. 

Bear in mind if you stick some to the stove side they only work if the other side of the cell is kept cool. How will you do that? 

I will use my current stove fan which keeps the top side cool currently as per my previous message. 

 

Here is the spec spec for one I found online:

 

Specification:

Size: 40mm x 40mm x 4mm

Operates from 0~15.2V DC and 0~6A

Operates Temperature: -20'C to 100'C

Max power consumption: 72 Watts

[MtB]

1 hour ago, Mitchellmoxo said:

I will use my current stove fan which keeps the top side cool currently as per my previous message. 

 

But the stove fan will stop spinning when you connect your water pump. The whole of its output is soaked up spinning the blades so if you nick some, the blades will stop or slow down.

1 hour ago, Mitchellmoxo said:

 

Here is the spec spec for one I found online:

 

Specification:

Size: 40mm x 40mm x 4mm

Operates from 0~15.2V DC and 0~6A

Operates Temperature: -20'C to 100'C

Max power consumption: 72 Watts

 

That's the spec in 'cooling' mode, where you supply it with power and it cools something down.

[Detling]

Some issues, but it may be possible.

1, Peltiers work best with a large temperature difference, if you used the input side (return flow) water to cool the cold side of the peltier you would hopefully get about 70 ish degrees C temperature difference hot to cold, which should be OK.

2, Peltiers for sale on ebay generally have a max temperature of 120/140 degrees C, your stove will exceed that easily (measured mine at 270 and not roaring), maybe using the back of the back boiler will limit the hot side, but if the pump failed then you will boil over and possibly melt the peltiers.

3, The Peltiers output is not easily controlled, to get 12 volts with say a 30 degree teperature difference you will need to put 3 or 4 in series, this will output 30+ volts at 70 degree temperature difference. You will need a buck boost controller (a bit like a MPPT solar controller) which will accept a large input voltage range and give out a controlled voltage range. To get 0.5 amps you may need more than 1 series chain so perhaps 8 peltier devices.

The principle is fine, I would suggest clamping the peltiers between the back of the back boiler near the top and a cooling plate carrying the CH return water to the pump. This should avoid melting the peltiers. You can buy High Temperature Peltiers which will cope with 300-400 degrees C but they are extremely expensive.  The usual difficulty is the cooling side, as air near the stove is hot it is not very useful for cooling, but you have a source of low to mid temperature water which is very useful. In theory if you have big enough plates to have many peltiers say 20 ish with a good controller you could get 2-3 amps to charge your batterys (3 amps may sound small, but it will be 24 hours a day in winter and 36 amphours charge then is worth a lot)

 

[WotEver]

The hull would probably be a good source of coolness

[Detling]

On 02/09/2017 at 12:22, WotEver said:

The hull would probably be a good source of coolness

But the heat transferred through the peltiers would go into the canal, using the heating return warms that up a bit thus increasing efficiency. As the peltiers are only about 10 percent efficient if you want 30 watts out you need to transfer 300 watts through them and you don't want to waste that.

 

[mrsmelly]

Just remember the danger points!! If you put too much fuel on the fire such is the efficiency  of the stove fan that it will blow you over whenever you try to walk past it.

[cereal tiller]

12 minutes ago, mrsmelly said:

Just remember the danger points!! If you put too much fuel on the fire such is the efficiency  of the stove fan that it will blow you over whenever you try to walk past it.

I sold mine, walked past it when the Stove was at full tilt then realised my Trousers were INSIDE OUT!

Flogged to a Hot Air Balloonist, he wanted it for a Turbo Boost.

[mrsmelly]

5 minutes ago, cereal tiller said:

I sold mine, walked past it when the Stove was at full tilt then realised my Trousers were INSIDE OUT!

Flogged to a Hot Air Balloonist, he wanted it for a Turbo Boost.

Yeah thats the trouble with them. I used to power my washing machine and tumble dryer with one but I always thought the extra power above that they generated was wasted and the heat blown around the cabin used to give us both serious burns.

[rusty69]

12 minutes ago, mrsmelly said:

Yeah thats the trouble with them. I used to power my washing machine and tumble dryer with one but I always thought the extra power above that they generated was wasted and the heat blown around the cabin used to give us both serious burns.

Mine was used as a hair dryer, but way too powerful. I had to stop using it after all my hair blew out. 

[cereal tiller]

10 minutes ago, mrsmelly said:

Yeah thats the trouble with them. I used to power my washing machine and tumble dryer with one but I always thought the extra power above that they generated was wasted and the heat blown around the cabin used to give us both serious burns.

It is possible to Tame an Ecofan, yes really! Sneak up on it and use Mooring Pins and Ratchet Straps to affix it to the Skin of a Rice Pudding and , Hey Presto!Calm will abound...Pure Inertia-less Calm