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peltiers power generation

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Thunderchild

New Member
I've spotted these on ebay;
**broken link removed**

now they are sold for cooling, will they produce power if heated one side and cooled the other / they are very cheap, might be worth a go...
 

Roff

Well-Known Member
Yes. It's called the Seebeck effect. Seebeck generators are available commercially. Google is your friend.:)
 

Boncuk

New Member
Finding a natural thermal difference high enough to produce enough electricity to be worthwhile is the problem.

Hi Bill,

I don't want to be cruel, but you are asking for a "perpetuum mobile", which is simply impossible because of laws of physics.

I also guess making a perpetuum mobile "bending" laws of physics won't work either. :)

Sorry!

Kind regards

Hans
 
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tcmtech

Banned
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Depends on the type of Pelter device.
They are not as efficient as the Seebeck units when used to generate power. The usable electrical energy is maybe 5 - 15 % of the total energy being transfered.

However I have found the typical 12 volt rated 168 watt ones on eBay will produce around 4 - 6 volts at several amps given a 250 degree temperature differential. For me thats the average temperature differential of my boiler stack to the air and that runs from November to April. :)

I made one for a local elementary school last year out of an old 25 watt CPU cooler. The hot side was a small heat sink that sat in a pan of hot water and the large one was where you put snow or crushed ice on.
It put out about the same power as a D battery. 1.5 volts at 1 amp on average. Not spectacular but given a few hundred of the modern high powered ones you could definitely make some power! ;)

The kids really think its cool that snow can make electricity! :)
 
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Thunderchild

New Member
well my thought here was the low cost, I was thinking of making a little furnace and putting them on the side. maybe it could double up as a cooking hotplate/barbeque just a bit of fun really. only thing is I'm worried at how hot i may get these, what are the limits ?
 

dknguyen

Well-Known Member
Most Helpful Member
Radioisotope thermoelectric generator - Wikipedia, the free encyclopedia

A fan will need more energy than the Peltier will provide.
Obviously- you lose energy every time it is cycled through the system because nothing is 100% efficient. Otherwise you would have a perpetual motion machine if the cooling fan was being powered by the peltier which was being cooled by the fan. All of which is still a moot point because a fan can't cool something below ambient lol so you'd still need a heat source on the other side, or a cold source.

It'd be kind of cool to power something form a camp fire though. THe problem is that with the efficiency of a peltier device or thermocouple is that you're better off just winding the darn thing up like those wind-up radios.
 
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tcmtech

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The pelter coolers I have are rated for around 450 F maximum if I am remembering correctly. Realistically the information I have found relating to typical pelter coolers is what ever the melting point of the solder is that holds the junctions in place is what will determine the top thermal limit.
The way they work is the greater the temperature difference across them the higher the electrical output.
The old style pelter devices were far less efficient than what they are now. Not outstanding as power generators but still they do work well enough in conditions that are within typical persons ranges.

I had played around with mounting mine on all sorts of different things. The boiler stack was the only thing I had that was under the top limit but yet had open air flow to keep the cool side heat sink temperature down.


With a little cooker unit I think that if the cold side heat sink was made out of square or rectangular tubing so the pelter units had a flat surface to attach to water could be circulated through it and aid in increasing the heat transfer effects considerably.
Then just use a small radiator or what ever to dissipate the heat from that.

If I ever get my shop concrete poured it will have the in floor heat tubes And I have been pondering on how to use a bunch of pelter units in between the boiler supply and the floor coils. Concrete floor heat doesn't need the full 200 F boiler water and will take 100F just fine. Given a 100 F drop across a good number of pelter units I should be able to get a reasonable amount of electrical power that way. :)
Even if I only get 2% of 200K BTU that gets transfered to the floor coils turned into electricity that is still nearly 1 KW of usable power! Take that times 12 hours a day for 5 months and thats a good deal of free power! :D

In theory of course! cost of set up may determine the actual out come.:(
 

blueroomelectronics

Well-Known Member
There's no free lunch with energy, the Peliters will draw heat away from your heat pipes and simply make the system inefficient.
How do you plan to cool the Peliters cool side?
 

Diver300

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Most Helpful Member
There's no free lunch with energy, the Peliters will draw heat away from your heat pipes and simply make the system inefficient.
How do you plan to cool the Peliters cool side?

The hot side of the Peltier is 200F water from the boiler and the cold side is 100F water that goes to heat the floor. The efficiency will be poor, but the alternative is a mixing valve which would have no electrical output.

Obviously, any electricity that comes from the system is a loss of heat, but electricity is normally worth more than heat from the boiler.

The other question is whether the boiler would be more efficient if run at 100F rather than 200F. There may be reasons why that isn't possible (need for hot water, risk of condensation in the boiler).

The "no such thing as free lunch" comment doesn't really apply where some wasted energy can be used. Most car heaters don't use heat that wouldn't otherwise be thrown away.
 

blueroomelectronics

Well-Known Member
Collecting waste heat is great. But a Peliter is not a thermal insulator, it will try to equalize the two sources and it has to be thermally coupled to both.
 

Thunderchild

New Member
my plan was to make a furnac eto burn garden waste in and try and harness the heat for electric whilst i'm at it, if i can cook on it too all the better !
 

tcmtech

Banned
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The hot side of the Pelter is 200F water from the boiler and the cold side is 100F water that goes to heat the floor. The efficiency will be poor, but the alternative is a mixing valve which would have no electrical output.

Obviously, any electricity that comes from the system is a loss of heat, but electricity is normally worth more than heat from the boiler.

Thats basically what I am thinking. The heat to electricity conversion will be low but the heat is going to get used any way so why not make it do a little work along the way.
By using the temperature differential and the high thermal transfer effects the pelter's work sort of like the mixing valve or at least together with the mixing valve assembly. For me a 2% loss in heat from the boiler is irrelevant being my fuel is mostly free wood any way. The 1 KW per hour times around 2000+ hours a year adds up to a reasonable amount of power. Around 18% or $200 of my total annual usage as it sits now.
Plus being Pelter units have near indefinite life spans thats 2000+ kWh every year for decades.

For my system the boiler has to run at around 200F in order to keep the wood smoke from condensing in the flues and I also need that heat level for thermal reserve when the fire goes out. Plus the house is what runs off the boiler right now and the heat exchanger under my furnace needs that high of water temp any way.

In my situation its feasible and almost justifiable.:D


Ideally given the much higher working temperatures they can handle if they were to be used for more power generation and then the access heat energy reused for heating a home or building I would be tempted to design the boiler or heat source device to work with a non flammable oil or fluid that can run safely at 350+ degrees F. Then use the heat transfered from the cool side of the devices to heat the building. By keeping the heat load on the cold side fairly large the thermal difference could be kept much higher and greatly increase the electrical output per device.
A 250 degree F temperature difference from one side to the other would give a much higher electrical output without needing as many devices.
 

tcmtech

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my plan was to make a furnac eto burn garden waste in and try and harness the heat for electric whilst i'm at it, if i can cook on it too all the better !

I would think that as long as you have a way to keep the hot side from exceeding the melting point of the devices internal solder connections and then have a way to keep the cool side as cool as possible you would have a practical and cheap way to make power! ;)

Well worth playing with in my book! :)
 
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