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yugomodder · 06-24-2012, 02:23 AM

I bought some Peltier coolers, and while I haven't done any serious experimentation with them, my limited experience with them may be of use.

The ones I got were $5 ones off of ebay. They have a maximum draw of 136.8W, with 15.2V, 9A. They're 40mm by 40mm, and have a maximum temperature rating of 67 degrees C (152.6 F).

One of the things that struck me about them is that they create a large temperature differential very quickly after applying a voltage. One side gets fairly cold, like the inside of a refrigerator, and the other gets hot actually pretty hot. As soon as power is disconnected both sides feel slightly warm. I think this is because it acts as a generator as soon as you stop applying voltage. I have not experimented with using them as generators, but might be able to.

Now looking from a broad standpoint, thermoelectric generators are very inefficient. That being said, they are already efficient enough to generate lots of power, just not the ones that are commercially available.
KOMATSU : Komatsu to Launch Sales of the World's Highest Efficiency Thermoelectric Generation Modules Developed In-house
These are experimental thermoelectric generators, with a conversion efficiency of 7.2% and an output of 24W each for a 50mm x 50mm device. They can withstand temperatures up to 280C (536F). Now the problem is that they have an announced price of ¥ 30 000 per piece (approx 373USD). This is a cost of $15.54/W, for a device that only generates power while the engine is running. The cost is definitely the prohibitive factor in this case.

If we look at a standard engine, it's efficiency is approximately 18%-20%. This means that out of the 100% of the energy released, about 80% is released as heat or sound. So if we take that 80% and could convert it at 7.2% efficiency (now I realize we cannot take all of the heat and convert it, this is just for the math) we get 5.76%. Now this may sound like a 5.76% increase in FE, but it's not, it's 5.76% of the total energy released. For example if the motor produces 20kw of power, then 80kw are put into heat and sound, and 5.76kw could potentially be harvested from the heat at 7.2% efficiency. This is an increase of about 28.8% in the energy we get from the engine. That is massive! Now unfortunately we cannot harvest near 5.76kw from this engine at 7.2% efficiency, as we cannot trap all the heat and exchange it with the devices perfectly.

In summary, the devices are very cool, and look promising. They however at this point they are too expensive for use in vehicles that only use them for a few minutes or hours at a time. The conversion efficiency is already more than enough to make a significant impact on fuel economy, but not at their current cost.

If the cost of Peltier coolers is reduced to a reasonable level, like even $6/W they would have huge potential in power plants converting excess heat into electricity. They could also be used to harvest waste heat from blacktops. To reach the point that they could be used in cars however, they would have to be cheap enough that they could pay for themselves in the few minutes or hours a day that they are used. (note for the 136.8W $5 Peltier coolers off of ebay, 136.8W is the maximum load, the output would be far less, but as to how much I do not know)

TEC1-12709 TEC Thermoelectric Cooler Peltier Module New | eBay
Here a link if anybody would like to experiment with them. I would be happy to perform an experiment using the ones I have, if anybody has parameters they want tested please ask me.

06-24-2012, 02:23 AM	#4 (permalink)
yugomodder EcoModding Lurker Join Date: Mar 2012 Location: Mississippi Posts: 40 Thanks: 11 Thanked 5 Times in 3 Posts	I bought some Peltier coolers, and while I haven't done any serious experimentation with them, my limited experience with them may be of use. The ones I got were $5 ones off of ebay. They have a maximum draw of 136.8W, with 15.2V, 9A. They're 40mm by 40mm, and have a maximum temperature rating of 67 degrees C (152.6 F). One of the things that struck me about them is that they create a large temperature differential very quickly after applying a voltage. One side gets fairly cold, like the inside of a refrigerator, and the other gets hot actually pretty hot. As soon as power is disconnected both sides feel slightly warm. I think this is because it acts as a generator as soon as you stop applying voltage. I have not experimented with using them as generators, but might be able to. Now looking from a broad standpoint, thermoelectric generators are very inefficient. That being said, they are already efficient enough to generate lots of power, just not the ones that are commercially available. KOMATSU : Komatsu to Launch Sales of the World's Highest Efficiency Thermoelectric Generation Modules Developed In-house These are experimental thermoelectric generators, with a conversion efficiency of 7.2% and an output of 24W each for a 50mm x 50mm device. They can withstand temperatures up to 280C (536F). Now the problem is that they have an announced price of ¥ 30 000 per piece (approx 373USD). This is a cost of $15.54/W, for a device that only generates power while the engine is running. The cost is definitely the prohibitive factor in this case. If we look at a standard engine, it's efficiency is approximately 18%-20%. This means that out of the 100% of the energy released, about 80% is released as heat or sound. So if we take that 80% and could convert it at 7.2% efficiency (now I realize we cannot take all of the heat and convert it, this is just for the math) we get 5.76%. Now this may sound like a 5.76% increase in FE, but it's not, it's 5.76% of the total energy released. For example if the motor produces 20kw of power, then 80kw are put into heat and sound, and 5.76kw could potentially be harvested from the heat at 7.2% efficiency. This is an increase of about 28.8% in the energy we get from the engine. That is massive! Now unfortunately we cannot harvest near 5.76kw from this engine at 7.2% efficiency, as we cannot trap all the heat and exchange it with the devices perfectly. In summary, the devices are very cool, and look promising. They however at this point they are too expensive for use in vehicles that only use them for a few minutes or hours at a time. The conversion efficiency is already more than enough to make a significant impact on fuel economy, but not at their current cost. If the cost of Peltier coolers is reduced to a reasonable level, like even $6/W they would have huge potential in power plants converting excess heat into electricity. They could also be used to harvest waste heat from blacktops. To reach the point that they could be used in cars however, they would have to be cheap enough that they could pay for themselves in the few minutes or hours a day that they are used. (note for the 136.8W $5 Peltier coolers off of ebay, 136.8W is the maximum load, the output would be far less, but as to how much I do not know) TEC1-12709 TEC Thermoelectric Cooler Peltier Module New \| eBay Here a link if anybody would like to experiment with them. I would be happy to perform an experiment using the ones I have, if anybody has parameters they want tested please ask me.