# Any Experience using Peltier cells for Heating/Cooling on EVs



## madderscience (Jun 28, 2008)

Peltier modules are extremely inefficient (on the order of a few percent) as far as cooling is concerned so they are simply not practical as an air conditioning solution. For heating (where all that energy loss goes) you are better off with a simple and inexpensive ceramic heater core that can be had from a portable heater purchased at any hardware store.


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## jockepocke (Nov 24, 2009)

I have a friend who managed to cool his computer CPU with the mentioned device. It worked really good for him (too good - he had ice on the cpu unit!!!). Maybe cooling of the chopper?


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## Tesseract (Sep 27, 2008)

madderscience said:


> Peltier modules are extremely inefficient (on the order of a few percent)....


It's a little more complicated than that, but I agree that Peltier modules aren't a good choice for a/c or heating in a car. 

It's not so much that they are inefficient in general, but that they are inefficient when asked to maintain a large temperature differential. Their Coefficient of Performance (COP) - which is basically watts moved divided by watts consumed - goes up dramatically as the temperature difference goes down (oversimplifying, but that's the general case).

So for example, a Peltier module that uses 40W of power might move 60W of heat with a 5C differential but only 40W of heat with a 10C difference and 15W of heat with a 20C difference. So, asking the Peltier module to cool down the interior of a car to 15C when the outside/underhood temp is 40C results in a very low COP, which is the same as saying their efficiency is awful 

However, they are a good choice for cooling down electronic equipment cabinets when you don't necessarily want to make the interior colder than the exterior, you simply want to keep it from getting any hotter.

Here's a useful site to learn more about the specifics from a TE cooler manufacturer:

http://www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html


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## _GonZo_ (Mar 23, 2009)

So in other words they can be only some efficient for cooling if a lot of heat is removed from the hot side and viceversa. in order to keep the ºT differential as loow as posible.
Is this right?


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## Tesseract (Sep 27, 2008)

_GonZo_ said:


> So in other words they can be only some efficient for cooling if a lot of heat is removed from the hot side and viceversa. in order to keep the ºT differential as loow as posible.
> Is this right?


More or less. To put it another way, the closer in temperature the hot and cold sides are, the more heat (Watts) you can transport from the cold side to the hot side.

jockepocke's friend is using a TE module in a popular fashion - to cool a CPU down so much it ices over - but the module might be using 100W of power to only move 30-40W of heat from the CPU, so the COP would 0.3 to 0.4 in such an instance (compared to 3-6 for a mechanical refrigerator... if you could get them that small and for so little a heat load... maybe you can - would be awfully cute looking, eh?).


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## _GonZo_ (Mar 23, 2009)

Well may be not so good idea then but is so simple sistem that may worth a try...
Actually I just found a peltier manufacturer that theyr cells have a good characteristic, they can be polarity reversed so the cool and hot sides changes.
You can see it here: http://www.fujitaka.com/pub/peltier/english/products/products2.html

I was thinking for cooling to install it on the car floor so the heat is removed by the air down flow and the cell is always in the shadow under the car. (I live in a hot area, so I need more cooling than heating)

For heating the best will be to install it on the roof so gets some sun... (not my case)


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## _GonZo_ (Mar 23, 2009)

Tesseract said:


> More or less. To put it another way, the closer in temperature the hot and cold sides are, the more heat (Watts) you can transport from the cold side to the hot side.


Actually that is the same for a mechanical system if I do not remenber badly when I studied.


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## PhantomPholly (Aug 20, 2008)

I may be way off base, but my understanding is that Peltier units are actually the MOST efficient way to cool / heat provided you don't need to generate a huge temperature differential. Thus, they have 12v "coolers" which will chill beverages to around 45 on a 95 degree day, but won't generate much more than a 50 degree differential.

They used Peltier coolers for electronic equipment carried on fighters (thermal seekers; radar jammers; etc.) because they "did enough" and were far lighter than any mechanical solution. So, if you can stand to have your car "cooler but not cold" on a hot day, it might be a more efficient / lighter solution than a mechanical AC. However, price will be a consideration as the amount of coolers you will need will be fairly high.


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## DavidDymaxion (Dec 1, 2008)

What about heating? The inefficiency is a virtue in that case, any heat you also move is a bonus. Another idea is to pull heat from exhausted air and move it to incoming air.



_GonZo_ said:


> Does any one have tested, installed or researched about Peltier cells for heating and/or cooling an EV?


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## _GonZo_ (Mar 23, 2009)

DavidDymaxion said:


> What about heating? The inefficiency is a virtue in that case, any heat you also move is a bonus. Another idea is to pull heat from exhausted air and move it to incoming air.


In an EV there is suposse to not be a exaust sistem 
Actually I think in IC cars the heat system is well resolved, it uses the super extra heat from the motor...



> They used Peltier coolers for electronic equipment carried on fighters (thermal seekers; radar jammers; etc.) because they "did enough" and were far lighter than any mechanical solution. So, if you can stand to have your car "cooler but not cold" on a hot day, it might be a more efficient / lighter solution than a mechanical AC. However, price will be a consideration as the amount of coolers you will need will be fairly high.


The simplicity of the system and light weight is what I like.
Do not know about price yet.
Another point to check will be longevity of the cells...


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## DavidDymaxion (Dec 1, 2008)

Is there any reason Peltiers wouldn't last indefinitely?

Hmmmm, I was thinking about the exiting passenger air as being a form of clean exhaust -- but maybe not right after soccer practice! Anyway, on my car I have two hot air inputs. I'm thinking of making one a heat input, the other a heat exhaust, and using a heat exchanger to pull heat out of the exhausting air and put it into the intake air. This would provide some of the benefit of recirculating the air, without the detriment of increasing humidity fogging the windows (particularly right after soccer practice!).


_GonZo_ said:


> In an EV there is suposse to not be a exaust sistem
> Actually I think in IC cars the heat system is well resolved, it uses the super extra heat from the motor...
> 
> The simplicity of the system and light weight is what I like.
> ...


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