Thermoelectric Generators (TEGs)

Okay, so I've been hearing about these chips.  They convert changes in air temp into electricity.   I've seen only one in action; a cast iron stove-top fan that spins more rapidly the hotter the cooktop gets (and insanely fast when you put a pot of snow behind it to melt!).  The fan's purpose is to push that warm air through the dwelling.  But it's powered solely by that little chip (or pair of chips?)

I am having a hard time finding out what they're called, who makes them, what they cost, how they can be put to use, and if they're worth their salt.  Anyone here have experience with these things?  I can think of all kinds of crazy applications for a tiny chip that supposedly has a superiorly efficient electricity production just powered by temp differences!  But I need to know more!  Much more!

Hi Jen, they're called TEG's.  One place I've seen them for sale is Tegmart.  I don't know much about them other than they sound awesome.

Jen Fan wrote:...a tiny chip that supposedly has a superiorly efficient electricity production

I'm afraid it's the exact opposite - their efficiency is awful - 5% to 8% according to the Wikipedia page. TEGs are really only worth the trouble if you live in the arctic circle, or in deep space (basically where solar PV panels are not viable.

http://www.genthermglobalpower.com/products/thermoelectric-generators-tegs

These have been in use here (Canada) in the oil & gas industry for 30 years.  Efficiency is not a requirement, the application usually command and control.
in the dead of winter at 55+ Deg north Solar is not really an option. Gen-sets require fuel and maintenance, TEG just needs a clean fuel, propane or natural gas.
steady voltage and current keeps battery's charged and well sites running. I have also run remote mountain top communications installations with TEG,

Thanks for the link Ron, I hadn't seen bigger units like this.  Do you know if anyone sells a unit where you supply the heat (hot water or equiv) and it just makes the electricity?  

For the amount of energy they produce, TEGs are REALLY expensive.

That said, if you want a complete unit ready to go, BioLite makes some for camping:
https://www.bioliteenergy.com/

The CampStove 2 creates up to 3 watts of power for charging cell phones, etc. and only costs $200 (did I mention these things are really expensive?)

Note: Biolite also makes cheaper stoves that just have battery powered fans on them (no TEG), don't buy one of those by mistake.

Peter VanDerWal wrote:The CampStove 2 creates up to 3 watts of power for charging cell phones, etc. and only costs $200 (did I mention these things are really expensive?)

That's a very expensive stove then, 3W TEG chips are less than $3 on ebay.

I was responding to the request for information on complete, ready to run, products.

Most (if not all) of the cheap TEG modules on eBay are actually Peltier modules.  

Peltier and TEG are basically the same, but the construction is optimized for one or the other.  Peltiers can sometimes work as TEGs (sort of) but they generally have even worse efficiency than TEGs that are designed to be TEGs.
There are quite a few articles online about people that have build TEGs using Peltiers, most either don't work, or work poorly.

TEGs, ones that are actually manufactured to be TEGs, run about $50 each for 3W modules.  I'm pretty sure the only reason they are that expensive is supply and demand.  Not a lot of demand, so not a lot of manufactures make TEGs.

Okay, so it looks like the peltier modules don't produce electricity?  Or at least anything worth trying to utilize.  They simply heat and cool?  And the actual TEG chips do produce electricity?   Or if that is not correct, what is the difference?  I'm having a difficult time finding info on the different models.  

For lack of finding an informative site, I'm mostly relying on web reviews and specs for available products.  It's a bit tedious!

And if they ARE truly different, how does one weed out a true TEG from a peltier model?  Just about every product I find online looks identical with little or no info about the differences/specs, even when one is 3-5x the price.

Jen Fan wrote:Okay, so it looks like the peltier modules don't produce electricity?  Or at least anything worth trying to utilize.  They simply heat and cool?  And the actual TEG chips do produce electricity?   Or if that is not correct, what is the difference?  I'm having a difficult time finding info on the different models.  

For lack of finding an informative site, I'm mostly relying on web reviews and specs for available products.  It's a bit tedious!

And if they ARE truly different, how does one weed out a true TEG from a peltier model?  Just about every product I find online looks identical with little or no info about the differences/specs, even when one is 3-5x the price.

Jen, do not be discouraged by the nays. TEG devices are not common and knowledge of their operation and use, even less common.

I am learning about them and there is quite a bit of information.
this is some of the best. What can be purchased today versus the test bed used in the article is a wide gap, much better modules available today, but the data is awesome.

https://triz-journal.com/generating-electricity-families-northern-sweden/

People use these devices all over scandinavia and they are common in oil/gas as another comment pointed out. (Those industrial units look capable and expensive, i like it!).

Here are a couple usefull links for a some otems of interest in my research.

http://thermoelectric-generator.com/product/wood-stove-thermoelectric-generator-rabbit-ear/

Stoked about the 100w model!
http://www.devilwatt.com/products

And a previous thread i started on the topic. There are quite a few in here and there are some great leads, not much project documentary though. Im trying to get one and feature the installation here as an alternative to a wind generator. If you heat with biomass, the efficiency is not paramount, just the practicality and capacity per dollar for converting a portion of "waste heat" common to operation of wood heaters and stoves.

https://permies.com/t/72441/Thermoelectric-Generators-supplement-wintertime-solar

https://en.m.wikipedia.org/wiki/Thermoelectric_effect

Good luck, hope to see your project in here!

Here's another Permie who has a teg in operation:  Byron in the Yukon

To explain slightly, you can either put electricity (lots) *into* the peltier module aka TEG and have it be a heat pump / refrigerator, or you can let heat (lots) flow across the peltier module and it will output a small amount of electric power. Most peltier modules are designed for cooling electronics and micro-refrigerators, since that is what they are most practical for. Solid-state TEG/peltier units like we are describing are much less efficient (in either direction) than normal engines/heat pumps/refrigerators with compressors and moving parts, but they are extremely compact and reliable as long as they are not overheated or exposed to moisture (if unsealed).


In the 1950s, there were Russian TEGs used to power small radios from a (large) oil lamp. You had to hang the (hot) lamp outside in the (cold) Russian air. This was in an age when radios still used tubes (eat batteries), and kerosene was more common than batteries and easier to store.

Today, I doubt that in our kinds of applications it is ever going to be more practical to use TEGs rather than solar panels, which are available at less that 1USD a watt versus several USD a watt for the ones I saw at TEGmarket. For cases where the sun is not shining, there are better types of generators such as steam engines or internal combustion engines powered by gasified biomass. They have a kind of narrow temperature range, which is exactly what you don't want for efficiency with heat engines of any kind. The ideal application is something where your high temperature is no more than about 80 C (lest you cook the module) and the cold temperature is not realistically going to be colder than the ground or the weather. So realistically, "rotting compost/manure/whatever in the snow". This will provide miniscule amounts of power. Good heat sinking is absolutely essential.

(What you do want is something like a jet engine running white hot... with air going into the intake at 40 below. Or a gasoline/diesel/steam engine running at room temperature, for normal people.)

(Two realistic applications for this kind of technology that I've encountered: Small fans that automatically run when placed on a wood stove, and wristwatches powered by body heat, though the latter are viewed as a bit of a gimmick and I find my solar watch(s) work fine anyway)

I think that the manufacture and lifetime of solar panels is more ecological anyway, thermoelectrics are made of some weird materials and you need a lot more of them for the same amount of power.

OTOH, you can use peltier modules as heat pumps -- treat them like heating elements, but supply the cold side with something to hold them at room temperature and you will get twice as much heat out as you put electric power in. A specific application that I see for this is a regenerative heater for composting toilet ventilation. Warm air exhausting from the toilet will first pre-heat cold make-up air from outdoors, and then be heated by a small bank of peltier modules that transfer heat from either indoors ambient or from the warm exhaust air. As a result, the toilet can be continuously ventilated and stay warm for composting even in winter. Power would be provided by an independent small solar panel of about a hundred watts.



Another viable use of TEGs is to recover waste heat from anything that produces waste heat in the right temperature range. Some engineering is needed to keep this from just being silly and pointless, but in the right place they can be decisive. squeezing the last watt out of the flue of a rocket mass heater, maybe...?

Although they have a low efficiency, one should consider that the once installed there is no cost to operate, as long as you have a hot area to place the unit(and a relatively cooler atmosphere) you are getting electricity at no cost. I believe this negates their 5-8% efficiency claims by wiki(providing you are not making additional modifications to accommodate the placement of the TEG)

For me the issue isn't their low efficiency.  Free energy is free energy.
For me the issue is the cost per watt (solar PV is MUCH cheaper) and the fact that for most people they will only be useful during the winter (which makes the cost per watt even worse)

On the other hand, if you  live somewhere that has long winters without much sunlight, then they might be cost effective.  Pretty much has to be a case by case issue.

For me, our winters are mild and we actually get more average sunlight during February than we do in July.

Matt Coston wrote:their efficiency is awful - 5% to 8% according to the Wikipedia page.

Is that 5-8% efficiency as in, "lost", or "not-converted"?

Perhaps on a wood stove, that's the same thing, but here's what I'm thinking:  You have an insulated barrel of hot water gathered by your solar batch water heater during the day.  Then, at night (when it's cooler), you let it dissipate through your TEG.

Back to my question, is the heat leaking off through the TEG and lost/wasted, or merely not converted?

Anybody ever play with these?  I'd sure like to know!

No the 5 to 8 percent efficiency means of the say 100 watts of heat energy that passes through the teg assembly 5 to 8 watts of electricity is created. If you heat with wood already and have a good passive energy sink like a tank of water or some low wattage pumped radiant floor then it might be a good solution. A passive solution can work but its efficiency will be even worse since the cold side will heat up too fast. I use two teg powered fans on my stove to move air and have thought If I was serious I would channel the cold air intake for the house over the cold side fins to add some wattage to it.  
David