How to use TEGs to create power with your exhaust heat

[serialk11r]

320C is not enough, I would not want to take chances with roasting them. Even the muffler on my car easily melts some mineral wool insulation and fiberglass.

What you want is this one:
https://www.alphabetenergy.com/product/powercard/

I also would use a boost converter to extract maximum power from the units.

[Daox]

PART 4

OMGz the wires!

Next up we need to take care of the electrical wiring. In this example, you would wire 2 TEGs in series, and 18 of them in parallel. It'll look something like this. Yep, its a bit messy, but really its nothing compared to an EV with BMS wires haha.





Controlling the heat!

Beyond this, if we've done things right, we'll also need some way to control the generator. We can't just hook it up to the battery and let'r rip. Its possible that the generator could overcharge the battery. We also need to stop the TEGs from discharging the battery when they aren't producing power. If you put power through a TEG, it will create heat on one side, and cool on the other. While this is neat, its not really what we're looking to do.
Therefore, we need a charge controller of some sort. This could be as simple as a switch if you want to keep things extremely simple. You'll also want a voltmeter to monitor things if you go that way. However, a much better idea is a purpose made charge controller. Something that is made for a solar panel or wind turbine would be what we're looking for. It will protect the battery from overcharging and from discharging as well. The charge controller will have to handle the max amps of this setup of 15A. Here is a cheap example of what I'm talking about. I just searched amazon real quickly and found one.

[freebeard]

http://www.layitlow.com/forums/16-post-your-rides/65803-show-pipes-4.html

Bellfower pipes (named for Bellflower, CA), with spikes or a high-bypass shroud would look [Valerian/Mad Max/Fifth Element/pick one]. I saw a 59 Chebby two-door with Bellflower pipes on I-5 this weekend.

Why isn't this on the front page yet? It's hard-core Ecomodder.

[Daox]

PART 5


image by BA1969

Holy cow, it cost how much?!?!

Now, assuming you've done all these things, which is totally possible. I've specifically left out one very important detail to this all, the price. If we need 36 TEGs, those TEGs are going to cost us $31 a piece (that is with their volume discount). That brings us to a total of $1116 just for the TEGs. That doesn't include the pipe, welding work that will need to be done, the mounting system, heat sinks for the cold side, or charge controller and wiring. So, this is where things sadly really fall apart. I've bought entire cars for less than what this system would cost. Granted, you could do this, and transfer the TEG modules from vehicle to vehicle assuming they last that long. In a automotive application I have my doubts though. In these high temperature situations, they estimate the TEGs to last about 4 years.

So, while this is all completely doable, its insanely expensive. But, that is how you do it folks! Hope you enjoyed the engineering exercise.

[Daox]

Originally Posted by serialk11r

320C is not enough, I would not want to take chances with roasting them. Even the muffler on my car easily melts some mineral wool insulation and fiberglass.

What you want is this one:
https://www.alphabetenergy.com/product/powercard/

I also would use a boost converter to extract maximum power from the units.

That may very well be true. We wouldn't know without testing. Tecteg does have what they call a 'hybrid' TEG that is good for 360C / 680F. It is actually a bit cheaper than the TEG I selected at $3.18/watt vs the one I selected which is $4.67/watt. I didn't go with it because it is 56mm vs the 40mm I wanted, and it also required 3 in series vs 2 or 4 which is a bit more ideal for the pipe setup I wanted to go with. Certainly doable though, and probably for a bit less cashola.

If 360C still isn't good enough they do have higher temp TEGs similar to the ones you linked. They have TEGs that will withstand temperatures of 850C / 1562F. The price is an order of magnitude more outrageous than the two listed above though. We're talking several hundred to over $1k for ONE TEG that produces only a few watts.

[California98Civic]

Originally Posted by serialk11r

320C is not enough, I would not want to take chances with roasting them. Even the muffler on my car easily melts some mineral wool insulation and fiberglass. ...

Originally Posted by Daox

That may very well be true. We wouldn't know without testing. ...

One could install them a bit "away" from the exhaust pipe or muffler in order to reduce how much of the exhaust heat can get communicated to the TEG. Obviously any such idea reduces output and efficiency, but if it extended the life of the system significantly and reduced the need for more costly and complex coolant systems ... still... all this points to perhaps why it is not a common mod: kinda complex and fairly expensive without the certainty of being able to fully replace the alternator reliably. My alternator is nearly 20 years old and still kicking, on demand, cold engine or hot engine. If a $1000 TEG system burned-out after 4 years, I would be bummed-out!

[teoman]

Ill dig up what i had found some time ago. I remember it as 1$ / watt

[serialk11r]

The Alphabet Energy TEGs are supposed to be cheaper because they're silicon based, but because the hot side temperature can be higher they are still effective. The only tidbit of info on cost I found was this:
https://www.alphabetenergy.com/alpha...gy-efficiency/

"Pricing for the PowerModule Developer Kit™ starts at $1,995."

That includes the TEGs, a stainless steel heat exchanger, coolant radiator, pump, and will generate >900W at higher temperature. That means the TEGs themselves are near the 1 dollar/watt range I believe, because that heat exchanger has got to be really expensive with all the little fins.

I think a good strategy would be to use only a few of them to generate say 90W so that you have just enough electrical power for most of the critical things like ignition/fuel pump, and cooling the generators with the heater circuit. That way the alternator isn't struggling at low engine speed, and you can underdrive the alternator for minor efficiency gains. The amount of extra heat going into the coolant is modest and the weight/complexity/cost would be very reasonable.

Engine exhaust at WOT is actually hotter than 700C, so temperature could still be a problem but given they advertise its use for truck exhaust, I am guessing it is probably capable of handling those temperatures. Then again they say 350C maximum continuous operation... I dunno.

I think this will be truly viable the day when someone comes out with a cheap 700C hot side capable TEG.

[CapriRacer]

This sounds like something that an F1 team could develop into a viable system for street usage. They spend a lot of money and the fruits of this are right where they would benefit.

[Daox]

I agree Capri. I think a lot of these TEG places could substantially lower prices if they got some real volume to sell. An OEM looking to do this may be able to build a TEG exhaust for 2-3x the cost of an alternator. This seems like a lot, but to gain 5-10% in fuel economy is a huge feat. On small cars, we know this can be done.