[Jim Rowland]

Here is some info on thermoelectric tech.
http://www.enn.com/top_stories/article/37307/print
This could possibly be applied to the ICE running the generator! every little bit helps. Go GM Go!!

 

[BigRedFed]

I've been wondering why this hasn't been researched more heavily before now. There are many points in the car that this tech could be utilized, not just the exhaust pipe. You could theoretically coat the whole engine compartment that the ICE is contained in to capture the waste heat from the whole thing. If my understanding is correct, thermoelectric compounds could also act as a good insulating blanket. Say you wrap the battery in this stuff, while at home, you start charging, this keeps the battery warm, it starts to get cold outside, you generate a small current in the material that can be redirected to the battery. While this might not cause any significant increase in the battery power, it might keep the temperature of the battery up and take longer for the battery to reach the temp where it can not operate. Someone will probably weigh in here and call this idea crap, but I don't claim to understand the physics of thermoelectric compounds completely.

The cost of (creating a)/(or covering the) battery case (out of)/(in) a thermoelectric compound is probably prohibitive as well, even if the idea is sound.

 

[JoeReal]

The recent thermoelectric implementation that they have done is still one of the less inefficient ways of converting heat energy into electricity.

There are others, such as the modified form of Organic Rankine Cycle, can utilize more heat to mechanical energy to help power the wheels or turn the generator, but requires massive footprint.

 

[dagwood55]

There's probably a good reason... efficiency (as opposed to the cost), toxicity, reliability, engineering to other constraints, etc. The effect is pretty well known, so I suppose there's some basic problem with using it to generate power or whatever (my guess is low efficiency).

Wiki has a decent article on thermoelectric which answers all your questions with a lot of symbols and nowhere does it say, "it's useful!" or "it's a waste of time!"

I know of one consumer device, a thermoelectric generator that sits atop a kerosene lamp to run a small radio. That's not a lot of juice from a pretty potent heat source.

However, if you look at the Wiki article, there's some related links that you might find interesting and helpful.

 

[JoeReal]

One way of utilizing heat is to heat up water and split the hydrogen and oxygen and feed into the range extender engine. Little electricity is needed if water is heated and you'll recover more from the heat energy.

Here's a new concept car recently shown that uses hydrogen on demand via onboard electrolysis of water:

from CNET:
http://news.cnet.com/8301-11128_3-9960833-54.html?tag=cd.blog

 

[dagwood55]

One way of utilizing heat is to heat up water and split the hydrogen and oxygen and feed into the range extender engine. Little electricity is needed if water is heated and you'll recover more from the heat energy.

Here's a new concept car recently shown that uses hydrogen on demand via onboard electrolysis of water:

from CNET:
http://news.cnet.com/8301-11128_3-9960833-54.html?tag=cd.blog

Hendler posted something like that the other day. I'm very doubtful that there's any advantage to the on-board water cracking system. Cutting the water apart takes energy. Some of it gets lost. The H20 tank and cracking equipment weighs something and gets carried around. This is extremely unlikely to create any advantage.

 

[JoeReal]

The CNET article mentioned on demand cracking of water, so they don't need to use a large pressurized tank to store hydrogen. And yes I agree that we don't know the exact advantages, if any, of using hydrogen mixed with gasoline.

But if ever, as I am suggesting, they should take advantage of the fact that it takes far fewer electric power to split heated water than colder water. Thus you'll get more power in the hydrogen produced than the electricity you put in because of the waste heat energy used to heat the water. At least, that's the theory. As to the practice of doing that in an actual vehicle, the only reference that I can find are HHO scammers.

There is a company, the name escapes me at the moment, that have split water at by heating at high temperature without using electrolysis but with the use of catalysts. Water is pressurized so that it can continue to raise temperature above its boiling point. And car engines and exhaust gases have a lot higher temperature than the boiling point of water.

 

[dagwood55]

As in, some of the energy comes from waste heat? Mmmmmmaybe. I remain highly skeptical.

However, back to thermoelectrics. Perhaps it's not as far-fetched as I might have thought...

BMW Improves Efficiency with TE

And it links to another article with interesting details...

 

[Jim Rowland]

look into it GM

The way it looks, there is no power loss when this tech is applied. So, even if the gain is small it is still a gain in generation of electricity. If BMW can gain MPG just by reducing the amount of power generated then it would be a nice touch for the Volt. It is an EV so depending on the cost of this devise, it could very well be efficeint use some extra volts!

 

[Jason M. Hendler]

Sounds like a solid state approach, similar to the Rankine cycle approach Honda is testing:

Link

1/3 of the energy created in combustion goes out the tail pipe and radiator, so capturing any / all that heat for other uses is a good idea.

 

[srmarti]

I remember seeing articles on thermoelectric generators on the Chevy Suburban exhaust could provide 1 mpg and 800 watts at highway speeds. No mention of cost though. Searching around the web, it looks pretty expensive to add to the vehicle; maybe on the order of $10 per watt.

 

[John-99]

Sounds like a solid state approach, similar to the Rankine cycle approach Honda is testing:

Link

1/3 of the energy created in combustion goes out the tail pipe and radiator, so capturing any / all that heat for other uses is a good idea.

Thanks. Here it is, Honda Rankine Cycle -click 1/3? And the rest. Having ancillaries all electric, then this would be feasible if sized properly. But it gets complicated. BMW claimed 20% better fuel consumption, by elimination of parasitic engine loses.

So if this Rankine unit was coupled to say the Lotus range extender. more mpg would be had.

Absorption a/c units can run off waste exhaust heat. I believe Cadillac were using one.

 

[John-99]

I remember seeing articles on thermoelectric generators on the Chevy Suburban exhaust could provide 1 mpg and 800 watts at highway speeds. No mention of cost though. Searching around the web, it looks pretty expensive to add to the vehicle; maybe on the order of $10 per watt.

The efficiency is dire. That is why a small Stirling or Rankine unit is better to turn an alternator.

 

[John-99]

There is a small heating boiler used for boats run off diesel. BMW put this in their 4x4s and large cars. It is 80% efficiency. So it is used to heat up the engine and the car. When idling to warm up, the engine is about 15% efficient, so big savings in this respect. It can be remotely switched on with the heater fan and small electric pump as well. The engine is warmed up, the screen de-iced and the cab warm. It can be used normally, even in summer, giving a quick warm up as it sends hot water directly to the cylinder head to get the choke off quicker, eliminate glow plugs, and heater is hot quicker if needed, then it cuts out.

It does improve overall mpg significantly. How much? Depends on your climate.

BMW have done a lot to tweak around the edges to claw back. They are behind in EVs, etc, that's why.

 

[wtiger]

Teg

You should be able to get a descent output from a thermal electric generator from the tailpipe. A 150hp car should produce several Kw of peak power from a well designed TEG. From what I understook one of the big drawbacks is the cost.

I found this while looking around for numbers. It looks like it could be very promising for making such a setup cost effective

http://www.physorg.com/news186409698.html

 

[John-99]

http://green.autoblog.com/2008/02/18/honda-testing-rankine-cycle-hybrid-to-recapture-energy/
Honda Rankine exhaust heat -click
Looking at this, it gets complicated and big. To the point you may as well dispense with the IC engine and Rankine unit and install a full external combustion Stirling unit - another unit ideal as a range extender, or even a small compact steam cell engine.

.

 

[John-99]

You should be able to get a descent output from a thermal electric generator from the tailpipe. A 150hp car should produce several Kw of peak power from a well designed TEG. From what I understook one of the big drawbacks is the cost.

I found this while looking around for numbers. It looks like it could be very promising for making such a setup cost effective

http://www.physorg.com/news186409698.html

Depending on size, the cost will come down as they always do, it may be worth having a large version of this heated only by a small diesel oil burner to make electricity. All Solved!!

.

 

[Andy0x1]

can run off waste exhaust heat. I believe Cadillac were using one.

Stripping heat from your exhaust has a cost too. The hotter your exhaust pipe, the thinner the air, the easier it can be expelled from the system.

Cooling the exhaust will increase its density reducing efficiency.

(Not to say the benefits don't outweigh the cons.)