VW Golf with exhaust thermoelectric power: +5% MPG

[MetroMPG]

Search the forums here and you'll find more than a couple of threads about using waste heat from the exhaust to generate electricity.

Here's a working example:

The first demonstration in Europe of a family sized Volkswagen car fitted with a thermoelectric generator was unveiled at the Thermoelektrik-Eine Chance Fur Die Atomobillindustrie meeting held in Berlin, October 2008. Under motorway driving conditions a 600W(e) output is claimed. The additional electrical power serves to meet around 30% of the car's electrical requirement. This reduces the engine's mechanical load such as that due to the alternator and results in a reduction in fuel consumption of more than 5%.

Source: [ZTnews] VW & BMW Putting TEGs Automobiles | International Thermoelectric Society via Green Car Congress: Volkswagen Shows Thermoelectric Generator for Waste Heat Recovery

[Daox]

Sounds like they need a larger deep cycle battery so they can capture and use more of the energy. 600W is 50A @ 12V. Thats not too far from the max output of a normal alternator. I sure as heck know that a car doesn't use 50A just running down the highway, yet they only get 30% of electricity production from it?

[Piwoslaw]

I wonder what's the cost of installing a gizmo like that? Maybe they could show up in the aftermarket, or just DIY.

[jamesqf]

The real problem is that thermoelectric devices just aren't real efficient, so only a small part of the exhaust heat gets converted.

[basslover911]

A closed loop water to steam system would be much more efficient in my opinion.

How much heavier it would be? Well, thats the problem...

[MetroMPG]

Heavier and more complicated. The plus side of the thermoelectric approach is it's (probably) solid state & dead reliable.

Tim: you're right, their figures don't add up. 600w production in highway use, yet they're claiming that offsets 30% of power needs. Which means the car needs 2000 watts to drive down the highway? Don't think so. Their figures need explaining.

Maybe the clue is "600 W(e)". What's (e)? I haven't seen that before.

[Ryland]

only thing that i can see is that 600 watts is fully warmed up and that it might take a while for it to warm up, even tho it really shouldn't, either that or it might be an estimation of power out put in all weather conditions as it's output might be more in sub freezing weather and lower in hot weather.

[ConnClark]

I don't buy it. It may get 600 Watts running flat out in first gear on the highway but typical driving I doubt it. I also have serious doubts about the 5% better mileage. If the thermal electric generator supplies 1/3 the electrical power that would mean that the alternator saps 15% off your mileage. Its bunk and bogus claims.

This is just sensationalistic marketing hype.

[jjackstone]

Actually if I recall, from MetroMPG's and other's posts, the alternator disconnect has been showing about a ten percent gain in overall FE. Please correct me if I'm wrong. The TE generators do work but as has been stated are highly inefficient-- unless a newer technology has been released, they are generally between 3-5% efficient.
Doesn't matter what gear the vehicle is in, just the temperature differential between the "cold" side and the "hot " side of the junction.

Here is a link to one manufacturer of these junctions.
Hi-Z Technology, Inc.

Here is a link to a study performed using their devices a few years ago.
http://www.hi-z.com/papers/ICT%20200...ing(China).pdf

The main problem(just like solar panels) is the hi cost. Apparently the prices are decreasing if the devices are actually going to be placed in cars.

JJ

[blueflame]

"Doesn't matter what gear the vehicle is in, just the temperature differential between the "cold" side and the "hot " side of the junction."

Does this mean thermoelectric exhaust generators as these, work better in cold climates?

There has been a lot of talk here recently re retaining, reusing wasted heat...all these proposed/suggested systems do in fact work, but cost is high in retrofit mode...

Probably by the time we get it right everyone will be going electric?