How to use TEGs to create power with your exhaust heat

[Fionn]

J. Langley, M. Taylor, G. Wagner, and S. Morris, “Thermoelectric Energy Harvesting from Small Aircraft Engines,” SAE International, 2009.
I haven't found a free source for the paper yet but it may be of interest.

Thermoelectric Generator Development for Automotive Waste Heat Recovery
This one is right up our alley.
https://www.energy.gov/sites/prod/fi...10_meisner.pdf

[RedDevil]

Originally Posted by Fionn

J. Langley, M. Taylor, G. Wagner, and S. Morris, “Thermoelectric Energy Harvesting from Small Aircraft Engines,” SAE International, 2009.
I haven't found a free source for the paper yet but it may be of interest.

Thermoelectric Generator Development for Automotive Waste Heat Recovery
This one is right up our alley.
https://www.energy.gov/sites/prod/fi...10_meisner.pdf

From that last PDF:

Originally Posted by GM

We expect ~ 1 mpg (~ 5 %) fuel economy improvement for
Suburban (average 350 W and 600 W for the FTP city and
highway driving cycles, respectively.)
This technology is well-suited to other vehicle platforms such as
passenger cars and hybrids.

That is something. That would flip many cars over here into a lower tax category, dropping the purchase price or lease cost significantly - never mind the fuel saved.

[teoman]

Ill try to doewnload that paper tomorrow.

[IamIan]

FYI

If you're not wanting to build it yourself .. the TEG modules, heat sinks , etc .. but have some cash to burn .. you can just buy the TEG device .. ~80% pre-done/made .. just have to install and plum coolant.

---
Hot Air / Cold Liquid.

Plum the coolant to a radiator.

TEG-HL350-48V

~350W electrical output .. if ~300Celcius Hot (400C max) and ~50Celcius Cold .. ~3 Liters per minute coolant flow.

18.8kg
500mm x 151mm x 259mm
48VDC nominal .. 96VDC Open Circuit

$6,000 +Shipping for 1
$3,000/ea +Shipping for 10+
$1,500/ea +Shipping for 50+
$1,300/ea +Shipping for 100+

----
Or .. just a hot plate to cold liquid .. need to attach the plate to exhaust , and run the coolant to a radiator.

TEG-HL100-12V-2

~100W electrical output
@ ~270C Hot ~30C cold ~2.8Liter per minute
3 kg
302mm x 150mm x 58mm
12VDC Nominal 24VDC open circuit

$600 +Shipping for 1
$300/ea +Shipping for 10+
$250/ea +Shipping for 50+
$220/ea +Shipping for 100+

[Galane]

What I'd be interested in is putting enough TEGs on the exhaust to run some TECs for air conditioning.

From what I've read, the best efficiency for TECs is at half their rated maximum voltage. Higher than that the heat produced from the hot side goes up much faster than the cold side. Instead of trying to cool a volume with one big TEC at 12 volts, try two of the same size at 6 volts (put them in series to divide the voltage) to get more cooling with the same power input. If you need an extra chill, switch the TECs to parallel.

Clamp TECs between aluminum blocks with channels for coolant. Plumb the hot side to an air conditioning condenser and the cold side to the vehicle's heater core. Add some valves to isolate the TEC unit and heater core from the engine coolant, while using part of the power from the TEGs on the exhaust to run electric pumps on the hot and cold sides of the TEC unit. The heat exchangers on the TECs have to be thermally isolated from each other so heat doesn't flow through to the cold side. TEC coolers usually have shouldered plastic bushings at one or both ends of the mounting bolts through their heat sinks.

[Fionn]

The efficiency both ways is pretty horrible so I don't think it's practical at this point to use them to power AC. It's only harvesting waste heat with them that makes sense since the efficiency is of no relevance. You'd be lucky to end up with 50W worth of cooling on a setup that would be practical to install on a vehicle if you used TEGs/ TECs on both sides.
You'd be far better off to run a DC AC unit from the TEGs but even better would be to just use a normal AC compressor driven from the engine I think!

[IamIan]

Originally Posted by Fionn

The efficiency both ways is pretty horrible so I don't think it's practical at this point to use them to power AC. It's only harvesting waste heat with them that makes sense since the efficiency is of no relevance. You'd be lucky to end up with 50W worth of cooling on a setup that would be practical to install on a vehicle if you used TEGs/ TECs on both sides.
You'd be far better off to run a DC AC unit from the TEGs but even better would be to just use a normal AC compressor driven from the engine I think!

FYI
They also have DC driven compressor heat pumps .. which will save a step in DC to AC conversion losses .. but , the AC driven are usually more mass produced (economies of scale have benefits).

One such example (there are others) the small ~3kg , ~1,000 BTU/HR electric air conditioning compressor based heat pump I have is run from 12VDC .. although its SEER of ~9 is nothing to write home about .. it is much better than what any TEC based SEER would be.

---
That having been said .. I'll add .. as far as this particular topic is concerned .. Any waste heat recovered / recycled is beneficial (net energy efficiency) .. but only in so much as it reduces/offsets the energy you would have otherwise consumed anyway .. such as reducing parasitic alternator load on ICE with a ~350W exhaust waste recovery .. if you end up spending it in some way that you would not have otherwise spent energy to do .. that isn't a net energy efficiency benefit .. it might be some other type of benefit .. comfort .. convenience .. etc.

[Fionn]

Originally Posted by IamIan

FYI
They also have DC driven compressor heat pumps .. which will save a step in DC to AC conversion losses ..

Sorry, my post was totally unclear, I was actually referring to DC powered air conditioning units as opposed to an inverter.
DC compressors are rare beasts outside of RV fridges though in my experience.

[Galane]

RV refrigerators don't use compressors. They use an absorption cycle, usually with ammonia and hydrogen. Input energy is heat, either from a gas flame or CD or AC electric heater. Some of them can use all three. https://www.rvrepairclub.com/article...eration-works/

[Fionn]

You'll find that nobody really uses 3 way or absorption fridges any longer, DC compressor based ones are far more efficient and rule the market now.
Check out the ones sold by Waeco, IndelB and others. Mine uses as little as 0.1kWh per day and can cool down to -20C if required. I can run it from a solar panel in a van even in winter here in Ireland.
There are also control boards available for those DC compressors to run directly from a solar panel with no battery or charge controller at all.