How much power do Peltier thermoelectric modules generally produce? Is it likely to be enough that a load of them could be attached to the exhaust system) (and other hot bits) of a car, in order to partially supply the electrical system?
-I appreciate this adds weight to the system - which means fuel is expended in just carrying the equipment around*, however, a decreased load on the alternator should result in better overall fuel efficiency - and the modules themselves would be running on energy that is otherwise simply thrown away.
Do they generate power in sufficiently appreciable amounts to make this even a tentatively worthwhile idea? - bearing in mind also that (I think) much of the weight of hobbyist-available Peltier modules is made up of metal heatsink plates, whereas in this application, they could be coupled directly to the metal of the exhaust - at least on the hot side.
*(So if your answer is going to be something to the effect that this would violate the laws of thermodynamics, you haven’t thought it through properly - they cost more to carry around, but it isn’t the simple act of carrying them that generates the power)
Well, you’d still need the big ass heatsink, only for the cold side in this application. Like the McDLT of yore, you want to keep the hot side hot and the cold side cold or your junctions won’t function.
As most cars have shields between the exhaust, and the metal car structure, I’d say that they are currently making an attempt to NOT heat the structure of the car. I do recognize that it’s concentrated heat v. distributed heat. While exceptionally useful in winter, I could see it making summer driving very uncomfortable. A large portion of the heat would transfer into the cabin of the car.
Though for taking the heat away to keep the McDL-Peltier hot on one side, and cold on the other (Thanks for the jingle stuck in my mind QED :eek:), the underside of the car does have significant airflow potential, the underside of the car could certainly be designed differently to either incorporate heat sink material, or redirect airflow to most efficiently cool a given heat sink.
We have a water bath that is maintained at 0.01 °C. We use it to maintain water triple points. It’s a fairly volumetric bath, and it’s completely cooled using TE modules. It works well. Though a few years ago I had to replace the TE modules. And it was a pain in the ass to do it. :mad:
Generally speaking, TE modules suck. They’re very inefficient.
Crafter_Man, is it the one Hart sells? Just curious.
Peltier modules are pretty inefficient heat engines, and pretty expensive. They get used for power generation in RPGs, radioisotope powered generators, for spacecraft that is going so far from the sun that sunlight is too weak for good solar power. They use an unusual semiconductor for the legs of the Peltier device, one which is otherwise only used by a Canadian company making power units for wood stoves in very remote and poorly sunlit areas. There have been something like 22 RPGs built in the entire history of the US space program and they average, I think, $20,000 per Watt to build (most of the cost being in the management of the radioisotope, most commonly either Neptunium or Plutoniom - I forget which).
I had a couple of conversations with some of the few people working on exhaust heat recovery, and while it sounded like the kind of thing a few people should keep looking at in case one of the constraints changes in a helpful way, it wasn’t a very exciting field.
I think the return on investment is much better in trying to get the engine to extract more heat energy out of the exhaust and releasing it at a lower temperature. Moreover, I bet you could make better use of exhaust heat to power an air conditioner heat pump (like a gas refrigerator does, using exhaust heat instead of natural or propane gas). Mostly, though, exhaust isn’t much worth chasing.
It was originally built by Yellow Springs Instrument Company (YSI). Isotech bought their line of temperature metrology equipment a while back.
Yea, it’s called a thermopile.
In a previous life I worked for a DOE R&D lab in Miamisburg, OH. One of the things we did was build thermoelectric generators for deep space satellites. The heat source for the generators was Pu-238: