I was reading a cool article on a new electric car called the Think, and one of the things they mentioned was the Sterling engine. I would LOVE too buy one of these electric cars but I’m thinking they won’t be available in the US for quite some time (if ever).
Anyway, it got me thinking…is it possible too use the heat in a cars cab during the summer months in some way too power or recharge the car? Here in the Great South West anyway, one thing we have in abundance, especially in the summer, is heat. Lots and lots of heat…especially in our enclosed cars. Is there any way too use that? Is anyone looking into this possibility? Even in the winter out here the interior of our cars is quite toasty, especially compared too the outside temperature.
The Stirling engine you link to is essentally a temperature-difference engine - if you can find close to each other a source of heat and a source of cooling whose temperature difference is, say, a few hundred degrees C, then you can do useful work. (I think it might be hard to find that sort of difference between the inside and the outside of a car parked in the sun.)
Apologies…I didn’t mean to imply the Sterling was the engine I had in mind. It was just an interesting part of the Think car. My question was simply could the heat in a car cab be used?
Well, your car’s engine is basically a heat engine.
But I understand what you’re getting at. It’s called “energy scavenging.” There are many ways to do it, but they probably wouldn’t be practical or efficient in a car. One that comes to mind is the thermopile, which is an electrical device that directly converts a temperature difference into DC electricity.
There’s no work available in static heat. In order for heat to do work, it has to move from a higher temperature to a lower temperature. Just like the energy available in a like on top of a mountain, which has to move from a higher gravitational potential to a lower one to generate electricity.
A thermocouple can generate current from a temperature difference, but in your car, for example, the outside temperature is high as well, and given the small temperature difference, the heat difference will probably only generate enough electricity to measure. Here’s a Wikipedia page on the thermoelectric effect.
With all that outdoor heat, you should be able to use it directly.
I’ve seen lots of science shows show off cooking hot dogs with just mirrors, but never seen where an actual café used it. Even if it’s just auxiliary heat, there should be a way to send it down from the roof to the grill surface, bypassing the inefficiencies of solar cells.
Hell, why do it the hard way? I remember a new show when i was in high school in Sacramento, CA that stuck a roast in the window of a car, and 8 hours later, it was done quite nicely.
Of course, I imagine doing that would end up making your car smell like roast, but that’s certianly not a BAD thing, per se.
If the outdoors is hotter than the indoors, the only way you can use the outdoor heat is by heating up the indoors, too. And probably the reason that it’s hotter outdoors in the first place is that whoever owns the building is spending energy to run an air conditioner, and you can’t possibly gain more energy from the outside heat than you’re spending on the air conditioner.
I realize that the Stirling operates best with large temperature differences, but can a low temp system make usable power if it is large enough, or does the friction of a large system prevent that?
As an example: Figure using a system with something the size of 55-gallon drums as cylinders and pistons. The hot side is above ground with reflectors wrapped around it to give it as much heat from direct sunlight as possible. The cold side would be buried in the ground, perhaps with ducting to it from longer laterals so as to get the benefit of the cooler temps typically found just a few feet below ground level.
On a sunny day, would a setup like this make a couple of horsepower, enough to power a small generator?
The easiest way to get power back is through a Peltier generator. A Peltier generator is a solid state device that converts a temperature difference directly into electrical power. It’s practical and relatively easy to generate energy from waste heat using these devices. However, the amount of energy captured from the waste heat doesn’t come close to covering the capital cost of the Peltier units.
It should be easy to do. However, the small amount of energy generated wouldn’t even come close to justifying the capital cost. I’d also wager that Solar Panels are going to be more cost effective.
If you are talking about a car with a regular gas engine or a hybrid, the engine produces tons of waste heat. BMW has come up with a system to recover some of this waste heat as energy – http://www.greencarcongress.com/2005/12/bmw_developing_.html