Reply #13: An idea in there, perhaps with some confusion on terms.

[Ready4Change]

Global warming isn't due to the heat that comes from cars exhaust pipes or factory smoke stacks. It is due to materials in those exhausts, which get into the atmosphere and then cause that atmosphere to trap a bit more of the heat that the Earth would otherwise radiate into space. (Heat which originally comes from the sun, and which outweighs what our cars and factories put out by a heavy margin.) The over all average temperature change due to the materials we add is actually very small. But since it effects such a large area, the energy it represents can make large changes in weather patterns, making them more extreme. Thus global 'warming' can result in deeper cold and heavy snow falls, because making those more extreme than normal takes more energy. In other words, global 'warming' can make it colder at times, and should be called something like 'global energizing' instead.

However, that doesn't negate the idea of, for example, using the heat in a cars exhaust that would otherwise be wasted. Note, however, that your car already uses some of that. You catalytic converter gets very hot, helping to clean up the exhaust. So whatever you do needs to be 'downstream' from that. Also note, whatever you do which uses that heat will cool down the exhaust, which will make it more dense and heavier, which will make your cars engine work a bit harder. (Takes more work to push heavier gases out the exhaust pipe.) And it gets worse if you stick heat exchangers into the exhaust flow, making that flow turbulent. Better to extract heat via some sort of wrap around the exhaust pipe. You still make the air denser, and may collect less heat, but at least you aren't adding turbulence.

Now, can you do something with that heat? I dunno. Use the difference between it and the ambient air to run a sterling engine? Concentrate it to boil a closed loop of water to run a little turbine generator? I dunno if that could work. And if it did work, I dunno if you would recover enough power to make loading the car with the weight of the equipment worthwhile. Pushing that weight around makes the engine work harder, which costs fuel. It's a numbers game, and I don't know the numbers.