Can I replace an alternator with peltiers?
 

I came up with the idea of using peltiers on the engine to create electricity to run, or at least help run the electrical system. Would that work? If I could turn waste heat into a little bit of useful energy that would be great. I am sure there is a reason this would not work, but oh well. What do you think?

Only if they weigh as much as the rest of the car. You might be able to run the clock off them.

Yes, you can. Its incredibly expensive. I've actually been meaning to make a post on how to do this just so it can be referenced by questions like this in the future. I best get on it! :)

I was toying with the idea myself,

Last time i checked it was 1$ per W.

I always thought that using engine coolant (a much more controlled heat source) for the peltier elemts was a good idea.

Peltiers require a temperature differential to generate electricity. This means one side has to absorb the waste engine heat, and the other side has to remove the heat through a heatsink or water cooling (which is then cooled by a heatsink).

I wonder how much surface area you would need, and how much weight it would add, not to mention the cost.

Some modules i have seeen can get 14W form 6x6cm with a temp diff of 250 degc.

But they cost more than 10$/W.

...and then the small matter of creating a 250 C temp differential. You'd have to get that off the exhaust header since 190 F coolant isn't enough of a temperature difference to maximize the potential.

No.

Alternators are round and Peltiers are square - and sticking square things into round holes isn't really the right thing to do.

[Edit] ok - just joking. Toyota got it to work already sometime back.

I think it is doable.

With coolant you can use the cheaper thermoelectric coolers as generators.

Peak power tracking and adjusting the voltage needs a bit of work but it is all doable.

Or idk maybe solar panels and a real MPPT charge controller?