If it\’s got an engine. . .

Dorri probably likes it

Speaking of crazy ideas . . .

Posted by ifitsgotanengine on October 13, 2005

Here’s another one.

This is something I’ve been considering for several months now; I just haven’t taken the time to do any serious number crunching on it. Preliminary calculations look promising.

It’s pretty clear that massive improvements in electrical storage density (read: batteries) aren’t going to be made any time soon. It’s also clear that that’s what is needed to make electric cars viable today. Traditional batteries don’t store anywhere near the amount of energy per pound as gasoline.

My proposition is to use a heat battery instead of an electrical (chemical) battery.

Take a block of something fairly cheap, concrete maybe, and run tubing through it (more on this later). It needs to have a fairly high specific heat capacity. Wrap it in some pretty serious thermal insulation. Sink some heating elements into it. Then connect it to the heat engine of your choice: steam engine, stirling engine, etc.

When not in use, the heaters would be plugged into the grid, heating the battery to a predetermined temperature. When you were ready to drive, draw heat from the battery by passing the working fluid through the tubing.

Maximum efficiency (see Carnot engines) is limited by the temperature difference between the battery temp and the ambient air temp. Charging efficiency is excellent (all losses show up as heat, which is what we want), limited only by the ambient losses.


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