[IamIan]

Originally Posted by CFECO

Back when I was designing a car to compete in the Auto X-Prize Competition, I was working on a exhaust heat recovery generator. I planned to create steam which would drive a small engine, either piston or turbine, which would turn a generator. My first test boiler was a length of stainless brake line coiled inside of a housing, that the exhaust from a small engine emptied into the middle of the boiler at the bottom. It went up the inside of the coil, flowing over the top of the coil and and exited at the bottom outside of the coil. On the few tests I was able to perform, steam was produced in less than a minute, so the ability to remove heat from the exhaust was easily accomplished. Work was halted when I was forced to move, lost my workspace, and most of my computer files including drawings and calculations. Such is life. The "engine" I was going to test first, was a turbine out of a pneumatic wrench, and the second was a multi cylinder 2 stroke engine for RC aircraft. There would have to be other systems constructed, pressure pump, condenser, and the generator head itself. The F-1 guys have simplified this greatly by have a direct drive generator driven from the turbo shaft, Nice! I wonder what kind of generator works at those RPM levels? Oh well, my two cents worth.

Looks like others are still moving forward with the steam approach to gather energy from the exhaust line.

Some nice things about that approach.

• The sleeve around the exhaust can be smaller than air based heat exchangers and directly applied TE modules.
• As steam it lowers the required high temperature requirements of the TE used.
• The contact surface area involved in heat transfer will be better than a flat / square trying to extract heat energy from a round exhaust tube inside of the square / flat.