> They use the heat from the exhaust gases to power the device, the calculations are in the paper.

Wouldn't this effect the efficiency of catalytic converters? As I understand it, those need to be hot to work well. Or is the heat taken out of the exhaust after it passes through the cat? Skimming through the paper, I don't see mention of this.

Maybe it would make sense to shrink the engine's radiator and use some of the engine heat instead of exhaust heat.