David,
You are possibly misreading this article. It is poorly written to begin with. Carnot efficiency affects all heat engines in a similar way. Moreover, it is a basic limitation which deducts “off the top” so all other inefficiencies deduct from the lower number. From: David Jonsson Hi I have imagined using thermophotovoltaics to produce a highly efficient conversion from heat to electricity. Imagine having a heat source in a very thermally well insulated container. In the same container there is a thermophotovoltaic cell converting the heat radiation into electricity. Wouldn't a cell like that be very efficient? What stops it from being 100 % efficient, or having its efficiency reduced only by leaks in the thermal insulation? Even if the Carnot efficiency http://en.wikipedia.org/wiki/Thermophotovoltaic#Efficiency is low it doesn't affect the total efficiency. The emitter will always be hotter than the converter, since the converter converts some of the heat radiation. There will always be some efficiency. Increase of dark current, as Wikipedia mentions as a reason for efficiency decrease at higher temperature, should be the same in both directions in the converter and could not lower efficiency. Either efficiency could be higher or the explanations of the efficiency lowering effects are wrong. Best would be to build a device and see what will happen. David
