Twenty years ago there was a company trying to commercialise thermoelectric cooling based on a vacuum gap: https://web.archive.org/web/20031213235132/http://www.coolch...

They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausible but never went anywhere as far as I know.

Incidentally that means all their patents will have expired...

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dvh a day ago | parent [-]

But isn't condensation based cooling like 500% efficient?

	▲	cjbillington a day ago \| parent \| next [-]
		The Carnot limit is the theoretical upper limit of the efficiency of a heat pump, so the stated number is presumably with respect to that, not heat moved per unit energy input like you're quoting.
	▲	londons_explore a day ago \| parent \| prev \| next [-]
		A Carnot heat pump maintains the temperature in a house at 20C on a day when the temperature outside is 5C. What is the coefficient of performance of the heat pump? The coefficient of performance (COP) of the Carnot heat pump is 19.5. The coefficient of performance of a typical heat pump in a british home is around 4. There is obviously a huge difference between 4 and 19.5 - although a good chunk of this is explained by large temperature differentials in the condenser and evaporator, and a british desire to use a water heating loop.
	▲	a day ago \| parent \| prev [-]
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