Re: Hole in a box

From: Robert J. Bradbury (
Date: Fri Feb 15 2002 - 07:51:58 MST

On Thu, 14 Feb 2002, Anders Sandberg wrote:

> Thermodynamically speaking, wouldn't higher frequencies be more
> efficient?

I don't think the standard heat engine concepts apply to photon
harvesting. If your radiators are at the background temperature
once you get above a few thousand degrees as an input you are
getting > 99.9+% efficiency anyway.

> We have spent most work on photovoltaics at wavelengths close
> to solar radiation, but I don't see why similar ideas can't be used for
> higher frequencies.

I'm not so sure. Anything at the UV-C frequencies or above has energy
levels that exceed atomic bond strengths. I'm moderately sure that
gamma radiation embrittles most materials, see for example:

Probably a fair amount of transmutation going on as well.
So I suspect you are going to have rather hefty recycling costs
associated with harvesting any energy produced as gamma rays.

> but there might be some interesting nuclear photovoltaics that
> catch gammas and use them to do charge separation.

I'd be interested in any references where people actually try to do this.

Given the lack of powerful gamma ray sources that exist in our
neighborhood, I would doubt much work has been done in this area.


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