[extropy-chat] Singularity heat waste

[Eugen Leitl]

On Mon, Jul 17, 2006 at 05:49:26PM +0100, Russell Wallace wrote:

> Fractal helps with convective cooling, but not with radiative cooling, which is
> what structures not immersed in an atmosphere/hydrosphere will require.

I'm curious why you think a fractal versus a flat radiator surface
would do worse. The amount of surface seeing cold space is bigger with
a fractal versus a flat surface, it is a better wide-band radiator.
With a large surface you've got an approximation of a black-body
radiator, though there are even better things, at least for some
spectral areas:

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000084000011001997000001&idtype=cvips&gifs=yes

Comment on "Three-dimensional photonic-crystal emitter for thermal photovoltaic power generation" [Appl. Phys. Lett. 83, 380 (2003)]

    Thorsten Trupke, Peter Würfel, and Martin A. Green 
    Centre of Excellence for Advanced Silicon Photovoltaics and Photonics, University of New South Wales, Sydney, 2052, NSW, Australia 

(Received 28 July 2003; accepted 20 November 2003)

In a recent article, Lin et al. [Appl. Phys. Lett. 83, 380 (2003)] reported on the light-emitting properties of three-dimensional tungsten photonic crystals and their potential applications as improved thermal emitters in thermophotovoltaic (TPV) systems. Their findings have attracted considerable interest throughout the media and the application of this type of materials has been praised as a potential superior future energy source; e.g., in waste heat-driven electrical generators (http://www.photonics.com). The results of the theoretical modeling in the work of Lin et al. suggest that a TPV system can achieve higher heat to electric energy conversion efficiencies in combination with a three-dimensional tungsten photonic crystal than with any conventional selective thermal emitter. These theoretical results are based on the experimental observation that the photonic crystal, when heated to a given temperature, emits more radiation in certain spectral regimes than a black body of the same temperature. This experimental observation shall briefly be discussed here. ©2004 American Institute of Physics.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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