Alt-BEAM Archive
Message #01016
To: beam@corp.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Fri, 26 Feb 1999 10:33:27 +0100 (CET)
Subject: [alt-beam] Re: Solar cell recommendations?
On Fri, 26 Feb 1999, Justin wrote:
> A dumb question on a related note, since these things obviously won't be
> drawing much energy from visable light, which end to they get it from -
> IR or UV?
The Suncerams use mostly visible light.
Solar cells in general depend on their `band gap'; incoming photons
have to bump electrons into the conduction band of the
semiconductor, which converts a very specific amount of energy per
photon. Photons with too long a wave length lack the energy
to do it, and thus have no effect at all. If the wave length is
shorter than required, the extra energy isn't used. This is the
main reason for the low efficiency of current solar panels. There
has been some talk of `rainbow' panels using a prism to split the
light in different colors (energies), each aimed at cells with a
matching band gap. This would allow 60% to 70% efficiency.
Other designs put translucent panels with different band gaps in
layers, which increases efficiency to about 30%. But all these
tricks also increase cost, and don't help much in bad light. So
here on earth, simple, inefficient but cheap panels tend to win.
> Would I be right in assuming that it is roughly the same part
> of the spectrum as normal solar cells? Could I go further and assume
> that
> 1) Dave knows a fair bit.
> 2) He designed the photopopper with IR sensors.
> Therefore:
> 3) Solar cells use (predominantly?) IR light?
I think that combination had more to do with availability of
components :)
It doesn't hurt to use IR sensors, even if the solar panel likes
higher frequencies. Plenty of IR in both sunlight and artificial
light.
> Maybe we could do heaps of BEAM promotion over the next 6 months, and
> raise it's populatarity from the current hundreds to somewhere in the
> multi-millions (we don't want it _too_ popular, just enough to have
> market power :) and then order enough of the new cells in bulk to get
> the technology established.
>
> Sound like a good idea?
Yes! And all become millionaires by selling little solar powered
`robotic' gadgets.
> After that, we'd probably have enough market power to get them to make
> cells that run on moonlight. That would just rock. Then we'd be one step
> away from starlight. And after that, cells that run on darkness. Just
> imagine the potential applications!
You're not taking this very seriously, are you :)
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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