Re: ENERGY: State of the Art in Photovoltaics?

From: Robert J. Bradbury (
Date: Sun Oct 08 2000 - 16:04:39 MDT

Mike wrote:
> Which is much as I said in my post. However, the average American roof
> (only half of which is useful as a collector, the other half facing away
> from the sun (and only if the home is lucky enough to have one side facing
> south. Facing east and west is useless)) is around 12 x 5 meters, or 60
> square meters. A 10% efficient system that covers the entire roof, with
> no skylights, will generate 6 kilowatts ONLY at the peak period at noon.
> Power generation will begin at a very low level around 7 am and end at
> about 7 pm, and increase along a bell curve up and down through the day.
> Such a system will generate around 20-24 kilowatt hours per day,
> assuming no cloudy weather. This is less than 10% of the power needs
> of the average home.

I think your roof size may be too low (depends a lot on how many stories
the home is) and your energy peak may be too high (Robert Freitas keeps
beating me up anytime I use a number over 400 W/m^2). But I don't see
why you say 10% since my electric bill says I'm averaging 40 kWh/day
(and thats with a lot of computers on all the time).

Your point is taken though. The efficiency needs to go up. You can
always double the roof area by doing a little reconstruction. And
if the material is really cheap (like tar paper), you would put
it on the exterior wall surfaces as well. You probably couldn't
disconnect yourself from the grid, but you could make a good dent
in your electric bill. The real trick will be lowering the electrical
requirements of the refridgerator, since that is generally the biggest
draw in the house. We need some more progress with magnetic cooling
using gandolinium or acoustic cooling.

> You have to HAVE self replicating systems BEFORE they can beat overcoming
> gravity. How much R&D do you think it will take?
Maybe 50 man-years worth. I think I can do it within the next 2 years.
I don't know if I can build solar cells with them yet but H2 or CH3
production will definately be doable. I'll send you a copy of the
patents once they get filed.


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