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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: Solar Insolation Levels
Organization: The Armory
Date: Fri, 5 Aug 1994 06:51:23 GMT
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In article <af.6906.33.0NAF8FC6@mecheng.fullfeed.com>,
Steve Jones <steve.jones@mecheng.fullfeed.com> wrote:
>
>E>Message-ID: <ykgcqc4w165w@sfrsa.com>
>E>Newsgroup: comp.robotics
>E>Organization: SFRSA BBS 14.4K N81 415-648-6427
>
>E> 
>E>Can't find my reference for how many watts per square meter of 
>E>convertible energy there is in sunlight at the earth's surface <I can 
>E>figure out the effects of lattitude!>.  Anyone know this?  Also, last 
>E>time I asked, it was said that the cheap solar cells were in the range
>E>of  up to 6% efficient.  Anybody know what progress has been made in
>E>the last  few years or so?
>E>And how about the more expensive yet commercially available types?
>
>E>Thanks.  Post or email    eds@sfrsa.com
>
>E>Ed
>
>Above the atmosphere (extraterrestrial) solar radiation equals approx. 
>1367 W/m2.  What actual penetrates the atmosphere is approx. 1000 W/m2 
>which is a good standard used by such organizations as the Nat'l 
>Renewable Energy Laboratory.  What do you mean by "cheap" solar cells?  
>Stable or field efficiency ranges at 4 to 11% for single and polycrystal 
> silicon cells, which are more popular and less expensive than more 
>exotic, higher efficient cells.  Thin-film amorphous silicon cells range 
> in the 1 to 5% efficiency.  The most commercially available and yet 
>least expensive for the highest efficiency cells will be the single 
>crystal silicon cells.  There is current R&D work being done with TI 
>spherical silicon cells which are supposed to possess higher 
>efficiencies without the increase in costs.  Remains to be seen.
>-Steve Jones, San Diego Gas & Electric Co.
------------------------------
Even in Death Valley, according to my passive solar technology instructor,
you cannot get over about 150 Watt's per meter squared at noon in the
summer on a clear day. I don't know why you think the atmosphere passes
that amount of flux so well. We'd all be par-boiled!! The reflectance is
much higher than that. I was instructed that orbit has, as a rule of thumb,
11 times more solar flux for conversion to heat, such as for smelting, etc.
We could melt steel in a pot with a 1' square Fresnel lens if that were
true, at its focus! We can only melt lead with a 1 footer.

The 100 to 150 Watt figure was the one used very successfully to predict
the hot water ouput of all the old turn of the century hot water heaters on
roofs in Los Angeles and much of southern California till the natural gas
and petroleum got cheap!!! Few people know that the passive solar water
heater was well on its way to over 50% usage till cheap petrochemicals!
-Steve Walz 

