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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: Solar Insolation Levels
Organization: The Armory
Date: Sun, 7 Aug 1994 09:24:29 GMT
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References: <ykgcqc4w165w@sfrsa.com> <af.6906.33.0NAF8FC6@mecheng.fullfeed.com> <Cu1v1p.JqB@armory.com> <Cu2Es6.I48@news.cis.umn.edu>
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In article <Cu2Es6.I48@news.cis.umn.edu>,
Brynn Rogers <roger034@gold.tc.umn.edu> wrote:
>In article <Cu1v1p.JqB@armory.com>,
>Richard Steven Walz <rstevew@armory.com> wrote:
>
>>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 
>>
>
>This 150 W per square meter, is that what you can get out of the cells
>or what you think the total solar flux is?
>
>My source worked on Mankato States SunRaycer solar car and with the
>8 square meter panel they would get 900W in bright sun, maybe even 
>1000W occasionally.  Either their cells were way better than they
>paid for (%15 is what they had) or your number is what a solar cell
>can convert to power, NOT the total solar flux.
>--
>Brynn Rogers     roger034@gold.tc.umn.edu
----------------------------------
Brynn, I am puzzled. I have a book for the passive solar course I took as
well as a figure for the Sun's intrinsic brightness in Watts and the simple
formula for the area the earth subtends and the area of a sphere,
(4*pi*r^2), and a figure for the earth's albedo that indicates we are quite
bright, perhaps not so much as Venus, but very reflective. The insolation
here in orbit and at ground is of necessity quite different, as even with
rotisserie mode, spacecraft have to radiate quite a bit of heat, and they
have a major job of cooling their occupants even if they do only absorb for
45 out of 90 minutes per orbit. Interestingly, the book for the course
agrees perfectly with a astronomy book by Abell. Could it be that the cars
were allowed to charge batteries at night so that their contribution comes
into play? I believe that I saw that mentioned in a science show about that
race. Do you have a figure for the terrestrial albedo different from about
66% reflectance of total insolation? And on top of that is the atmospheric
absorption of infrared as well.
-Steve Walz   rstevew@armory.com

