Solar Arrays. [RE-wrenches]
Dean T. Newberry
deant at dcn.org
Mon Dec 1 22:03:00 PST 2003
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Hi Marco,
It is the emissivity of the panels working for you.
The modules tend to heat up to well over ambient around here that is
135F or so.
The glass on the front has a low emissivity and some resistance to heat
transfer as well. The back of the modules is a radiant panel parallel
and close to the pool panel.
I had a friend who is an old solar engineer and professor of mechanical
engineering to take a guess at the shading losses. He guessed 30%. Keep
in mind that the shade is not from a tree or adjacent building, but a
hot surface real close to the pool panel.
Another analysis is that the modules convert 15% of the energy to
electricity. Some is lost to reflectance, some to emissivity out the
top, the balance is available to be absorbed by a parralel panel at the
back. I have a great picture of a lawn where 30 odd panels were laid for
about 15 minutes on the grass. It is burned in nice little squares just
the size of the panels. The roof gets damn hot behind the PV. I have no
complaints from my pool customers where we have installed the systems. I
have a request from one pool module manufacturer to monitor the systems,
but have no time to do so.
It just made sense to me so I did it.
cul deant
marco mangelsdorf wrote:
>>From Dean Newbury:
>
>When possible I mount PV over pool panels. Leaving 4" for ventilation
>the same as a plane fo roof mount. We estimate 30% shading losses, so
>add a panel or two to the pool heating to get the required insolation
>for that system.
>
>--Say what?! Cover metal or plastic pool panels with PV modules? Since the
>very large majority of the heat produced from thermal panels comes from
>direct insolation, how can it make sense to cover thermal panels with PV
>modules? I gotta believe that the shading losses is way more than 30
>percent, no?
>
>marco
>
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--
* Cooperative Community Energy* *Dean T. Newberry*
430 D Street, Davis CA, 95616
Tel: 530 758-6064
Fax: 530 758-3684
Email: deant at dcn.org
Web: CCEnergy.com
Talbott Solar <http://www.dcn.davis.ca.us/go/deant/>
Contr. Lic. # B-667908
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