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Photovoltaic cell efficiency question. - Page 4

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Posted by Eeyore on March 25, 2009, 12:35 pm
 


BobG wrote:


It's not a resonance.

Graham


Posted by Eeyore on March 25, 2009, 12:30 pm
 


frigitar wrote:


I vaguely recall this at school. I think it's bandgap energy dependent on
the material used and the wavelength of the light shining on the surface.
Shorter wavelengths have more energy in each photon, hence why UV would be
great if it came though the atmospohere ( but not so good for us of course
).

http://en.wikipedia.org/wiki/Photo_voltaic#Simple_explanation

Graham



Posted by Mike on March 27, 2009, 7:27 pm
 On Sun, 22 Mar 2009 11:19:59 -0700 (PDT), "zzbunker@netscape.net"


So if you make your pv's track the sun, precisely what issue stops you
cooling the rear face with water?

I certainly can't think of one.


--

Posted by Eeyore on March 27, 2009, 8:30 pm
 

Mike wrote:


Depends if you have to pay for the water and where does it go afterwards ? Down
the drain ?

You have inadvertently just made the case for solar thermal water heating. A far
more attractive source of 'green energy'.

Graham


Posted by evan on March 24, 2009, 7:09 am
 
Hello to all of you,
The issue with PVs is based on their conversion efficiencies, at
various parts of the solar spectrum. The majority of of the PVs work
(convert) the infrared part of the solar spectrum and peak around the
830 nm mark, which is only 14% of the received radiation. The solar
radiation that hits the Earth's surface, ranges from 330 nm to 3500 nm
(lower numbers hold higher energy levels). So most of it reflects back
into space and a small part dissipates as heat. Mind you, the dark
side of the PVs MUST be kept at 25 Celsius to obtain the 18%
efficiencies. In open field installations (please sit down), their
efficiency rarely goes above 2.6%.

Regards
Evinos

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