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Posted by wmbjkREMOVE on June 2, 2010, 12:18 am
 
On Tue, 1 Jun 2010 23:56:08 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:



Where'd you get that impression? Here's a typical module.
http://sunelec.com/index.php?main_page=product_info&cPath=5&products_id7 .
~135W per sq. meter.



Posted by Ahem A Rivet's Shot on June 2, 2010, 8:38 am
 
On Tue, 01 Jun 2010 17:18:57 -0700
wmbjkREMOVE@citlink.net wrote:


    Probably from reading the specs and knowing about the typical
efficiency of PV cells. The output rating of PV cells is usually quoted
under "full sun" conditions of around 1000 W per sq. metre.


    That's the electrical output of that panel, which given the normal
efficiency of panels like that (10-15%) means an insolation of around 1000 W
per sq. meter. Actually the specs for that panel claim 13.1% efficiency so
slightly over 1000 W per sq. metre is required to achieve that output.


    Not so - those were pretty accurate calculations.

    Of course if you want efficient use of solar energy then solar
thermal is the way to go - it's not too hard to get 70-80% of the
insolation energy available as usable heat.

--
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:>WIN                                      | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

Posted by wmbjkREMOVE on June 2, 2010, 3:35 pm
 On Wed, 2 Jun 2010 09:38:28 +0100, Ahem A Rivet's Shot


No kidding?


If Klipstein mounts one of the modules I referenced above in full sun
in Philly on a cool day and measures the output, he'll conclude that
it costs out at ~$ per Watt, not the $0-$0 he managed to arrive at.
To avoid starting with worst case PV costs he could google "best price
PV". And he could skip even more GIGO by using HOMER or some such.
http://homerenergy.com/  Which would prevent erroneous assumptions such
as his 5% of production for tracking. Seriously? Try ~20Whrs per day,
which on a 1000W array in Philly might net out to ~.5% minus for the
motor, but >20% plus overall. PV economics aren't great, especially if
one is willing to ignore the unbilled-cost of grid energy and the
unsustainability of the billed cost. So those who seek to be negative
about the economics really don't need to exaggerate.

Wayne


Posted by Martin Brown on June 2, 2010, 4:01 pm
 On 02/06/2010 16:35, wmbjkREMOVE@citlink.net wrote:

That is their price per peak output per watt installed and seems
unusually low. $/W is still about the going rate and some are closer to
$/W where you paying a premium for higher efficiency.

But unless you can arrange continuous sunlight the average output over
the year allowing for clouds and including diffuse light is something
like 1/8 to 1/10 of peak installed capacity. So his $0-40/W delivered
for use is basically in the right ballpark in the long term.

Operating at peak efficiency with a clear sky and normal incidence
sunlight then the array can achieve peak performance, but the rest of
the time it does not by a long way. And obviously at night it is idle.


I think you just have to be clear about what measure you are using.

The PV array link you pointed at is the cheapest I have seen on offer -
has anyone here obtained one? Or are they vapourware?

Regards,
Martin Brown

Posted by Ahem A Rivet's Shot on June 2, 2010, 4:45 pm
 On Wed, 02 Jun 2010 17:01:29 +0100


    The string ribbon process mentioned appears to belong to Evergreen
Solar, it looks to be a very clever process for producing silicon PV cells.

--
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:>WIN                                      | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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