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Posted by BobG on April 20, 2009, 5:01 pm
 
wrote:

==========================
==================
Finally the discussion gets around to the problem that all the panels
in a row cant turn 90 deg horizontal to face East in the morning,
because the other panels are in the way. You have to wait till the sun
is up say 30 deg and the panels are rotated 60 deg, but there is still
shadows of the sunward panel on the leeward panel. Tradeoff.

Posted by daestrom on April 20, 2009, 10:13 pm
 

wrote:

===========================================
Finally the discussion gets around to the problem that all the panels
in a row cant turn 90 deg horizontal to face East in the morning,
because the other panels are in the way. You have to wait till the sun
is up say 30 deg and the panels are rotated 60 deg, but there is still
shadows of the sunward panel on the leeward panel. Tradeoff.

--------

Bottom line is that on a large scale you can't collect more sunlight than
what would fall on the ground your system is spread out over.  Large arrays
of trackers cannot increase the sunlight collected over what falls naturally
on the ground when the sun is low in the sky.  The best it can do is collect
the sunlight that would have fallen on a given ground area and focus it into
a smaller area.

As the sun moves away from directly overhead, each tracking array element
shadows it's neighbor.  To avoid this, you must move the elements further
and further apart or accept that a portion of the elements will be shaded.

daestrom


Posted by Fran on April 21, 2009, 1:28 am
 
So much is obvious, but there are large areas in many jurisdictions
with large tracts of highly insolated but otherwise low-value land.
Placing heliostats at intervals sufficient to avoid shading isn't a
huge cost problem.

Molten salt or pumped storage are viable options.

Fran

Posted by Eeyore on April 21, 2009, 3:44 pm
 

Fran wrote:


See......
http://en.wikipedia.org/wiki/Solar_power_in_Spain
http://en.wikipedia.org/wiki/PS10_solar_power_tower

Sadly at present the cost of the electricity produced is still 3 times that of
conventional generation. Not sure what scope there is to improve that.

Graham



Posted by Fran on April 22, 2009, 1:18 am
 wrote:

This one in Spain was only quiote a small scale plant. In a very
interesting paper, Professor Mills

http://www.usyd.edu.au/research/about/nrp_examples/solar.shtml

argues that 92% of load in Ca and Tx at about 7.8cents per KwH using
solar thermal plus storage

http://www.ausra.com/pdfs/T_1_1_David_Mills_2049.pdf

No doubt, the levelized cost could be even lower if the model had
access to system-based pumped storage rather than having to build its
own dedicated storage units.

Fran

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