Re: Large scale solar plant?
From: The Enlightenment (bernxard_at_yahoo.com.au)
Date: 03/27/05
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Date: 27 Mar 2005 05:29:04 -0800
"dexx" <D3xx@hotmail.com> wrote in message news:<1111651583.898612.96380@o13g2000cwo.googlegroups.com>...
> Which would be more cost efficient: A solar plant using solar cells,
> possibly with concentrators? Or a farm of mirrors focusing on a solar
> furnace which heats molten salt and uses it to power a turbine?
There is little difference between them, though photovolatics would
tend to come out ahead slightly in most cases. Parabolic dishehes
using stirling cylcele engines at the focus have achieved efficiencies
of over 30% whereas Gallium Arsenide cells at the focus of
concentrators have achieved also over 30%.
Large scale linear parabolic trough systems using usually synthetic
oil rather than direct heating of water for production of steam
achieve about 12-13% with the overall efficiency per unit area of land
around 6%. Heat storage is in beds of rocks heated by the oil with
molten eutectic salts another possibillity.
10-15% is about the efficiency of good quality photovolatic systems.
Photovoltaic systems have one big advantage besides simplicity: even
in the worst most overcaste rainy day they still produce about 22% of
the output of a sunny day in the same season. This is becuase of
their abillity to opperate using indirect or diffuse radiation. They
infact work brilliantly in snowy environments and some people have
reported increases in power due to snow. They even work through the
snow.
Solar thermal linear parabolic trough collectors however appear to be
much cheper and probably produce electricity at about twice that of
conventional power: ie 10-13c per kw.hr with the advantage of a modest
amount of backup.
There were 4 very large solar thermal systems installed in California
some years that opperated quite well apart from the need for
subsidies.
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