How is Solar Energy Stored Efficiently?
One main problem
faced by developers of solar energy systems
is the effective and efficient storage of
the surplus solar energy so that during times
when direct sunlight is weak or inaccessible
over the solar energy collection system, people
can still manage to use the stored solar energy
from past sunny days anyway. This is why government
leaders are afraid of switching even one city
to solar power alone and why there is still
a ready market for conventional energy sources
like wood, coal, and fossil fuels at present.
How is solar energy stored so that solar energy
collection and storage is efficient yet effective?
Ausra, a start up solar power company based
in Palo Alto, California, is touting the potential
of solar-thermal power plants which can collect
sunlight, transform it into steam, which in
turn can be stored for use on days when sunlight
is inaccessible. Ausra founder and chairman
David Mills stressed that this would work
because to store heat is easier than to store
electricity itself. Even storing a maximum
of 16 hours of this type of heat in solar-thermal-power
plants in the US is believed to have the capacity
to supply over 90% of the present power demand
of the US alone – at a cost that can
rival that of natural gas and coal.
This technology is fast turning into solar
energy reality because a solar-thermal power
plant is presently being constructed in the
Mojave Desert in California as a 25-year joint
venture between Solel Solar Systems (based
in Israel) and the Pacific Gas & Company.
Under the terms of their contract, Pacific
Gas & Company will purchase the energy
to be produced by the 553-megawatt facility
after construction has culminated in year
2011. In turn, the energy will be sold in
turn by Pacific Gas & Company as power
for 400,000 homes located within central and
northern California.
Solel Solar Systems also has another contract
from Florida Power & Light for the Israeli
company to upgrade the solar-thermal facilities
of the latter which are also located in the
California Mojave Desert. These facilities
date back to the 1980s so they do need to
be refurbished to modern standards. However,
if solar-thermal technology has been existing
that long, that bodes well for the future
of efficient storage of surplus solar energy
in solar-thermal power plants.
So what about Ausra? What is it doing to further
its cause of promoting solar-thermal power
plant storage of surplus solar energy? Well,
although Ausra and Solel are competitors,
they use different types of solar-thermal
power plant energy storage technology. Ausra
claims it relies on less expensive technology
to produce energy to be stored (compared to
the technology employed by Solel.) One reason
Ausra technology is less costly is that they
rely on mass-produced and less expensive mirrors
to capture then reflect sunlight onto water-filled
tubes which then create steam. Though the
Ausra technology produces less energy this
way compared to the Solel system, on the whole
the Ausra technological process is also less
expensive to pursue. So everything in the
output remains in proportion to the input
anyway.
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