The power of concentration
Feb 21st 2008
From The Economist print edition
A new type of power plant harnesses the sun-and taxpayers
ON FEBRUARY 22nd, at an event featuring film stars, astronauts and
technology gurus, Acciona, a Spanish conglomerate, is due to inaugurate a
new power plant a few miles from Las Vegas. In fact, the plant has been
running since last June. But the technology it uses, known as "concentrating
solar power" (CSP), is hot right now, as the Hollywood luminaries might put
Acciona's new plant, called "Nevada Solar One", can generate up to 64
megawatts (MW)-enough, it says, to power more than 14,000 homes. The Solar
Energy Industries Association (SEIA) says that more CSP plants, with a total
capacity of 4,000MW, are in the pipeline and have signed contracts to sell
their future output. An 11MW plant opened in Spain last year (pictured). New
Energy Finance, a research firm, estimates that 2,000MW of capacity is in
the works in Europe.
As their name suggests, CSP plants generate electricity by concentrating the
sun's rays, usually to boil water. The resulting steam drives turbines
similar to those found at power plants that run on coal or natural gas.
There are several different designs. The Nevada plant uses long curved
mirrors, called parabolic troughs, to focus light on a tube of fluid running
just above them. The Spanish plant uses a forest of smaller mirrors to focus
light on a tower in their midst. Other concepts involve long flat mirrors
and devices resembling satellite dishes.
Solar power, of course, does not produce climate-changing greenhouse gases.
But it also excites utilities because it generates the most power just when
it is needed: on hot, sunny days when people turn on air conditioners. And
CSP provides a way around the main drawbacks of solar power from
photovoltaic cells. Unlike them, it does not involve expensive silicon
wafers. And some designs provide power round the clock, not just when the
sun is shining, by storing energy in the form of molten salt.
Even so, CSP is still not as cheap as coal- or gas-fired plants. America's
CSP boom is driven by state laws requiring utilities to generate a certain
share of their power from renewable sources, and by generous federal tax
breaks, which offset as much as 45% of development costs, according to SEIA.
In Spain, meanwhile, utilities must pay an extra ?0.25 ($.37) per
kilowatt-hour on top of the market price for power from CSP.
America's tax breaks are due to run out at the end of the year, and without
them, says Rhone Resch of SEIA, no more CSP plants will be built there. But
in the long run, he argues, costs should come down. And if fossil-fuel
prices continue to increase and American power-plants have to start paying
for their greenhouse-gas emissions, CSP might just achieve "grid parity"
with the wholesale power price. That really would be an excuse for a party.
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