Florida takes giant step with huge solar-power plant
Jun 01 - The Orlando Sentinel
Florida Power & Light Co.'s newest solar-energy plant will have enough
mirrors to cover 80 football fields. But those mirrors will focus
sunlight onto surfaces that add up to slightly less than the area of a
single football field.
That concentration of solar power will generate temperatures of more
than 700 degrees -- hot enough to make electricity for 11,000 homes.
The Martin Next Generation Solar Energy Center here will rank as the
world's second-largest solar plant when it begins pumping out as many as
75 megawatts of electricity late this year. It will also be the only
system of its kind in the world.
Conventional wisdom holds that solar plants using mirrors -- which
generate heat that produces steam that, in turn, spins an electrical
generator -- aren't worth the effort in Florida because of the
regularity of afternoon rain clouds much of the year. So far, all of the
solar plants built in the state convert sunlight directly into
electricity using photovoltaic panels, which produce a charge, if only a
reduced one, even on cloudy days,
But FPL is building its "thermal" solar plant on a campus near
Lake Okeechobee that already has 13 generators fueled by oil and natural
gas. Steam from the solar plant will be combined with steam produced
with the heat exhaust from four natural-gas plants to spin an existing
generator -- an approach not taken before. FPL thinks that makes thermal
more feasible, because the utility won't have to spend millions of
dollars building a generator for the solar plant.
The project costs about $420 million, which will add about 16 cents a
month to the average FPL residential customer's bill.
FPL also owns the world's biggest solar plant, a thermal unit in
California's Mojave Desert that is four times the size of the Martin
County project. The Florida plant is based largely on the technology of
the 30-year-old Mojave system, though it has been given far stronger
pylons, frames and mirrors to withstand hurricane winds of up to 130
mph.
John Gnecco, FPL project development director, said dropping one of the
California plant's glass mirrors could lead to much bad luck, because it
would shatter. But the Martin County solar mirrors, though also made of
glass, bounce unscathed when they hit the ground.
To demonstrate, Gnecco laid one of the curved mirrors on a gravel
parking lot recently and jumped on it repeatedly, causing it to flex
trampoline-like. The special mirrors were made in Spain, one of the few
countries where FPL could find a suitable manufacturer with kilns large
enough to temper the 56-by-67-inch pieces of glass.
The thermal unit's mirrors are also highly reflective -- much more than
a typical bathroom mirror -- and there are a lot of them: more than
190,000.
Workers are installing the mirrors in aluminum frames to create long,
linear dishes. The more than 6,800 frames each contain 28 mirrors and
will be arranged in parallel rows that are linked together for a total
length of about 50 miles.
Each frame also holds a tube a few feet in front of the mirrors. The
tube contains a synthetic, oil-like fluid that costs $15 a gallon and is
designed for heating to 740 degrees. The hot fluid flows through a
separate component that acts something like a boiler to create steam.
The tubes are made of stainless steel and painted black but encased in
the airless vacuum of a glass tube. Birds can land on the glass tubing
and not be roasted, Gnecco said.
Nearly 150 miles of pipe and related plumbing, some as much as 30 inches
in diameter, will hold 1.2 million gallons of the synthetic fluid.
The relatively costly project is likely to fuel the debate among state
lawmakers about the risks and rewards of government incentives and
mandates for solar-power development. FPL and other power companies --
including Central Florida's two other major utilities, Progress Energy
and Orlando Utilities Commission -- have been experimenting with solar
in response to growing government concern about climate change
triggered, in part, by relatively cheap power plants that burn coal and
natural gas.
One thing utility engineers hope to solve once the Martin County plant
is operating is the problem posed by partly cloudy days, when some of
the plant's mirrors will be reflecting full sunlight but others will be
shaded. Plant engineers don't want alternating pulses of cooler and
hotter steam arriving at an electrical generator that runs most
efficiently, and with the least wear and tear, when operating conditions
are kept constant.
But they'll have plenty of time to figure that out: Gnecco said the
Martin Next Generation Solar Energy Center is likely to be operating for
the next 50 years.
Kevin Spear can be reached at kspear@orlandosentinel.com or
407-420-5062.
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