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.

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.

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.