Mirrors spark fire at world's largest solar-thermal plant

A small fire shut down a generating tower at the world's largest solar-thermal power plant, leaving the sprawling facility on the California-Nevada border operating at only a third of its capacity, authorities said.

Firefighters had to climb some 300 feet up a boiler tower at the Ivanpah Solar Electric Generating System in California after the fire was reported on an upper level around 9:30 a.m. Thursday, fire officials said.

The plant uses mirrors to focus sunlight on boilers at the top of three 459-foot towers, creating steam that drive turbines to produce electricity.

But some misaligned mirrors instead focused sunbeams on a different level of Unit 3, causing electrical cables to catch fire, San Bernardino County Fire Capt. Mike McClintock said.

David Knox, spokesman for plant operator NRG Energy, said it was too early to comment on the cause, which was under investigation.

The fire ignited about two-thirds of the way up the tower, said Jeff Buchanan of Nevada's Clark County Fire Department, which also responded. Plant personnel had the fire out by the time firefighters got there.

Photos showed melted and scorched steam ducts and water pipes.

Knox said the tower was offline while crews assess the damage. He could not immediately say when it would restart.

When fully operational the plant can produce enough power for 140,000 homes, but a second tower is shut down for maintenance, leaving only one running.

It was the first fire at the plant, which opened two years ago on federal land in the Mojave Desert about 45 miles southwest of Las Vegas. The $2.2 billion complex has nearly 350,000 computer controlled mirrors — each roughly the size of a garage door — that sprawl over roughly 5 square miles of desert.