A fire last Friday that shut down one of three massive concentrated solar power plants in the Mohave Desert was caused when mirrors that focus the sun's rays on a boiler tower instead locked up and set the tower ablaze.
NRG, which manages the Ivanpah Solar Electric Generating Plant near the California-Nevada border, said the error was caused by software problems that occurred during regular maintenance.
The San Bernardino County Fire Department said the fire lasted about 20 minutes and damaged pipes and wires about two-thirds of the way up the boiler tower. Plant workers extinguished the fire with handheld fire extinguishers before the fire department arrived.
"The Ivanpah Unit 3 fire on May 19 was caused by the heliostats [mirrors] being locked in place in preparation for a maintenance activity...causing the solar flux to briefly move over a portion of the boiler tower," NRG spokeman David Knox, spokesman for Ivanpah plant operator NRG Energy, said in an email to Computerworld. "The mirrors were unlocked and moved to remove the solar flux from the tower."
Solar flux refers to the concentrated rays being reflected by the heliostats.
Knox said Ivanpah Unit 3 is expected to be back online within about three weeks. The fire at the plant was unprecedented, Knox said.
"The damage to Unit 3 was primarily limited to the aluminum covering of the insulation around pipes, as well as wiring and some valves which can be repaired relatively easily," Knox said.
In the meantime, NRG has "put in place new safeguards that will prevent this from happening again," Knox said. The changes were made to both software and hardware.
Knox would not say how much the damage will cost NRG to repair.
The Ivanpah Solar Power facility's three units each have more than 100,000 computer-controlled mirrors that focus the sun's rays on three separate boiler towers. The fire broke out on Unit 3, which had to be shut down. Unit 2 is currently undergoing maintenance, Knox said, meaning only one of the three units is supplying power to California residents.
When it opened in February 2014, the Ivanpah Solar Power Facility was the world's largest Concentrated Solar Power (CSP) plant. Instead of using photovoltaics, which convert solar energy into direct current using semiconductor materials, CSP plants generate electricity in much the same way as conventional fossil fuel power plants do, by boiling water into steam. The steam then drives an electric turbine.