Arriving at NRG Energy Inc.’s Ivanpah solar electric generating system while it is making power is nothing less than an awe-inspiring experience.
If you drive southwest of Las Vegas on Interstate 15 on any given sunny day, just as you cross over the Nevada-California border at Primm, Nev., you will see on the right-hand side of the road up to three towers glowing from the power of the sun reflected off thousands of mirrors spread out across acres of desert floor.
That is what a group of attendees of PennWell’s Power Generation Week were treated to on Dec. 7 on a technical tour of the Ivanpah concentrated solar power facility. As the tour bus approached the facility, attendees saw two of the three towers in full operation. The tour included a presentation about the facility and the safety and environmental protection measures employed there, as well as a drive through the fields of heliostats to the base of tower 2.
The Ivanpah facility, which was completed in 2014, features 175,000 heliostats that hold 350,000 mirrors. The heliostats, which are situated in three separate fields, are devices that hold the mirrors and can be adjusted so the mirrors reflect sunlight onto thermal receivers that sit atop the three 460-foot towers at the center of each field.
Unlike the solar photovoltaic panels that are used on rooftops, for example, and which soak up sunlight to generate power, the mirrors reflect sunlight onto the thermal receivers, which in turn heat water to power steam turbines.
According to an NRG spokesperson, when those thermal receivers are glowing, the system is generating electricity that is going to the grid under a must-take agreement. On Dec. 7, with two towers operating, Ivanpah generated 822 MWh of electricity. With the combined capacity of the three towers – 126 MW for tower 1 and 133 MW each for towers 2 and 3 – the Ivanpah facility will be able to generate 392 MW of electricity in an hour by 2018 after a four-year ramp-up period.
The spokesperson said that under the best conditions – i.e., a sunny, dry day with no wind – the facility can be generating at full power from about 10 a.m. to about 2 p.m. Where the Ivanpah facility is located in the Mojave Desert, sunny conditions do prevail, but the spokesperson said that there are many environmental factors that affect operations.
“It’s finicky,” he said. “It likes perfect weather.”
Clouds, for example, have a big effect on the day-to-day operations, and predicting their type and presence is not easy. The spokesperson said NRG is working on ways to better understand when and to what extent clouds will form. Other factors, such as moisture, wind and dust, also influence the ability of the mirrors to reflect sunlight onto the thermal receivers.
The technical tour of the Ivanpah facility concluded with a visit to the main control room, where staff members watch banks of computer screens that deliver endless amounts of data on the operation of the facility. From there, the staff uses software systems to calculate how the mirrors should be positioned to get the desired MW output from the facility. The control room is set up with three stations, each covering one of the towers. Another station allows staff to watch the weather. The spokesperson said their weather data is predictive, but not 100 percent accurate.
Now that Ivanpah has reached full commercial operations, what is next for the facility? The spokesperson said there are no plans to expand the project, but NRG is looking into the possibility of building energy storage functionality into the system. For now, however, the 65-member staff is focused on ensuring the project is ready to run whenever the sun shines.