Closing Units at Ivanpah

I'm surprised they intend on closing units at Ivanpah, supposedly because of improvements in solar photovoltaic technology. I was part of the permitting process, by doing air-quality modeling for them:

Power plant operator and co-owner NRG Energy Inc. is preparing to close down part of its Ivanpah Solar Power Plant in San Bernardino County, Calif., a little more than 11 years after it began operating.

...Ivanpah is a concentrating solar power plant, which uses 173,500 heliostats—essentially mirrors on movable mounts so they can track the sun—to reflect sunlight onto boilers at the top of 450-ft-tall towers to make steam that turns turbines to generate power. 

The plant has three units, each with its own tower surrounded by an array of heliostats, for a total capacity of 386 MW.

The utility contracted to purchase power from two of the units through 2039. But it said in a statement that in 2021— after the California Public Utilities Commission ordered investor-owned utilities to evaluate their energy sources—it identified its Ivanpah power purchase agreements as a potential area to find cost savings, with plant owners offering the opportunity to terminate the agreements. The companies, along with the U.S. Dept. of Energy, finalized negotiations to end the agreements last month. DOE provided $1.6 billion in loan guarantees for the project.

...Ivanpah was the largest concentrating solar power plant in the world at the time of its construction, and NRG said the project still demonstrated the technology’s viability.

Construction of the $2.2-billion plant started in 2010 with Bechtel Corp. as engineering, procurement and construction contractor. It began operations in late 2013 and remains the largest plant of its kind built in the U.S. .

...Improvements in solar photovoltaic wafers and panels and battery energy storage have made them more affordable options at large scale, Howerton added. The technologies have “raced ahead” in terms of affordability, according to PG&E.

Photovoltaic, or PV, technology uses silicon crystals that are laminated into layers, often called wafers, with opposite charges. When solar light hits the crystals, it creates a direct electric current through a process called the photovoltaic effect.

Ivanpah's generation is believed to have prevented 500,000 metric tons of carbon dioxide emissions annually, according to the Energy Dept. But once operational, it drew criticism following reports that insects and birds were burned to death when they flew too close to the white-hot tower tops. A 2015 report prepared for the state by ecological consulting firm H.T. Harvey & Associates estimated the plant killed about 3,500 birds in its first year of operation.

Ivanpah also faced performance issues. In 2014, plant owners got permission from state officials to increase its annual limit of natural gas for its boilers from 328 million cu ft to 525 million cu ft, citing a need to use more fuel to power turbines to compensate for intermittent cloud cover.

“When the power purchase agreements were signed in 2009, the prices were competitive, but advancements over time in PVs and battery storage have led to more efficient, cost-effective and flexible options for producing reliable clean energy,” NRG said in an emailed statement.

The plant occupies more than 3,200 acres of federal land in the Mojave Desert near the California-Nevada state line. In its statement, NRG suggested the site could be repurposed for solar silicon photovoltaic energy production after decommissioning of the existing plant, but did not share any specific plans for that future work.