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Solana project near Gila Bend tries storing solar energy for night use

PHOENIX — A utility near Gila Bend, Ariz., is leading the way with a technology that could revolutionize the solar industry.

The New York Times reports the new solar project called Solana harvests energy that can be used at night or anytime the sky is overcast.

The energy is gathered in a three-square-mile patch of desert bulldozed flat near Gila Bend, about 50 miles southwest of Phoenix. A sprawling network of parabolic mirrors focuses the sun’s energy on black-painted pipes, which carry the heat to huge tanks of molten salt. When the sun has set, the plant can draw heat back out of the molten salt to continue making steam and electricity.

Solana’s technology may remedy what is considered one of solar’s major pitfalls — the ability to provide energy when the sun isn’t out. The project is catching the attention of regulators across the county, especially in California, where the state’s legislation is passing laws that require utilities to install energy storage capabilities by 2024.

Arizona and, increasingly, California see the same problem in the evening, when the sun is too low for the panels to work, just as thousands of people are returning home and workplaces are still humming. Solar panels can help utilities meet afternoon peaks, but not morning or evening ones; by 6 p.m., panels are producing only about half their maximum, even if they are installed on tracking devices that tilt the panels to follow the sun across the sky.

Solana is a $2 billion project that uses mirrors the size of garage doors that focus sunlight on a tower with a tank painted black; the tank is where the plant’s operators try to store the extra energy. The Times says the plant will enter commercial operation by the end of October.

Solana is not the first renewable energy plant with storage; several have added banks of electric batteries. But battery storage is so expensive that these have been used mostly to smooth the output of the plant, not to store huge amounts overnight.

Batteries are expensive and have a limited lifetime. They are more economical in a car, where they help electricity substitute for something more expensive, like gasoline. But for utilities, they are nowhere near cheap enough to justify using them to avoid buying high-priced, late-afternoon electricity.