Since late 2013, four Concentrated Solar Power operations have begun operating in the deserts of Riverside and San Bernardino counties.

Developers of the nine-square mile Palen solar project in eastern Riverside County recently asked state energy officials for another year to meet a deadline that now requires them break ground Dec. 15.

The delay comes just two months after plans for another big solar farm appeared to be in jeopardy. Los Angeles’ electric utility, citing high costs and environmental concerns, decided it would not buy power from the Soda Mountain project near Baker.

Officials with Abengoa Solar, the Spain-based developers of the Palen project, could not be reached this week.

But papers the company filed Aug. 4, 2015, with the California Energy Commission say Abengoa needs more time so it can improve the project with an energy storage system that would enable the plant to produce electricity day and night.

Such a project “will benefit grid reliability and aid achievement of California’s renewable energy and greenhouse gas emission reduction goals,” said the petition filed by Palen SEGS I, a company set up by Abengoa to develop the project.

The deadline extension needs approval by the full California Energy Commission, and the company’s petition is under review by staff members, said commission spokesman Mike Ward in an email.

Abengoa successfully built the Mojave Solar project near Barstow, which began generating power in December 2014. That plant can produce power for about 91,000 households.

Last year, an energy commission panel recommended that the Palen project go forward with one 750-foot boiler tower heated by thousands of mirrors on the ground. The commission also agreed that a second tower and energy storage system could be built later, during a second phase of the project.

At the time, Palen appeared to be on track despite objections raised by environmentalists and Native Americans concerned about the possible impacts on wildlife and the loss of archeological sites.

But in September, the developers, then a partnership of Abengoa and the Oakland-based BrightSource Energy, announced the project would not be going forward.

Just two months later, Abengoa announced they had acquired BrightSource’s share of the project, and they intended to build the project with towers and energy storage.

The energy storage would use the sun to heat molten salt, which can be stored for nighttime use. The hot salt is used at night to make steam to generate electricity.

During the solar plant’s on-again, off-again, on-again drama, the window was closing for the developers to take advantage of a federal subsidy that could save them millions dollars in construction costs.

Since late 2013, four large-scale solar operations have begun operating in the deserts of Riverside and San Bernardino counties. That solar boom was fueled in part by federal tax credit that covered 30 percent of the cost for these $1 billion-plus projects.