The push for clean energy to reduce greenhouse gases has led to multibillion-dollar investments in wind and solar projects, but finding an economical way to store renewable energy that comes and goes like the breeze or the sun has proved challenging.
An alliance of four companies say they have found an answer in an underground salt formation.
On Tuesday, the group proposed an $8 billion power project that would start with twirling turbines on a huge wind farm in Wyoming and end with enough electricity for over 1 million households in Southern California.
Key links between the two would be an energy storage site inside Utah caverns carved out of the salt formation and a 525-mile electric transmission line cutting across several western states.
"Energy storage, paired with renewable energy, has been the holy grail of utilities and energy companies," said Travis Miller, an analyst for investment research giant Morningstar.
Construction is far from assured — the proposal faces years of regulatory reviews, and success will also hinge on striking agreements to sell the power that would be essential to secure financing to build it.
Jeff Meyer of Pathfinder Renewable Wind Energy, one of the companies behind the plan, called it "a landmark of the clean energy revolution."
"This project would be the 21st century's Hoover Dam," he said in a statement, referring to the 726-foot-high span across the Colorado River that produces hydroelectric power for Nevada, Arizona and California.
The announcement came on the same day that President Barack Obama urged world leaders to follow the United States' lead on climate change in a U.N. summit aimed to gather support for a treaty to reduce heat-trapping pollution.
The new proposal, with a tentative completion date of 2023, would potentially generate twice as much energy as the 1930s-era dam.
But with potential shifts in government policy, environmental regulation and the economics of producing green power "any infrastructure project that looks out nine, 10 years, has a lot of uncertainties," said Miller, the analyst.
Pathfinder Energy, Magnum Energy, Dresser-Rand and Duke-American Transmission Co. said in a statement that they plan to submit the blueprint to the Southern California Public Power Authority by early 2015.
California agency officials said they were unaware of the proposal before the Tuesday announcement. The authority has been seeking proposals to supply the Los Angeles region with renewable power required under state law.
The new plan "would be competing with 200 other proposals," said Steven Homer, the director of project management for the authority, whose members deliver electricity to about 2 million customers.
Wind development in Wyoming's wide expanses has surged in the past decade as companies and state officials seek cleaner alternatives to coal.
The proposed wind power development near Chugwater would be a boon to the sleepy ranching town of 216 residents nestled below sandstone bluffs on the high prairie.
A decade ago, in a desperate bid to revive their economically depressed community, town officials sold city lots for $100 apiece on the condition that the buyer would build a house and live there at least two years. Results were mixed, at best: Chugwater's population dropped 11 percent from 2000 to 2012, even as Wyoming's overall economy grew and population increased.
If completed, it would become Wyoming's second-largest wind power project. The biggest is a 1,000-turbine site planned by the Anschutz Corp. That project near Saratoga, in south-central Wyoming, is the largest under development in the U.S.
The rapid growth in wind power has come with a cost, however. The U.S. government estimates at least 85 eagles are killed each year by wind turbines. An Associated Press investigation in 2013 revealed that the Obama administration was not prosecuting wind energy companies for killing eagles and other protected birds.
A lynchpin in the plan would be a $1.5 billion energy storage site near Delta, Utah, 130 miles southwest of Salt Lake City. The rural area already is home to one coal-powered plant that generates electricity for Los Angeles County.
Under the proposal, the energy would be stored through a compressed-air system using caverns, similar to a system that has been used in Alabama since the early 1990s. When energy demand is low, excess electricity would be used to compress and inject high-pressure air into the four caverns, each of which would have 41 million cubic feet of volume. At times of high energy demand, the high-pressure air would be combined with a small amount of natural gas to power eight electricity-producing generators.
Company officials said the underground storage site could yield as much electricity as a large nuclear power plant, or enough to serve an estimated 1.2 million homes.