How an odd feature below this Utah county could become the largest battery in the world

This story is part of The Salt Lake Tribune’s ongoing commitment to identify solutions to Utah’s biggest challenges through the work of the Innovation Lab.

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It’s like a high school chemistry experiment at geologic scale.

The technology behind IPP Renewed is well understood. Apply electricity to H₂O, and you can split the hydrogen from the oxygen. Put a flame to the hydrogen, and it will burn hot and carbon-free. Burn it in a gas-fired turbine, and it can produce electricity.

Now multiply by billions, and you have what could one day be one of the largest clean energy sources in the world.

Beneath the desert floor in Millard County – where the tallest thing is sagebrush – there are caves taller than the Empire State Building and wide enough to hold a small lake.

The caves soon will be filled with hydrogen produced from solar energy. One day they could supply about a 10th of Los Angeles’ electricity, as well as power thousands of Utah homes and businesses.

“To put things into perspective, each cavern can store up to 150 gigawatt-hours of potential energy, and we have two salt caverns that will hold 300 gigawatt-hours,” said Rob Webster, founder of ACES Delta, the company that has leased the land from the Utah Trust Lands Administration (formerly SITLA) and will produce and store the hydrogen for IPP.

By comparison, the entire United States currently has about 12.5 gigawatt-hours of utility-scale battery storage, or about 4% of what ACES can potentially store. And that’s just two caverns. Webster said up to 70 more caves are possible.

Utah’s power corridor

With its 40-year history as a coal-fired power source laying the groundwork, this spot near Delta has now become an energy hub. At a time when there are not enough transmission lines to meet the West’s growing demand for power, Delta will be a key transfer point between the wind farms and power plants in Wyoming and the solar farms and massive customer base on the West Coast.

And where coal-rich Carbon and Emery counties were Utah’s 20th century energy kings, western Utah is now emerging as a 21st century powerhouse. Solar and wind farms stretch north from Iron County across Beaver and Millard counties. The area north of Milford has become a literal hotbed for geothermal prospects. Even the pig farms near Milford – or what’s left of them – capture methane from the pigs and turn it into power.

And nothing in Utah’s new energy picture looms larger than IPP.

When it comes online in 2025, it will be much like the natural gas plants that have been replacing coal as the “baseload” electricity source across the country. Two 430-megawatt combined cycle units will rely on natural gas from Wyoming, thanks to a connection line that has been built to Kern River Gas Transmission Co.’s pipeline near Holden and Interstate 15.

But unlike any other natural gas plant, it will also blend in hydrogen from the salt caverns. When the gas plant is fired up in 2025, it may start with just natural gas. But soon after it will start mixing in about one-quarter hydrogen. By 2045, the plan is to run completely on hydrogen produced from the electrolizers, making it a carbon-free source of power.

The U.S. Department of Energy is a major supporter of the hydrogen storage, providing ACES a massive half-billion-dollar loan guarantee. “They made very detailed due diligence before approving that loan,” said Webster. All told, the new power plant and storage caverns could top $4 billion in investment.

And, in a sign of shifting winds in the energy sector, Chevron’s New Energies Division bought a majority interest in ACES in September.

A fateful location

By pure coincidence, the coal-fired IPP plant was built in the 1980s virtually on top of a unique set of salt deposits 2,500 feet below the surface. They were known to geologists when the plant was built, but there was no use for them. Such salt formations are more common along the Gulf Coast, where they have been used to store commodities for decades. The nation’s Strategic Petroleum Reserve is held in Louisiana salt domes.

By drilling down and injecting water, ACES opened up caverns in the salt deposits, and the salt seals them well enough to hold the hydrogen. The water for those injections came from IPP, which owns more water rights than it uses at the power plant. The resulting brine is deposited in evaporation ponds on site.

Now, the caves are the key component to keeping it alive as the country turns from coal to renewables.

Hydrogen, the first element on the periodic table and only one proton, doesn’t occur naturally in quantities that can be captured. It has to be made. And making it requires putting electric power in so power can come out later. In other words, hydrogen is a rechargeable battery.

As with any battery, there are no 100% returns. In fact, the power that is put in is more than twice the power coming out. With those kinds of losses, the power going in has to be cheap and plentiful.

Enter the sun and a 2,400-megawatt direct-current power line to Adelanto, California. That line is how IPP has (and soon IPP Renewed will) delivered power to its largest customers in Southern California.

And that line is reversible.

Largely because of California’s early and aggressive embrace of utility-scale solar farms, solar power costs next to nothing when the sun is shining bright and California has all that it needs.

That cheap power can flow back from California through to IPP, where ACES can use it to run 40 huge “electrolyzers” from Norway. Mitsubishi, a key technology partner in ACES Delta, is part owner of Hydrogen Pro, the Norwegian company that manufactured the electrolyzers.

When the electrolyzers run, they are splitting water molecules and storing the hydrogen underground. And when California needs IPP’s power, the electrolyzers shut down and the current is reversed so the plant can supply it.

The water will come from IPP’s water rights, which it has held since the 1980s. The water required to produce the hydrogen and run the power plant is expected to be well below what the coal plant uses now.

Months of storage

The amount of hydrogen that can be stored can potentially produce months worth of power. Where utility-scale lithium batteries can last hours to keep the grid running, ACES can provide a “seasonal” amount of power. This overcomes major obstacle for renewable energy: keeping the power coming when no sun or wind exists.

It can stock up on hydrogen in the spring when there is lots of California sunshine but not much demand for air conditioning, and then pull it back out of the ground in summer when air conditioners are working overtime.

And IPP will not be the only hydrogen customer. Rail service to the site means ACES can ship hydrogen by train car. Most of the hydrogen now used by industry is produced by a “steam-methane” process that releases greenhouse gases. A consistent source of “green” hydrogen could be a key component in reducing the carbon footprint of cement, steel and other industries.

“We are always looking at ways to develop additional markets such as the transportation and industrial sectors,” said Webster, who expects Chevron’s ownership will bring new opportunities.

That could also stimulate industry to locate near IPP to avoid the shipping costs. Even the oxygen released when the water molecules are split could find a market and attract industry to Millard County, although the plan right now is to just vent the oxygen away.

A future for coal?

For all the interest around IPP Renewed, it hasn’t stopped state legislators from trying to keep the old coal plant running. Fueled by coal country lawmakers, the Utah Legislature passed a bill in 2022 to create the state “Project Entity Oversight Committee,” which is intended to explore continued operation of the coal units. Intermountain Power Authority, the state entity that operates IPP, has also been the subject of a legislative audit.

That committee has received a preliminary report from a consultant that said a continued life for the coal plant is possible, but it also lists a host of challenges. The plant has violated EPA standards for coal ash management, and IPA negotiated a settlement with EPA that included an agreement to shut the coal units down in 2025.

But the biggest challenge to keeping the coal plants open is finding someone to buy the power. The vast majority of IPP’s power goes to Los Angeles, and Los Angeles has outlawed coal-sourced power after 2025 because it is such a large source of atmospheric carbon that is heating the planet.

As it is, the IPP Renewed plant will have less than half the capacity of the coal plant, and that’s because there are so many other clean power sources available that didn’t exist when IPP was first built in the 1980s.

IPA did get one offer to operate the plant as a source for data centers last year. That proposal included plans to add carbon capture to the coal units, something that has been proposed at other coal plants but never found to be economical. That offer was rejected over concerns it could interfere with the EPA settlement and therefore affect IPP Renewed.

Utah Sen. Evan Vickers, a Republican whose district includes the plant, told fellow legislators he was wary of doing anything with the coal plant that might endanger IPP Renewed. As has happened with other coal plants around the West, IPP could be replaced with a piece of flat desert instead of a new power plant.

“I also want to point out that, as I talk to people about what they want to see happen with the project, they want the project to continue to go forward and be viable,” Vickers told a legislative committee last month. “We need to be very considerate. Not only is this moving forward and taking shape, but there are other companies coming in.”

Added Roger Killpack, a Delta pharmacist who sits on the Project Entity Oversight Committee, “To derail this new project would be catastrophic to the area.”

Clarification: This article has been updated to clarify that water is injected into salt deposits to open up the caves.

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