There is molten salt in the town of Hayden’s future – maybe trout, too – but almost definitely molten salt.
The idea of using molten salt energy storage to fill part of the gap in employment and taxes left by the planned closure of the Routt County town’s coal-fired power plant is being planned by the unit’s operator, Xcel Energy, as it seeks to cut its greenhouse gas emissions.
The technology was developed for use at concentrating solar power plants, where hundreds of mirrors trained the sun’s rays on a tower to heat the salt, which would later be used to power an electric turbine.
“New players are looking at using the grid rather than the sun to heat the salt,” said Mark Mehos, a National Renewable Energy Laboratory researcher. “Then using the hot salt to make steam to turn a turbine.”
While it may sound exotic, company executives, local officials and labor leaders say the initiatives being taken at Hayden could be a template for helping transition other coal plant-reliant communities.
Coal-fired power plants are closing around Colorado and the United States – where coal-fired generation capacity has dropped by almost a third since 2008 to 223 gigawatts. In Colorado, by 2030 only one coal-fired facility, Xcel’s Comanche 3 unit in Pueblo, is slated to be in operation, as more than 30 units will have closed over 20 years.
The state has created an Office of Just Transition to help power plant and mining communities faced with the end of the age of coal, appropriated $15 million to the effort, and developed a Just Transition Action Plan.
The effort is, however, nascent. “We are at the beginning,” said Beth Melton, a Routt County commissioner and vice chairwoman of the state’s Just Transition Advisory Committee. “What we need is state support and federal support as well for locally driven solutions.”
This puts the efforts at Hayden ahead of the curve.
“We are thinking about what technologies are advanced enough to put on the property as we retire the plant,” said Hollie Velasquez Horvath, senior director for state affairs and community relations at Xcel’s Colorado subsidiary. “What gives the community hope of tax revenues and jobs.”
Xcel has created a community advisory committee that meets monthly with utility executives to discuss life after the aging coal plant is closed. Hayden Unit 1 is 44 years old and Unit 2 went online in 1965.
“Xcel is still looking to see what works best for them in their situation,” said Tim Redmond, a Routt County commissioner and former Hayden mayor. “Still, there was quite a bit of relief when they sat down with us.”
Mathew Mendisco, the Hayden town manager said, “Xcel has promised no layoffs and to retrain workers … at least they’ve been upfront and honest about it.”
The coal-fired plant employs about 63 people. It is estimated that a molten salt storage facility might employ about half as many.
“We know the molten salt project doesn’t replace all the tax revenue and all the jobs,” Horvath said. “We are considering what else we can do, potentially considering a hydrogen project, a biomass project. We are talking with Colorado Parks and Wildlife about their interest in developing a fish hatchery.” The company already has a cooling pond on the site.
“CPW could use the property and water rights we have,” Horvath said. “It would create employment and tourism, but doesn’t help with tax revenue.”
When it comes to taxes there isn’t a serious hit for Hayden, which relies on sales taxes and has seen the town growing at about 10% a year, Mendisco said.
“On a countywide basis we are not too concerned,” Melton, the Routt County commissioner, said. “We have a pretty diversified tax base.”
The Hayden plant and the Twentymile Mine, operated by Peabody Energy, which supplies coal to the power plant, accounted for 8% of all county taxes in 2019, Melton said.
At the moment, the Routt County entities in the financial crosshairs, with no clear solution, are the special districts. The West Routt Fire Protection District and the Hayden School District each get more than half their revenues from levies on the power plant. Then there are the hospital, library and cemetery districts.
“Special districts, they were going to get crushed,” Redmond said.
In 2020, Xcel paid $3.8 million in property taxes to Routt County for the Hayden plant with about 28% going to the county and the rest to the special districts, the company said.
Under state law, Xcel must reduce its greenhouse gas emissions from 2005 levels by 2030. In March, the company filed a clean energy plan with the Colorado Public Utilities Commission that would cut emissions 85% in the next nine years.
As part of that plan, the utility, pending a greenlight from the PUC, is looking to call for bids next year for a molten salt energy storage facility to be located on the site of the Hayden plant.
“We thought that was the best technology to start with,” Horvath said.
As a prelude to this effort, Xcel, Routt County officials and labor leaders, during the last legislative session, got behind the passage of House Bill 1324, which gives a utility a pathway to recovery costs for low-emission, innovative technologies.
“We lobbied in favor of House Bill 1324,” said Rich Meisinger Jr., business manager for Local 111 of the International Brotherhood of Electrical Workers, which represents about 1,800 Xcel employees.
“It allows for experimental technology and that’s what we need,” Meisinger said. “Environmentalists have been focused solely on solar and I’m a journeyman lineman by trade and I know what it takes to power the grid and solar isn’t the sole answer.”
Xcel is also seeking U.S. Department of Energy funding for planning the project. “We realize it’s a long-shot,” Horvath said.
Molten salt technology is relatively simple. The salts are inexpensive and non-flammable. The process runs at low pressure, so no pressurized tanks needed.
A mixture of salts — nitrates, carbonates, chlorides — is melted in an insulated tank at a temperature of about 554 degrees Fahrenheit.
This molten salt is then heated in a second tank, in Xcel’s plan using electricity from the power grid, in a “hot tank” raising the temperature to more than more than 1,000 degrees.
That hot mixture is run through a heat exchanger to make steam to turn a turbine and then sent back to the cold tank at a temperature around 550 degrees.
“The temperature losses are very low over time for both the cold tank and hot tank,” Mehos said. “You can let it sit there for days if not weeks before using it and you can store a lot, dozens of hours” of energy storage.
Between 2014 and 2019, the amount of storage added to the grid, often twinned with new photovoltaic solar installations, quadrupled to 899 MW and the U.S, Energy Information Administration projects it could reach 2,300 MW of capacity by 2023.
Most of that storage has been in lithium-ion batteries, whose price has fallen 89% since 2010 to $137 a kilowatt-hour in 2020, according to energy consultant BloombergNEF.
Nevertheless, molten salt storage offers several advantages. Even with the drop in the price of lithium-ion batteries, molten salt technology is 33 times cheaper, according to an analysis by the German Energy Storage Association, and it can go bigger and longer.
Lithium-ion batteries can provide just four to six hours of energy and scaling-up facilities can be a challenge. In 2019, a “cascading thermal runaway” led to an explosion at a large lithium-ion battery array in Arizona, according to an incident report.
“Right now, lithium-ion batteries are commercial and inexpensive for low-duration storage,” Mehos said. “But batteries don’t scale well.”
In the Xcel scheme the Hayden plant would still have some of its original functions. “You still need operations folks to maintain and run the turbine,” Mehos said. “It is easier to maintain than a coal plant—you’re not dealing with the combustion.”
That is why a molten salt storage unit and turbine will need fewer workers than currently employed at Hayden. Xcel has, however, pledged there will be no layoffs.
“Over the last couple of years, the relationship between Local 111 and Xcel has improved drastically,” Meisinger said. “We are collaborating on several issues” involving the retirement of the company’s coal-fired plants.
“What the company is proposing to do makes a lot of sense, makes sense for our members who can continue to work at the plant, it makes sense for the environment and it makes sense for the community,” Meisinger said. “These are the types of energy options we ought to be looking for in the future.”
And what of trout? “IBEW represents a lot for workers in a lot of different jobs,” Meisinger said. “I’d love to sit down with the company and discuss fish classification.”