Utility moves away from coal

CASPER – Wyoming’s largest utility doesn’t see much coal in its future. 
 
By 2030, only two of Rocky Mountain Power’s 11 Wyoming coal-burning units will remain, according to the biennial Integrated Resource Plan it filed Friday with state regulators. 
 
It plans to convert a handful of others to run on natural gas — and keep those gas units open until some combination of renewables, storage and advanced nuclear becomes established enough to take their place. 
The utility has opted to preserve coal use at one Glenrock unit for an extra 12 years, but it has also decided to ditch coal entirely at its Rock Springs plant — the largest of its kind in Wyoming — seven years ahead of schedule, according to Friday’s filing. 
 
Rocky Mountain Power’s parent company, PacifiCorp, currently has about 5,000 megawatts of wind and solar in operation across its six-state service territory. Over the next decade, it wants to come close to quadrupling that number, while adding more than 7,000 megawatts of energy storage to help balance out renewables’ intermittent power output. 
 
“We’re putting our foot on the gas,” said Rick Link, Pacifi Corp’s senior vice president of resource planning, procurement and optimization. 
 
The Wyoming Legislature has pressured the state’s public utilities — especially Rocky Mountain Power — in recent years to delay scheduled coal retirements. 
 
A trio of laws passed between 2019 and 2021 sought to make it harder for utilities to close Wyoming coal plants, including by requiring them to attempt to install carbon capture to prolong units’ lives. 
 
Rocky Mountain Power is still in the process of complying with the state’s carbon capture mandate. It’s actively considering proposals for Dave Johnston unit four in Glenrock and Jim Bridger units three and four in Rock Springs. 
 
Link declined to comment on how the utility’s negotiations are going with potential developers. But since it filed its last Integrated Resource Plan in 2021, he said, “I don’t think there’s been any real changes in our priorities.” 
 

 
From the perspective of PacifiCorp — whose 144,000 customers in Wyoming are dwarfed by its more than 1 million customers in Utah and Idaho and its 800,000 in Oregon, Washington and California — renewables will dominate the electric grid in the coming decades. Coal will not. 
 
Natural gas, meanwhile, is expected to be a temporary stepping stone as the utility embarks on what Link called a “fundamental remaking of our regional generation and transmission network” that’s on track to eliminate its greenhouse gas emissions by 2050. 
 
Rocky Mountain Power hopes to build a lot more wind in Wyoming in the coming years, Link said, along with a more modest amount of solar and storage. 
 
Additional advanced nuclear projects could follow, too — but will depend largely on the results of the utility’s in-progress study evaluating other potential sites. 
 
Despite its focus on renewables and emerging technologies, this year’s plan does make quite a few tweaks to the utility’s coal plant retirement dates. 
 
Jim Bridger units three and four, which were set to continue burning coal until 2037, will be converted to gas in 2030. In place of shuttering the entire Dave Johnston plant in 2027, Rocky Mountain Power will close unit three in 2027 and units one and two in 2028, but keep unit four open until 2039. 
 
Link said the change at Jim Bridger unit four doesn’t have much to do with Wyoming’s carbon capture laws, but is instead “an inherent outcome of the broader economics in the company,” including federal air quality requirements affecting coal plants in multiple states. 
 
In keeping with the 2021 plan, the solitary unit at Gillette’s Wyodak plant will also stay on through 2039, while Jim Bridger units one and two will be converted to natural gas later this year. 
 
Kemmerer’s Naughton plant will switch off coal in 2026, one year later than previously expected. But in the wake of TerraPower’s announcement late last year that its nearby advanced nuclear project will be delayed until at least 2030, the utility has decided to convert Naughton’s two coal units to natural gas — and keep the entire plant operational potentially until the mid2030s. 
 
“It’s almost like somewhat of an insurance policy,” Link said. Naughton won’t go offline, he said, “until we’re certain that the unit coming on behind it is up and running and functioning as intended.”
This story was published on April 4, 2023.