Wind and solar may produce more energy than coal in the US this year
For the first time in U.S. history, renewable energy sources have generated more electricity than coal for seven consecutive months.
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- Salt River Project wants to convert a coal-burning unit to natural gas at the Springerville Generating Station. The proposal passed an initial committee, but needs a final vote from its board.
- The conversion is a response to new EPA emission standards that take effect in 2032.
- Utility officials said the move would reduce emissions while meeting Arizona’s increasing electricity demand.
Salt River Project hopes to convert a coal-burning unit to natural gas at one of Arizona’s last remaining coal plants.
It owns a sole unit — called Unit 4 — at Springerville Generating Station, located in Apache County, on the far northeastern edge of Arizona. The plant faces new emission rate standards set by the U.S. Environmental Protection Agency that take effect at the start of 2032.
To hit those metrics, SRP and other utilities would have to invest heavily in new technology or retire their coal-powered units, either by shuttering them permanently or transitioning them to a new form of energy generation.
Two coal-burning units at the plant — Units 1 and 2, owned by Tucson Electric Power Co. — are already slated to be regeared to gas by 2030. Another, Unit 3, owned by Tri-State Generation and Transmission Association of Colorado, is in limbo.
SRP’s Board of Directors must now decide whether to follow suit or explore other options. Those could include transitioning to lithium-ion battery storage at the site or purchasing and installing new natural gas turbines to expand the facility’s power capabilities.
Officials said the proposal to convert the utility’s existing coal-powered unit to gas is a bid to reduce emissions while keeping the facility open as electric demand increases statewide. It passed through a power committee meeting on Oct. 23, and will now go to the full board for approval.
The news comes as the nation grapples with what its transition to cleaner energy sources should look like — or if it should migrate to renewables at all.
Director Robert Arnett, who serves as the chair of the power committee, expressed support for utility officials’ plan to convert the coal-fired unit to gas, calling it a “gift” that would responsibly lower emissions while maintaining power output and ensuring SRP can meet customers’ electricity needs.
“It gives us flexibility,” he said. “It gives us opportunity. It lowers our emissions at the same time, and saves on costs.”
But Director Sandra Kennedy, who previously served on the Arizona Corporation Commission, questioned why utility leaders wouldn’t consider bringing battery storage online alongside the gas conversion.
She also said they should look at various types of batteries, including ones with sodium-ion technology. Those batteries are more affordable than lithium-ion versions, but are less energy dense, meaning they must be larger to store the same amount of energy. The technology behind them is still developing, but they are increasingly emerging as an option for utility-scale power storage.
“We seem to be bringing an awful lot of gas online,” said Kennedy, who is among a contingent of board members who strongly advocate for expanding the use of renewable energy.
SRP officials have long said they will pursue an all-of-the-above approach to procuring more energy generation as the state sees rapidly rising power demand. Bobby Olsen, who heads planning, strategy and sustainability groups at the utility, told Kennedy that it was bringing on “significant” amounts of solar, battery storage and other types of energy resources.
The utility also recently got the greenlight from its board to transition another coal-fired power plant — Coronado Generating Station — to natural gas by 2030. Plus, it is part of a joint effort by the state’s largest power providers to explore nuclear generation, a venture that includes consideration of small nuclear reactors.
“It’s an asset that provides certainty throughout the 2040s and really serves as a bridge while other technologies mature,” said Bill McClellan, SRP’s senior manager of resource planning, of the plan for the Springerville Generating Station.
Conversion, new natural gas or battery storage? A look at the options
SRP will need to refurbish the generating station, select a gas supplier and build a new pipeline to enable the facility’s transition to natural gas.
CEO Jim Pratt, who also serves as the utility’s general manager, said SRP would work “hand-in-glove” with TEP to install that pipeline. Since both utilities are converting their coal-powered units, both will need a gas supply and a pathway to get it to the site.
The pipeline will likely connect with one planned for Coronado Generating Station, which is located about 30 miles north of Springerville Generating Station.
In total, the conversion is expected to cost about $60 million. Once it’s operating, SRP officials estimate it will take an additional $89 million per year to keep the plant running. That’s a total of $724 million through 2049.
Most of the state’s large utilities have sought rate increases in recent years as energy demand forecasts have risen, necessitating new infrastructure.
SRP recently approved an annual base revenue increase of $169 million to support upgrades to the electric system, among other things. That is expected to bump the average customer’s monthly bill by a little over $5, starting in November.
Still, the cost of transitioning the generating station to natural gas is affordable for customers compared with other options that were considered for the site, according to the utility’s estimations.
Officials anticipate the plan will save customers about $45 million relative to building a new natural-gas facility, and about $826 million relative to using new long-duration lithium-ion batteries.
Any of those options would have reduced overall emissions. Gas is a fossil fuel, but burning it to produce energy is far cleaner than burning coal — in part because natural gas units can turn on and ramp up quickly.
By contrast, coal plants can take days to start up. That means utilities typically run them at low levels around the clock, consistently producing greenhouse gases.
Utility officials estimated that the refurbished plant would produce 2.5 million metric tons of carbon emissions through 2049, assuming that it was run to pump out roughly the same amount of energy as what is currently provided by the generating station. That’s more than 450 megawatts — enough to power nearly 100,000 homes simultaneously.
They estimated emissions from a new natural gas plant at about 5.4 million metric tons, and emissions linked to the lithium-ion battery storage option at 3.1 million metric tons. That number was wholly attributable to the extra two years it would take to implement that technology, during which the coal plant would continue to run.
Battery storage itself would not produce any emissions, assuming the stored power was coming from renewable resources like solar or wind.
Sasha Hupka covers utilities and technology for The Arizona Republic. Reach her at sasha.hupka@arizonarepublic.com or 480-271-6387. Follow her on X: @SashaHupka. Connect with her on LinkedIn: Sasha Hupka. Follow her on Instagram or Threads: @sashahupkasnaps. Follow her on Bluesky: @sashahupka.bsky.social.
