The Platte River Power Authority cleared a major hurdle this week in its plan to install natural gas-fired aeroderivative turbines at the Rawhide Power Station.
On April 21, the Larimer County Board of Commissioners voted unanimously to approve a state-mandated land use permit, adding six new conditions to the 32 already imposed on the regional power wholesaler.
The decision advances PRPA’s efforts to meet aggressive decarbonization targets for its municipal customers, including Estes Park, Fort Collins, Longmont, and Loveland, while also spotlighting growing concerns about air quality along Colorado’s Front Range. Supporters view the turbines as a necessary bridge to a carbon-free energy future. Opponents warn that the project may exacerbate an already serious ozone pollution problem.
“We are pleased to continue making progress on our board-directed decarbonization efforts for the communities we serve,” PRPA chief executive officer and general manager Jason Frisbie told The Coloradoan. “This is another step forward on this collaborative journey.”
PRPA argues that natural gas-fired turbines are essential to maintaining a reliable electricity supply as they transition away from coal. Storage technologies like batteries are not expected to be available at necessary scales before Rawhide Unit 1, a coal-fired plant, retires by the end of 2029. Renewable sources alone, the organization notes, cannot fully meet demand given Colorado’s frequent calm and cloudy weather.
Estes Park draws all of its electricity from PRPA and accounts for about 4% of the organization’s total municipal load. Kate Miller, a spokesperson for the town, said in an email that Estes Park serves 11,043 electricity consumers and accounts for 135,237 megawatt-hours of power annually.
Today, coal provides about 30% of PRPA’s electricity generation. Under its 2018 Resource Diversification Policy, the utility has committed to delivering 100% renewable energy by 2030. That goal aligns with Colorado’s legal mandate to cut greenhouse gas emissions from electricity production by 80% from 2005 levels by the end of the decade.
Estes Park officials believe PRPA’s move to install aeroderivative turbines will help the utility meet those targets. Miller said town leaders anticipate an 85% reduction in emissions from 2005 levels within the next five years. “This is 2.3 million fewer tons of carbon dioxide emitted per year in northern Colorado,” she said.
Aeroderivative turbines, originally adapted from jet engines, operate at higher pressures and smaller sizes than heavy-frame industrial turbines. They use a compressor to draw air into a combustion chamber, mix it with natural gas – primarily methane – and ignite it. The expanding heated air spins turbine blades, generating electricity and powering the compressor.
Because they are smaller and designed for quicker startups and shutdowns, aeroderivative turbines typically emit fewer waste gases than larger heavy-frame turbines.
Still, not everyone sees the technology as a clear environmental win.
During Monday’s hearing, opponents of the project argued that PRPA’s application did not meet Larimer County’s land use standards. They pointed to the Front Range’s ozone problems and asserted that the turbines could worsen pollution and directly emit methane, a potent greenhouse gas.
“Platte River’s application does not meet all the requirements of the land use code,” said Mike Foote, a lawyer for Northern Colorado Partners for Clean Energy and a former state representative. Foote argued that PRPA failed to prove the turbines represented the “best available alternative” and had not proposed sufficient operational limitations to address air quality concerns.
The American Lung Association ranks Fort Collins as having the 13th-worst ozone pollution in the country, while Denver ranks sixth. The Front Range remains a federally designated non-attainment area for ozone under the Clean Air Act, and emissions from the Rawhide facility are among Larimer County’s largest contributors to ozone precursors.
According to the Environmental Protection Agency, new natural gas-fired combustion turbines are among the largest emerging sources of greenhouse gas emissions. Fossil-fuel power plants overall remain a leading source of nitrogen oxides (NOX) and sulfur dioxide (SO2), major contributors to smog and fine particle pollution.
NOX emissions, produced when natural gas burns, play a key role in the formation of ground-level ozone.
PRPA acknowledged that the turbines could generate some greenhouse gas emissions and contribute to local ozone levels. However, officials emphasized that overall emissions from the Rawhide site are expected to fall dramatically after the coal unit shuts down.
“Larimer County developed a countywide greenhouse gas emissions inventory as part of its Climate Smart Future Ready initiatives,” said Michelle Bird, a spokesperson for the county. “When the coal unit at Rawhide Energy Station retires by 2030, carbon emissions from energy production in Larimer County are expected to decrease by approximately 1.88 million metric tons of carbon dioxide equivalent (CO2e). After the transition, emissions from PRPA operations are projected to total about 625,703 metric tons of CO2e – a significant reduction.”
Bird also noted that the ozone problem must be viewed in a broader context. “The shift away from coal is expected to reduce overall emissions, including ozone precursors, benefiting air quality in Larimer County and across the state,” she said.
Several conditions attached to the land use permit are intended to mitigate air quality impacts. Bird said they include requirements for an air quality management and emissions control plan during construction and operations, mandatory state air permits, and operational strategies to limit turbine use during periods of forecasted high ozone levels.
The commissioners’ approval was necessary because Colorado’s 1974 Land Use Act requires a “1041 permit” for infrastructure projects with potential statewide impacts.
The Town of Estes Park formally endorsed PRPA’s permit application. “The Town Board passed a resolution of support for the 1041 land use permit required to build the aeroderivative turbines,” Miller said.