Setting aside arguments that it is moving too fast, the Platte River Power Authority decided earlier this month to proceed with the purchase of aeroderivative natural gas turbines to supplement existing coal-fired generating capacity at the Rawhide Power Station. The equipment will also backup renewable energy infrastructure that is on tap to supplant that reliance on coal.
The decision commits the electricity wholesaler to an investment of more than $350 million in a 200 megawatt fossil fuel-driven capacity. That capacity will be in the form of several units with a generation capacity of 30-50 megawatts each, according to a PRPA document published in 2024.
“We are advancing our dispatchable capacity solution with aeroderivative turbines, energy storage and a virtual power plant,” said Javier C. Camacho, a PRPA senior manager. “In 2025, we will continue permitting and procurement activities for the aeroderivative turbines and begin related projects like site preparation and substation expansion.”
The allocated funding will be spread over several years.
“In 2025, approximately $80.6 million of a total estimated multiyear $352.9 million investment through 2028 is needed, primarily for partial payments on the aeroderivative units and for engineering, procurement and construction services,” according to PRPA’s 2025 Strategic Budget.
PRPA, which is partially owned by Estes Park and which provides the town’s municipal utility with the electricity that powers local homes and businesses, is in the midst of a transition to a portfolio that is solely reliant on renewable energy. That 2018 commitment pushes PRPA to seek a generation portfolio that does not include any resources likely to cause carbon dioxide emissions while assuring system reliability, the organization’s financial stability, and compliance with applicable environmental standards. PRPA aims to fully implement that approach by 2030.
The organization anticipates that 88% of the energy it supplies to PRPA municipalities after 2030 will come from wind and solar resources. The other 12% will be made available by battery storage, a virtual power plant, and the aeroderivative turbines. The turbines can, PRPA hopes, switch to hydrogen as the input fuel when that alternative becomes commercially feasible.
As of now PRPA continues to obtain about a third of its electricity by burning coal at the Rawhide Unit 1 near Wellington and at two Craig coal-fired power plants. PRPA announced in June 2020 that Rawhide Unit 1 will be retired by 2030. As for Craig Units 1 and 2, also known as the Yampa Project, PRPA will remove Unit 1 from its generation mix by the end of 2025 and Unit 2 from it by Sept. 30, 2028.
The decision to purchase the aeroderivative turbines contemplates installation by early 2028 so that PRPA has time to test them and assure their reliability before Rawhide Unit 1 is decommissioned.
PRPA is in the midst of investing in renewable energy capacity, too.
At present, the organization has 225 MW of wind-driven generation capability, 52 MW of solar energy capability, 80 megawatts of hydropower, and 2 megawatt hours of battery storage, PRPA spokesperson Kendal Perez said in an email.
In 2026, PRPA will add 257 MW of additional solar capacity, while in 2027, the organization expects as much as 250 MW of new wind generation capacity to come online, Perez said. She explained that battery storage capability is expected to increase by 75-100 MW by 2027.
“We’re pursuing distribution-level storage projects, specifically seeking to place a 5 MW, four-hour battery in each owner community to enhance flexibility within the distribution systems’ load,” Perez added.
Natural gas-driven turbines produce electricity when the burned gases spread inside a turbine, which causes blades to spin. The aeroderivative version that PRPA will obtain also uses natural gas but they are similar to jet engines in that exhaust gases produce the thrust needed to move the turbine blades. The aeroderivative turbines will produce more greenhouse gas emissions than the non-aeroderivative counterparts, but among their advantages is a capability of quickly handling load changes.
That is important to assure reliability of the power supply when neither wind nor sunshine are available to generate electricity. Such “dark calm” moments, also known as “dark doldrums,” are unusual, though PRPA experienced one during Winter Storm Uri in Feb. 2021.
Perez said in an email that the organization considers mitigation of the risk that these events happen to be a priority. “Our review of historical weather at 70 locations west of the Mississippi illustrates that 24-hour dark calms can happen multiple times per year,” she said. “Dark calms lasting two days occur 1.25 times on average per year, and dark calms lasting three days occur every other year, on average.”
PRPA expects the new turbines to operate 5-20% of the time, up from 1-3% use that characterizes the five older gas turbines now in operation at the Rawhide energy station. The power cooperative will also join Southwest Power Pool, a regional transmission organization, in 2026 as a way to assure access to necessary additional power and an avenue to sell excess renewable energy it generates.
Opponents of PRPA’s decision to acquire the aeroderivative turbines have pushed for a third-party review of the organization’s need for them. In a November letter to Fort Collins officials, the Fort Collins Sustainability Group argued that the project is “superfluous.” They claimed that PRPA overestimated reserve power capacity needed beyond its annual peak demand. “In its recent IRP, the PRPA stated that it needs to have a planning reserve margin of 19.9%,” wrote Kevin Cross, a spokesperson for FCSG. “PRPA’s new ELCCs show that it would have a planning reserve margin of 39.8% in 2030 without building a new gas-fired power plant.”
Cross referred to PRPA’s Integrated Resource Plan, which guides the organization in efforts to meet electricity demand and achieve carbon dioxide emission reductions and other environment-related and financial objectives. He also used an acronym for PRPA’s effective load-carrying capacities.
Fort Collins municipal leaders turned away FCSG’s plea. In a Dec. 4 letter, Fort Collins Power and Light’s director said FCSG misunderstood the reasons for PRPA’s ELCC calculation. “Why not just buy/build more renewable energy now?,” Travis Walker rhetorically asked. “I think it is a balance. If we try to make up the difference, what we could end up with is way too many renewables when it is sunny and the wind is blowing, and still not enough at other points. Then, we’d be forced to sell the renewables at a very low cost or possibly even a negative, meanwhile having spent a lot of money on the wind/solar infrastructure or purchase-power agreements.”
Walker also emphasized the need to assure reliable power if a dark calm event occurred. PRPA “must also evaluate whether their resources can serve all owner community load through extended dark-calms (periods where neither wind nor solar resources produce energy),” he wrote. “Existing peaking units plus the new gas turbines would cover the 2030 peak demand forecast with a margin of +1% – not a large margin, but [it] keeps the lights on and the heat going in one of those events.”
The request for a third-party review was presented again at the December PRPA board of directors meeting and rejected. Perez said Longmont mayor Joan Peck asked for that step to be taken, but her motion failed. “There was not a second, so that did not pass,” Perez explained.
Perez said in an email dated Dec. 30 that no PRPA director now supports a third-party review of the decision to move ahead with the investment in aeroderivative turbines. “Our board unanimously agrees that a review is unnecessary,” she said.
Fort Collins, Longmont, and Loveland also obtain electricity from PRPA. The four municipalities govern PRPA through two representatives each on the organization’s board of directors.
CORRECTION, Jan. 7, 2025: The story was corrected to clarify that PRPA’s new aeroderivative turbines will not replace coal-fired power plant capacity, but will instead be used to supplement renewable energy production when needed. PRPA is scaling back coal use in favor of renewable energy sources. In addition, the story now includes details about PRPA’s investments in various forms of renewable energy production.
It’s ridiculous that it took this long. They’ve had to ship in coal from Wyoming and beyond this whole time while they’ve been practically sitting on top of one of the country’s largest natural gas deposits.