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Xcel Energy’s comprehensive modernization of the Cabin Creek pumped-storage facility—featuring an innovative 11-blade turbine runner—earned the station a POWER Top Plant award. The retrofit project not only extended the facility’s operational life by decades, but also reaffirmed its position as a vital resource supporting Colorado’s clean energy transition.
Perched at an elevation of more than 10,000 feet in the Colorado Rockies, where thin air and extreme conditions challenge even the most robust machinery, the Cabin Creek pumped-storage hydro facility has been quietly performing vital power grid services for nearly six decades. But as Colorado’s renewable energy revolution transformed the grid below, this high-altitude marvel faced its own transformation—one that would push the boundaries of turbine design and redefine what’s possible in pumped storage modernization.
A Historic Creation
From the end of World War II to 1970, Colorado’s system load increased more than six-fold. The state’s increased power needs during this time were largely supplied by a growing fleet of coal-fired power plants. Yet, there were lingering issues with system operation in the early 1960s. The Cabin Creek pumped-storage hydro project was conceived to remedy some of those issues.
The Cabin Creek plant is located on Cabin Creek and South Clear Creek in Clear Creek County, Colorado, about 4 miles south of Georgetown. The Cabin Creek project occupies about 326 acres of land in the Arapaho National Forest, which is managed by the U.S. Forest Service.
The original license for the Cabin Creek project was issued on March 23, 1964. The project was spearheaded by the Public Service Company of Colorado, now Xcel Energy. The project’s major features include an upper and lower dam and reservoir, a power tunnel, two penstocks, a powerhouse, two step-up transformers, and access roads. The original station included two 150-MW turbine-generator units.
The site selected posed some extraordinary challenges for constructors in the early 1960s. Located high in the mountains, at elevations ranging from 10,018 feet to 11,200 feet, it was the highest-altitude pumped-storage facility in the world at the time. This extreme elevation required innovative design and construction techniques to manage the high hydraulic head of more than 1,200 feet—an engineering feat that pushed the limits of turbine and pump technology available in the 1960s.
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Full issueAdditionally, the facility employed reversible pump-turbine units, which were cutting-edge technology for the era. These units allowed the plant to switch between pumping and generating modes with remarkable efficiency, enabling it to store energy during off-peak hours and dispatch it rapidly during peak demand. This dual-functionality was not only novel, but also critical in supporting Colorado’s rapidly growing electricity needs. The plant’s innovative design, high-altitude construction, and strategic role in grid modernization earned it the prestigious Edison Award in 1968, cementing its legacy as a pioneering achievement in energy storage and hydroelectric engineering.
“The Cabin Creek facility acted as a giant battery for the grid,” Kris Fox, senior manager for Hydro West with Xcel Energy, told POWER. “During periods of low demand—typically at night—excess electricity from coal-fired baseload plants was used to pump water from the lower to the upper reservoir. Then, during peak demand periods—like hot summer afternoons—the stored water was released to generate electricity almost instantly.”
This capability provided several critical benefits:
- Load Balancing. It smoothed out the daily peaks and valleys in electricity demand, improving the overall load factor of the system.
- Operational Efficiency. It allowed coal plants to run more consistently at optimal output levels, reducing wear and fuel costs.
- Grid Reliability. It provided fast-response generation capacity, which was especially valuable in a mountainous region with variable weather and growing urban centers.
In the decades after the project entered commercial operation, only routine annual inspections and maintenance were required. In the 1980s, however, major overhauls of individual powerhouse machinery components were completed. Many of the 1980s changes focused on replacing worn mechanical parts and working to stabilize and improve slopes and reservoir structures to keep up with changing state and federal engineering standards.
Modernization Ushers in a New Era
While the Cabin Creek facility has undergone additional changes since the 1980s, perhaps the most comprehensive modernization project was conceived in the mid-2010s. “A pumped-storage plant’s turbine, generator, and balance of plant mechanical and electrical components typically have a design life of 40 to 50 years, so it is common to see a lot of modernization programs occurring after 50 years of operation,” Matt Pevarnik, sales manager for Hydro Power North America with GE Vernova, told POWER. Modernization programs often improve efficiency, output, and reliability, among other things. In the case of Cabin Creek, the project also coincided with the facility’s license renewal.
The components updated (Figure 1) as part of the modernization included the turbines, generators, excitation systems, plant controls, isolated phase buses, and transformers. All of these were replaced with modern features and benefits to meet the demands of today’s grid for the next 50 years or more, reduce operations and maintenance costs, and improve safety. An 11-blade runner, designed and supplied by GE Vernova, was a notable retrofit. The design required extensive model testing and new welding techniques, and represents a significant improvement over previously existing designs, providing substantially more power than concepts submitted by other bidders.
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1. The Cabin Creek modernization project included upgrades to the turbines, generators, and many other components. Courtesy: Xcel Energy |
The project engineering, procurement, and construction (EPC) budget was initially developed in 2015, and a contract was signed in 2016. The project experienced some schedule delays, primarily due to the scope of discovery work, as well as additional time to test and manufacture the novel rotor design. Yet, the project budget remained close to the initial estimate.
The project logged 205,620 man-hours between 2018 and 2024. The project’s safety record was admirable, with very few recordable incidents over the six-year period—none of which included hospitalizations or permanent injuries.
The new turbine design did create some welding challenges due to the tight geometries. Yet, collaboration and close coordination, including across multiple time zones, countries, and continents, allowed Xcel Energy, GE Vernova, and other consultants to manage and overcome obstacles. Discovery work related to the 60-year-old asset, and the COVID pandemic, which disrupted global supply chains, quality, and delivery schedules, also made the job challenging, but these issues were also successfully conquered.
Doug Roskop, Cabin Creek’s operations manager with Xcel Energy, noted that operating the plant during the modernization project required balance. “Large team coordination, focusing our operational excellence and attention on the available unit and not allowing that to take away from the importance of maintaining the quality and schedule of the modernization project, was important,” he told POWER.
Flexibility Is More Important Than Ever
Today, the units are running better than ever. Yet, they don’t balance coal-fired generation the way they once did; now, they provide grid stability and integrate renewables into Colorado’s energy mix. “We now support the grid more by run time in synchronous condensing operations as a spinning mass able to increase and decrease voltage on the line for reliability purposes,” Roskop explained.
“Our ability to regulate voltage as a synchronous condenser is a huge value that was not realized with the original project and has become one of the highest impacts of the plant,” Fox added. “With the growing renewable portfolio for Xcel Energy, we see Cabin Creek becoming even more valuable to better manage energy storage and voltage regulation. The industry is always evolving and having a plant that is so flexible and reliable is going to be very important for Xcel Energy going forward.”
Pevarnik agreed that flexibility is fundamental for almost all energy storage projects being built today, but especially for pumped-storage units like Cabin Creek. “To have the ability to switch from synchronous condensing to generating and then pumping modes, multiple times per day, coupled with quick starts and fast ramps, this offers the Xcel Energy system operators a suite of products to support the grid and help ensure the lights stay on,” he said.
Roskop noted that it’s hard to describe a normal day or week of operation at Cabin Creek. “Things can vary with weather patterns, wind generation, and seasonal variabilities that require our new units to be accessible at all times for a variety of purposes. That is what makes Cabin Creek important for Colorado, its flexibility and versatility are like nothing else in the region,” he said.
—Aaron Larson is POWER’s executive editor.
