Hidden away alongside the Twin Lakes, below the tallest mountain in Colorado, is the Mount Elbert Powerplant, a huge secret power battery.
The majority of this 14-story-high concrete powerhouse structure lies underground and produces 200 MW of hydroelectric energy. The power plant balances the power needs in the area by diverting mountain runoff on the opposite side of the Continental Divide.
At nighttime when the power demands are low, giant motor generators are used in reverse mode to pump water back uphill.
Harnessing mountain water across the Continental Divide
The Fryingpan-Arkansas Project was approved through Public Law 87-590, passed in August 1962.
The multiple-use project was planned by the federal government to provide water to cities, farmers, and industries in southeastern Colorado.
An elaborate transmountain diversion system was engineered to be located in the Rocky Mountains.
Water collection systems take excess water from tributaries of the Fryingpan River and Roaring Fork River.
The process of taking mountain water and transferring it across the Continental Divide results in transferring an average of 69,200 acre-feet each year to the Arkansas River valley.
Water is supplied to eastern slope reservoirs for municipal water users and irrigated land users.
The Mount Elbert Powerplant is the key energy facility of the federal water diversion system.
Concealing a massive hydroelectric powerhouse beneath the surface
The construction team was able to dig deep into the shoreline bedrock to create the underground powerhouse.
Construction of the all-concrete underground powerhouse ensured that the beauty of the natural scenery around the lakes was maintained.
The powerhouse is comparable to a 14-story building, despite having the majority of its floors lying underground.
Mount Elbert Forebay Dam stores the upper reservoir water that is supplied from Turquoise Lake.
The alpine water falls down the penstock pipes under a hydraulic head of 448 feet.
Spinning the two huge Francis turbines located within the subterranean powerhouse is the rushing water.
The power plant has installed equipment capable of generating up to 200,000 kilowatts of electricity.
Reversing massive turbines to store grid energy
Typical hydro plants provide clean energy as the water moves downward through the turbines.
The pumped storage system allows the plant to operate in two different hydraulic modes.
The electrical generators serve as 170,000-horsepower motors that can run in reverse mode.
In the early mornings, the demand for electricity drops, and the price of wholesale electricity falls considerably.
The electricity from the interconnected generating plants is purchased by the operators and used to run the motors.
By reversing the action of the Francis turbines, the water is being pumped back up into the forebay from Twin Lakes.
The replenished upper reservoir holds large amounts of potential energy to be used later on.
Delivering rapid power during peak electrical demand
Regional electricity grids are subjected to huge load fluctuations because of increasing consumption of consumer electricity throughout the day.
Rechargeable pumped storage provides instant stabilization of the grid to regional power grids during sudden load fluctuations.
Mount Elbert plant control systems can commission generating units much faster than the traditional fossil-fuel-based thermal plants.
Instantaneous response helps to adjust power production instantly with changes in load peaks that occur on a daily and seasonal basis.
Releasing the forebay water during peak time generates instantaneous electricity for the peak consumer population.
Flexibility in generation ensures voltage stability in the Western Area Power Administration service region.
Outlining physical limits of high-altitude storage
Pumped storage power stations provide important grid storage capabilities; however, there are limits to the capacity of the plants due to physical considerations.
Mount Elbert’s generation restrictions stem from steel penstock flow capacities rather than electrical generator limitations, as reported by the Bureau of Reclamation.
Fluid dynamics within penstock tubes limit the maximum water flow during periods of continuous generation at full capacity.
The pumping process is entirely dependent on getting steady power overnight from other regional power plants.
Several decades of use mean that there will be constant maintenance needed, such as updating the main control panels and switchyard circuit breakers.
Considering the physical limitations of the penstocks helps engineers make the most out of their operations.
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