Water power re-emerges as tool to balance grids
Self-contained, waterpowered electricity generating systems historically have been a regular tool some utilities have used to quickly provide substantial amounts of power to meet spikes in load demands.
And as today’s power grids are supplied by more renewable energy sources that are vulnerable to generating drop-offs because of changing weather conditions, interest in these systems appears to be on the rise.
Groups of developers have looked at building such a system, called a “closed-loop” pumped hydroelectric storage system, in Oklahoma. Some have toyed with the concept for years, with one developer continuing to work on plans to build a project off the Kiamichi River in Le Flore County.
Another has filed a preliminary permit request with the Federal Energy Regulatory Commission, notifying it that it also proposes to build one.
The developer also proposes to build and operate a power line that would extend from the generating system’s southeastern Oklahoma location across the Red River, connecting to the grid operated by the Electric Reliability Council of Texas.
Loyd Drain, an energy consultant who regularly deals with power generating and distribution issues, isn’t surprised the concept is getting some interest.
Drain said a need for systems that can provide power quickly into grids continues to climb as more of the nation’s older, coal-fired power plants are retired.
“It is a form of energy storage that provides great standby power,” Drain said.
“Unlike some other forms of energy storage (batteries), pumped storage has been around for a long, long time. And generally speaking, it is cheaper than battery storage. It is a good, low-cost alternative, for sure.”
How it works
A pumped hydroelectric storage system creates power the same way a dam power house does, using generators that are driven by water-propelled turbines.
A self-contained system doesn’t depend on a constant flow of water to operate, though. Instead, it makes electricity by releasing water that flows downhill through the power house generators’ turbines from a reservoir that has a higher elevation.
After passing through the power house, the water is captured in a lower reservoir, where it is stored until the system operator pumps the water back to the higher reservoir to prepare for a future release.
The operator sells the power generated by the system into a grid for a high price at times when a grid operator needs the energy to keep its power levels constant, preventing either brownouts or blackouts.
While the system uses electricity to move the water back to the upper reservoir, it takes that power at times when the juice costs less. That’s how operators make their money.
The Oklahoma project
A representative for Southeast Oklahoma Power Corp., the entity seeing the temporary permit from FERC, couldn’t be reached this week to comment about its plans.
Its application said it proposes to develop the pumped storage hydroelectric generating station and the associated 132-mile-long, 345 kilovolt power line on private lands in Le Flore, Choctaw, Bryan and Pushmataha counties in Oklahoma and in several Texas counties.
The system would get its initial water for its 985acre lower reservoir and additional water to replace evaporation losses by building a concrete-lined channel from the Kiamichi River to a 68-acre reservoir built at the same elevation.
The channel to collect the river water would be built at an elevation three feet above the river’s bottom, ensuring it would take water from the river only during heavy flow periods.
The pumped storage hydroelectric generating system would transfer water between its lower reservoir and 408-acre upper reservoir through tunnels.
The system’s proposed headrace tunnel (between the upper reservoir and power house) would be 6,370 feet long and vary from about 18.7 to 27.8 feet in diameter. The system’s tailrace tunnel (between the power house and lower reservoir) would be 7,439 feet long and vary from about 21.3 to 27.8 feet in diameter.
The power house, built underground using reinforced concrete, would contain four 300-megawatt generators capable of generating 1,200 total megawatts for the Texas grid.
The permit request states Southeast Oklahoma Power Corp.’s plans are conceptual in nature and won’t be finalized until agreements are reached with landowners and potential buyers of its power. Geological and environmental studies also are planned.
It requests that its preliminary permit be granted for a three-year period.
Previous plans
Southeast Oklahoma Power Corp.’s plan is similar to others worked on by other developers in recent years.
Dan Tomlin Jr., a partner with Tomlin Investments, said the only significant difference between the Southeast Oklahoma Power Corp. project and those earlier ones are that they planned to use aboveground pipes to move around the water, rather than tunnels.
Tomlin said he and partners continue to work on putting together a project, adding they’re working to secure agreements from landowners before any permit requests are filed with regulators.
Tomlin said the last time he is aware that a pumped storage hydroelectric generating station was built in the United States was in the early 1990s as a way to provide quick-start power a utility could call upon to support nuclear generation.
“One thing that is different is that now you have all this wind and solar coming on and that can be very erratic. Coal plants are too slow, and even most natural gas plants aren’t capable of meeting immediate dispatch needs.
“The generators for these pumped storage hydroelectric generating stations can go from zero to 1,200 megawatts in minutes, and that gives grid operators the ability to stabilize the grid when a coal or gas plant goes down.”