Ice Harbor Project Aimed at
Three federal agencies are leading a project aimed at improving the design of hydroelectric turbines in Northwest dams to make them friendlier to future generations of fish.
With a trio of 1961-vintage hydroelectric turbines approaching the end of their useful life at Ice Harbor Lock and Dam in 2008, the Bonneville Power Administration and U.S. Army Corps of Engineers officials recognized a window of opportunity. They say Ice Harbor Dam, on the Snake River near Pasco, Wash., has proven to be a fruitful site for developing technical innovations aimed at raising survival rates of endangered and threatened fish in the region.
Private and government biological and engineering experts are working together on the Ice Harbor project, which is unique because it elevates fish passage improvements to the highest goal, ahead of power and turbine efficiency gains. The turbines are also expected to be more efficient at generating electricity, providing 3 to 4 percent more power from the same volume of water.
If they achieve their promise, the new turbines could be available for other Corps dams on the Columbia and Snake Rivers.
Engineer George Brown of BPA called the work an "excellent example of collaboration among BPA, the Corps, NOAA and a capable contractor."
The Corps awarded a $10.9 million contract in 2010 for two turbines, the first in the next generation of advanced equipment that could provide safer passage for young salmon and steelhead migrating to the Pacific Ocean. BPA is funding the project, like other power-related investments in the 31 dams of the Federal Columbia River Power System, through its regional ratepayers. Voith Hydro Inc. of York, Pa., is designing and building the major components, including the runner, the part of the turbine that spins with the force of the river to generate power. This spring, the federal agencies decided to fund a third new turbine runner at Ice Harbor, expected to be in operation after 2020.
"The emphasis had been to keep fish out of the turbines, with the thought that the blades are really, really bad for fish," said Kevin Crum, turbine project manager at the Walla Walla District of the Corps. "But we're finding with new designs, they are not that bad -- we're actually seeing survival rates of 92 to 96 percent."
The Corps and BPA crafted the contract as a model to demonstrate a science-based turbine design and development process that could guide replacement of other turbines around the Columbia River Basin. Scott Bettin of BPA's Fish and Wildlife division says building a safer turbine was just the next logical step in a sequence of major improvements to fish passage in the FCRPS in recent years.
"There's three ways fish can get around a dam," Bettin explains. "We installed bypass systems and improved the effectiveness of spill with surface routes. Now we're replacing the turbines with state-of-the-art designs to improve survival through this route."
The project partners have been through multiple design cycles over the past three years, using advanced computer modeling as well as tests with physical models to examine water flow and pressures. The drop in water pressure as young fish travel downstream through the runner presents one of two primary hazards. In the new design, the project team intends to maintain a higher and more stable water pressure through the runner.
"The way we elevate those minimum pressures is through modifying the blade shape," said Martin Ahmann, senior hydraulic engineer with the Walla Walla District of the Corps.
The other major peril arises when fish strike turbine parts, such as runner blades and structures called stay vanes and wicket gates that guide water to the blades. During this project, engineers redesigned these structures by changing their shape and orientation to minimize impacts. Additional improvements result from reducing gaps in the runner, as well as reducing water recirculation, eddies and dead zones so that fish can exit the turbine and move downstream immediately.
"The modification to the turbine's rotating and stationary components is significantly greater than that undertaken in a typical turbine rehabilitation," says Tom Freeman, senior mechanical engineer with the Corps' Hydroelectric Design Center in Portland, Ore. "The scope of the project demonstrates the federal agencies' commitment to improving turbine fish passage survival."
With a diameter of 23 feet, the turbines may appear to resemble a giant water wheel, but the project team resists the notion it is re-inventing the wheel.
"The basic principles of the turbine haven't changed, and to a casual observer our improvements probably would not be very obvious," Crum says. "However, the cumulative effects of the hundreds and hundreds of design tweaks we've made result in substantial flow and efficiency improvements through the turbines."
Two types of turbines, with fixed or adjustable blades, are being developed for Ice Harbor. The first new runner will have a fixed blade. Although it provides less operational flexibility -- meaning it can't respond to changing needs as well as turbines with adjustable blades -- having fewer moving parts makes it less costly up front and easier to maintain later.
Both types will sport stainless steel blades, which resist pitting and corrosion caused by water forces called cavitation. Repairing this damage takes today's less-resistant steel turbines out of service for six to eight weeks every other year at dams around the FCRPS.
"A better material over time will enable us to reduce maintenance costs," says Rick Werner, district chief of operations for the Walla Walla District of the Corps. "For us, it's a win-win: You're getting improvements in fish survival, and I'm having to spend less resources maintaining it."
The second turbine being developed for Ice Harbor has adjustable blades. Brown says both design efforts have far-reaching potential in the Northwest.
"In addition to providing some much-needed turbines at Ice Harbor," he says, "this R&D effort has provided essential information that will help us make smart and responsible decisions in the future when it comes time to replace the federal turbine fleet in the Northwest.
"It is always a challenge to balance reliability, generation and environmental stewardship goals, but this project better enables us to do that. We have grown our understanding of the tools available to us and the potential for improvement that lies ahead."
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