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Home / Washington Business - November/December 2005 / Better Turbines for Fish |
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Better Turbines for Fish |
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Written On: November/December 2005 |
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Written By: by Ron Dalby |
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New Fish-Friendly Turbines are Coming to Wanapum Dam
State-of-the-art hydropower turbines increase electrical production and may enhance the survivability of salmon and steelhead smolt heading downstream.
Is it possible to design a more efficient turbine that also allows a greater percentage of juvenile salmon to survive the tumultuous seven seconds as they pass through? A new turbine undergoing tests at the Wanapum Dam suggests the answer is yes.
It’s called the Advanced Hydro Turbine System. The first one was installed at Wanapum earlier this year and tested against one of the nine older turbines in the dam, which are all scheduled to be replaced in the next few years.
It produces more power without a doubt, 14 percent more to be exact with an average 3 percent increase in water-use efficiency, according to an article in the March issue of Connections, the monthly newsletter of the Washington Public Utility Districts Association.
The new turbine is also expected to improve the survival of young salmon and steelhead moving down the Columbia River. Its new design addresses the entire hydraulic passageway and incorporates a host of refinements to reduce fish mortality. Basically, the design of the unit allows for the smoothest possible water flow through the unit, eliminating much of the turbulence that contributed to fish injury in previous turbines.
"We operate with the belief that power generation and fish protection are compatible and sustainable," Steven Brown, natural resources director for Public Utility District No. 2 of Grant County, told Connections.
The U.S. Department of Energy is also very enthusiastic about the new turbine. Its web site notes that, "Advanced hydropower turbine technology could minimize the adverse effects yet preserve the ability to generate electricity from an important renewable resource."
While the extra power the new turbine can generate is appreciated, it’s the survival of the fish passing through it that is front and center among everyone’s concerns. In the seven seconds it takes for a fish to pass through the turbine, it is subjected to high pressures, shear forces, turbulence and the possibility of mechanical strikes. Even so, the vast majority of the estimated 2.5 million salmon and steelhead smolt passing over the Wanapum Dam every year survive.
According to the Oak Ridge National Laboratory, the mortality rate of fish passing through turbines ranges from 5 percent to 15 percent and occasionally more. DOE’s goal is to reduce this figure to 2 percent or less.
The turbine passed its first test on fish survivability in February of this year, but only with an average grade. Some 7,200 balloon-tagged and radio-tagged yearling Chinook salmon were introduced simultaneously into the new turbine and one of the old turbines and then retrieved after passage for evaluation. Approximately 1,000 sensor fish—mechanical fish used to record pressures and acceleration—were sent through as well. After recovery, the fish were held for an additional 48 hours to be reexamined for late-developing injuries.
Survival rates for the salmon passing through the turbines were 96.9 percent for the AHTS and 97.5 percent for the older turbine, a statistical dead heat.
Before approval for the new turbine could be had, it had to demonstrate at least as much fish survivability as the older turbines. This requirement was met.
It is, however, significant that both turbines caused only a 3 percent mortality rate, far better than the mortality rate estimated by ORNL. This means we are within "spittin’ distance" of the 2 percent goal. In fact, it’s a figure that’s almost better than anyone could hope for.
"One of the goals of the Department of Energy hydropower program is to find engineering solutions that will make the route of passage through turbines safer for fish," said Glenn Cada from ORNL. "If we can accomplish that goal, hydropower will become a more acceptable form of clean, renewable energy."
Editor’s Note: Hydropower accounts for between 7 percent and 12 percent of the electricity generated in the United States. It plays a far bigger role in the Pacific Northwest, where it produces more than 50 percent of our electricity.
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