Ninth turbine going in at Wanapum Dam

BEVERLY - Construction crews are presently installing the ninth turbine and third generator at Wanapum Dam.

Grant County PUD started replacing the turbines in 2004 with the goal of improving the efficiency of the turbines and the safety of fish passing through the gates. The utility estimates it will cost about $220 million for the turbines and about $175 million for the generators.

The new turbines have several new features designed to improve electricity production and fish passage issues, said Stuart Hammond, a hydro engineering supervisor. The two items work in concert with each other.

"What's bad for fish is bad hydraulic situations and we were correcting those in order to get more energy out," he said.

Hammond explained the new turbines stay efficient over a longer range of possible water levels. Engineers analyzed possible designs to determine what would create the most efficient turbine.

"We're able to capture more of the passing flow with the blades and have less losses with the flow as it goes through," he said. "It's not just the blade design ... We've combined that with a hub design and a discharge ring design ... You tweak each one of those things and gather a fraction of a percent efficiency and it adds up."

The blades on the new turbines are wider, and feature a lip to help deal with cavitation. Cavitation is when a low pressure pocket of water collapses explosively in high pressure water.

"The blades move on these turbines. They move in order to give us the most efficient blade setting for whatever amount of energy we want to generate," he said. "The amount of energy we want to generate changes all the time. We get signals every four seconds that can change the turbine setting."

The hub holding the blades is a sphere, which allows the gaps between the blades and the hub to stay the same.

"If this is any other shape, then the geometry would be such that as you moved (the blade) the gap would widen and vary depending on where it was," he said. "That means you have gap flows, which costs you for energy production, and sets up vortices and turbulence and sheer zones which are all really bad for fish."

In studies the PUD conducted, it discovered hydraulic disturbances kill more fish than being hit by the turbine blades, Hammond said.

"We have a more efficient turbine. We get about 3 percent overall more energy out of this turbine than we get out of the other turbines," he said.

The ninth turbine is expected to be finished in December, Hammond said. The PUD plans to finish the final turbine next year.

"We started the turbines sooner because the generators have a longer life, but now we have a new generator going in that allows us to generate more energy because it has a bigger capacity," he said.