An $11 million hydroelectric facility that will harness flows from an irrigation canal in the same way power is tapped from rivers is planned west of Fairfield, with NorthWestern Energy lined up to buy the electricity.
The Turnbull Hydroelectric Project, which will produce 13 megawatts of electricity, will be constructed 4 miles west of Fairfield on the Spring Valley Canal in the Greenfields Irrigation District. That district distributes water from the Sun River to farmers and ranchers, said hydroelectric engineer Ted Sorenson of Idaho Falls.
Turnbull Hydro LLC, which is building the facility, is a joint venture of Sorenson, rancher Wade Jacobsen and the Greenfields Irrigation District.
The 13 megawatts is enough electricity to power 8,000 to 10,000 homes. Most of the power probably will be used in the immediate vicinity, he said.
“All of Fairfield will be energized from this power,” Sorenson said.
When the project is finished, Turnbull will be considered a “summer peaker” because it will provide power when water and air conditioner use is high. The system will operate during irrigation season from May to September. Construction is scheduled to begin in fall 2010.
Using irrigation canals to generate electricity at times of peak demand is common in Idaho and California, but the Greenfield’s project is the first Sorenson knows of in Montana.
“It’s a new application of old technology,” said Sorenson, who was the project engineer on a 7.5-megawatt hydroelectric project completed at Tiber Dam in 2004.
Separate generating facilities will be placed at two concrete canal “drops,” or flumes, known as Upper Turnbull and Lower Turnbull, along the Spring Valley Canal.
Upper Turnbull is 1,100 feet long and drops 100 feet, while the 2,600-foot Lower Turnbull descends 140 feet. The flumes carry water from Pishkun Reservoir across steep declines.
“They’re kind of like a big waterslide,” Sorenson said.
Pipelines parallel to each flume will divert the water. As the water descends through the contained pipelines, the resulting pressure will be captured at the bottom of the flumes with turbines, which will convert it into electricity.
It’s the same concept as having a tank of water in the attic of a home that produces good faucet pressure on the main floor, Sorenson said. Energy from the flumes, which were constructed in 1928, is going to waste right now, Sorenson said.
The diverted water will be returned to the canal system without disrupting delivery to producers, Sorenson said.
NorthWestern Energy, which provides electricity and natural gas to 656,000 customers in Montana, South Dakota and Nebraska, announced Tuesday that it had signed a 20-year contract with Turnbull to purchase the power.
NorthWestern spokeswoman Claudia Rapkoch said the company requested bids for renewable energy supply agreements a year ago, then reached a deal with Turnbull after a lengthy negotiation.
“This particular project is very cost effective, very favorable to customers,” she said.
The green power will help NorthWestern meet the state’s renewable energy standards, which require public utilities to procure a minimum of 10 percent of their retail sales of electricity from renewable resources by 2010, and 15 percent by 2015, Rapkoch said.
KARL PUCKETT, Great Falls Tribune – http://www.greatfallstribune.com/article/20091111/NEWS01/911110305/Project-aims-to-turn-irrigation-ditch-into-power