Wind development had taken off in the Altamont, as it is known, in the 1970s and 1980s, boosted in part by support from the state government. In more recent times, California's 33% renewable portfolio standard hasprovided incentive for more electricity production, noted Nancy Rader, president of the California Wind Energy Association.
Several sites in the pass are being repowered, with most on track to be completed in 2015 or, more likely, 2016, said Sandra Rivera, assistant planning director of Alameda County, where most of the repowering is taking place.
"You can't have repowering without the PTC," Koebbe said. "Power prices are at a historic low in California. We're competing with solar. We're competing with gas. The economics for repowering aren't there without the PTC." PowerWorks' repowering project, Summit, consists of old 100kW Kenetech turbines that would be replaced with multi-megawatt models — but only if the subsidy is reinstated. Projects had to be under construction by year-end 2013 to quality for the ten-year tax credit.
The area's much-publicised bird kills are the main factor behind the repowering. "Repowering is seen as a way to alleviate some of the bird mortality. The [new turbines] are also more efficient and help economic development," said Rivera.
Indeed, eagle deaths in two of the earliest repowered projects are so far considerably lower. NextEra's repowered Vasco project was completed as part of a legally binding settlement reached in December 2010 by parties including bird groups and California's top law-enforcement official, the state attorney general. The bird advocacy groups had sued because of reports of high numbers of bird kills, especially of golden eagles.
The Vasco project, inaugurated in May 2012, saw a 97% decrease in eagle deaths in its first year of operation and a 65% decrease in overall avian kills, said Will Nelson, principal planner in neighbouring Contra Costa County. The data for the second year has yet to be finalised. The Vasco repowering saw 438 turbines from the 1980s, with a total capacity of 80.5MW, replaced with 34 Siemens 2.3MWs. Although the total capacity has remained roughly the same at 78.2MW, the new turbines produce 147% more electricity, he said.
Also in Contra Costa County, Pattern Energy's Buena Vista project, repowered by Babcock & Brown, replaced 179 old turbines with 38 1MW Mitsubishis in 2006. Eagle deaths there have dropped by 82-85%, said Rivera, whose county will soon issue an environment impact report to guide development in its entire Altamont Pass wind resource area.
Two more NextEra projects — both in Alameda County — will also be repowered as part of the legal settlement. Golden Hills phase 1 and 2, each about 80MW in size, are to be completed by December and by September 2015 respectively, according to the settlement. Phase 1 has yet to be completed, confirmed NextEra spokesman Steve Stengel.
Also in Alameda County, EDF Renewable Energy's Patterson Pass project currently consists of 336 Nordtank and Bonus 65kW turbines. They will be decommissioned and replaced. And the Sand Hill 4MW repowering, by Ogin Energy, will see 40 small FloDesign shrouded wind turbines installed.
In Contra Costa County, Pattern Energy's Tres Vaqueros repowering, which has yet to permitted, will see 91 old turbines replaced with 19 Siemens 2.3MWs. Meanwhile, hundreds of old turbines nearby are currently being dismantled by Wintec Energy. Wintec declined to comment on why it was not repowering the site. The company's "use permit" expires in August, said a county spokesman.