Work on the Palouse wind farm, a two-year project to construct turbines meant to generate electricity for Spokane-based Avista Corp., is now complete, an addition that the energy company says will pad its growing renewable energy portfolio.

The 40-acre, 58-turbine wind farm, named Palouse Wind and situated eight miles west of Oakesdale, Wash., went online Dec. 13 and generates 105 megawatts of energy, or the equivalent of providing power for 30,000 Avista residential customers, company spokeswoman Anna Scarlett says. Oakesdale is about 43 miles south of Spokane.

Boston-based First Wind, a renewable energy company, developed and owns the wind farm, says Ben Fairbanks, business development manager for First Wind's western region. First Wind operates 16 wind farms across the U.S., including the one located on the Palouse.

Avista is buying all of the energy generated at the Palouse wind farm under a 30-year agreement, Fairbanks says.

While the turbines were being constructed between October 2011 and the end of last year, Fairbanks says the land impacted was closer to 400 acres. He says more than 80 percent of the affected land is located in wheat fields, and in most cases, farmers can plant up to the base of the turbines.

"Once the project is fully constructed, those areas are reclaimed and restored," Fairbanks says. "In most cases, the farmers have already been back in there planting."

About 40 different land owners are affected by the project, he says. Along with 28 land owners who have turbines located on their property, 12 have access easements or transmission easements, Fairbanks says.

First Wind leases the property it uses from farmers and Fairbanks says those leases, which range between 20 years and 40 years, will be extended if demand for wind energy in the Inland Northwest remains strong.

Fairbanks says First Wind currently employs four full-time workers who manage a team of 10 full-time Vestas employees at First Wind's office in Rosalia. Vestas, a Danish wind turbine manufacturer with U.S. headquarters in Portland, Ore., has blade, tower, and nacelle manufacturing facilities in Colorado. Scarlett says Avista doesn't have any employees stationed at the site.

Those associated with Vestas are on site to handle turbine maintenance.

Vestas provided the turbine parts for Palouse Wind. Fairbanks says parts were manufactured at Vestas' Colorado plants and shipped from there to Pasco, Wash. on rail lines and then trucked to the Palouse.

Fairbanks says it logged more than 250 tractor-trailer loads of turbine-part components while constructing the Palouse Wind complex.

During construction, Fairbanks says more than 40 Inland Northwest contractors and suppliers worked on the project, with around 15 contractors based in Spokane County and 14 based in Whitman County. At the peak of construction, between 250 and 300 people worked on the site daily in various roles, Fairbanks says.

Alan Thomson, Whitman County planner, says the county treasurer's office estimates it received roughly $1.1 million in sales tax payments related to the project between November 2011 and October 2012, before a roughly 75 percent state sales tax rebate Palouse Wind is slated to get back. Thomson says the 25 percent of remaining sales tax will be divided between the state and the county.

First Wind estimates Whitman County will receive $700,000 on average annually in property tax payments associated with the wind farm. Thomson says that property tax, which won't kick in until 2014, will help fund expenditures by taxing entities such as library and school districts.

"They'll all get a share of the overall moneys from this project," Thomson says.

Over a 20-year span, the county is expected to receive about $12 million in property tax revenues.

The 58 Vestas v100 turbines stand 426 feet tall. From the ground to the hub, where the blades attach, the turbines stand 250 feet tall, with the blade diameter sweeping a space that is roughly the length of a football field, he says.

"One of the reasons why a project like this is feasible is advancement in turbine technology," Fairbanks says.

The turbine model used at Palouse Wind is different than those that might be used at other wind farms developed by the wind energy company.

Fairbanks says a turbine usually doesn't produce electricity unless it reaches a certain number of revolutions per minute, or RPM. The turbines will spin, but internal computers won't enable the transmission of electricity unless enough force is applied to the blades. With the model used at the Palouse, the power curve is flatter, meaning the turbines start producing electricity at a lower wind speed. Coupled with a longer blade, Fairbanks describes it as turning a bigger Ferris wheel, applying more force on the components.

A height-wind resource map published in partnership with the U.S. Department of Energy's Wind Program and the National Renewable Energy Laboratory examines the wind resource potential in the state of Washington for utility-scale development, referring to turbines between 262 and 328 feet high. Average annual wind speeds of 14.5 mph or greater are typically considered to be high enough for wind development, the U.S. Department of Energy says. The turbines installed by First Wind exceed the maximum height of resource map by almost 100 feet.

Fairbanks says Neff Ridge, where Palouse Wind is situated, is windiest between October and March.

In addition to Palouse Wind, Avista in 2008 acquired the development rights for a site in Reardan, located about 21 miles west of Spokane. Since then, the company has been evaluating and studying the site for potential development.

"For us, bringing wind on is a good thing because it helps us continue to give our customers energy at some of the lowest prices in the country," Scarlett says.

According to the resource map, Palouse Wind and the area west of Spokane that Avista is eyeing for future development both average 14.5 mph wind speed annually.

"It's really pairing the right technology with the right wind resource," Fairbanks says. "Engineering has gone into that understanding of matching the right turbine with the right wind speed to produce the most efficient and most energetic project."

In addition to Avista looking at the potential for wind energy in the Reardan area, Fairbanks says First Wind is permitted to erect upwards of four additional turbines at Palouse Wind in the future if warranted.

Scarlett says Avista has met state renewable energy mandates for 2012, without taking into account the electricity generated by Palouse Wind. The company was able to meet those minimum requirements through upgrades at its hydroelectric plants, Scarlett says. Under the voter-approved mandates, electric utilities must obtain 15 percent of their power from renewable sources by 2020.

With Avista's Kettle Falls Generating Station, a biomass plant, eligible to count toward the company's renewable energy portfolio as of last March, Scarlett says the Palouse wind farm's generated electricity may not even be counted toward the next round of mandates.

"The Palouse wind is just to meet energy needs and add renewable energy to the portfolio," Scarlett says.

Avista Corp.'s operating division, Avista Utilities, provides electricity to 361,000 customers and natural gas to 320,000 customers throughout the Inland Northwest and parts of Oregon.