A second wind project on Oahu’s North Shore, designed to be twice as large as the recently completed Kahuku plant, could be producing power as soon as next year.

First Wind LLC has completed an environmental impact statement for a proposed 70-megawatt wind energy project on former sugar cane land northeast of Haleiwa that would be the state’s largest, generating enough energy to supply 14,500 homes.

Boston-based First Wind said it hopes to begin construction on the Kawailoa Wind Farm in late 2011 and have it pumping electricity into the Hawaiian Electric Co. grid sometime in 2012. The project would significantly expand the state’s wind energy output, which consists today of 112 megawatts of generating capacity on Oahu, Maui and Hawaii island.

First Wind, the state’s largest wind energy developer, operates the only other wind project on Oahu, the 30-megawatt Kahuku Wind Farm, which opened in March. First Wind also operates the 51-megawatt Kaheawa Phase I and II wind projects on Maui.

The company worked closely with community groups on the North Shore in the planning process to ensure it had broad support, said Wren Wescoatt, First Wind spokesman. He said the positive feedback First Wind received from the community on its Kahuku project helped lay the groundwork for the Kawailoa Wind Farm.

With the state’s acceptance of the EIS, First Wind can now move forward with securing the necessary permits for construction, Wescoatt said. First Wind also will have to negotiate a power purchase agreement with HECO to buy the electricity.

"This project together with the Kahuku Wind Farm creates a combined 100 megawatts of wind energy capacity on Oahu. This is important for an island moving toward meeting its renewable energy goals," Wescoatt said.

The project drew little criticism when First Wind made its presentation to the North Shore Neighborhood Board, said board member Carol Philips.

"We tend to be supportive of renewable energy and things that point toward sustainabilty. There was discussion about the potential visual blight — how big would the wind turbines be, how far away would they be," Philips said.

"I see wind as a good renewable energy source as we move into the future. I see it as positive change even though I’m not too excited about looking at the structures. It’s better to generate energy with the wind than blowing smoke or having a nuclear plant," she said.

The project will be built on land owned by Kamehameha Schools that was part of the Kawailoa Plantation operated by Waialua Sugar Co. before it closed in 1996. While the plantation is spread over several thousand acres, the area "disturbed" by the project will be limited to 335 acres, according to the EIS.

The wind project’s site encompasses a range of topographical conditions from "relatively flat or moderately sloping agricultural lands to steep gullies and intermittent streams," the company said in its EIS. Elevations range from 200 feet above sea level at the makai edge of the property to 1,280 feet at the mauka boundary.

In its EIS, First Wind said it had not made a final decision on whether it would include a battery storage system similar to what it installed at its Kahuku and Kaheawa II projects. The battery systems are designed to smooth out short-term fluctuations in the energy output of the wind turbines that occur when wind speeds increase and decrease. Without such a buffering system, the volatility in wind turbine output could be harmful to the electrical grid.

The actual energy output of a wind project is often substantially less than its stated capacity. For example, the Kawailoa wind project would produce about 25 percent of its 70-megawatt capacity over the course of a year, according to an analysis of data provided by First Wind in its EIS. The Kahuku Wind Farm’s so-called capacity factor is higher at 30 percent.

The more reliable winds on Maui have resulted in much higher capacity factors. At First Wind’s Kaheawa I Wind Farm, the project’s capacity factor has averaged about 43 percent during the five years it has been in operation, with a peak of 48 percent reached in 2007.