San Diego-based Sempra Generation said yesterday it has acquired Auwahi Wind Energy LLC, which is developing a 22-megawatt wind energy and battery storage project on Maui.

Sempra bought the Auwahi Wind Energy Project from Shell WindEnergy Inc. for an undisclosed price, according to a news release from Sempra.

Shell WindEnergy is a subsidiary of Royal Dutch Shell, while Sempra Generation is a unit of Sempra Energy

Sempra said the proposed Auwahi Wind Energy project would begin construction in 2011 and start commercial operation in 2012 on Ulupalakua Ranch.

"Consistent with our growing renewable presence in the southwestern United States, this project further expands Sempra Generation's footprint in one of the fastest-growing renewable energy markets while further advancing the sustainability goals of Maui and the state of Hawaii," said Michael W. Allman, president and chief executive officer of Sempra Generation.

Sempra said an important element of the project is development of a battery energy storage unit.

The battery could store as much as 28 megawatt-hours of wind energy generated by the project's windmills during the typically windy morning and night hours. The power could be stored until late afternoon, when electricity consumption typically peaks.

Sempra recently submitted a proposal to the U.S. Department of Energy to help pay for costs associated with an expansion of the battery energy storage facility to 72 megawatt-hours.

Sempra said the project could help Maui attain its goal of obtaining 95 percent of its electricity from renewable sources by 2020.