Sempra Generation of San Diego has acquired a 22-megawatt wind energy project on Maui for an undisclosed price.

Sempra bought Auwahi Wind Energy LLC, which is building the wind farm on Ulupalakua Ranch, from Shell WindEnergy, a subsidiary of Royal Dutch Shell.

Construction is expected to begin in 2011, with the wind farm in operation by 2012.

Michael W. Allman, president and chief executive officer of Sempra Generation, said the acquisition expands the company's footprint in one of the fastest-growing renewable energy markets while furthering Maui and Hawaii's sustainability goals.

First Wind (formerly UPC Wind), a Massachusetts-based company, built a 30-megawatt wind farm in the West Maui mountains, the Valley Isle's first commercial-scale project three years ago.

Shell had first announced plans for the $200 million wind power plant on Maui three years ago.

Sempra says a key component of the project is a battery energy storage unit which can store up to 28 megawatt-hours — generated from morning and night winds — for peak electricity consumption in the late afternoons.

The storage unit also can help regulate intermittent wind power, providing grid stability for Maui Electric Co.

Sempra Generation is applying for funds from the U.S. Department of Energy to more than double the storage unit to 72 megawatt-hours.

The San Diego company, which built El Dorado Solar, a 48-megawatt, thin-film solar power plant near Las Vegas last year, is also planning Energia Sierra Juarez, a greater-than-100-megawatt wind farm in Baja California, Mexico, in 2012.

Sempra Energy, the parent of Sempra Generation, recorded nearly $11 billion in 2008 revenue and has about 13,600 employees.