A project to replace big, energy-gulping air-conditioning systems in Downtown Honolulu buildings with a technology that uses piped cold deep-sea water is one step closer to reality.

Honolulu Seawater Air Conditioning has released the preparation notice for its environmental impact statement, the first step in a required review process.

"It's a big step for us," said Dave Rezachek, associate development director for the company.

The proposed system uses a 4-mile-long, 63-inch-diameter intake pipe that would extend seaward from a point in Kaka'ako between Kewalo Basin and the Honolulu Harbor main channel.

The company will use horizontal drilling equipment to push the pipe below the surface from onshore to a point 2,200 feet from shore, where the water is about 40 feet deep. The pipe would lie in a filled trench from 40 to 80 or 100 feet in depth. After that, it would lie on the ocean floor, anchored by large concrete structures.

The pipe would be about 4 miles long, and would collect water 1,600 feet deep at a temperature of about 45 degrees Fahrenheit.

The cool water would come ashore, and be run through a heat exchanger to chill fresh water. The sea water would be returned to the ocean at between 80 and 200 feet in depth, at a temperature of 56 degrees Fahrenheit.

The fresh water from the heat exchanger would then be piped into Downtown buildings, providing cooling. Rezachek said the company will need to do fairly extensive trenching in Honolulu's streets. It anticipates about three miles of trenching to deliver the cold water to Honolulu buildings.

The project cost is estimated at $145 million, toward which the company has $100 million in state tax-exempt revenue bonds. The remainder of the money will come from investors and conventional borrowing.

Rezachek said the company hopes to have the system operating by late 2009, after a 14-month construction period.

The big benefit of the system is reduced energy use. Pumping cold seawater uses dramatically less energy than using compressors in conventional air-conditioning units. That's a particular bonus in a high-energy-cost state like Hawai'i.

The study says the new project would save 174,000 barrels of fuel oil, which otherwise would be burned in Hawaiian Electric Co. power plants.

Honolulu Seawater Air Conditioning says there also is a reduced use of the chemical refrigerant in conventional systems.

Honolulu Seawater Air Conditioning will be delivering cold water to buildings, where it will be linked up to existing chilled water distribution systems, replacing cooling towers.

Rezachek said most buildings should see about an 8 percent decrease in their air conditioning costs in the first year. And as oil costs rise, their savings should increase, he said.

Seawater air conditioning, although new to Hawai'i, is a mature technology. A system in Stockholm, Sweden, started cooling buildings in 1995. There also are systems at Cornell University in New York; Toronto, Ontario; and Bora Bora, French Polynesia.

"Most of the parts are from off the shelf," Rezachek said.

The company EIS notice, prepared by TEC Inc., was delivered to the state Office of Planning.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.