The turquoise blue waters surrounding Hawaii's emerald green isles have long been a source of food and recreation. Now the chilly waters deep below the ocean's surface are being eyed as a source of cool relief from the tropical heat.
HONOLULU — The turquoise blue waters surrounding Hawaii's emerald green isles have long been a source of food and recreation. Now the chilly waters deep below the ocean's surface are being eyed as a source of cool relief from the tropical heat.
Isolated in the middle of the Pacific, Hawaii's energy industry depends heavily on the world's finite supply of imported oil and coal.
So the state began to examine whether cold seawater could be harnessed to meet the islands' year-round air conditioning needs.
"The offshore cold water is certainly the largest source of alternate energy available to the state of Hawaii. And you're not going to run out of it" said Reb Bellinger, vice president of sales and marketing for Makai Ocean Engineering Inc.
The company has worked on a number of projects employing seawater cooling, including a system that opened in Toronto last year, and at this nation's trailblazer -- Cornell University. The technology has also been used in Stockholm, Sweden, since the 1990s.
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A $100 million system proposed for downtown Honolulu could reach about 65 buildings, including several state office buildings, said David Rezachek, associate development director of Honolulu Seawater Air Conditioning, which is working with Kailua-based Makai to put cold seawater technology to work in Hawaii.
Bills to help move the project along, including providing the company with special purpose revenue bonds, are being considered by Hawaii's Legislature. Then it's just a question of getting customers to sign up.
Once underground pipes leading from an oceanside plant are in place beneath the city streets, buildings would be able to tap into the system and save about 75 percent of the electricity used by conventional cooling systems, said Rezachek.
The technology is relatively simple. Cold ocean water is pumped up to the plant through a closed system, cooling down fresh water in an adjacent system. That cold fresh water is then used by buildings to bring down the temperatures of their interiors, similar to a conventional air conditioning system.
The University of Hawaii has built a similar system using deep seawater wells for its new oceanside medical school buildings near downtown Honolulu.
Cornell's system, operating since 2000 at its Ithaca, N.Y., campus, draws cold water from Cayuga Lake and saves 86 percent of the power used by conventional air conditioning, said W.S. "Lanny" Joyce, the project's manager.
Conditions are particularly favorable in Hawaii where the sea floor plummets along with the water temperatures not too far offshore, less so in bodies of water such as the Gulf of Mexico, which is more shallow.
It was on Hawaii's Big Island where one of the likely first examples of the concept was pieced together by a few sweltering scientists back in 1981.
During the 1980s, the Natural Energy Laboratory near the Kona Airport was the only place in the world to bring up cold water from a depth of 2000 feet with the intent of studying its usefulness as an energy source.
An aquaculture facility was also operating on the site out of an old sea shipping container, said Jan War, operations manager for the lab.
"What we did is we took an old truck radiator and ran cold seawater through and put a box fan behind it and air conditioned the van for a year with very little energy and cold seawater. ... Sort of the stone age approach to air conditioning but it showed us it could be done for very little investment," War said.
Four years later, the Natural Energy lab tested a seawater system on one of its larger labs and now uses the cold ocean water to cool three of its buildings -- saving about $3,000 per month on its electricity bills, War said.
The technology is touted for using a renewable -- and local -- resource and saving potable water usually lost to evaporation in conventional systems.
And besides the environmental benefits, it should also save money on electricity bills -- eventually.
"Everything in utilities is capital intensive. That's the problem. But once people start to accept the inevitability of renewable energy there will be a greater and greater demand," said Bill Mahlum, chief operating officer of Minnesota-based Market Street Energy Co., Honolulu Seawater's parent company.
Jeff Mikulina, director of the Hawaii chapter of the Sierra Club, says that while seawater air conditioning appears far more environmentally friendly than the current alternative, he's awaiting the findings of an environmental impact statement.
The potential for ecological damage depends on how the system is designed to return the seawater to the ocean, said John T. Harrison of the University of Hawaii's Environmental Center in Honolulu.
"If you get cold, deep seawater it's going to be nutrient enriched. It's going to have a higher concentration of nutrients. If you discharge those nutrients into shallow waters where there's lots of sunlight they're going to cause -- you know, it's just like putting fertilizer on a field. So that is a definite concern," Harrison said.
Engineering a system to put the water back at a level below the reach of sunlight would eliminate the problem, he said. That's exactly what Rezachek said Makai planned to do.
Harrison fully endorses the well-conceived use of seawater cooling.
"In this day and age looking for any and all sources of renewable energy that don't release greenhouse gases, that don't require fossil fuels and that basically have extremely low operating costs -- I mean, it's money in the bank."
Source: Associated Press
