Honolulu to implement cooling with deep-sea water
CHRISTOPHER PALA
the day, driven by air-conditionand sulfur oxides by 165 tons per More than half of the buildings in ing use, so this approach saves year. It will also reduce the use of Honolulu’s skyscraper-studded not only power, but premium refrigerants such as HCFC-22, downtown will be cooled by power, notes Mikulina. “This HCFC-123, and CFC-11/500. ocean water pumped from the project will help relieve some “Most green-energy projects deep by 2012. The project should strain on the power grid.” focus on generating clean elecsave money for building owners, The system does not warm the trons,” says Jeff Mikulina, head of and greenhouse gas emissions ocean, says the company’s vicethe Blue Planet Foundation, should be cut, according to an president for engineering, environmental impact stateIngvar Larsson. “If you look ment published in fall 2009. at the heat we emit in both The technology is already the ocean and the atmoused in Toronto and Stocksphere, it’s 40% less than a holm to balance temperaconventional air-conditiontures inside large buildings, ing system, and of course, by notably to cool areas with cutting greenhouse gases, we computer servers and teleslow global warming.” phone exchanges during the Peter Rosegg, a Hawaiian summer months. But, says Electric Company spokesWilliam M. Mahlum, presiman, has nothing but praise dent of Honolulu Seawater for the project. “By reducing Air Conditioning LLC, which our load, it allows [us] to is undertaking the $240 mil- Honolulu will soon become the first warm-climate increase our reliability to lion project, “This is the first city to use deep-sea water to cool part of its other customers,” he says. time it will be used to cool a downtown. “The next logical step would be warm-weather city center.” The which promotes clean energy. [to add] Waikiki, the tourism-oricompany, owned by investors in “The beauty of this one is that it ented part of the city, where 40% Hawaii, Sweden, and Minnesota, avoids electrons altogether by of the power use is taken up by is managed by Renewable Energy tapping into a vast local reair conditioning.” Innovations, a unit of Ever-Green source.” Honolulu Seawater Air CondiEnergy Co. of St. Paul, Minn. In this system, a five-foot-wide tioning officials confirm that once Groundbreaking is expected pipe extends four miles out to sea the current project is finished, next summer, and the first 40 to a depth of 1700 feet and brings they expect to create another buildings are expected to come in 44,000 gallons per minute of unit, with its own pipe into the on-line in late 2012. Another five water at 45 °F. Once ashore, the ocean, in Waikiki; that project will be added the following year water goes through a conventionwould take another five years. to reach maximum capacity of ally powered chiller that brings its It’s not surprising this came 28,000 tons. temperature down to exactly 44 about in Hawaii. On the Big IsOnce the system is up and run°F, then loops through a heat exland in 1974, the Natural Energy ning, predicts Mahlum, it should changer with a closed-circuit Laboratory of Hawaii Authority inspire tropical coastal cities freshwater system, and is released did the first U.S. tests of ocean around the world to harness the back into the sea at a depth of thermal energy conversion to see technology. “We know this could 200 feet at 56 °Fsthe natural temif temperature differences bework in Miami, Acapulco, and a perature at that depth. tween the deep and the surface lot of other coastal cities,” he Meanwhile, the cooled freshwacould be turned into electricity says. “All you need is a steep ter makes its way to the buildings’ economically. The answer was enough coastal gradient and conair-conditioning units, and cools “not yet,” but as a sideline, the centrated demand.” air passing over the coils in front laboratory created the world’s The system, he says, will save of the fans. This allows the buildfirst air-conditioning system to its clients about 20% in cooling ing to turn off the energy-hungry use cold seawater pumped in costs. By reducing power use by compressor that previously chilled from the deep. 77 million kilowatt hours per year, the coil and the cooling towers. or 75%, it will cut CO2 emissions Hawaii sees a surge in the de—CHRISTOPHER PALA mand for power in the middle of by 84,000 tons, NOx by 169 tons,
10.1021/es9033364
2010 American Chemical Society
Published on Web 11/18/2009
January 1, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 13
