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SWAC in Hawai'i

Hawai'i already has three active seawater air conditioning systems, all of which have a much lower capacity than any system that would be built in Waikīkī. There are also a number of proposed SWAC projects, one of which – Honolulu Seawater Air Conditioning – is due to begin construction in 2012.

Existing Systems

University of Hawai'i John A. Burns School of Medicine

A new campus for the University's medical school opened in 2005. With two wells pumping seawater from a depth of 750 feet, the system supplies cold water, which is then further cooled to air-condition the school's main buildings, which have a total area of approximately 1,840,000 square feet. Highlights of the project so far:

  • 20 million gallons of potable water saved annually (as compared with business-as-usual)
  • Operating costs savings of approximately $750,000/year.

Natural Energy Laboratory of Hawai'i Authority (NELHA)

In use since 1987, NELHA's SWAC system was the first in the world. A 55-inch supply pipe reaches a depth of 3,000 feet, making it presently the largest and deepest pipe of its kind in the world. Prior to being utilized for SWAC, deep-water pipelines had already been laid to provide cold, nutrient-rich seawater for research into alternative energy and aquaculture. Today, the older pipes serve as backup supply lines. The SWAC system has been expanded to supply a new administration building and a second laboratory. The system provides 30-50 tons of cooling (Rezachek 2005).

Kahala Resort

This Honolulu hotel pumps deep seawater from wells to supply cooling for its chiller systems. As a value-added feature of the system, the return seawater flows over a decorative waterfall to dissipate heat and absorb oxygen. This water then flows into dolphin and tropical fish-stocked lagoons. The hotel estimates that it annually saves 380,000/kwh of electricity and 4,500,000 gallons of water. The hotel was granted a Green Business Certification by DBEDT's Green Business Program on March 17, 2011.

Prospective Systems

Downtown Honolulu

A seawater air-conditioning system with a 25,000-ton cooling capacity has been proposed for downtown Honolulu. The system is projected to cut AC energy costs by 75% and save the equivalent of 178,000 barrels of oil a year. Estimates of annual reductions in emissions are as follows: CO2 – 84,000 tons, VOC – 5 tons, CO – 28 tons, PM10  – 19 tons, NO2 – 169 tons, SO2 – 165 tons. In July 2011, the HSWAC project took a step forward when the state Department of Land and Natural Resources (DNLR) gave permission for the offshore development part of the system. 

Follow the progress of the HSWAC project.

Hickam/Pearl Harbor Naval Shipyard

The cooling demand for these two sites is approximately 5,500 tons. Due to the distance of the client sites from the supply source, the construction costs were estimated to be at the upper limit of what was considered economically feasible. At the time of research, the cost savings just for the shipyard were estimated to be $2,000,000 a year if electricity costs were $0.10/kWh.

The estimated financial benefits of the secondary uses of the system were not calculated. One of these benefits would be the use of the exhausted seawater as ground cooling, similar to what has been suggested for the Ala Wai Golf Course. Condensation on the subsurface piping would help with grounds maintenance and it would also bring the temperature of the water closer to the temperature of the water in Pearl Harbor, thus reducing the impact on the near shore environment. One additional benefit to cooling could be the use of the outlet water to help preserve the USS Arizona Memorial. Flushing a similarly submerged monument with seawater is currently being done in South Carolina (DBEDT 2002).

Ko'Olina

In 2005, the Ko'Olina Resort and Marina were not yet completed. At that time it was believed that in the future, cooling demand would develop to the point where a SWAC system would be feasible (Rezachek 2005). With its proximity to deep seawater, a SWAC system could have supplied the three Ko'Olina resorts with cooling, however when the resorts were built, conventional chillers were used. The potential for SWAC had been a proposal to use deep seawater for the supply water of a planned aquarium but the aquarium was never built. Secondary uses for the water included desalinated drinking water production and air-conditioning. The plans for the aquarium were shelved, as were the plans for the other uses of the water (Gomes 2007).


References:
- DBEDT. (2002). Sea Water District Cooling Feasibility Analysis for the State of Hawaii (R. State of Hawaii
  Department of Business Economic Development and Tourism; Energy, and Technology Division, Trans.).
  Honolulu, HI: State of Hawaii Department of Business Economic Development and Tourism; Energy,
  Resources, and Technology Division.
-Gomes, A. (2007, 06/28). Resort to tap seawater under Honolulu,Honolulu Advertiser. <http://the.honoluluadvertiser.com/article/2007/Jun/28/ln/FP706280353.html>.
-Rezachek, D. (2005). Docket No. 05-0145. Honolulu.