Seawater system proposed to cool medical school
| • | Graphic: Proposed saltwater cooling system |
By James Gonser
Advertiser Urban Honolulu Writer
A saltwater technology that could change the way buildings on O'ahu are air-conditioned and save money, electricity and natural resources is being proposed by the Honolulu Board of Water Supply for the John A. Burns School of Medicine under construction in Kaka'ako.
The deadline to comment on the Board of Water Supply's saltwater cooling facility at Kaka'ako is Feb. 23. Send comments to City and County of Honolulu Board of Water Supply, 630 S. Beretania St., Honolulu, HI 96843, Attn.: Lorna Heller. Include three copies for the consultant, the approving agency and the state Office of Environmental Quality Control.
The technology, which uses cold seawater as a coolant for air-conditioning systems, is used in dozens of cities nationwide and at the National Energy Laboratory of Hawai'i on the Big Island, but those systems use pipelines that are miles long to reach cold lake and ocean water and cost tens of millions of dollars.
Public comment
What the board has in mind is a unique twist on the idea — drill a well 3,000 feet straight down to reach cold seawater and pump it directly to where it's needed.
It would be the first time a well to bring up cold water for air conditioning has been tried anywhere, board officials say, and it would cost millions less in capital investment and could eventually reap a profit for the city.
The technology could cut a building's cooling costs by as much as 85 percent, said Clifford Jamile, the board's manager and chief engineer. He estimated that the University of Hawai'i could save $750,000 annually in air-conditioning costs for the medical school.
As an island state, "it just kind of made sense for us to look at that" technology, Jamile said. "We will go right through the formation that supports this island. It has a larger benefit for us all down the road."
If the project works as he expects, Jamile said he can imagine Waikiki hotels, downtown office towers and other oceanfront developments converting to the system.
However, the city has yet to determine water temperature at that depth. A critical test will come in April when the board drills a test well at the medical school site to gather temperature data.
Jamile said the water temperature needs to be in the low 40s to properly chill the fresh water used in the air-conditioning system, but it can be as warm as the low 50s and still be effective by simply cooling the salt water a little.
The well idea came to Jamile as the board built its desalination plant in Kalaeloa. As workers drilled a 1,600-foot-deep well to bring up salt water, Jamile noticed that its temperature was 53 degrees. He knew about the air-conditioning technology and the idea struck him that if they just dug deeper, colder salt water could easily be reached.
"It uses technology that we understand very well — well drilling and pipe laying," Jamile said. "We are venturing that the water is going to be approximately 40 to 42 degrees. We are banking on it."
The board has filed a draft environmental assessment for the cooling facility with the state Office of Environmental Quality Control, which is accepting public comments. The system is expected to cost between $3.5 million and $6 million and pump about 10 million gallons of salt water a day.
That compares with the $21.5 million spent recently by the National Energy Laboratory of Hawai'i to install a 2-mile pipeline to provide 27,000 gallons per minute of cold seawater for its aquaculture enterprises and for air conditioning.
In the BWS-medical school project, the cold ocean water would be brought up to a cooling station on university property where it would pass through a heat exchanger that chills fresh water in an enclosed water distribution system. The chilled fresh water then would be circulated into the medical center's air-conditioning system.
After cooling the fresh water, the salt water would be warmed to about 75 degrees, which is about ocean surface water temperature, and discharged into a drainage canal west of the project site.
A conventional air-conditioning system at the medical center would use a large compressor and cooling tower that would consume 2.25 million to 6.75 million kilowatt hours of electricity and 30 million to 40 million gallons of fresh water a year, Jamile said.
Jamile said if the city were to receive just half of what UH saves annually at the medical school by not running a conventional air-conditioning system, the board will have recouped the investment costs and start making money on the project by 2010.
The board looks at the work as a water conservation project, making use of an abundant natural resource and saving O'ahu's drinking water from being wasted in a conventional air-conditioning system.
Allan Ashan, UH Medical School planner, said the first building is scheduled to open in March 2005 and the cost savings as well as the environmental benefits are good reasons to support the project.
Daniel Dinell, executive director of the Hawai'i Community Development Authority, the state agency developing the 670-acre Kaka'ako area adjacent to downtown
Honolulu, said the project might be expanded to other tenants if test results indicate it makes good sense.
Maurice Kaya, chief technology officer at the state Department of Business, Economic Development and Tourism, said the technology is not complicated, but depends on an inexpensive source of cold water.
"It costs a lot of money to put those pipelines in," Kaya said. "If you can find a source of inexpensive cold water, it's a very good way to go. As to whether it is the wave of the future, that depends on the economics of the project. The geology of Hawai'i is such that there is potential elsewhere in the state."
Reach James Gonser at jgonser@honoluluadvertiser.com or 535-2431.
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