As we consider strategies for kicking Hawaii’s 5-million-gallon-per-day oil habit, our tendency is to focus on alternative sources of fuel and electricity. We look to clean, renewable energy sources to replace dirty fossil-fuel power. We also look for ways to reduce the amount we use — and waste — through efficiency and conservation.
What we often overlook is that fuel and electricity are means to an end. Electricity is not what we really want. What we really want is light when it’s dark, hot water for a shower and a comfortable temperature indoors.
What if we could cut out the middle man and put an abundant natural resource to work in place of electricity?
Seawater air conditioning is an energy solution that does just that.
Air conditioning is a voracious consumer of electricity. On Oahu, more than 20 percent of the electricity sold is used just to cool buildings. Honolulu Seawater Air Conditioning (HSWAC) has proposed a solution for downtown that precludes the need to cool water with electricity, one that could save more than 70 million kilowatt hours of power annually.
Applying the same technology that has been cooling buildings in Toronto, Stockholm and Amsterdam, the Honolulu SWAC team has proposed a district cooling system that will serve the downtown vicinity by 2014.
This fall, it will begin installing a pipeline four miles offshore Kakaako that will pump seawater from a depth of 1,700 feet to an onshore cooling station. There, the 44-degree water will pass through a heat exchanger that transfers the seawater’s coldness to a pipeline of freshwater that circulates in a closed loop. The chilled freshwater connects to downtown buildings’ existing air conditioning infrastructure, providing natural AC that doesn’t require large, electricity-hungry chillers in each building.
The seawater, slightly warmer than when it left the ocean, returns home through a diffuser at 330 to 425 feet — deep enough that no coral ecosystems are affected. The underwater pipe actually becomes an artificial reef, providing substrate to new coral and shelter to fish.
The Honolulu district cooling system has a capacity equivalent to 25,000 tons of ice, enough to cool some 40 buildings. Currently, more than 18,000 tons have been reserved for customers, including the First Hawaiian Center, Hawaiian Electric Co., One Waterfront Towers and the Finance Factors buildings. Those who have signed on recognize the savings they’ll reap thanks to the stabilization of long-term energy costs.
Electricity is versatile, but it is difficult and costly to make and store. The genius behind SWAC technology is that the cold seawater can chill buildings 24/7, much like solar water heaters provide hot showers even after the sun has set. The project’s seawater system design engineer, Makai Ocean Engineering, also designed the deep water pipes off Keahole Point that have successfully provided cooling for the Natural Energy Laboratory of Hawaii Authority in Kona.
The district cooling system will generate an estimated $200 million in construction spending, creating more than 900 new construction jobs. Besides lowering greenhouse gas emissions by nearly 75,000 tons per year, it also will save 260 million gallons of potable water and reduce wastewater discharge by 84 million gallons a year.
On World Ocean Day, observed Friday, we appreciate how much the ocean directly improves our lives in so many ways: food, medication, therapy, recreation, scenery. Let’s also recognize its enormous potential in helping to meet our energy needs.
While researchers continue to work on ways to harness wave power and ocean thermal power, buildings in downtown Honolulu should readily convert to seawater air conditioning, a renewable energy solution that is practical and proven.