NELHA-pioneered seawater air conditioning growing in popularity
In his office at the Natural Energy Laboratory of Hawaii Authority building, Jan War has a collection of products made using deep-sea water.
He also has a picture of even more items — cosmetics, salt, fish dried with sea salt, desalinated water — that are produced because of technology like that used at NELHA. But none of those things represent how he thinks more people should be using cold seawater. That best use isn’t something a visitor to the office could see, but it is something visitors can feel.
“These are all wonderful products, but the best utilization is chilling and cooling,” said War, NELHA’s operations manager. “You get the biggest bang for your buck.”
The “bang” that comes with using sea water air conditioning systems is big, he said, generally saving municipalities or building owners that switch to it 75 percent to 85 percent on their electrical costs. The upfront costs of retrofitting an air conditioning system can be expensive, but War said the return on the investment comes about fairly quickly, within five to seven years. And the technology has been in use for decades, using cold water to cool warmer freshwater, is just regular air conditioning equipment.
“There’s zero technological risk,” War said.
NELHA pioneered seawater air conditioning 30 years ago, he said.
“The first one was basically a truck radiator and a box fan,” he said.
It lasted six months, doing exactly what its designers hoped for — cooling a Matson container in which salmon eggs were being hatched. The most recent upgrades to the NELHA office system was in 2009. The office is about to be remodeled into a business center, at which point the system will get another upgrade, War said.
Several large municipalities, including Toronto and Stockholm, have switched from traditional systems, using chemicals and chillers that create water that goes into their respective wastewater systems, to seawater systems.
To cool a building, cold seawater flows on one side of a plate inside a plate type heat exchanger. On the other side, warm freshwater is flowing. The colder water cools the warmer water through the plate, then the freshwater is pumped into the air conditioning system inside the building, where it cools the air that is distributed inside the offices. In the NELHA office system, as in many other seawater systems, the warmed freshwater remains in a closed-loop system and is routed back to the heat exchanger to be cooled again.
At NELHA, the slightly warmed seawater is then returned to a distribution pipe, from which energy lab tenants draw water for their own uses.
If Kona International Airport ends up with enclosed buildings, state Department of Transportation officials have said they are considering a system to cool the terminals with seawater air conditioning. War said if that happens, NELHA officials are willing to extend a pipe to the airport property, which is adjacent to the energy lab, as well as a pipe to take the warmed seawater, to sell down the line to NELHA tenants.
Most of NELHA’s tenants are mixing warm and cool seawater to achieve the perfect temperature for their aquaculture and other projects, he added.
The need for seawater air conditioning at NELHA is fairly low, he added. It wouldn’t be a cost effective project for the region if NELHA wasn’t bringing up the seawater for other uses. Large buildings, such as resorts and hotels, have enough need to make installing in the deep-sea water pipeline economical. The buildings that will be cooled by the seawater need to be relatively close to the water and have a need for cool air. That doesn’t mean just buildings in warm climates, though, he said, noting that large office buildings often generate enough heat to need some air conditioning even in the winter.
More people should be developing seawater cooling systems, War said.
“It’s an underutilized technology,” he said.” Because of the cost of fossil fuels, more and more people are realizing they have a resource underneath their feet.”
Developers on Oahu have proposed a large project for downtown Honolulu, and are considering proposing one for Waikiki as well, War said, and officials in more areas around the world are considering implementing the technology.
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