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Photo © Franzen Photography
Thermal chimneys projecting from the building's roof provide passive cooling under most conditions.

PROJECTS:

Hawaii Gateway Energy Center

Ferraro Choi and Associates
Kailua-Kona

Seawater Sailor: Passive systems work almost perfectly to cool and light this showcase project.

By Nadav Malin
November 2011

Four years after GreenSource originally published the Hawaii Gateway Energy Center, and seven years after it was completed, the facility continues to attract drop-in visitors fascinated by its larger-than-life photovoltaic arrays. Hawaii Gateway is part of the Natural Energy Laboratory of Hawaii Authority (NELHA), which is a state-operated ocean-science and technology park. NELHA is home to nearly 40 innovative enterprises engaged in innovative aquaculture, desalinating and bottling mineral-rich deep seawater for drinking, and developing renewable energy alternatives.

KEY PARAMETERS

Location Kailua-Kona (Big Island of Hawaii, western shore)

Gross area 3,600 ft2 (335 m2)

Cost $3.5 million

Completed October 2004

Program Offices, conference facilities, laboratories, visitors’ center

TEAM & SOURCES

Glass PPG, Azurlite Aqua-Blue

Ceilings Tectum acoustic ceiling planks

Flooring Tajima Free-Lay Vinyl tile with 100 percent post-consumer recycled content

View all team & sources

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The Energy Center houses the nonprofit Friends of NELHA. Director Guy Toyama and his team of volunteer docents use the facility to educate and engage over 5,000 visitors each year. "Visitors are amazed when they come in from the heat outside and we show them how cool our space is with no conventional air conditioning," Toyama says. On most days, the Energy Center's passive-stack ventilation works beautifully, drawing air across cooling coils chilled by deep-ocean water, through the space, and out through solar-heated stacks in the roof.

When the wind is from the north, however, the stack effect, or thermosiphon, isn't strong enough to overcome downdrafts created by the solar arrays, and the occupants have to prop doors open to remain comfortable. Fortunately, it's not typically as hot on those days, Toyama notes. The solar panels came late in the design process; the trusses that support them were originally designed for much taller ventilation stacks. NELHA is still seeking funding to extend the ventilation stacks to solve the problem.

This situation has given project architect Bill Brooks of Ferraro Choi a new respect for the sensitivity of passive airflow: "A thermosiphon is a very gentle, subtle system. It only takes a subtle counterforce to combat it," he notes. In retrospect, Brooks questions his choice to use only fixed windows. They did that to make sure that nothing would short-circuit the thermosiphon, but he now believes that flexibility is critical to this type of building: "Having operable windows would allow them to trim the sails for any condition, instead of relying on one concept."

Another innovation at the center was supposed to be the use of seawater to cool the soil for landscaping. In theory, tubing with cold water just below the surface would cool the soil enough to create condensation, minimizing the need for irrigation and encouraging plant growth. That system suffered for lack of attention when the facility was first completed and lacked a tenant, and has never lived up to expectations.

The Energy Center is daylit well and not used at night, so the lights are never on. Without lights or fans, the largest energy load is for a booster pump that provides enough pressure to move the seawater through the cooling coils. That pump is only needed because the project is at a high point in the complex, according to Brooks. Even with that load, the PV arrays generate more energy than the building uses, and they generate lots of visitor traffic too.

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