With San Diego Airport Microgrid, No More Blackouts and $6.4M/year Saved

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Before the San Diego International Airport microgrid was built, the airport experienced four to five blackouts a year, each which lasted two to eight hours, according to Darr Hashempour, CEO of DH Green Energy, the consulting firm that designed and built the microgrid.

The blackouts — which occurred during San Diego Gas and Electric’s (SDG&E) outages — embarrassed airport executives, upset airport customers, and spurred losses for airlines, he said.

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Now, thanks to the utility-scale microgrid, the airport operates 24-7. But as Hashempour pointed out that’s not its only advantage. The microgrid has saved the airport about $6.4 million a year in energy costs and reduced the airport’s carbon dioxide emissions by 24,000 tons per year.

What’s more, when it’s fully completed and capable of islanding from the utility, it can serve as an emergency shelter during disasters, said Hashempour.

“That’s one of the beauties of the system and one that the upper management of the airport was so proud to achieve,” he said. “Politically this puts the airport on a different planet because the airport can offer its facilities during emergencies.”

The microgrid will be able to island when enough solar and storage are installed to serve the facilities, within the next two to three years. The airport will also install a small cogeneration system, he said.

The San Diego International Airport’s microgrid story began in late 2009, when the airport asked DH Green Energy to help identify how to supply energy to new infrastructure and facilities — including new buildings and a rental car facility — that were part of a multi-billion-dollar expansion.

SDG&E proposed providing the power and building two substations at a cost of $30 million, said Hashempour.

“The airport wanted to find a solution to get rid of the power blackouts and connect power to new facilities,” he said.

DH Green Energy proposed a microgrid solution with total costs — including design, equipment, construction, and airport personnel — were about $24 million, he said. “If you take away airport personnel costs, the actual costs of design and construction were $21.5 million,” Hashempour said.

The consulting firm found that the existing substation was sufficient to feed power to the entire airport, but the airport needed to change the power distribution system, which was owned and operated by SDG&E. The existing system had a lot of power losses because of its design, he said.

Loops forms airport microgrid

The consulting firm decided to create a large loop around the airport campus. On that loop, three main circuits — Circuits A, B and C — transport power from SDG&E to the airport. Each circuit comes from a different SDG&E source, so it’s unlikely that all three will go down, explained Tommy Luong, energy engineer for DH Green Energy.

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The circuits are controlled by a Supervising Control and Data Acquisition (SCADA) system, which enables load shedding and load shifting that augments the solar PV on the site, said Luong.

At the recommendation of DH Green Energy, the airport removed all SDG&E meters and began purchasing electricity from the utility at less expensive, bulk rates, said an airport spokeswoman. The airport now owns the distribution system not SDG&E, said Hashempour.

In essence, by creating the airport-owned and operated loop, DH Green Energy formed a utility-scale airport microgrid, he explained. This created numerous levels of redundancy, compared to zero redundancy before this change.

“If one line (from the utility) goes down, the other circuit will take over and provide power so no power is shut down,” he explained. While the airport has an emergency diesel generator, it’s not used unless all three circuits go down, he said.

Solar to provide up to half of load

In addition to installing the loops, the airport installed 3.2 MW of solar PV. It plans to add 5 MW and 2 MW of storage. Right now solar serves about 15 percent of the airport’s load, according to Hashempour.

airport microgrid

Airport parking canopy with solar panels, courtesy DH Green Energy

Rather than feeding the solar to the utility under a net metering scheme, the airport utilizes all the solar. When the additional solar-plus storage is added, solar will be able to serve about 45 percent to 50 percent of the load. The energy storage will store the solar for release during the utility’s peak hours.

The microgrid will be able to island when solar, storage and some cogeneration are all added.

“Not only is our microgrid fully automated, it also has the ability to take all the power generated at the site for its own use only. That’s how the airport can eventually become an island down the road. Once you generate up to 70 percent of your usage, you can island,” he said.

And that’s when the beauty of the microgrid will be truly revealed. During emergencies, it will be able to island from the utility and provide power to critical portions of the airport, while serving as a refuge for the general public, he said.

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