On December 17, 2017, a fire at an underground electrical facility damaged two substations that serve Atlanta's Hartsfield-Jackson International Airport — then and now the world’s busiest airport. The resulting 11-hour-long power outage led to the cancellation of nearly 1,200 flights.

The Atlanta outage, and another that disrupted power for several hours at Los Angeles International Airport in June of this year, is motivating airport operators across the United States to take steps to ensure an uninterruptible supply of power.

In this quest for more reliable power, an increasing number of airports are turning to microgrids — self-contained grids capable of operating independently from the traditional grid. In the latest such project, Pittsburgh International Airport will become the first major American airport to be 100 percent powered by a microgrid.

In an interview, Tom Woodrow, VP of engineering at the Allegheny County Airport Authority, said being able to maintain operations and always be open for business was top of mind for Pittsburgh’s airport.

“The primary goal was to avoid being the next Atlanta or L.A. and to be able to get that resilience and reliability. And, secondarily, to reduce the cost of electricity to the airport authority and our tenants,” he said.

The microgrid will include 22.5 megawatts of generating capacity, with 20 megawatts coming from natural-gas-fired generators and 2.5 megawatts from a ground-mounted solar photovoltaic installation.

Construction of the microgrid is scheduled to take 19 months, with the system expected to be online and fully commissioned in June 2021.

Numerous airports embracing microgrids

Pittsburgh International Airport’s microgrid continues a trend that has gained momentum since Atlanta's 2017 outage, said Isaac Maze-Rothstein, a microgrid analyst with Wood Mackenzie Power & Renewables.

Atlanta's outage has led to a "shift in thinking for airport operators," Maze-Rothstein said.

"Before, control towers and some related emergency equipment were seen as critical infrastructure," he said. “After that event, operators saw an increasing portion of airport operations including terminals as critical infrastructure that needs a resilient, cost-competitive solution.”

Pittsburgh joins a growing number of U.S. airports that have installed or plan to install microgrids on all or a portion of their facilities over the last two years. According to WoodMac, the list includes JFK Airport Terminal 1; San Diego International Airport; Chattanooga Metropolitan Airport; California Redwood Coast-Humboldt County Airport; and now Pittsburgh International Airport.

Resilience may be the primary driver for airport microgrid adoption, but the improving economics of alternatives to grid-supplied power make these projects even more attractive.

“Cheap gas and distributed energy resources [are] making potential customers able to justify using a microgrid and not be connected entirely to the macrogrid in an urban environment,” said Maze-Rothstein.

Pittsburgh International Airport also happens to sit atop one of the nation’s most productive natural gas plays, the Marcellus Shale; two active drill pads operated by CNX Resources are located on airport property. Onsite access to plentiful, cheap gas helps to explain the project’s dependence on gas-fired power.

The Allegheny County Airport Authority receives an 18 percent royalty for gas from Pittsburgh airport’s wells.

Microgrid services at no upfront cost

Pittsburgh airport’s microgrid will be owned and operated by Peoples Natural Gas, a natural gas distribution company with customers in western Pennsylvania, West Virginia and Kentucky.

Under the 20-year energy services agreement the airport signed with Peoples Natural Gas, the airport pays nothing but a monthly electric bill starting in June 2021.

“Peoples is completely, 100 percent financing the project. There are no tax dollars involved. There are no subsidies involved,” said the Allegheny County Airport Authority's Woodrow. “They are the designer, permitter, constructor, owner, operator and maintainer of the system.”

Woodrow also said developers who responded to the request for proposals for the microgrid project “were given the opportunity to provide us with generally any combination of energy generating technologies” that could meet the airport’s resilience and reliability requirements.

“We encouraged natural-gas-fired generators, and we encouraged some form of renewables — although we did not mandate what they decided to do."

The project comprises five 4-megawatt turbocharged natural-gas-fired generators, as well as the 2.5 megawatts of solar PV. It does not include battery storage or a combined-heat-and-power system.

According to airport spokesperson Bob Kerlik, “Our energy plant has the ability/option to recover waste heat in the future if we can find a cost-effective way to recover and reuse the heat.”

Kerlik added that the airport expects the microgrid’s high efficiency and solar power generation will result in “a net reduction in [greenhouse gas] emissions regionally” compared to grid-supplied power.

The 22.5 megawatts of generating capacity is substantially more than the airport’s current peak electricity demand of 14 megawatts. The margin is designed to offer reserves and redundancy and to accommodate possible future demand growth by 2023 based on the design of the airport’s terminal modernization program.

Woodrow said Peoples Natural Gas may have the opportunity to sell excess electricity to the grid, but added that the airport has “the right of first refusal to 100 percent...of all the energy that we need.”

For Peoples, the project amounts to a long-term bet that it can deliver power from the microgrid for less than the cost of grid-supplied electricity.

Woodrow declined to disclose the per-kilowatt-hour price of power delivered under the energy services agreement with Peoples Natural Gas, but, he said, “we’re expecting at least $500,000 a year in electrical savings” compared to what it pays Duquesne Light Company, its current electricity supplier.

According to the most recent data from the U.S. Energy Information Administration, the average price of electricity for Duquesne Light’s commercial customers is 11.43 cents per kilowatt-hour.

Woodrow said the airport will pay a nominal fee to maintain an interconnection to the traditional grid for access to backup power if needed.