Special Report

How Microgrids are Bolstering the Nation’s Power Infrastructure

Rather than drain power from a nearby plant, these systems create energy of their own, making for a more sustainable future

(© Edward Rozzo / Corbis)

At noon on October 22, 2007, the University of California, San Diego, received an emergency call from the local utility. Regional wildfires had damaged and disabled power lines and the California grid operator had declared an energy transmission emergency. San Diego Gas & Electric asked the university to reduce the amount of electricity it was drawing from the grid and, if possible, start generating power for use by other utility customers.

Within 10 minutes, the campus swung from drawing 4 megawatts of electricity from the power grid to feeding it 3 megawatts, says Byron Washom, Director of Strategic Energy Initiatives for UCSD. “That 7 megawatts was the razor-thin margin between the San Diego Gas & Electric grid remaining up or collapsing.”

The San Diego campus was able to react so quickly in part because a half-century earlier its founders had decided to lay the groundwork for a self-sufficient power supply, or what energy experts today call a “microgrid.” The first structure erected on campus in 1962 was a central power plant designed to provide gas-fired electricity as well as district heating and cooling for the school’s buildings. That in itself was and is not unusual for an academic, or even a corporate campus. But over the years, UCSD gained self-sufficiency by adding steam turbines, solar photovoltaic panels, fuel cells and energy storage, in addition to installing power lines to transmit electricity to and from SDG&E’s electrical grid.

All of these assets now operate under the control of a sophisticated energy management system, and the campus microgrid enables the university to generate, store and dispatch electricity as needed—ultimately providing 92 percent of electricity used on campus. Although the university normally draws electricity from the SDG&E grid to meet its roughly 38-megawatt load, it can also switch to “island” mode in the event of off-campus power problems or outages, meeting all of its own electricity needs. And when electricity is in short supply on the main electrical grid serving greater San Diego, UCSD can sell power to SDG&E.

In response to the 2007 emergency call, the university fired up a 3-megawatt steam turbine and reduced power demand by adjusting climate control settings and switched to drawing cold water for its cooling system from highly efficient thermal storage tanks instead of electric chillers. “With two clicks of a mouse, with our control system, we can change 4,000 thermostats on campus,” Washom says.

UCSD and other microgrid operators are offering a modern take on the small direct current power systems installed in factories and city centers beginning in the 1870s. Like those early systems, these new designs feature local generation and distribution of electricity rather than the long-distance transmission lines and remote centralized power stations that characterized the 20th century power grid. “We’re currently deconstructing the power grid, back to [Thomas] Edison,” says Jim Reilly, whose consulting company Reilly Associates advises the Department of Energy on microgrid operation.

The roots of this deconstruction trend go back to the late 1990s, when the U.S. Department of Energy decided to jump-start research into power transmission and reliability. The move came as a response to electricity deregulation and anticipation of a coming wave of rooftop solar panels and other forms of decentralized power generation. “We did not at that time really have a concept of ‘microgrids’ per se,” says Chris Marnay, one of the pioneers of microgrid research. The idea of generating energy locally was an old one. But it took advances in controls and power electronics to enable a true microgrid that could interact with and “island” from the larger power grid. Within a few years, Marnay’s research group at Lawrence Berkeley National Laboratory formalized the notion of a microgrid in a project for the California Energy Commission.

The benefits provided by UCSD’s microgrid—agility and self-sufficiency—are now in high demand among energy users who risk severe consequences in the event of power interruptions, such as universities running sensitive lab equipment, military bases holding weapons control systems and data centers handling vast troves of information. “It’s the facilities that want abnormally high-quality power where we see most of the action at the moment,” says Marnay, who retired in June from the Berkeley Lab’s Grid Integration Group.

Extreme weather events in recent years, such as Hurricane Sandy, have reminded business, military and political leaders of the fragility of electricity infrastructure in the United States. “The increasing frequency of natural disasters is driving a stronger interest in microgrid and back-up power solutions,” says Brian Carey, who leads the U.S. cleantech advisory practice for accountancy firm PricewaterhouseCoopers, known as PwC.

A $71-million microgrid built at the headquarters of U.S. Food and Drug Administration, for instance, supplied power to the campus during and after Hurricane Sandy when the regional power grid went down. In March 2011, the Sendai Microgrid, located on the campus of Tohoku Fukushi University in Sendai City, Japan, continued to supply power and heat to customers after the devastating Tohoku earthquake and tsunami brought down power supplies throughout the surrounding region.

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