Lights on while off grid

One of San Antonio’s military bases is ground zero to test how renewable energy can keep the lights on for mission-critical infrastructure even when the grid is down.

The $950,000 microgrid system at Joint Base San Antonio-Fort Sam Houston was funded by CPS Energy and implemented by a partnership between Omnetric Group and Siemens. The system utilizes a 20-kilowatt solar system and a 75-kilowatt battery that can power the Keith A. Campbell Memorial Library for up to 40 minutes.

The project is part of the Energy Department’s National Renewable Energy Laboratory Integrated Network Testbed for Energy Grid Research and Technology Experimentation program, or INTEGRATE, which seeks to better integrate intermittent sources of power such as renewables into the grid.

“We have DoD, Air Force and Army goals that state mission assurance through energy assurance or energy resilience, and (this project) is right in line with that goal,” said Brenda Roesch, Joint Base San Antonio base civil engineer.

The system at Fort Sam generates and stores electricity, allowing CPS to draw off the system while offering a backup for the 23,000-square-foot library if grid power turns off. The library was chosen as a test site because it’s not mission-critical to Fort Sam.

Frank Almaraz, CPS’ senior vice president of strategy and commercial operations, said systems such as the one at Fort Sam are part of the utility’s future.

“The way we’ve done business historically is not the way that things are going to happen forever. We’re in a period of accelerated change,” Almaraz said.

Such microgrids are usually known for their use on remote islands throughout the world, where a combination of solar or wind power is stored in batteries. Other systems can use diesel generators to store electricity, but they require expensive fuel to be delivered to remote locations.

Siemens’ Clark Wiedetz, director of micro-grid and renewable integration, says microgrids make renewable assets — such as the more than 1,200 megawatts of wind and solar power that CPS buys — more valuable as a part of their overall system.

“It allows them within their service territory to redistribute the load based on if something happens — weather issues somewhere, a station goes down — now they can move loads,” Wiedetz said.

CPS’ getting to that point hinges on battery costs coming down. Almaraz said such costs are currently prohibitive, but he hopes that the testing on the Fort Sam micro-grid will help CPS prepare to take advantage of batteries when their costs come down.

“One day, it could be a neighborhood, it could be a facility like the airport, or our military or the hospital — or an individual who never wants to be out of power and produce some of their needs by a solar system on their roof,” Alamaraz said of how microgrids could be used.