Just north of Las Vegas, a shimmering array of solar panels captures energy from the blazing sun to power some of the Air Force's most advanced work, including testing and flying drones. Nellis Air Force Base's 14.2-megawatt solar power plant has been lauded by the military as a showpiece of a sweeping effort to boost energy security and resilience at bases by integrating renewable energy. Bases get 99 percent of their electricity from the commercial grid, which officials increasingly acknowledge is vulnerable to everything from storms to terrorist attacks. Wind, solar and biomass plants on military facilities can provide vital power if the local grid goes down, they say. But the 140 acres of solar panels at Nellis are useless when commercial power is out, thanks to a provision in the project's agreement with the local utility that lets NV Energy turn off the array if the grid goes down.