What’s keeping solar and wind power from fully taking over the electric grid? For starters, the sun only shines during the day. Wind blows intermittently, is seasonally variable, and is not always blowing when the energy is needed. But what if solar and wind work together? “Wind resource tends to complement solar resource,” said Sarah Kurtz of the U.S. Department of Energy’s National Renewable Energy Laboratory. “Here in Colorado, for instance, the windiest time is…