In an industrial corner of Oakland, wedged between a 10-lane freeway and a freight terminal, sits California’s newest source of renewable energy: a squadron of shiny yellow electric school buses. It’s the first all-electric bus fleet serving a major US school district. Starting in August, the 74 vehicles will also supply 2.1 gigawatt-hours of electricity to the Bay Area power grid, enough energy for 300 to 400 homes. The buses are expected to reduce carbon dioxide emissions by about 25,000 tons...