As it tries to find ways to get more green energy, San Diego is studying spots to install new solar arrays across the city. Clean Coalition, a Menlo Park-based nonprofit, is spending the next year and a half looking for places that can host “meaningfully-sized” solar projects. The effort is paid for by a federal grant meant to help the city reach its goal of receiving only clean energy by 2035. Environmentalists have argued that smaller, local solar projects can help the city wean itself off power from big companies with big projects, like San Diego Gas & Electric.