Solar-powered microgrids may give two patches of West Marin relief during future blackouts. Dillon Beach and Tomales are among nine rural communities selected for grants from PG&E to build the grids, which could provide enough clean energy to power key infrastructure and emergency shelters for at least 24 hours—and perhaps up to a week or two, depending on the sun. PG&E selected the projects from among 50 applications; others proposed for Point Reyes Station and…