GreenBiz: San Francisco took a major step today toward building California’s largest solar photovoltaic system — a plan that would more than triple the city’s solar energy output by carpeting the rooftop of its biggest reservoir with almost 25,000 panels. Recurrent Energy, a San Francisco firm, will install and operate the 5 megawatt array atop the reservoir, an area roughly the size of 12 football fields. Standing atop the Sunset Reservoir — so named because it lies in the city’s …