“After studying the technical and economic issues for a year, my colleagues and I concluded that BART could increase the amount of on-site solar by means of PV installations on stations, parking lots, maintenance facilities, and other properties.
“This has important implications for cities around the nation. Most of the United States receives enough sunshine to generate a substantial amount of solar power. (The country sees far more sun than Germany, which now gets over 7% of its overall power output from solar.) Transit agencies from coast to coast could therefore take advantage of PV generation.
“But this would require them to contend with the mismatch between peak travel hours (morning and evening commute times) and peak solar hours (midday). Maximizing solar generation’s potential would require energy storage as well as energy “wheeling,” or exporting power around a system’s internal power distribution network.
“Our team initially considered this a drawback of solar due to the costs associated with energy storage. Upon further consideration, however, we determined that this solution confers unexpected benefits. By providing an independent power supply in the event of a grid failure, it makes transit systems more resilient.”