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"If the city goes out and borrows money to build infrastructure, we've got to pay it back," said Rob Black, vice president for public policy at the San Francisco Chamber of Commerce, which opposes CleanPowerSF. "We would be on the hook for that [$1.2 billion]. That's a lot of money."
One of the few local examples of what such huge sums of cash would buy can be found downtown, on top of Moscone Center. The convention center's roof is home to the largest renewable-energy facility in the city, an array of more than 5,000 solar panels that, on sunny days, gleam like silver scales. If CleanPowerSF moves ahead, San Franciscans can expect to see many more of these panels: The plan calls for at least 31 megawatts of solar power to be generated within the city, an amount almost 46 times the maximum output of the Moscone array.
On a recent afternoon, Lori Mitchell, a renewable-energy specialist with SFPUC, gave a tour of the facility with two colleagues — energy-generation specialist James Andrews and communications official Jim Marks — and Fenn. Atop the roof beneath a hazy December sky, Mitchell explained that in-city solar power on the scale called for by CleanPowerSF, while a worthy ideal, will not be easily achieved.
Photovoltaic panels can't be relied on to steadily generate power, and thus require backup facilities to feed electricity to customers at night or on overcast days. Ironically, greater reliance on solar power could bring with it the need for more gas-fired "peaker" plants — so called because they gear up only during peak hours of energy use in the afternoon and evening — and the accompanying spew of ozone-depleting exhaust. "It's tough, because solar is an intermittent resource," Mitchell said.
The day of the tour was a case in point. Mitchell said that the Moscone solar array had been producing only 150 kilowatts of its full 675-kilowatt capacity that morning because of hazy skies. Dreams of a sun-powered city notwithstanding, the convention center's massive rooftop installation currently accounts for only 3 percent of the electricity the building consumes annually.
Andrews, on the way downstairs, stopped to take a look at the facility's power meter. Mid-afternoon, the panels were still producing only 150 kilowatts. "That's not that much," he observed, and smiled. "Don't write that down."