Which renewable technology holds the key for a sunnier (and more democratic) energy future?
Rooftop solar has gained traction in California over the past five years with a $3 billion program to subsidize installations. The California Public Utilities Commission recently touted the California Solar Initiative (CSI) program's success — a 47 percent growth in installations since 2009. All told, the Golden State boasts 924 megawatts of solar generation capability, installed at 94,891 locations. Consultants for the California Public Utilities Commission found that 11,543 megawatts of solar could be generated on large urban rooftops statewide, while another 27,000 megawatts could be generated on empty lots near rural substations.
The potential is huge, but a cost barrier remains. Even with incentives, residential solar remains largely inaccessible to people who aren't rich enough to own property or finance the upfront cost. In San Francisco — recently declared the greenest city in North America by Siemens — roughly 70 percent of residents are renters who almost never have the option of going solar. Proponents of desert solar farms claim that the large-scale, centralized technology offers something that rooftop panels can't — the potential to bring renewable energy to the masses.
The largest desert solar plant under construction worldwide is BrightSource's Ivanpah plant, which Bechtel is building in the Mojave Desert. Spearheaded by an Oakland company, the plant uses sunlight and mirrors to generate steam to power a turbine. The energy will flow onto the grid to serve PG&E and Southern California Edison customers. It's a dramatic improvement compared with burning coal, but there are other issues. On a yearly basis, it will use enough groundwater in the arid desert to cover 100 acres, one-foot deep. And it riled environmentalists who worried that it would affect the habitat of an endangered tortoise.
No one disputes that on a per-watt basis, it's cheaper to install desert solar than rooftop solar. According to estimates from Go Solar California, it costs more than $8 per watt to install small-scale rooftop solar systems, while recent costs for desert solar farms have been calculated at around $4 per watt. "Because they have the economy of scale, they can be built at less cost," notes John White, executive director of the Sacramento-based Center for Energy Efficiency and Renewable Technologies.
Yet a renewable energy expert who formerly worked for the California Energy Commission (CEC) says comparing costs of desert and rooftop solar from the point of view of the customer tells a different story. In April, Sanford Miller delivered a presentation at UC Davis that could have been considered subversive. His analysis essentially found that ratepayers shell out less to subsidize rooftop solar installations than they do to finance the purchase of energy from desert solar farms once the full cost of transmission and environmental mitigation are factored in.
"From a ratepayers' perspective, rooftop solar would be significantly cheaper than the desert solar," Miller says. When he sent his findings around to his colleagues at the CEC, "no one disputed it," he said. "But the view was that desert solar was inevitable."
But that still leaves the question of who can afford solar — and this is where Tom Price, former executive director of Black Rock Solar and now part of a solar investment firm called CleanPath, believes he's found a middle way. As things stand, every utility customer chips in to subsidize the cost of individualized solar panels for the lucky few who are installing them, he points out, and those same customers are footing the bill for energy companies to buy power from giant solar farms. He's pushing the Community Solar Gardens bill as an alternative.