Do vast deserts or small rooftops hold the key to a sunnier and more affordable (and more democratic) energy future?
At a business conference this past May hosted by Wired magazine, billionaire Microsoft chairman and influential philanthropist Bill Gates offered his two cents on solar energy: “If you’re going for cuteness,” he said, “the stuff in the home is the place to go. … But if you’re really interested in the energy problem, it’s those big things in the desert.”
It’s too early to say whether California’s energy future will follow Gates’ maxim that rooftop solar is “cute” while desert solar farms represent the serious stuff. Others argue just the opposite, and momentum is building on both fronts.
Gov. Jerry Brown has endorsed the idea of installing 12,000 megawatts of rooftop solar and was expected to bring stakeholders together this week to discuss how to accomplish that goal. Sacramento advocates and regional politicians also are pushing for changes in solar policy. At the same time, large-scale desert solar is attracting billions in investment, and big-name companies such as the Bechtel Corporation, Chevron Corp., AECOM, and PG&E are engaged in its development. The California Energy Commission approved nine desert solar-thermal projects last year alone.
Those “big things in the desert,” or solar farms, are designed to concentrate energy from the sun using arrays of mirrors or parabolic troughs spanning vast swaths of land. They’re green versions of the types of power plants big energy companies have always relied on—centralized, dependent on transmission lines, requiring billions of dollars in investment. Some rely on water from desert aquifers for cooling, cleaning and steam generation.
It’s a dramatic improvement compared with burning coal, but there are other issues. On a yearly basis, solar farms will use enough groundwater in the arid desert to cover 100 acres 1 foot deep. They also worry that farms will affect the habitat of an endangered tortoise.
Another issue is cost: 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,” said John White, executive director of the Sacramento-based Center for Energy Efficiency and Renewable Technologies.
Yet renewable-energy expert and former California Energy Commission employee Sanford Miller, who delivered a presentation at UC Davis this past April, says 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 ratepayer’s perspective, rooftop solar would be significantly cheaper than the desert solar,” Miller explained. And when he sent his findings around to colleagues at the CEC, “No one disputed it,” he said, “but the view was that desert solar was inevitable.”
A new bill by Yolo County Democrat state Sen. Lois Wolk would foster a middle way between deserts and rooftops: Senate Bill 843 would allow any customer to purchase a subscription to a community renewable-energy facility and receive credit on their utility bill in exchange for the monthly fee.
Tom Price, former executive director of Black Rock Solar and now part of a solar investment firm called CleanPath, is pushing Wolk’s bill. He points out that, as things stand, every utility customer already chips in to subsidize the cost of individualized solar panels for the lucky few who install them. Those same customers also foot the bill for energy companies to buy power from giant solar farms. Price supports Wolk’s community solar gardens bill as an alternative.
CEERT’s White agrees that these different solar technologies are needed—rooftop, desert, “intermediary”—including the kind of small-scale, centralized facilities that are located closer to the customers, such as the planned Otras Producciones de Energia Fotovoltaico solar plant in West Sacramento, which would be the largest in the country.
“After Fukushima, we need to begin talking seriously about reducing our dependence on nuclear power,” White argued. “When you look at what we’re trying to replace and what we’re trying to avoid, it’s like we’re trying to assemble a new portfolio.”
But as California moves toward fulfilling a mandate of generating 33 percent of electricity from renewable power sources by 2020, there’s a growing political edge to solar development, too.
Giant utility companies profit by sending power along their transmission lines from desert solar farms to the grid. If energy-conscious customers generate more power than they use with rooftop solar panels, the utility company has to cut them a check. Some argue there’s little incentive for utilities to encourage customer-owned and distributed generation of renewable power.
Self-empowerment, however, is a major draw for proponents of rooftop solar. Al Weinrub, of the Sierra Club, wrote in a report earlier this year that “businesses with large rooftops or parking lots can become small power companies that feed electricity into the grid.”
“Community cooperatives can pool the rooftop area of their neighborhoods to form [small power companies],” he explained. The revenue then could be rolled into job creation and more green-energy development.
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 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.
Meanwhile, the largest desert solar plant worldwide is under construction in the Mojave Desert: BrightSource Energy’s Ivanpah plant, which Bechtel is building. 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.
Yet even with incentives, residential solar remains largely inaccessible to people who aren’t rich enough to own property or finance the upfront cost. In Sacramento County, roughly 40 percent of residents are renters who almost never have the option of going solar. And 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.