Deserts and remote fields are popular spots for building vast arrays of solar panels, which generate dramatically more energy than individual homeowner rooftop installations. These areas are rich in sunlight while offering plenty of clear, flat land to work with. But what if we didn’t always have to go all the way out to these remote and potentially ecologically fragile areas? What if we could simply drive down the street and make use of the buildings and lands in areas we’ve already developed?
A new study suggests that such a strategy could work in a state like California, which is working aggressively to boost its renewable energy use. And it could provide a lot of power. There’s enough space suitable for solar power on or near land that humans occupy in the state to power three to five of today’s Californias, researchers report in Nature Climate Change today.
California is a clean energy trailblazer on a number of fronts. It’s a part of a carbon emissions trading program with other Pacific states, and has also set a goal of supplying one-third of its electricity from renewable sources such as solar and wind by 2020, and cutting its carbon dioxide emissions 80 percent by 2050.
Of course, no energy source is perfect, and solar is no exception. Not only does it work only at certain times of the day, but it also requires a lot of open, flat land to generate solar power at the scale of power plants. As a result, a lot of solar power projects are undertaken in deserts and other remote areas where open land is plentiful.
But some of these lands could host delicate ecosystems that might become more difficult for creatures to live in if they’re covered with solar panels. Also, these sites can be far from where power is actually needed; in these cases, miles of transmission lines have to be built to deliver that electricity to consumers.
So to reduce these problems, it might behoove us to take as much advantage of open spaces in developed areas as we can, whether on roofs or on the ground. Rebecca Hernandez and Christopher Field at Stanford University and the Carnegie Institution for Science decided to see how feasible that would be in California, given the state’s aggressive push for clean energy.
They focused their attention on the two main forms of solar power generation: photovoltaic cells, which generate electricity by absorbing sunlight directly, and concentrating solar power (CSP), which involves using arrays of mirrors to focus sunlight into one area where it can be converted into electricity (though these projects require more area to operate than the smallest photovoltaic projects do).
The researchers assessed California’s land to see how suitable it would be for solar power projects of either type, whether on scales suitable for powering individual homes and businesses or for powering entire communities. The most “compatible” places, they said, found in just around 8.1 percent of the state’s land, would be in areas that humans have modified or developed in some way, and it would have enough open and mostly-flat space to work with. These places might include not just the rooftops of homes, businesses, warehouses and other buildings, but also parking lots, farmland, grassy fields and golf courses.
California has 10,535 square miles (roughly the size of Massachusetts) and 2,422 square miles (roughly the size of Delaware) of this “compatible” land for photovoltaics and CSP systems, respectively, the researchers found. On these compatible lands, photovoltaics could provide about 14,600 terawatt-hours (or 1 billion kilowatt-hours) a year in power, and CSP systems could provide about 6,000 terawatt-hours a year. Compare that with California’s total energy use across all sectors, from residential to commercial to transportation and industrial, in 2011: 2,231 terawatt-hours.
All in all, depending on what combination of photovoltaics and CSP systems you choose to use on these lands, the resulting amount of energy would fall somewhere roughly between three and five times what California used in 2011. And that’s all before we’ve even discussed other places that aren’t ideally compatible but could still potentially host solar projects, such as federally protected lands.
That’s not to say that we can go all-in on solar power or abandon desert projects outright. People won’t want to cover every last parking lot or rooftop with a CSP system or solar panel, and other factors such as the availability of transmission lines serve as another limiting factor.
But the findings do drive home one point that’s often lost in the discussion over solar power: To get it, you don’t have to go to the desert or to that far-away, fragile ecosystem. You may just have to drive down the street.