​Rooftop solar on the Space and Naval Warfare Systems Command Headquarters in San Diego. ​Wikimedia

To Save Our Cities, We May Need to Turn Them Into Power Plants

​New research shows that small-scale solar built in cities could generate enough energy to light up California three to five times over. Think of it as a blueprint for the future.

Mar 19 2015, 12:30pm

​Rooftop solar on the Space and Naval Warfare Systems Command Headquarters in San Diego. ​Wikimedia

Solar could run the entire Golden State, and it wouldn't take tearing up any wild lands to do it: We could build enough tiny clean power plants into the very fabric of California's cities to keep all of its lights on.

That's the conclusion of intriguing research published in Nature Climate Change—if solar power were installed on the rooftops and urban spaces in just the fraction of the state that's already been developed, it could generate enough electricity to meet California's energy needs, three to five times over.

"We have tons of sunlight," lead study author, Rebecca Hernandez of Stanford University, told me. "And we are not capitalizing on the resources that we have—not just in California but in the entire United States." 

Cities across those United States, sunny as they may be, still get most of their power from coal and natural gas plants. Burning those fossil fuels is driving global warming, which is of course beginning to inflict a number of increasingly damaging impacts onto those very cities: heat waves, drought, sea level rise, and more powerful hurricanes, to name a few. 

So, to save them, we may need to turn our cities into power plants. Hernandez's research shows that, technically, it can be done. 

And it'd actually be better for the environment. That's why Hernandez's findings excited conservationists, who've been (justifiably) worried that sprawling solar farms in wild places might disrupt local habitats (woe betide the desert tortoise): It means those massive plants aren't necessary. What excited me about this research is that it paints a picture of a localized, clean-powered urban future, where our power sources are built directly into our homes and workplaces, and along existing infrastructure like roads, parks, and factories.

Pair that with a plummeting cost of panels and promising developments in home solar battery technology—which the Elon Musk-backed SolarCity, in conjunction with Tesla, is currently pursuing at breakneck pace (its architects are already experimenting with compatible microgrids, too)—and you've got one possible future where homes and communities can not only generate but store their own power, free from carbon-polluting fossil plants and the crusty utilities that run them. (That's why Morgan Stanley thinks Tesla's going to kill ConEdison.)

"It's going to take all of these different actors, to get that storage technology so that it can be scalable," Hernandez said. "I'm confident that we're reaching that tipping point."

It's more evidence that what's popularly referred to (in nerd circles anyway) as "distributed generation"—as opposed to centralized generation, a la a single fat coal or nuke plant—is not only a viable path forward, but, potentially, a vastly rewarding one.

President Obama surveys urban rooftop solar. Image: the ​White House via Wikimedia.

It'd be cleaner, to start. California currently gets nearly half its energy from natural gas, a carbon-polluting fossil fuel, and over 15 percent from coal, which is even worse. Secondly, small-scale solar (and wind) have among the lightest-possible environmental footprint. We've already built the apartment complexes and the strip malls, might as well load them up with clean energy.

"Integrating solar facilities into the urban and suburban environment causes the least amount of land-cover change and the lowest environmental impact," Hernandez wrote in the statement announcing the findings. "Because of the value of locating solar power-generating operations near roads and existing transmission lines, our tool identifies potentially compatible sites that are not remote, showing that installations do not necessarily have to be located in deserts."

In other words, we should bring the solar closer to the cities they power; onto rooftops, parking lots, and otherwise useless industrial waste sites. Distributed generation is cheaper to build and maintain, and it's more resilient in the face of (increasingly common) extreme weather: When transmission lines go down, they don't take the power of entire regions with them. And, thanks in part to companies like SolarCity, which offer home solar leases, and like Urban Green Energy, which installs solar for businesses, distributed power is increasingly consumer-friendly.

"Distributed solar (energy being produced where it's consumed) provides huge benefits," UGE CEO Nick Blitterswyk wrote me in an email. "In fact, distributed energy is the world's fastest growing source of energy, being in the early stages of a growth curve that will fundamentally change how energy is produced and consumed." 

That it may be, but partly because the market is currently so tiny—"we're starting at one percent," as Hernandez said.

"The California study further highlights the potential of distributed solar, but I'm certain this will not be the last study of this kind," Blitterswyk told me, "on-site renewable energy use is rapidly expanding and we will see more of it all over the country, not to mention worldwide. In many of the markets where UGE works, distributed solar energy is already cheaper than the grid, and as the cost of the technology comes down further, the choice will become a no-brainer in more cities and regions."

This, of course, is a nightmare for the entrenched utilities, which depend on a base of bill-payers to turn a profit and maintain their own infrastructure. That's why many are fighting home solar tooth and nail—the vision laid out in the Nature study is a threat to their very existence. Right now, many states offer companies and consumers tax breaks for carbon-free power source; utilities are trying to kill them off.

Solar roof. Image: Marlith / ​Wikimedia

Elsewhere, though, the governments have gone all-in to cover its cities with solar—Germany rewarded solar buyers with a feed-in tariff that let residents to earn money from feeding their clean power to the grid. Now, Germany is a solar juggernaut, regularly generating a full third of its electricity needs from solar, and sometimes getting as much as 74 percent. And, of course, there's China, the global champion in manufacturing and installing solar. Its cities are already flooded with solar, especially ​solar-powered water heaters.

"China is now the world's leading installer of solar panels, and their target includes roughly 50 percent distributed," Blitterswyk said.

Hernandez and her team plan on publishing their model in a follow-up study, which she says "can be used anywhere in the world" to help officials build out distributed and utility-scale solar in and around cities—a roadmap, if you will, for cities and communities to power themselves. "We want to see governments employ these types of spatial technologies to ID land that's going to facilitate solar effectively," she said.

Bear in mind: Just 8 percent of California's land has been colonized by human development—and that's all the space it would take to keep the lights on. Hernandez found that nearly 10 million acres are "compatible" with urban solar development.

If the same is true, roughly, of mostly-sunny, populous, and reasonably developed civilizations round the world, it could serve as a blueprint for a sustainable, disaster-resistant society. And it's not that pie-in-the-sky, either; last year, a separate Stanford study by Mark Z. Jacobson showed that it's entirely feasible to run California entirely on clean energy. For his part, Jacobson actually told me that the new study "is likely an underestimate" of California's solar potential—and that you'd really only need about 2 percent of the state's land area to power the entire state.

Certainly, there's a long way to go before we're anywhere close to realizing self-powered, solar-covered cities: Installing enough panels to cover millions of acres of city is a gargantuan project, no matter how affordable the panels become. They will have to be linked to smart grids to function most efficiently, and there's a surfeit of political obstacles to overcome. But it beats the alternative: remaining tethered to the carbon-spewing plants that are clogging the atmosphere with climate-warming gases.

There is still time to reduce carbon emissions enough to stave off the worst of what could be truly disruptive, catastrophic warming. Distributed power, paired with home batteries and microgrids, could be the palliative to the centralized, fossil-heavy paradigm of the past. If we get to work, our future city/power plant hybrids could help us sustainably weather the coming storm.