Environmentalists have a long-held contempt for the sprawl of suburbia, where the low rooftops of tract housing sometimes seem to stretch to the horizon and where commuters spend their days spewing carbon dioxide into the air. But now some researchers are viewing this differently, as an opportunity for an energy revolution.
Scientists at the University of Auckland in New Zealand estimate that those suburban rooftops can generate enough solar power to make commuting carbon-free with enough juice left over to power cities for brief periods, as well.
In a recent paper, the researchers mapped Auckland's solar potential by determining the maximum potential energy that could be made available by efficiently installing photovoltaic (PV) systems on a sample of buildings throughout the city, from downtown skyscrapers out to the suburbs.
The suburbs stood out. "Low, dense suburbia is not only the most efficient collector of solar energy, but enough excess electricity can be generated to power daily transport needs of suburbia and also contribute to peak daytime electrical loads in the city center," the researchers wrote in the study.
Transport and urban planning debates have often ended with the assumption that compact cities would be more energy-efficient, given the shorter traveling distances and easier access to the grid. In this context, the Auckland study has "big planning implications," according to Hugh Byrd, a professor of architecture at the University of Auckland and lead author of the study.
"Suburbs have always been seen as a horrible thing in terms of fossil fuels, and they are," Byrd said. "But clearly, if you use the energy sources from your own roof and use electric vehicles, it suddenly turns the whole equation upside down and makes suburbia, from a transport view, very attractive."
'A mind shift is required'
The study, as modeling studies generally have to do, made a series of assumptions to reach its conclusion. Perhaps the biggest assumption is that every home in the Auckland suburbs would install solar panels and be equipped with an electric car. Culturally, that level of solar integration just doesn't seem realistic in most countries, although some localities are experimenting with it.
Shay Brazier, head of design and innovation at SolarCity, an Auckland-based solar power company, said he found the study "interesting" due to its unique approach. However, physical implementation of the model might take a while, he said. He mentioned one hurdle: Renters are much less likely than homeowners to install solar panels on their homes.
"Obviously, it's not going to happen straight away, because a mind shift is required that solar is a worthwhile investment," he said.
Brazier -- who owns a zero-emission home in the Auckland suburbs -- noted, however, that solar is getting much more popular in New Zealand.
"It's not a widely used technology, but it's more used than was two years ago," he said. "The feedback we get is people are really starting to understand it."
New Zealand is already a prime candidate for aggressive solar development. About 70 percent of the country's electricity supply comes from renewable resources -- mostly hydropower generated far from most of the country's population centers -- and it imports almost all of its fossil fuels.
More importantly, perhaps, Byrd estimates that New Zealand could achieve "grid parity" in which electricity from the grid costs as much as, if not more than, electricity generated from home installations in four or five years.
"In many countries, that's getting fairly close now," he said.
Several recent studies have pointed out possible snowball effects for the adoption of residential solar PV. A 2009 study from the National Renewable Energy Laboratory predicted that, as various regions in the United States achieved grid parity, it would become gradually easier for other regions to do so. And a 2012 study from the Yale School of Forestry and Environmental Studies found a "viral effect" for solar power in residential neighborhoods: As more homes installed solar PV, other homeowners in the ZIP code were likely to also make installations.
Obstacles in the U.S.
Not everyone is sold on the primacy of suburban solar power, however.
Scott Sklar, president of the Stella Group Ltd., a renewable technology company, said he thinks commercial buildings would be more productive bedecked in solar panels. Buildings like restaurants, manufacturing plants, universities, Walmarts and Home Depots -- all typically found in suburbs -- would be superior to homes, given their larger roof space and less shading from trees and other objects.
"We should be papering this stuff on there," he said.
Commercial buildings and institutions also have the advantage of not being under the auspices of homeowners associations, Sklar said. And in America, at least, homeowners associations could be a major obstacle to the kind of solar ubiquity envisioned in Byrd's study.
About half of all American homes are members of homeowners associations, and 90 percent of homeowners associations ban solar installations on homes, generally for aesthetic reasons and because it could decrease the value of the home.
"Probably 40 percent of roofs in the United States, you're not allowed to install solar because of some arbitrary rule," said Sklar, who also lives in a zero-emission home in Virginia.
"There's going to have to be a lot of education on the residential side before you can even have that play [to allow solar installations]," he added.
A Christchurch experiment
Renewable energy experts in New Zealand think they have the perfect testing ground for this new solar-powered suburb, however.
In September 2010, Christchurch, New Zealand's third-largest city, was rocked by a magnitude-7.1 earthquake that caused widespread damage but no fatalities. Almost six months later, the city was hit by a magnitude-6.3 earthquake that was among the strongest ever recorded globally in an urban area and resulted in 185 fatalities.
The city has been rebuilding ever since, and Byrd said the recovery effort could provide a unique opportunity to develop solar-powered infrastructure from the ground up.
"It's a city where we have the opportunity to rethink infrastructure again," he said.
Brazier said Solar City is working on installing solar on all the homes in a new 2,000- to 3,000-property development in Christchurch, possibly 10 percent of all new houses to be built.