The best place to put an array of solar panels may be on Mt. Everest instead of the Sahara Desert, according to new research that looks at the geography of solar power.
The paper recommends placing photovoltaic arrays at high-altitude locations because they collect more sunlight, even though the outside temperatures are colder.
"Most people think radiation-heavy places such as a desert are a good location to produce photovoltaic energy," said Kitaro Kawajiri of Japan's National Institute of Advanced Industrial Science and Technology. "But the collection function decreases with increased temperature. That's why I thought there would be some other good locations in the world."
In a paper published in the journal Environmental Science and Technology, Kotaro created a map that combines solar radiation and global average ambient temperatures to find the best potential for photovoltaic energy.
The top spots: Antarctica, the southern Andes and the Himalayas, each of which would produce 20 percent more energy than photovoltaics based at sea level.
Given that Antarctica is too remote, and is covered in darkness for six months of the year, Kawajiri believes that the Himalayas and Andes are more practical. He notes that Tibet now supplies hydropower to China through long transmission lines which could be also used to send electricity made from solar power.
"It could be possible to transfer electricity from Tibet to China," Kawajiri said. "So the potential can be used in the future."
This analysis does not take into account, however, things like construction and transmission costs, which may be higher in remote locales.
Sometimes small PV units located close to the consumer may be more cost-effective than huge solar arrays hundreds of miles away, according to Sarah Kurtz, reliability group manager at the National Renewable Energy Laboratory in Golden, Colo.
"If you look around the world the amount of sunshine varies from a factor of three," Kurtz said. "If you walk outside, you can feel it. Sun also is stronger at high altitudes, which is more important for concentration. There is definitely an advantage at higher altitudes, but I would not claim it would dominate the entire picture."
Kurtz notes that in the United States, if sunny spots like Arizona (or high mountain Colorado) were the most efficient place to put solar panels, than they would congregate there. Turns out that muggy New Jersey is actually the country's leader in solar power construction and use, Kurtz said, because of incentive programs that make them cost-effective for industries, businesses and individual households.
"A mountaintop may be the cheapest place to install solar panels," Kurtz said. "It's a tradeoff and there's no one right answer."
Kawajiri says he wants to further refine his calculations taking into account snowfall at high altitudes, which could block solar energy collection, as well as the cooling effect of wind. He hopes to find a place on his map that makes both geographic and economic sense.