for National Geographic News
In the ghettos of Egypt's largest city, solar panels are sprouting on apartment rooftops, providing residents with clean power and water and a chance to directly improve their lives.
Since 2003 the nonprofit Solar CITIES project has installed 34 solar-powered hot water systems and 5 biogas reactors in Cairo's poor Coptic Christian and Islamic neighborhoods.
"Our program is unique, in that we're implementing rural-type solutions in an urban environment," said project leader Thomas "T.H." Culhane, an urban planner and 2009 National Geographic emerging explorer. (The National Geographic Society owns National Geographic News.)
"It's the kind of stuff you would do in the Peace Corps in an African village, but we're doing it right smack dab in the slums of a city."
(Read about the promise of solar power in National Geographic magazine.)
Solar CITIES's activities are currently limited to Cairo, but the team posts tutorials on how to build and install solar water heaters on YouTube.
Harnessing the Sun
Solar CITIES' hot water systems are constructed from recycled materials and are uniquely tailored to the parts of a city where water and electricity availability are often sporadic.
"The problem with professional solar hot water systems is that they're made for cities with continuous water," Culhane said.
By contrast, Solar CITIES's water heaters use a city's water when it's available but draw from a backup storage tank when it's not.
The setup consists of an insulated rectangular box covered in clear glass or plastic on one side. Inside the box are copper tubes wrapped in sheets of aluminum, which are painted black.
Sunlight striking the darkened aluminum is converted to heat, which is then used to warm water flowing through the pipes. The glass sheet on top of the box prevents the heat from being carried away by wind.
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