The National Geographic News has an interesting story about a project in Cairo, Egypt, that is successfully introducing solar power (albeit on a small scale) in several poor areas of the city. The nonprofit Solar CITIES project has installed 34 solar-powered hot water systems and five biogas reactors since 2003.

“Our program is unique, in that we’re implementing rural-type solutions in an urban environment,” says project leader Thomas “T.H.” Culhane, an urban planner and 2009 National Geographic emerging explorer.

“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.”

The group had to develop a unique approach to making the installations work.

“The problem with professional solar hot water systems is that they’re made for cities with continuous water,” Culhane says.

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.

The biogas reactors use garbage to generating gas that can be used for cooking stoves. The hot water systems can be used in tandem with the reactors to maintain optimal temperatures.