National Geographic Daily News
Photo: Men standing near a rooftop solar panel
Solar CITIES project leader T.H. Culhane (right) and organization intern Omar Nagy stand next to a solar-powered water heater on the roof of an apartment building in the Zabaleen neighborhood of Cairo, Egypt.

Photograph courtesy T.H. Culhane

Ker Than

National Geographic News

Published August 28, 2009

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.

The water, which can reach temperatures of 176 degrees Fahrenheit (80 degrees Celsius), is then pumped into an insulated plastic barrel for storage. The water, which remains warm long after sunset, can be connected to an apartment's plumbing system.

(See photos of other solar projects.)

Putting Microbes to Work

Solar CITIES also installs biogas reactors, which are based on designs Culhane saw while working in India.

The reactors use microbes harvested from animal guts to break down food wastes into flammable gas that can be used for cooking and heating.

If necessary, the reactors can draw hot water from the solar water heaters to maintain the warm temperatures the bacteria need to survive.

By attaching a simple plastic tube to the reactors, gas can be piped down several stories for residents to use.

"In 24 hours, you've got 2 hours of cooking gas from yesterday's cooking garbage," Culhane said.

The biogas reactors provide a more reliable supply of cooking gas than most residents currently have.

Among Cairo's poor, "nobody uses electric stoves. That's probably the least efficient way to heat food, and it would cost you an arm and a leg," Culhane said.

Instead electricity is used only for lighting and to keep the refrigerators running.

Cooking is typically done on stoves by burning garbage or buying bottled gas, which has to be replaced every few weeks.

Catalyst for Change

Blake Jones, the president of the solar-electric company Namasté Solar in Boulder, Colorado, said solar energy makes sense for Cairo because many parts of the city are "off the grid," just like rural villages.

"The clean water, electricity, and sewage sanitation services just aren't available or reliable," said Jones, a former Cairo resident who has experience setting up community solar-energy programs in Nepalese villages.

Jones believes that if Solar CITIES is successful, the project could serve as a catalyst for change throughout Egypt.

Nonprofits like Solar CITIES "can show that a new technology works, feed the market, and then pass the baton on to government and the private sector," he added.

(Related: "Roll-Up Solar Cells Printed Like Money.")

Yes We Can

The energy solutions Culhane is pioneering in Cairo are also finding their way into other countries.

This fall Culhane will team up with Frank Di Massa, an independent utility consultant in the United States, to retrofit a three-bedroom home in a low-income Hispanic neighborhood in Santa Rosa, California.

The team will use the same kinds of solar and water-recycling technologies that have been successful in Egypt.

"Rolling up your sleeves and saying, Yes, we can, works wherever we are in the world," said Culhane, echoing the campaign slogan of U.S. President Barack Obama.

"It's just a matter of connecting and letting our collective intelligence work."

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