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The second in a series* of on-site reports on little-known energy and climate initiatives in Northern Europe.

HAMBURG, GERMANY — Four thousand people could once hide in this bunker, a Nazi-built air-raid shelter that — at 135 feet tall — still looms over the Wilhelmsburg quarter of this city. After British forces destroyed the bunker’s interior, it was left unused for more than 60 years, a dark monument to World War II.

But in March, the former air-raid shelter reopened with a new name: the Energy Bunker. With solar thermal and photovoltaic panels on its south side and roof, and a 70,600-cubic-foot tank for storing hot water, the building will eventually supply heating to 3,000 nearby households and electricity to 1,000.

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In addition to storing energy from solar panels, the hot water tank at the center of the 135-foot Energy Bunker can collect waste heat from an industrial plant close by.

Rolf Kellner, an architect and urban planner, clearly is aware that placing a hot-water tank deep in the ground — rather than in the bunker — might have been a more efficient way to store heat. But the symbolism of transforming the air-raid shelter into a place to produce and store renewable energy was important, he said: “As a monument for energy and as a sign, it works quite well.”

The bunker is just one of several places in the city where architects and developers have found new uses for sites with troubling pasts. Those places have been redeveloped as part of the International Building Exhibition in Hamburg, a seven-year project to research and test new ideas for urban development.

The Wilhelmsburg quarter, a flood-prone island in the Elbe River, once served as an industrial zone. During World War II, 30 forced-labor camps were located here, in addition to a sub-camp of the Neuengamme concentration camp. These days, the island is home to a diverse group of immigrants, many of them low-income, Kellner said.

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Algae growing in the façade of the Algae House can be used to produce energy for heating some of the apartments in the building.

An apartment building near the center of the island, the Algae House, is a pilot project demonstrating how buildings could one day harvest energy through photosynthesis. In panels built into a south-facing, transparent façade, algae capture energy from the sun. Once harvested, the algae can be fermented and used to generate biogas, producing enough energy to heat four of the building’s 15 apartments.

A fifteen-minute drive northeast of the Algae House lies a grassy hill dotted with wind turbines. For decades, this hill was the site of the Georgswerder dump. Two hundred thousand tons of toxic waste were deposited here, and in the early 1980s, poisonous dioxins were detected seeping into the nearby water supply.

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Wind turbines and a solar plant on the site of a toxic waste dump now produce enough electricity to supply 20 percent of Wilhelmsburg households.

After the dump was sealed at great expense, a few wind turbines were added in the early 1990s. Developers erected additional wind turbines and a photovoltaic solar system during the International Building Exhibition. The hill now supplies electricity to 4,000 households — or about 20 percent of Wilhelmsburg.

How could renewable energy transform a place where you live? Share your ideas in the comments section.

*Read part one.  Photo credits:  Sara Peach.

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