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How do you recycle a bunker? Part 3: the Wilhelmsburg Flakturm

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The Energiebunker with its solar panels looming over the neighbourhood

The Energiebunker with its solar panels looming over the neighbourhood

What is remarkable about this particular bunker is its setting. A Flak tower nearly as large as the Heiligengeistfeld giant, it had been left to decay in Wilhelmsburg, a suburban neighbourhood that, like the bunker, had itself been left neglected.

Wilhelmsburg is the largest island on the Elbe river. A semi-rural part of Hamburg, it was devastated by a flood in 1962. Wedged between downtown and the industrial harbour, it was considered an undesirable location, a place left for the poor and the immigrant. The presence of polluting industries and Hamburg’s largest landfill didn’t help. Restoring the bunker was no priority.

The Wilhelmsburg bunker a few years ago

The Wilhelmsburg bunker a few years ago

This started to change in the 2000’s. The cheap flats and empty lofts were starting to foster an artistic community (this is where the movie Soul Kitchen was set). Meanwhile, Hamburg was planning for growth in Wilhelmsburg, an initiative labelled the “Leap across the Elbe”. Wilhelmsburg had been identified by the city as the next logical place to expand; the island is near downtown and well served by transit. As with Vancouver, internal immigration to Hamburg is causing a housing shortage as the city is growing. Channeling some of that growth to Wilhelmsburg, then, seemed the next logical step. Except that no right-thinking burger would consider living on the island. Something had to be done.

Enter the 2013 IBA, the international building exhibition. This is a prestigious and uniquely European institution where cities showcase their best new architecture and housing ideas. Hamburg decided that this would be the perfect vehicle to spruce up Wilhelmsburg; and energy efficiency was to be one of the major themes of the exhibition – with a role for the old bunker.

Some of the south face solar PV panels

Some of the south face solar PV panels

From the onset, it was decided that the bunker was to be the focal point of the energy network. After major repairs to ensure structural safety, the bunker was festooned with solar panels. On the south facing side are photovoltaic panels, while the roof holds 1350 m2 of thermal collectors, the largest such roof system in Germany.

At least that’s what you see from the outside. What you don’t see is a panoply of generators: a wood chip boiler, a biogas-fueled cogenerator, and a gas boiler for peak demand. These all work together with the solar panels to provide heat for the district, fifty hectares home to three thousand households. The cogenerator, along with the solar panels, also provides electricity for a thousand households.

But the bunker is cavernous, so aside from the generators and boilers there is room for the showpiece: an enormous (2000 m3) insulated water tank for heat storage. Hot water from the thermal solar collectors is stored there overnight; the heat is released in the early morning when heating demand comes on. As a result, the power output from the boilers need only be about half the size as they would be without heat storage (6.5 MW as opposed to 11 MW without). This means huge savings with respect to the cost of the boilers, but it also means that much less fuel and therefore far fewer greenhouse gases are emitted as a result. The thermal storage also makes it possible to recover heat from the nearby Nordische Oelwerke plant, heat that would otherwise be wasted.

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Looking out from Cafe Vju

As an engineering prof from TUHH told me, “they threw in everything they could think of”; and indeed, the bunker has become a demonstration project for a variety of technologies. This really matters: people are understandably reluctant to invest in unproven technologies, which is why successful demonstration projects are so valuable. (Even so, acceptance is slow in coming in some areas; some the appartment building owners near the heating grid have refused the connection, even though it was shown to them that an annual saving of 40 Euro cents per square meter would be realized, and that the building would become eligible for an energy conservation subsidy. Go figure.)

Be that as it may, the massive building still looms over the neighbourhood, but is now a benevolent, warm, tamed giant. The elevator to the eight floor opens onto Café Vju (pronounced “view”), a pleasant setting with a bare-concrete-chic décor and one of the very best views of the city.

And the neighbourhood? Yes, it is gentrifying; that is unavoidable with projectys like these. But here’s the kicker: housing is, if anything, cheaper. The buildings now heated by the bunker pay less for energy than before. Yet most of these belong to SAGA-GWG, a government company that looks after social housing (social, or subsidized, housing comprises a much larger proportion of the housing stock than in Canada); so, rents are controlled. Not bad!

By the numbers:
Solar PV wall: 670 m2, 0.1 MW, generating 78 MWhr
Solar thermal roof: 1350 m2, 750 kW of hot water
Cogenerator: 510 kW electric, 2700 MWh/a; 600 kW thermal, 3750 MWh/a, using biogas from the wastewater plant
Wood chip boiler: 2 MW thermal, 10,500 MWh/a
Natural gas boiler: 2.15 MW thermal, 3570 MWh/a (used for peak loads only)
Recycled waste heat: 500 kW, 4000 MWh/a
CO2 savings: 6,600 tonnes/a
Production: 22,500 Mwh/a of heat for 3000 homes in a 0.5 km2 area , 3000 MWh/a of electricity for 1000 homes

How do you recycle a bunker, part one, is here, and part two is here.

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Written by enviropaul

November 11, 2015 at 9:42 am

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