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05. Apr 2013 - Flak bunker becomes an energy store

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The flak bunker on Neuhöfer Strasse in Hamburg-Wilhelmsburg was constructed in 1943. Thousands of people found refuge from Allied air raids in the two flak bunker pairs in Wilhelmsburg and St. Pauli. With its flak towers, the bunker at the same time formed part of the German war machinery. In 1947 the British army destroyed the building by means of a controlled explosion in its interior.

The building, which was in danger of collapsing, has now been restored as part of IBA Hamburg and preserved as a memorial. The history of the bunker and the former residents of the Reiherstieg District is documented in an exhibition in and around the building. With the Café Vju and its terrace at a height of 30 metres, the building offers a unique view across Hamburg and the Port of Hamburg. The total cost of the project is around 27 million euros, of which 11.7 million euros is being spent on the technology and the heating network.

The Energy Bunker links intelligent heating generators

A distinctive feature of the Energy Bunker is the solar shell on the roof and the south side of the structure. By intelligently linking the power generated from solar energy, biogas, woodchips and industrial waste heat, it shall supply a large part of the neighbouring Reiherstieg District with heat and at the same time feed renewable electricity into the public grid. In its final form the Energy Bunker will supply around 22,500 megawatt-hours of heat and almost 3,000 megawatt-hours of electricity. That corresponds to the heating requirement for around 3,000 households and the electricity requirement for roughly 1,000 households. This will reduce CO2 emissions by 95 per cent, which corresponds to around 6,600 tonnes of CO2 per year.

IBA project manager Karsten Wessel says: “The Energy Bunker is a key project at the IBA Hamburg as part of the 'Renewable Wilhelmsburg' climate protection concept. Renewable electricity and heat will be generated in the urban district. The core of the energy centre is the large heat storage system, which, with a size of 2,000 m³, buffers the daily peaks in the heating network.” It will be supplied with heat generated from a biomethane-fired CHP unit, a wood-burning plant and a solar thermal system as well as with waste heat from an industrial manufacturing company. The buffer effect of the storage system will significantly reduce the thermal generation capacity which must be installed from 11 to 6.5 megawatts, facilitating the cost-effective use of renewable energies within the heat supply concept.

“The concept is unique worldwide – it will enable us to gather data concerning the practicability of the control and hydraulic technologies used,“ explains Wessel. For this purpose the concept is being scientifically monitored by the EnEff:Stadt, IBA Hamburg and Smart Power Hamburg research projects. In future, surplus wind power from northern Germany could be converted into heat in the storage system. During periods with little wind or sun, an additional CHP unit secures the electricity supplies. Its waste heat is absorbed by the storage system. 

Viewing the future of energy

One of the flak towers houses Café Vju and its unique viewing terrace: the cantilevered slab that runs right around the building at a height of 30 metres provides a 360-degree view across Hamburg. The café and an exhibition on the history of the bunker will be officially opened on 23 March 2013.
As part of the EnEff:Stadt research initiative funded by the German Federal Ministry of Economics and Technology, selected building concepts and energy supply systems at IBA Hamburg are being evaluated in detail. This monitoring includes the “Energy Bunker”, the “Energy Hill Georgswerder”, the “Integrated Energy Network Wilhelmsburg Central” and the “New Hamburg Terraces” local heating network. Further details can be found in the project business card "Monitoring – Energy provision for the IBA Hamburg 2013".


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