Pressurized heat storage for local heating in Hafencity - enercity Hamburg
In 2020 and 2021, enercity Contracting Nord GmbH (eCNG), a subsidiary of Germany’s fifth-largest municipal energy service provider, enercity AG, built a new energy center on Georgswerder Damm in Hamburg to make CO2-free industrial waste heat from the Aurubis AG copper smelter usable for the heat supply. Via a local heating network, enercity now supplies its customers in the newly emerging HafenCity district as well as in Rothenburgsort and Veddel.
One challenge was the need to bring the highly fluctuating waste heat to a uniform temperature and to store it temporarily in order to make it usable. For this reason, eCNG had requested two alternative storage types, unpressurized and pressurized, in the tender. Max Straube, as a sister company of Kremsmüller, made a corresponding offer. After intensive discussions between Kremsmüller, Max Straube and the customer enercity, a joint decision was made in favor of the pressurized heat storage solution.
The reasoning behind this: With an unpressurized heat storage tank, it would be more difficult and more expensive in the long term to ensure constant pressure equalization between the heat storage tank and the pressurized pipe network. Electric pumps would also be required to charge and discharge the heat storage tank, which would incur running costs. In addition, the unpressurized version would require a gas buffer, for example made of nitrogen, above the water storage medium, as normal air in contact with water impairs the quality of the storage medium and leads to increased corrosion.
Another challenge in implementing the project in 2020 was, as everywhere, the restrictions and regulations at the start of the COVID-19 pandemic. Kremsmüller was able to ensure that the work could be carried out without any problems thanks to a suitable hygiene concept.
On the site of the energy center on Georgswerder Damm, not far from the new HafenCity, which is still partly under construction, there is now a 22-meter-high pressurized heat storage tank with a diameter of over nine meters. 1,200 m³ of water at 7.5 bar overpressure and with a temperature of up to 110°C now ensure a reliable and consistent supply of local heating as a storage medium. With the expansion of HafenCity and thus additional heat consumers, further expansion stages of the project have already been taken into account during planning and construction. While the storage tank in conjunction with the network pump system makes use of the highly fluctuating waste heat, two boilers with a maximum total thermal output of up to 20 MW ensure security of supply in the event of interruptions to the waste heat supply, which cannot be completely avoided due to the upstream industrial process.
The energy center is equipped for the connection of additional customers and the further expansion of the heating networks: The plant has been planned in such a way that the total thermal output of the boiler systems will be expanded to more than 40 MW for the provision of peak output. While the proportion of heat provided by the boilers throughout the year remains low, the expansion of the peak output will enable even more buildings in Hamburg to benefit from the use of CO2-free industrial waste heat in future.
Another special feature of the project: in addition to pure natural gas, the eCNG boiler system can also be operated with an admixture of up to 20% hydrogen. Even though hydrogen is still a topic for the future in energy supply, Max Straube has planned ahead and taken this pioneering technology into account from the outset when planning the system – for example by selecting suitable burner technology and associated components.
