Through its commitment to specific actions and projects, Stadtwerke Norderstedt is on an exemplary path to decarbonising its energy and heating concepts. One current project involves the data centre that Stadtwerke Norderstedt operates at its main site, the capacities of which are rented out for the most part to third parties. The refrigeration units previously used to cool the servers were replaced by heat pumps. In future, this will provide valuable input into the existing Norderstedt district heating network.
Another project in Norderstedt underlines the expertise and smart solutions being provided by Kraftanlagen to support Stadtwerke Norderstedt in its local energy transition process. Stadtwerke’s main site includes a natural gas combined heat & power plant (CHP) and a high-performance data centre.
Powerful servers produce a lot of heat. Previously, to prevent these sensitive IT systems from overheating, three refrigeration units were used in the data centre. The generation of this level of cooling capacity consumed a great deal of electricity. Since Stadtwerke leased some of this computing power to other companies, it had to protect its systems as comprehensively as possible against the risk of failure. These refrigeration units have now been complemented by the addition of heat pumps.
Heat pumps now provide the necessary cooling
The heat pumps utilize the heat generated by the server operation by using this heat energy as a source so that it can then be made available at a higher temperature level with the addition of electrical energy. This energy is then fed directly into the Norderstedt district heating network. This produces a “cooling capacity” of 900 kW, which is sufficient to keep the servers at a sufficiently cool operating temperature. The effect is therefore twofold: the heat emitted by the servers was previously recooled unused by releasing it into the atmosphere via recooling units (or table coolers on the roof of the building).
This is now being fed into Norderstedt’s district heating network. Another important building block for the decarbonization of Norderstedt’s energy concept has thus been installed.
Felix Reiser, Technical Consultant and Team Leader for heating networks and customer systems at Stadtwerke Norderstedt, and Robert Roß, Project Manager and Energy Manager at Stadtwerke Norderstedt, in the heat pump room at Stadtwerke Norderstedt's data center
© Cyril Abad
Additional benefits of heat pumps: Noise protection will be necessary for the foreseeable future
There is also another extremely far-sighted benefit to replacing the cooling system with heat pumps. Adjacent to the headquarters of Norderstedt Stadtwerke, the local development plan now envisages the construction of a modern residential area. Indeed, construction work for this new district has already been progressing for some time. As a result, different noise protection limits will be applied following completion of this construction work or possibly sooner. With the previous recooling concept in the data centre, it would have been difficult to comply with more stringent limits on noise levels. That is because, previously, several recooling units were installed on the roof of the data centre for cooling. For the most part, these table cooling units are installed on the roofs of buildings to ensure that heat gets dissipated to atmosphere in a controlled manner. A previous noise immission measurement had already demonstrated that the noise levels emitted by roof-mounted installations far exceed those stipulated for systems operating in the vicinity of residential areas.
An additional two-fold benefit is therefore derived from the installation of heat pumps: this is because the notion of replacing table coolers with a quieter system or of retrofitting them to enable them to comply with the applicable noise protection limits is now an obsolete one.
Directing the heat generated into the district heating network reduces the need to continue generating heat through the burning of fossil fuels in CHP and boiler systems. If we assume that renewable electricity will be getting generated in the near-term future, this could lead to entirely CO2-neutral cooling of the data centre. This would in turn translate into the generation of additional thermal energy that could be routed into the local district heating network.
The technical details of the heat pump project
- Each year, the ‘West’ district heating network supplies around 70 GWh of heat to Stadtwerke customers in Norderstedt.
- At present, about 80% of this heat is generated by CHP. The other 20% is provided by efficient natural gas boilers.
- On an annual basis, a heat pump could generate 10-12 GWh of heat, so the intention is that this method should replace the heat generated conventionally from natural gas and CHP plants.
- This will reduce the proportion of heat generated from natural gas while also providing the district heating network with a constant source of heating from the waste heat produced by the data centre. This can contribute up to 15 percent of the network’s supply.
What was involved in the installation of the two heat pumps?
- The new Stadtwerke Norderstedt energy centre was installed in its underground car park.
- The FC-Planung GmbH planning office was responsible for planning technical equipment and for developing the solutions needed to integrate the heat pump(s) into the district heating network as well as into the cooling supply for the data centre.
- When heat is fed into the district heating network, this is controlled from Stadtwerke Norderstedt’s network control centre. Connection to the data centre’s cooling system is carried out in coordination with the responsible departments at Stadtwerke Norderstedt and with the management team at its data centre.
Heat pump in the data center of Stadtwerke Norderstedt
© Cyril Abad
Continuous recording and evaluation of data combined with rapid amortisation
Stadtwerke Norderstedt operates a certified energy management system that complies with DIN EN ISO 50001:2018. During planning and implementation, Stadtwerke ensures that a smart end-to-end metering concept is created and adhered to. This concept makes it possible to use meter data to produce energy assessments and key performance indicators that indicate the efficiency rating and the contribution made to climate protection.
In 2024, the expectation is that 10-12 GWh of heat will be supplied to the district heating network. Based on the current rate of progress and the findings of this project, calculations of efficiency, cost-effectiveness and benefits to climate protection indicate that it should be possible to prevent an annual total of 2800 tonnes of CO2 emissions. Forecasts of operating costs that take account of the move away from fossil fuel generation, previous electricity consumption, the electricity requirements of the heat pumps and increases in CO2 taxes and energy prices, promise remarkably favourable annual results combined with rapid amortisation of associated investment costs.
The benefits of heat pumps in the energy concept of data centres
Transferability of this concept to other municipalities, other utility companies and their data centres
In Germany there are a great many data centres that generate waste heat. In February, there were 522 nationwide. This means that Germany has significantly more data centres than any other European country. In many cases, this waste heat could be utilised to great effect. The provision of a reliable form of cooling is of great importance in certified data centres. In order to create sustainable and climate-friendly synergies, this task should be solved in cooperation with municipalities and utility companies.
Modern data centres such as those that already exist or that are being planned in Scandinavia face the challenge of meeting the increasingly demanding requirements of their users. This translates into an increased demand for electrical power and cooling capacity. For this reason, from as early as the planning phase, potential synergies and combined energy solutions are subjected to intense scrutiny. Measures that have been or are currently being implemented contribute to the further development of expertise and to current technical standards.
For the heating transition process to succeed, it is essential to supplement or replace fossil-fuelled heat generation with renewable energies or waste heat. This is the only way that Germany’s municipalities and federal states can embark successfully on the path that leads to 1.5°C decarbonisation.
Robert Roß, Project Manager and Energy Manager at Stadtwerke Norderstedt, in the heat pump room of the Stadtwerke Norderstedt data center
© Cyril Abad
The prospects for the heat transition process to work in Norderstedt and further afield
The requirement for electrical power increases after this conversion process, even if replacement of cooling units with heat pumps achieves the outcome in energy terms of less natural gas being consumed, specifically through the heat provided from the CHP plants that provide the majority of district heating. However, it is an integral part of Norderstedt’s decarbonisation plan to switch gradually to 100 percent electricity from renewable sources. This will make it possible to achieve the goal of becoming entirely carbon-neutral even more rapidly.
SUMMARY: If modern heat pump technology is used to cool all of the more than 500 data centres in Germany, this would have an enormous impact on decarbonisation.
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