Some time ago, we reported on the construction of the new supercomputer, called HoreKa 2.
In such a setup, the focus of interest is usually on the associated computer cabinets with state-of-the-art water-cooled computing components, CPUs and GPUs interconnected in clusters via high-performance networks (technical details can be found in the report above).
However, the high power density achieved by HoreKa 2 in the final expansion also places special demands on the electrical infrastructure, which we would like to highlight here.
HoreKa 2 - New requirements for the building infrastructure
In order to operate the thousands of "power-hungry" computer chips safely and sustainably in the future, the infrastructure in the computer building also had to be expanded. This involved extensive structural preparations, as the power supply for HoreKa 2 requires more powerful cables and busbars than before (see image).
The busbar trunking previously located in the raised floor below the server racks was not suitable for supplying HoreKa 2 for reasons of capacity and space. A project to convert the building infrastructure was therefore launched at the same time as the procurement of the new cluster.
In future, each double row of racks will have four 800 ampere busbar trunking systems without an uninterruptible power supply and two 400 ampere busbar trunking systems with an uninterruptible power supply. These are located above the racks, which means that the space available allows for a much denser configuration of power outlet boxes than before.
Most of the necessary conversion work was carried out during ongoing operations. Both the steel construction work - a steel girder frame was installed in the computer room for the busbar trunking - and the electrical installations ran parallel to the normal operation of the mainframe computers bwUniCluster 3.0 and HoreKa and also parallel to the current set-up activities for HoreKa 2. A one-week downtime of the server systems was only necessary at the beginning of February 2026 for the electrical switchover from the old to the new distribution infrastructure.
Sustainable computer operation
HoreKa 2 is characterized by a particularly energy-efficient and sustainable operating concept, whereby the active computer components, including the power supply units, are cooled with warm water. In the current existing HoreKa building, up to 1.5 MW of waste heat can be dissipated very efficiently via open-air coolers, which significantly reduces the energy required for cooling.
In order to support the future extraction of more waste heat into modernized neighbouring buildings, the heat exchanger between the rack and building cooling circuits was also redesigned for HoreKa 2. This means that it can be operated with a temperature loss of just one Kelvin. The existing building can also serve as a module for climate-neutral heat supply with a view to a future district data center, which is designed in modular construction and is currently in the design phase.
The next big step
Now that the building has been made "HoreKa 2 ready", another important milestone has been reached: The CPU units have been installed and are being tested. The GPU servers will be delivered and installed towards the middle of the year. Here, HoreKa 2 relies on absolute high-end components on the market.
With a combination of massive CPU power and state-of-the-art GPU acceleration, HoreKa 2 will then be ideally equipped for the most complex simulations and AI applications of the future. User operation is targeted for the second half of 2026.
Contact: Dr.-Ing. Samuel Braun
Further information in the SCC-News 2/2025 (in German)