New Blog Post: From One Litre to 500 kWh

MODERATOR has published a new blog post from COWA Thermal Solutions AG, following the scale-up of the project’s thermal energy storage system from laboratory testing to a full-size pilot installation.

The work started with one-litre samples of phase change material (PCM), used to confirm that the material could remain stable through repeated heating and cooling cycles. Fifteen months later, the system has grown to 40 full-size Compact Cells, providing around 500 kWh of nominal thermal storage capacity and containing more than 10 tonnes of storage material. 

This step-by-step scale-up was essential. A material that performs well in a small laboratory sample also has to work reliably when hundreds of kilograms of material, heat exchangers and multiple storage units are brought together. The development therefore progressed from one-litre samples, to a single Compact Cell, then six connected cells, and finally the complete 40-cell configuration. 

Before deployment, the cells were tested at the Lucerne University of Applied Sciences and Arts (HSLU) at different charging and discharging power levels. The system is designed to take in waste heat steadily from an immersion-cooled data centre and release it more rapidly when a building or industrial process needs it. 

The 40 Compact Cells are now being prepared for shipment to the SYNAPSECOM data centre in Thessaloniki, where they will be integrated with the MODERATOR immersion cooling system together with HYSYTECH and SYNAPSECOM. The first charge and discharge cycles are planned for late 2026. 

The new blog explains how the system was scaled up, what is inside each Compact Cell, how it was tested, and what comes next as MODERATOR moves closer to operating its integrated pilot.

Read the full blog here.