CEA-Liten and GRIMS began working together in 2020 through an EasyPOC project to design an efficient latent heat storage solution for urban heat networks. The partners developed an innovative solution based on a lattice heat exchanger and bio-sourced phase change material (PCM). The main innovation lies in the metal honeycomb matrix, which is molded around the heat transfer fluid tubes, optimizing heat exchange with the PCM.

The patented solution, which now goes by the name of GRIMSBOX®, is undergoing further development. The next step is a 1:1 scale demonstrator, which will be tested in real-world conditions on an urban heating network managed by Energies du Sud in greater Montpellier, France. GRIMSBOX® is three to four times more compact than water-based thermal storage solutions. It is also modular in shape and size—ideal for the limited space available in urban heating network substations. The solution could also be adapted for industrial use cases.