Flexi-Sync (Flexible energy system integration using concept development, demonstration and replication) aims to optimise the flexibility in the district energy sector, a sector with untapped potential to balance the energy system. The project objective is to identify how flexibility in district energy can be optimized and, thereby, contribute to the management of the existing mismatch between weather dependent, electricity production and variable demand. The project has six demonstrations sites in Sweden, Germany, Austria and Spain. All six demonstration sites use the NODA Heat Network and NODA Power Grid platform.