Design and operation of a 180 kWh PCM heat storage at the Flaubert substation of the Grenoble urban heating network

Abstract In the framework of building of a new eco-neighborhood in Grenoble, France, an innovative urban heating network is under construction, which seeks to couple a low temperature substation (47°C – 72°C), a 200m2 solar thermal field, a 180kWh Phase Change Material (PCM) heat storage unit (based on a tube and shell assembly), and a smart management system. This paper focuses on the design and preliminary operation of the PCM storage component of the urban heating network. The design, presented briefly, highlights the instrumentation, the characterization of the PCM, and the thermal-hydraulic properties of the tube and shell heat exchanger. The charge cycles, analyzed for varying powers (20kW, 40kW, 55kW, 75kW, 100kW) and inlet temperature (80°C, 85°C) are also presented, along with the discharge cycles, analyzed for varying powers only (25kW, 40kW). The results for this analysis were used to determine the storage density of the system, which was found to be 45kWh/m3 (69.7kWh/m3 for the single PCM) in the temperature range of 56°C - 85°C (without considering the insulation).