Development of phase state detection method for latent heat thermal energy storages

Kurzfassung

Industrial heating accounts for 74% of the total energy consumption within the industry and latent heat thermal energy storage systems using Phase Change Materials (PCMs) as storage medium, offers an efficient and CO2-netrual solution for the provision of steam in the temperature range from 150 – 350°C [1]. However, determining the stored thermal energy in these systems during partial charging and discharging is challenging, mainly because the phase transition occurs under quasi-isothermal conditions. This study investigates density-induced fill-level changes for a eutectic nitrate-salt (54 wt% KNO₃ – 46 wt% NaNO₃). Cylindrical storage equipped with a laser distance sensor and thermocouples was used to measure fill-level variations during phase change. The liquid fraction from fill-level measurements agreed well with the thermocouple-based rule calculation, with maximum and mean differences of 0.125 and 0.115.