Parametric characterization of a full-scale plate-based latent heat thermal energy storage system

Abstract

Thermal energy storage is a key technology to overcome the structural mismatch between energy supply and demand in thermal energy systems. Its use is essential for a proper integration of renewable or efficient technologies in day-to-day applications, such as heating and domestic hot water. Latent heat thermal energy storage, which is based on the use of phase change materials, has been studied in depth in the literature due to its advantages over conventional storage methods. It can provide a higher compactness and lower thermal losses than traditional sensible heat storage systems.However, to optimize the operation of latent thermal energy storage systems into heating and domestic hot water applications, it is still required to obtain additional information on the effects of the system parameters that can be easily altered and/or controlled. These parameters mainly are: operating temperature range, mass-flow rate and prototype length. This paper aims at evaluating these parameters for an innovative plate-based latent thermal energy storage system previously developed by the authors. The used phase change material is a commercial paraffin wax (RT60) with an approximated phase change temperature of 58 °C.A full-scale experimental setup was developed and forty-two experimental tests were conducted. The tests combined six temperature ranges from 45 to 70 °C, three mass-flow rates from 1.8 to 3 l/min and two module arrangements: a single prototype and two prototypes connected in series.The results showed that, for a specified temperature difference between the charging and discharging inlet temperature, the stored energy depended strongly on the selected temperature range. The thermal power during charging and discharging was strongly affected by the difference between the inlet temperature and the phase change temperature of the PCM. Higher mass-flow rates linearly reduced the required time for completion of charging or discharging. Finally, the addition of a second LHTES prototype in series enhanced the storage capacity of the system, but also increased the required time to complete the process.The obtained results can aid the proper design and operation of the system under specific constraints imposed by a specific application. They are also valuable as a starting point for the design of new plate-based LHTES systems, considering both different geometries and phase change materials.