Latent thermal energy storage system for heat recovery: numerical study

Abstract

International audienceThe continuous increase in the level of greenhouse gas emissions and the rise in fuel prices are the main driving forces to encourage all stakeholders in the energy sector to improve the efficiency of the systems. A large amount of energy is rejected by the industry at low temperature level (between 0 and 150 °C). Indeed, considering all the industrial processes in France, the amount of energy lost in this temperature range is estimated at 75 TWh/year. Storage of heat is one of the major issues to bridge the gap between energy supply and demand. The thermal energy storage (TES) technology including phase change materials (PCM) appears particularly attractive in this specific application. This solution is attractive since it provides a high energy storage density and has the capacity to store heat as latent heat of fusion at a constant temperature corresponding to the phase change transition temperature of the PCM (in the case of pure substances). These parameters are especially suitable for heat recovery in industrial processes in which there is a delay between the process step at which the energy is lost and the process step at which this energy could be recovered. The general objective of our work is to propose a design of a TES system dedicated to the kind of applications detailed above. This paper describes a numerical study on a future experimental pilot composed of a cylindrical tank filled with encapsulated PCM. This model investigates the influence of various parameters on the charge mode. Among the studied parameters, the thermal conductivity of the PCM and the diameter of the capsule are significant parameters on the storage mode. An increase in the PCM thermal conductivity and a decrease in the capsule diameter increase the storage power