Multiphase transport phenomena in composite phase change materials for thermal energy storage

Abstract

Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage (TES) has a pivotal role to play in the energy chain and hence in future clean energy systems. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including materials, components and devices, and integration of the devices within energy networks and associated dynamic optimization. This requires fundamental understanding of the underlying physics particularly flow and heat transfer of a multiphase system across a very large spatial length scale from atomic/molecular scale to system scale. This talk will first briefly outline the background and challenges of energy storage. Discussion will then be on TES covering TES materials, TES devices (TES heat exchangers) and system integration, with a specific focus on flow and heat transfer across large lengthscales. TES can be sensible heat, latent heat or thermochemical based. This talk shall use the latent heat storage materials, often called phase change materials (PCM), as an example, particularly inorganic salts based PCMs for medium and high temperature applications. Two key challenges for such materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials use a structural supporting material and a thermal conductivity enhancement material. A right combination of the salt, the structural supporting material and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. Our recent progress in these aspects will also be covered in the talk.