A Concise Review of Nano-enhanced Phase Change Materials for Passive Cooling Applications in Buildings

Building energy consumption has been on a steady rise over the past decade. This is due to the ever-growing human population and the effect of climate change. Space conditioning accounts for over 40% of the final global energy production. Thermal energy storage (TES) systems have shown to be quite effective in reducing buildings energy demand while maintaining the desired comfort. It finds a useful application in solar thermal systems as and heat recovery systems. Phase change materials are used in building components for storing excess heat energy for use when the need arises. The ability of PCMs to store great quantity of heat in comparatively small volume makes them suitable for this application. Some of the set backs encountered by using PCMs is its poor thermal conductivity and subcooling characteristics. Nanoparticles have been found very useful in ameliorating the thermal conductivity of PCMs thereby improving its general performance. This review work brings to bear recent developments on the use of nanoenhanced PCMs for passive cooling applications in buildings, and there are very little articles in literature that emphasizes the application of nanoPCMs in passive cooling systems. We further discussed the physics of operation and phase transition behaviours with mathematical representations. Some gaps currently encountered in the research of nanoPCMs was also highlighted for further research purposes.