Phase change materials (PCMs) can be used in a variety areas for thermal energy storage, thermal management, and efficient temperature control. Two different applications will be presented to explain how to use PCMs for temperature control and thermal energy storage. The first case is using PCMs in building envelope to achieve better insulation performance for indoor temperature control. Incorporating insulation material (e.g. polyurethane (PU) foam) with PCMs could help enhance the insulation capability for significant building energy savings by reducing the HVAC loadings. Paraffin wax was considered as the PCM for the low-temperature building application. It was infiltrated into the pores of PU foam to form a PU-PCM composite. Through the building energy modeling for our unique Zero-Energy (ZØE) Lab using EnergyPlus, it was found that use of PU-PCM composite in the wall panel could provide 14% total energy saving per year and reduce the electricity use due to cooling only by around 30% compared to the traditional insulation material. The second case is using PCM for high-temperature thermal energy storage in concentrated solar power (CSP) plants. Magnesium chloride (melting point of 714 °C) was selected as the PCM for the latent heat thermal energy storage (LHTES). The PCM can store the thermal energy during daytime, and shift the stored thermal energy to nighttime usage for power generation after sunset. It can improve the efficiency and capacity factor of CSP. However, the thermal conductivities of most salt materials are very low, usually less than 1 W/m∙K. Therefore, graphite foam was applied as a thermal conductivity enhancement additive to considerably enhance the overall thermal conductivity of the resulting graphite foam-MgCl2 composite, and therefore, improve the charging and discharging efficiency of the LHTES system. Lab-scale prototypes have been built and tested to demonstrate the feasibility of graphite foam-PCM LHTES system for high temperature operation.
Weihuan Zhao obtained the B.S. degree in Mechanical Engineering from Shanghai Jiao Tong University in 2007. She received the M.S. and Ph.D. degrees in Mechanical Engineering from Lehigh University in 2009 and 2013, respectively. After achieving her Ph.D. degree, she was working as a postdoctoral appointee in the Energy Systems Division at Argonne National Laboratory (ANL) in Illinois for two years. She has joined the Mechanical and Energy Engineering Department at University of North Texas (UNT) as an assistant professor since Fall 2015. Her research expertise is in Thermal-Fluid Sciences, including computational heat transfer and fluid dynamics, thermal management technologies, thermal energy storage, phase change materials, and thermal-fluids experimental design. Her research can be applied to concentrated solar power (CSP) plants, building technologies, power electronics heat removal, etc. She is currently working closely with researchers at ANL on the numerical modeling and analyses of the high-efficiency thermal energy storage for CSP plants, funded by DOE SunShot Initiative program. Dr. Zhao is currently the research director of the Zero-Energy (ZØE) Research Lab at UNT.