Evaluation of the energy storage capacity of Phase Change Material cement-lime mortars by using heat flux meters and ultrasonic pulse transmission

Abstract

Materials with high energy storage capacity can enhance energy efficiency of buildings further than thermal insulation alone. The use of microencapsulated paraffin wax Phase Change Materials (PCM) in cement-lime mortars with cellulose fibres and lightweight aggregates (LWA) is a promising solution for this purpose. In this study, experimental techniques as flux heat meters and ultrasonic pulse transmission are used to evaluate the thermal performance and energy storage capacity of five cement-lime mortars with 20% of PCM, cellulose fibres and LWA (perlite) under different thermal conditions. A climatic chamber was used to simulate heating and cooling on one side of a sample plate of each mortar type, while the other side remained at lab conditions. Sample plates were instrumented with temperature-humidity sensors, heat flux meter plates and Ultrasonic (US) pulse transducers. US attenuation coefficient was used to identify the phase change PCM from solid to liquid and vice versa, during heating and cooling. The Heat flux difference between both sides of the plates was also measured during heating and cooling cycles. The specific enthalpy (energy storage capacity) of the mortars was calculated for heating and cooling cycles. Mixtures with LWA and PCM showed the best thermal performance achieving larger heat storage capacity than mortars with fibres or the combination of both LWA and fibres.