Phase Change Monitoring for Energy Content Determination in Gelled Latent Heat Storage Using Electromechanical Impedance Spectra

Abstract

To mitigate climate change, a more sustainable and efficient use of resources is cru- cial. As approximately 50 % of energy consumption is attributable to thermal appli- cations, insulation materials and thermal management offer great potential for savings. Latent heat storage materials (phase change materials - PCM) are suitable for storing and releasing large amounts of thermal energy, e.g. in industrial waste heat recovery, off-peak power generation, solar power plants, food industry, spacecrafts and medicine. In 2022, we were able to show that the use of sorbitol-based organogelators together with polyolefins allows the production of form-stable gels from organic PCMs. Un- like traditional PCMs, these gels do not flow in the molten state and show very low leakage and high energy storage capacity. This work presents a novel approach to deter- mine the stored energy content in these form-stable PCMs using the electro-mechanical impedance (EMI) spectrum, for which a patent was recently filed. Piezoelectric ele- ments, embedded within form-stabilized, organic PCMs, can detect and quantify the de- gree of phase transition from solid to liquid (and vice versa). Additionally, this method can potentially monitor the condition of implemented PCM systems, as the detection of potential leakage and degrading of materials is a common application for EMI and ultrasonic waves.