Marie Duquesne
Institute of Technology of Bordeaux, France
Title: Organic biosourced phase change materials for seasonal thermal energy storage
Biography
Biography: Marie Duquesne
Abstract
Our work focused on thermal energy storage in a seasonal basis for heating and domestic hot water supply in buildings. The objective is to develop and study innovative organic bio sourced phase change materials (PCM) able to compete with water and surpass the performances of commonly used PCM today (low cost, high energy density, compactness, thermal losses reduction, environmentally friendly etc.). Sugar alcohols (SA) and their blends could provide high storage energy densities in the range of 120–190 kWh/m3 at temperatures inferior to 100°C with limited thermal losses due to high undercooling. They are compatible with commonly used container materials and with cheap solar collectors. They present long-term stability (no separation, no segregation, controllable thermal degradation) and moderate-to-low volume changes. Their prices are acceptable. First, a screening of SA and SA-blends to select the ones with melting temperatures inferior to 100°C was done. Then, an experimental characterization of the selected SA and SA-blends was performed. This encompasses the measurements of their melting point, their latent heat of fusion and the experimental determination of all key physical properties (specific heat, thermal conductivity, thermal diffusivity, density, viscosity) as a function of the temperature. The activation of the energy discharge process (crystallization) is difficult and the subsequent crystallization rates (discharge powers) are very low. Therefore, it was important to find out an easy to implement and efficient solution to discharge the storage system at the required power when needed. When the energy is needed, the storage system is discharged by activating SA crystallization using the efficient method found out in previous step. The associated discharge power depends on the SA crystal growth kinetics. The final step aims at measuring and modeling crystal growth rates in undercooled melts of SA and SA blends according to the temperature and determining the involved crystal growth mechanisms.