Day 2 :
University of Nantes, France
Olivier Joubert is a Professor at Nantes University and Chairs the Fuel Cell group of Institut des Matériaux Jean Rouxel (CNRS-IMN). His major research interests concern new ceramic materials. He has participated to the development of novel ion and proton conductors as electrolyte for solid oxide fuel cell and electrolyser and also anode materials. He is co-author of 95 publications, 20 invited talks and 5 patents. He is chairing the HySPàC research grouping which assembles all French academic research groups in the field of production and storage of hydrogen and also fuel cell and electrolysers, about 108 laboratories mainly from the CNRS and CEA. He is the main organizer of the IDHEA meetings held in Nantes in 2014 and 2016. He is in charge of the expertise cell ERIMAT in Capacités SAS, a private subsidiary of the University of Nantes dedicated to the development of research, and provides assessment, advice to industries.
The research on solid oxide fuel cell (H+ or O2- SOFC) is based on both the synthesis of new materials and the design process of the cell. The main advantage of SOFC is that they can work under hydrocarbon fuel at temperature higher than ≈700°C. In the current SOFC systems, the most widely used electrolyte is yttria-stabilized zirconia (YSZ) which is inexpensive and shows an acceptable conductivity level. But YSZ is very refractory and its major drawback is its reactivity during the sintering process with lanthanum- and strontium-based cathode materials, which leads to the formation of an insulating layer such as SrZrO3 or La2Zr2O7. There is also a great interest to find ceramic based fuel cells, for mobile application, working at low temperature (≈400°C). This can be achieved in H+-SOFC with a ceramic membrane showing a good proton conductivity level. The state of the art perovskite type yttrium-doped BaCeO3 (called BCY) shows a proton conductivity level above 1 mS/cm at 400°C. But due to its high basicity, BCY tends to decompose, in this temperature domain, in air containing CO2. Finding new electrolyte material is one of the issues. In this presentation, after a briefly state-of-the art concerning SOFC electrolyte, we will report on high-temperature proton and oxide ion conductivities in two new class of oxyborates, La26O27(BO3)8 and doped Ba3Ti3O6(BO3)2 compounds. Both samples were prepared by solid-state reaction and characterized using x-ray diffraction and electrochemical impedance spectroscopy. Quite high conductivity level, about 6.8×10–4 and 1.5×10–4 S/cm at 700°C in air were observed respectively. The transport properties can be understood in terms of the presence in high concentrations of oxygen and barium vacancies as well as oxygen interstitials as observed in hybrid density-functional defect calculations.
Institute of Technology of Bordeaux, France
Time : 09:45-10:25
Marie Duquesne defended her PhD: Resolution and reduction of a non-linear energy storage model by adsorption on zeolites in 2013. She is an Associated Professor at the National Polytechnic Institute of Bordeaux since 2015 and Researcher at Trefle Department (Fluids & Transfers) of the I2M and a member of TESLab (Thermal Energy Storage Laboratory), I2M/Abengoa Joint Research Unit. She has expertise in thermal energy storage at low-to-medium temperatures and contributes to an ANR Project SIMINTHEC (National Project, 2008-2011) and to the European FP7 SAM.SSA Project (Sugar alcohol based material for seasonal storage applications, 2012-2015).
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.