Experimental results of an air-cooled lab-scale H2 storage tank based on sodium alanate

One possibility to store hydrogen in fuel-cell driven automobiles is the storage in solid state hydrides. Sodium alanate (NaAlH4) is a well-known hydride desorbing up to 5 wt.% H2 with reasonable rates at temperatures above 120 °C. Therefore a high temperature PEM fuel cell (HT-PEM FC) system with exhaust temperatures of about 180 °C can be used to provide the required enthalpy of reaction. In this study, the absorption and desorption behaviour of a lab-scale tank containing 304 g cerium-doped NaAlH4 is studied using (exhaust) air as heat transfer medium. For absorption reactions an optimal temperature for maximal reaction rates is identified. Additionally, the importance of an adapted heat management is shown for the present tank. For desorption experiments different operation procedures are used and the constraints in temperature and air-flow given by the HT-PEM are considered. For all 25 experiments a good cycling stability has been measured with a stabilised material capacity of more than 3.7 wt.% H2.