(Digital Presentation) Assessment of the Cyclic Stability of a Bench-Scale TiFe-Based Hydrogen Storage Tank

Abstract

Hydrogen storage devices comprising of low-cost and flexible metal hydrides have recently regained vivid interest as basic elements in energy conversion systems. Among many intermetallic compounds, TiFe-based alloys are one of the most promising candidates to hold atomic hydrogen because of their significant storage capacity of about 1.9 wt.% and moderate operating conditions. However, the alloy degradation in repeated hydriding- and dehydriding cycles inevitably affects the performance of the hydrogen storage system. In this work, the intrinsic degradation behavior of a bench-scale TiFe-based alloy tank has been investigated. Thermal cyclic life tests were performed between 5°C and 45°C, and the heat transfer properties of the storage device were tested over repeated cycles by obtaining temperature histories. A thermal imaging device was used for the internal heat transfer mapping and the charging time and pressure-composition isotherms were recorded for the hydriding- and dehydriding reactions. In Figure 1 thermal images of the discharge reaction at Begin of Life (BoL) and End of Life (EoL) of the storage device are shown. The hydrogen storage capacity was observed to decrease by almost 90% after 100 cycles. Heat transfer mapping revealed that the excess portion of degradation occurs in the middle of the storage device and is attributed to the formation of inactive TiFe clusters based on the measurements. Acknowledgment: Financial support by the Austrian Research Promotion Agency (FFG) through the 8th Call of “COMET-Projects” is gratefully acknowledged. Figure 1 . Thermal image of the TiFe storage device at Begin of Life (BoL) a) and End of Life (EoL) b) after discharging for 240s respectively. Figure 1