Hydrogen desorption using honeycomb finned heat exchangers integrated in adsorbent storage systems

One of the main technical hurdles associated with adsorbent based hydrogen storage systems is relative to their ability to discharge hydrogen effectively, as dictated by fuel cell requirements. A new honeycomb finned heat exchanger concept was examined to evaluate its potential as a heat transfer system for hydrogen desorption. A bench scale 0.5 L vessel was equipped with the proposed heat exchanger, filled with MOF-5® adsorbent material. The heating power, required to desorb hydrogen, was provided by a 100 W electric heater placed in the center of the honeycomb structure. Two desorption tests, at room temperature and under cryogenic temperatures, were carried out to evaluate the hydrogen desorption performance of the proposed system under different operating conditions. The bench scale vessel performance was verified from both an experimental and a modeling point of view, demonstrating the ability to desorb about 45% of the adsorbed hydrogen in reduced time and applying low heating power. Further modeling analyses were also carried out showing the potential of the proposed system to reach high hydrogen discharging rates at cryogenic temperature conditions and operating pressures between 100 bar and 5 bar. The proposed adsorption system also demonstrated to be able to discharge all the available hydrogen in less than 500 s operating at cryogenic conditions and with a nominal heating power of 100 W.