Out-Gassing Study and Species Measurement for Cryogenic Carbon Fiber Hydrogen Storage Vessels

Out-gassing Study and Species Measurement for Cryogenic Carbon Fiber Hydrogen Storage Vessels1

Joseph Reiter^†, Rajeshuni Ramesham, and Alexander Raymond

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

Cryo-adsorption and cryo-compressed hydrogen storage are two promising technologies for vehicular hydrogen storage.  These low-temperature storage methods have the benefits of increasing hydrogen density and material adsorption capacity, which enhance both the gravimetric and volumetric performance of these systems.  In both cases, carbon-fiber wrapped tanks appear to be preferable to metal pressure vessels for vehicular applications because of their higher gravimetric capacity; however, maintaining adequate thermal isolation for sustained dormancy at cryogenic temperatures is challenging with carbon composite vessels.  Cryogenic pressure vessels are typically surrounded by a vacuum jacket and multi-layer insulation (MLI.)  The effectiveness of MLI depends on the extent to which high-vacuum is maintained in the vacuum jacket.  Even moderate vacuum degradation can result in significant gas conduction across the separated layers and will render the MLI ineffective.  Carbon composite out-gassing is studied in this preliminary investigation with relation to its effects on vacuum insulation degradation.  Species and total out-gassing rates will be presented on both a gravimetric and on an areal basis using the sample porous surface area provided by the BET (Brunauer-Emmett-Teller) method.  Temperature dependence of the out-gassing rate will be deduced by conducting experiments at cryogenic operating temperature (77 K), room temperature (298 K), and elevated temperature (358 K).  A discussion of the allowable out-gassing rates will be presented along with potential mitigation strategies.

¹Copyright 2011 California Institute of Technology. Government sponsorship acknowledged.

Acknowledgments: The research work described in this paper has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA.  We acknowledge the Department of Energy (DOE) for  supporting this effort.