(378b) Out-Gassing Study and Species Measurement for Cryogenic Carbon Fiber Hydrogen Storage Vessels

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.