Glass micro-container based hydrogen storage scheme

Glass is the material of choice for inertial confinement fusion (ICF) targets due to its high strength [Bartenev GM, Sanditov DS. The strength and some mechanical and thermal characteristics of high-strength glasses. J Cryst Solids 1982;48:405]. There exist many technologies for producing fusion grade glass microballoons (GMBs) also known as hollow glass microspheres (HGMS) and filling techniques up to 1000 bars. These glass micro-containers offer a novel scheme of hydrogen storage [Rambach GD, Hendricks C. Hydrogen transport and storage in engineered glass microspheres. In: Proceedings of the 1996 USDOE hydrogen program review meeting, Miami, National Renewable Energy Laboratory; 1996. p. 765]. A comparative evaluation of hydrogen storage efficiency has been done for high tensile strength GMBs at different radius to wall thickness ratio termed as aspect ratio. By experimental and theoretical calculations, we propose the use of high aspect ratio GMBs with storage efficiency from 15% to 25% w/w for GMBs at pressures below 500 bars. Such efficiencies are unique, being greater than large cryostat (∼14%∼14% w/w), and safe compared to large pressure vessels, etc. For the pressure range 150–300 bars a prototype hydrogen filling system has been developed in our laboratory. We have experimentally attained gravimetric efficiency η=MH/(MH+MS)η=MH/(MH+MS) as 15–17% for the GMBs. The advantages and also some shortcomings of this technique are compared with other hydrogen storage methods such as metal hydrides, physisorption and chemisorption, etc.