Hydrogen Recharge Dynamics and Vessel Design for Porous Silicon Storage Media

P.J. Schubert, A. Urbanek
IUPUI, US

Keywords: hydrogen storage porous silicon gaseous recharge

Summary:

Porous silicon as a storage media can store up to 7.1% hydrogen by weight [1,3]. The round-trip energy difference is 1.2 kJ/mol, but the as-synthesized energy barrier requires 410 C for complete thermal discharge [2]. Barrier height reduction is possible via strategically-placed catalyst deposition, facilitating the spillover effect [3,4,5]. The temperature for thermal discharge of hydrogen can be modulated via catalyst loading [6]. Recharging with molecular hydrogen from a gaseous state is governed by surface diffusion [7,8]. This work presents new results of recharge time as a function of temperature and pressure. Balance of system designs are developed for two use-case scenarios, the “slow home” recharge (8 hours) and the “fast fleet” recharge (3.5 minutes). In each case, the vessel [9], fittings, and control electronics are included to allow computation of system-level storage metrics for hydrogen. These are compared against DOE system goals [10] for evaluation as viable candidates for the commercial marketplace. Preliminary estimates for cost have been made for the “slow home” configuration which yield $7.73 per kWhr media costs (a factor of 20 lower than Li-ion batteries) and 5.8% storage by weight.