System simulation models for automotive on-board hydrogen storage systems provide a measure of the ability of an engineered system and storage media to meet system performance targets. Thoughtful engineering design for a particular storage media can help the system achieve desired performance goals. This paper presents system simulation models for two different advanced hydrogen storage technologies a cryo-adsorption system and a metal hydride system. AX-21 superactivated carbon and sodium alanate are employed as representative storage media for the cryo-adsorbent system and the metal hydride system respectively. Lumped parameter models incorporating guidance from detailed transport models are employed in building the system simulation models. Simulation results to test the storage systems' ability to meet fuel cell demand for different drive cycles and varying operating conditions are presented. Systems are engineered to provide the ability to refuel a vehicle in a short time guided by DOE targets. Gravimetric and volumetric hydrogen densities are computed for the engineered systems and compared to the DOE system goals. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.