Yamashita, A., Kondo, M., Goto, S., and Ogami, N., "Development of High-Pressure Hydrogen Storage System for the Toyota “Mirai”," SAE Technical Paper 2015-01-1169, 2015, doi:10.4271/2015-01-1169.
The new Toyota FCV “Mirai” has reduced the weight, size, and cost of the high-pressure hydrogen storage system while improving fueling performance. The four 70 MPa tanks used on the 2008 Toyota FCHV-adv were reduced to two new larger diameter tanks. The laminated structure of the tanks was optimized to reduce weight, and a high-strength low-cost carbon fiber material was newly developed and adopted. The size of the high-pressure valve was reduced by improving its structure and a high-pressure sensor from a conventional vehicle was modified for use in a high-pressure hydrogen atmosphere. These innovations helped to improve the weight of the whole storage system by approximately 15% in comparison with Toyota FCHV-adv, while reducing the number of component parts by half and substantially reducing cost. The time required to fuel the FCV was greatly reduced by chilling the filling gas temperature at the hydrogen filling station to −40°C (as per SAE J2601). Furthermore, the layout of the tank temperature sensor and other aspects of the design were adjusted to increase the State of Charge (SOC) determined by SAE J2799 IrDA communications between the vehicle and hydrogen station. In the localized fire test for hydrogen tanks described in the newly established Global Technical Regulations (GTR), the tanks satisfied the drop and fire resistance requirements without changes to the external tank volume by incorporating fire-resistant material into the impact energy absorbing tank protector.