PNNL

Abstract

Fuel cell vehicles are entering the automotive market with significant potential to reduce harmful greenhouse emissions, facilitate energy security, and increase efficiency while providing expected driving range and fill times. One of the challenges for successful commercialization is transitioning the on-board fuel system from liquid gasoline to compressed hydrogen gas. Storing high pressurized hydrogen requires a specialized structural pressure vessel, significantly different in function from a gasoline container. In addition, the lower hydrogen energy combined with highly efficient fuel cell still requires a storage vessel that is four times the volume of a gasoline tank. In the late 1990s, the industry first developed hydrogen tanks based on traditional type 3 and 4 compressed natural gas (CNG) tanks designed for 250 bar service. As fuel cell vehicles developed along with the need for greater driving range, the OEMs increased the hydrogen storage pressure to 350 bar and then to 700 bar, which is currently the industry norm. However, the 700 bar pressure vessels continued to be manufactured using the materials and the design approach from the CNG tank technologies. In 2012 the U.S. Department of Energy, Office of Fuel Cell Technologies initiated a project to develop Enhanced Materials and Design Parameters for Reducing the Cost of Hydrogen Storage Tanks. The project took a holistic approach to improving performance by investigating: 1) the cost tradeoff of reduced composite mass at 500 bar versus the added insulation cost for cold gas operation at 200K, 2) using hybrid fiber layups to refine the tank composite design, 3) increasing the composite translation efficiency by adding nano-reinforcing particles to the resin, and 4) substituting a lower cost alternate resin in the filament winding process. This paper summarizes the effectiveness of these design modifications and considers the outlook for on-board 700 bar compressed hydrogen tank systems to achieve the commercialization goals for fuel cell vehicles.