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Ultra compact direct hydrogen fuel cell prototype using a metal hydride hydrogen storage tank for a mobile phone

Kim, Sung Han, Miesse, Craig M., Lee, Hee Bum, Chang, Ik Whang, Hwang, Yong Sheen, Jang, Jae Hyuk, Cha, Suk Won
Applied energy 2014 v.134 pp. 382-391
alloys, collectors, electric power, electrolytes, energy density, hydrides, hydrogen, hydrogen fuel cells, lithium batteries, polymers, prototypes
The small fuel cell is being researched as an alternative power source to the Li-ion battery in mobile phone. In this paper, a direct hydrogen fuel cell system which powers a mobile phone without a supplementary battery is compactly integrated below 25ml volume at the backside of the phone. The system consists of a small (8ml) metal hydride hydrogen storage tank with 4L hydrogen storage or an energy density of ∼640Wh/L, a thin air-breathing planar polymer electrolyte membrane fuel cell (PEMFC) stack (13.44cm²×3mm for a volumetric power density of 335W/L), miniature pressure regulator, and a high efficiency DC–DC voltage converting circuitry. The hydrogen storage tank is packed with the AB5 type metal hydride alloy. The eight-cell air-breathing planar stack (8ml) is very thin (3mm) due to a thin flexible printed circuit board current collectors as well as a unique riveting assembly and is capable of a robust performance of 2.68W (200mW/cm²). A miniature pressure regulator is compact with fluidic and electrical connections within 4ml. A miniature DC–DC voltage converter operates at an overall efficiency of 90%. Consequently, the estimated energy density of a fully integrated fuel cell system is 205Wh/L (70.5Wh/kg).