2009 Volume 34 Issue 4 Pages 46-51
High-pressure metal hydride tank, a combination technology of metal hydride and high-pressure tank, is one of promising option for fuel cell vehicles. Both high storage capacity and good charge-discharge performance can be achieved by this system. 1st generation system is “CFRP High-pressure Metal Hydride Tank”. 5.3 kg hydrogen can be stored within 100 L tank with 2.5 mass% BCC alloy at 35 MPa. A separated aluminum liner is designed for this system to install a tube and fin type heat.exchanger with metal hydride powder into the tank. In a burst test, a prototype was not ruptured at 100 MPa inner-pressure. And at a pressure cycle test, there was no leak during 22,000 cycles. It is possible to secure enough strength equal to conventional CFRP high-pressure tank. 2nd generation system is “Multi-cylinder High-pressure Metal Hydride Tank”. It has a bundling structure by 10-40 metallic vessels which install hydrogen-absorbing alloy. The bundle of the vessels is also a heat exchanger. To improve thermal conductivity, hydrogen supply pressure is lowered to 10-20 MPa, which makes it possible to reduce the wall thickness of vessel. Experimental results by prototype tank and simulation results by 1/1 scale on-board tank model show that 5 kg hydrogen can be stored within 83 L tank and also that more than 80 % of hydrogen can be stored within 5 minutes if a hydrogen-absorbing alloy with 3.0 mass% effective capacity is developed.
