Compressed hydrogen tanks for on-board application: Thermal behaviour during cycling

The thermal behaviour of several commercial hydrogen tanks (Type III and Type IV) has been studied during high pressure hydrogen cycling (filling from 2 - 3 MPa to 78 - 84 MPa, holding under pressure and emptying back to 2 - 3 MPa). The temperature of the gas at different points inside the tank, the temperature at the bosses and at the tanks outer surface has been measured during several hydrogen cycles. From the experimental results, the evolution of the measured gas temperatures during the complete cycling process has been studied. The effect of the filling rate on the temperature increase of the gas during the filling has been evaluated. The thermal response of the metallic bosses and the external surface of the tanks under different cycling conditions have also been investigated. The evolution of the external temperature has been correlated to the evolution of the gas temperature. The influence of the manufacturing materials on the thermal behaviour of the tank, the importance of the initial thermal state of the tank in the refuelling process and the difficulty of filling a Type IV tank without pre-cooling in a reasonable amount of time have been highlighted in the present work. The possibility of monitoring the external temperatures of the tank to follow the evolution of the inside gas temperature during the filling and emptying phases has also been considered.