During discharge, the pressure and temperature of the hydrogen in the storage tank decrease. The ZBT’s measurements reveal a pronounced vertical temperature stratification: in all cases studied, the coldest region was in the lower part of the storage tank, whilst the gas in the upper region remained significantly warmer. In seven of the eight experiments, the local gas temperature reached the lower limit of -40 °C specified for the experiment before the storage tank could be emptied to a low residual pressure.
For the experiments, a commercial 70 MPa Type IV storage tank with a volume of 244 litres was instrumented with a total of 16 temperature sensors inside. Unlike many previous studies on smaller storage tanks, the experiments took place outdoors at the ZBT hydrogen test site. The study shows that the thermal effects already described for smaller storage tanks also occur in a significantly larger Type IV storage tank.
