Modeling the thermodynamic behavior of cryo-compressed hydrogen tanks for trucks

The novel set of differential-algebraic equations models the thermodynamic behavior of a cryo-compressed hydrogen on board tank system. The internal energy ������ is used in the energy balance to be independent of the hydrogen phases in all relevant tank scenarios: refueling, discharge, and dormancy. The occurring phase changes in the tank during refueling from gaseous hydrogen through the two-phase region to fully liquid and finally, supercritical hydrogen can be described rigorously without changing the set of the model equations. The comparison of car and truck tanks shows that smaller car tanks have an at least 40% lower loss-free dormancy time than high volume heavy duty truck tanks with the same insulation. A rapid cool-down of the tank from ambient temperature without loss of hydrogen is shown during regular truck operation. For the cyclic-periodic driving and refueling cycle, an optimal stop density ������optstop is found where the refueling shall start such that a maximized usable density Delta ������use of 72.7 g/L is reached.