Finite element simulation for charge–discharge cycle of cryo-adsorptive hydrogen storage on activated carbon

Abstract

Due to the advantages of high hydrogen storage capacity, low cost of production, and long life cycle, activated carbon used for adsorption hydrogen storage has become a research focus in recent years. Cryo-adsorption of hydrogen on activated carbon is presently promising because it reaches a reasonable gravimetric density of more than 10 wt% and a volumetric density of 41 kg/m3. This paper builds a mathematical model based on a set of partial differential equations (PDEs) controlling the balances or conservations of mass, momentum and energy in the tank and simulates the charge–discharge cycle of cryo-adsorptive hydrogen storage on activated carbon, which is implemented in the finite element analysis software COMSOL Multiphysics™. A modified Dubinin-Astakhov (D-A) model is used to express the relationship between hydrogen adsorption density and the pressure and the temperature in the tank. The constant isosteric heat of adsorption is modified by variational isosteric heat of adsorption based on the Dubinin-Astakhov isotherm of adsorption. The stainless steel container packed with activated carbon is cooled by liquid nitrogen at 80 K. As the liquid nitrogen is evaporated slowly in the whole experiment process, in order to simulate the realistic environment we use a dynamic boundary condition in the model. To monitor the variations of pressure, temperature and adsorption density in the tank, we choose eight monitoring points along axial and radial directions of the hydrogen storage tank. The simulated results are compared with experimental data obtained at the Hydrogen Research Institute of the University of Quebec at Trois-Rivieres. A good agreement between the experiments and simulations has been achieved.