Abstract Thermodynamic analyses for a hydriding-dehydriding cycle process of a hydrogen storage system are carried out. Assuming the mass flow rate and the mass source term are both constant, the analytical solutions for lumped temperature in the metal hydride hydrogen storage tank are obtained in the absorption, dormancy and desorption processes. The analytical solution is important to understand the hydriding-dehydriding process, which can be used as a benchmark to validate lumped/distributed parameter models for further study. A lumped parameter numerical model is developed on the Matlab/Simulink software platform. The numerical solutions of this model with constant source term coincide with the analytical solutions. Different analytical solutions are solved with various combinations of the hydrogen inflow/outflow temperature. The analytical solution in present work is compared with the reduced model in the reference, and shows more accurate than the reduced model. The variable source term is applied to the validated lumped parameter model. The results of parametric study show that the source term of metal hydride is roughly constant when the hydrogen storage capacity is not beyond about 90% of its limited capacity.