The modeling, simulation, and setup of an energy storage system encapsulated with phase change materials in which energy is absorbed in the hot period and released in the cold period are discussed. An algorithm to solve the coupled partial differential equations for heat transfer and storage in the phase change regenerator on the bed scale and the phase change material scale is presented. The bed is simulated via the tanks in series approximation. The phase change material scale is solved by Orthogonal Collocation applied to the equations transformed to immobilize the melt/solid interface and eliminate the effect of spherical geometry. Parametric studies show the effects of specific dimensionless group. A phase change material consisting of water in spherical support is used in a lab scale to verify the mathematical model. Experiments with heated or cooled air passing through the system are described. The measured outlet temperature results are compared qualitatively with the model predictions.