Discusses materials used in thermal energy storage systems. Lists in a table phase-change material selection criteria. Evaluates the feasibility of using commercially available polysiloxane polymer to store energy in packed bed configurations in the 100-140°C (212-284°F) temperature range. Examines all important aspects of the storage concept, including the experimental characterisation of the material, experimental demonstration of the storage unit and analytical and numerical modelling of the system. Finds that the latent heat storage unit comprising a commercially available vinyl silane graft copolymer in a packed bed configuration was found to be technically and economically feasible.