Analysis and optimization of melting temperature span for a multiple-PCM latent heat thermal energy storage unit

•Thermal energy storage unit with a number of phase-change materials is explored.•Unit performance is investigated using a numerically-solved mathematical model.•An optimal way to choose the melting temperatures of the PCMs is established.•Generalization of the results is achieved and dimensionless presentation is used.•An extended more realistic model with sensible heat capacity shows similar trends.