The air conditioning market is in constant growth, which can lead to peak loads in electricity grids during summertime. To overcome such problems, Latent Heat Thermal Energy Storage (LHTES) systems can be used for summer comfort in lightweight buildings. These systems consume little energy by using the temperature gap between daytime and night-time. A numerical model presented here is able to simulate the thermal behaviour of energy storage systems made up of a bundle of rectangular tubes. The model takes into consideration the influence of the shapes and arrangements of the rectangular tubes on the efficiency of the heat exchanger. (C) 2013 Elsevier Ltd. All rights reserved.