摘要： Thermal energy storage (TES) unit has become an integral part of thermal energy conservation. As the name implies, the device simply stores heat when energy from the source is available in excess, and releases the same when energy from the source falls short of the requirement. By doing so, such devices deliver heat energy across the temporal barrier, making thermal energy available for extended working hours of solar thermal power plants (STPP). High energy density and stable operation for long duration are desirable qualities which may be found in latent heat thermal energy storage (LHTES) system. To exploit the advantage of LHTES, the most common design reported in the literature is shell-and-tube type latent heat thermal energy storage (ST-LHTES) systems with phase change material ?lled in shell side, while (heat transfer ?uid) HTF ?ows in the tubes (or vice versa). The present chapter gives a detailed classi?cation of ST-LHTES systems based on geometry, orientation and relative position of PCM and HTF in heat exchanger along with the classi?cation of phase-change materials. Numerical modelling of heat transfer phenomenon is presented along with some simulated results for enhanced PCM, clearly describing the coupling between PCM and HTF domain. Various heat transfer enhancement techniques and parametric analysis have been discussed with challenges and future scope.