Latent heat storage with phase change material is a superior way of storing thermal energy because of its high thermal storage density, isothermal nature of the storage process, and easy control. In recent years, latent heat storage systems have been increasingly used in building energy conservation, solar heating systems, and waste heat recovery systems. The water tank as a key component of solar heating systems has been widely applied in practical applications. This article first reviews the research on the water tank integrated with phase change material in terms of existing research methods and heat transfer enhancing technologies and then summarizes the applications of various phase change material-based water tanks. Finally, the further research suggestions on the phase change material-based water tank are proposed in this article. The successful completion of this review will not only deepen the understanding on the research development of phase change material-based water tank but also promote practical applications of such water tanks in solar heating systems.

The heat-source tower heat pump (HSTHP), as a novel energy-saving unit, extracts low-grade thermal energy from air that can be a promising alternative of boiler in Yangtze River basin, China. A numerical model for analysis of the heat and mass transfer characteristics of a counter-flow heat source tower (CFHST) operating in winter is developed and validated by using experimental results. In this proposed numerical model, the changeable Lewis number is considered, and the effects of various operating, environmental including inlet air dry bulb temperature, inlet air humidity ratio, inlet air flow rate, inlet solution temperature and inlet solution flow rate on the thermal behavior of the heat source tower are studied. Furthermore, the proposed model will also be used to analyze the impact of the porosity and spacing of packing on the heat exchange in the CFHST. Finally, the moisture transfer characteristics inside CFHST under various environmental conditions are also studied. This work can provide a theoretical foundation for performance evaluation and practical design of CFHST.

Thermal storage capacity and airflow rate of a solar chimney combined with different PCMs are numerically studied during nighttime. PCMs with phase change temperatures of 38°C, 44°C, 50°C, and 63°C are selected in this numerical study. Results show that the maximum average ventilation rate of 610 kg/m 2 and maximum thermal storage of 4750 kJ/m 2 are achieved at the phase change temperature of 38°C. However, for phase change temperature of 63°C, night ventilation does not occur under the identical conditions. The findings reveal that a lower phase change temperature can increase the chargeability (and therefore the dischargeability) of a solar chimney, since a higher phase change temperature demands higher solar radiation intensity and longer charging time for a solar chimney. For PCM with a phase change temperature of 44°C, most of the heat stored in PCM is lost to ambient through glass cover by radiation and only a small portion is used for heating the air within air channel.