NanoPCM Based Thermal Energy Storage System for a Residential Building

Implementation of thermal energy storage (TES) systems into a building and facilities improves the performance of the heating/cooling system by reducing energy waste. Thermal performance of a TES relies on the thermophysical properties of the thermal storage medium (TSM). In the present study, a novel two-step selection model has been implemented to choose the best TSM to improve TES system performance. Various types of thermal storage media are investigated considering phase change materials combined with nanoparticles. Thermal storage capacity, heat storage rate, and thermal storage efficiency have been considered as the main selection parameters in a hierarchy method. A significant contribution of this work is the development of a modelling methodology which can be used as a material selection process or tool. It enables the selection of the most efficient TES on a case-by-case basis. This TSM selection technique adds new understanding of selection tools, and new modelling capabilities to this field. It works with a variety of building cooling/heating loads, and helps minimize the environmental impact of extracting/releasing heat to the ground in geothermal applications. The TSM includes PCM and various PCMs have been considered with a melting range of 5–11℃. A material database of 90 different nano phase change materials (nanoPCMs) has been generated by considering ten types of TSMs and nine types of nanoparticles. First, a 2D numerical model has been used to investigate the heat transfer characteristics of the TSM filled in a cylindrical enclosure with a height of 5 cm and a diameter of 1.2 cm. Fourteen different nanoPCMs were selected to further study based on their thermal storage capacity, heat storage rate, and improvement coefficient and implemented into a second numerical model (3D) to calculate the thermal storage efficiency of the designed underground TES system with a height of 20 m and a diameter of 1.5 m. Finally, a building heating/cooling load has been implemented in the numerical model to evaluate the performance of the final designed system on the ground temperature throughout five years of operation. The ground temperature and its variation have an effect on the performance of the ground source heat pump. After five years of operation simulation of the no-PCM system, the ground temperature has increased by 1.78℃ to 9.78℃. However, by adding PCM and nanoPCM, the average temperature reduced to 8.95℃ and 8.72℃, respectively.