Liquid based diurnal thermal storage

A comprehensive study of using thermal energy storage (TES) tank was performed. In this report, the comprehensive literature review of various options of storing thermal energy in buildings was discussed. The objective of the project was to evaluate charging and discharging performance of a storage tank with and without phase change material (PCM) blocks. The general format of the energy balance for the storage tank considering losses, input energy, inlet and outlet mass flow rates, and PCM blocks was developed. Charging performance was analyzed by three different approaches. Initially, constant input thermal energy rate was considered to be delivered to the tank by different heat pumps from 4.5 kW to 9 kW heating capacity. Charging time, phase change process, and stored energy were analyzed under constant thermal energy rate input mode for charging process. Then, the effect of constant coil temperature on charging process was studied and results were compared to previous cases. Also, a solar assisted heat pump was implemented into the model to verify the effect of solar radiation on pre-heating the air for heat pump and how this process improves the overall charging progress of storage tank. Moreover, discharge procedure was discussed to evaluate various discharge modes based on different water draw flow rates. Based on this analyses developing a complete TRNSYS model of the tank is recommended in order to do whole building energy simulation.