Evaluation of Advanced HVAC Systems Equipped with Thermal Energy Storage and Booster Fans

A major portion of the energy consumed in residential buildings is used for heating, ventilation, and air-conditioning (HVAC) systems. In fact, globally, HVAC systems consume more than 50% of the energy used in buildings. Many HVAC systems do not operate efficiently and lose 25-40% of their cooling or heating energy. Furthermore, considering daily temperature fluctuations, the efficiency of HVAC systems can be improved through the use of thermal energy storage (TES). The focus of this thesis is to investigate the potential to enhance the performance of HVAC systems through the use of fans, dampers, and integrated TES. Low-powered fans placed in vents (booster fans) are investigated for their performance to improve heating and cooling and reduce HVAC system run times. Furthermore, "smart" booster fans and dampers are considered in the simulations by optimizing the times at which they can be turned on or off during the simulations. Results show that the smart booster fan can significantly improve, even by greater than a factor of two, the airflow at a bad vent and the duty cycle of HVAC systems can be reduced to 4.5 hr/day. Duct systems with silica-based TES are also investigated. The silica-based TES system is charged using hot air, coming from a fan equipped with a resistive heater. Thus, the stored thermal energy is generated using electric power, providing an avenue for efficient electrification of heating in buildings. Experimental results show more than 50% of the amount of thermal energy that can be stored in the silica gel can be stored and retrieved as heated air.