An Energy Efficient Approach to Thermal Comfort Control in a VAV HVAC System

HVAC systems are major contributors to the energy consumption of a commercial building. Amidst rising environmental concerns globally, it is critical to identify easily implementable solutions to optimize consumption. A comfort control-based approach emerges promising, since it provides increased leverage over controlling parameters that are more economical (for instance, control air flow via fan speed as against control temperature via chilling water load) and still achieve required comfort levels. Additionally, it offers the user a more seamless experience by adjusting setpoints that are based on human sensation. This paper describes a novel approach to establish comfortable conditions via indices that truly reflect human perception, while optimizing energy consumption. A two-level control architecture is proposed, where the upper level determines the setpoints (temperature, humidity & air velocity) by optimizing energy loads and maintaining comfort index at user specified value. The lower-level architecture controls the MIMO system at the three specified setpoints using decoupled PI controllers, which conventionally was controlled for temperature only. The results show good independent control over the three setpoints with good leverage on fan load.