Adaptive temperature set point of air handling units using fuzzy logics

Control technology is necessary for air handling units to maintain suitable conditions in buildings that trend to have low energy consumption and operation cost. This study proposes an adaptive scheme of determining temperature set point that is feasible for many existing control methods, such as return- and supply-air temperature feedback control, of air handling units. The implementation procedure and concrete contribution are described below. A wireless sensor network with Zigbee communication protocol is first established. The environmental dry-bulb temperature and humidity are sensed using end nodes while routers and coordinators pass on and collect data. A heat index, called apparent temperature, is then introduced to indicate the human sensation of thermal comfort. By simultaneously considering the environmental and targeted apparent temperature, an adaptive temperature set point of each air handling unit is derived using fuzzy logics. Next, the proposed scheme is employed to an air conditioning system, in which the PID control method is used in determining the quantity of chilled water entering the cooling coil. Experimental results demonstrate the achievement of stable variation of apparent temperature ranging in a thermal comfort region for occupants. Furthermore, the power consumption of chillers is reduced since the quantity of chilled water used in heat transfer is decreased.