Experimental Study on Extremum Seeking Control for Efficient Operation of Air-side Economizer

The air-side economizers have been developed as a major class of energy-saving equipment to enhance the energy efficiency of central air-conditioning systems by taking advantage of outdoor air during cool or cold weather. In current practice, the outdoor air damper is controlled to maintain either the maximum or minimum opening by comparing the outdoor air temperature/enthalpy with the setpoint temperature/enthalpy or return-air temperature/enthalpy. However, in practice many economizers do not behave as expected or even waste more energy due to the erroneous damper actions because of the inaccurate or failed temperature and/or relative humidity (RH) sensors. Recently, a self-optimizing controller based on extremum seeking control (ESC) has been proposed in an earlier study by Li et al. (2010) for efficient operation of an air-side economizer. This paper presents two experimental studies of the ESC air-side economizer control: one is a laboratory setup with a direct-expansion air conditioning unit, and the other is a chilled-water based air handling unit (AHU) facility at Iowa Energy Center. Experimental results from both studies validate the effectiveness of the ESC scheme as a model free optimal control strategy for air-side economizer operation.