A capstone project: Assessment of energy savings from retuning of air handlers

Abstract

One of the best ways to reduce operating costs for buildings is to reduce energy consumption. Energy is used to run equipment in classrooms and laboratories, provide area lighting and hot water, but heating and cooling typically account for the largest energy use in a building. Facilities Management at Western Carolina University (WCU) maintains over 300 air handling units (AHUs) covering almost 3.1 million square feet. These AHUs provide heating and cooling and operate continuously while their respective building is occupied. Some newer AHUs have variable frequency drives (VFDs) to reduce the current to an AHU's fan motor in order to throttle energy use when the demand for heating or cooling is low. However, some of these VFDs were only configured during installation, and run at a constant setting, regardless of the demand. WCU's Facilities Management has enlisted the help of School of Engineering and Technology in researching and determining a more energy efficient setting. During the 2015-16 academic year, a School of Engineering and Technology capstone team conducted a case study to determine potential settings for a VFD, in order to reduce energy use and electricity expenditures while maintaining a comfortable environment for students, faculty and staff. A specific AHU in the new Health and Human Science building was selected for testing by the capstone team. It was determined that the driving force behind the actions of the VFD was feedback from the programmable logic controller (PLC). The PLC monitors air flow requirements at the zone or room level in order to control the static pressure set-point. After conducting an on-site analysis, the team collected data from the AHU through the building's automation system. The energy use of the selected AHU was recorded during November 2015 while the static pressure was set to its normal constant setting. This provided the team with control data. Then the static pressure set-point was lowered on December 1, 2015. The energy use of our experimental unit was compared to our control data. After determining that further adjustment would not affect the AHU's ability to maintain a comfortable environment, the setpoint was again lowered in early April 2016. This change resulted a reduction in energy use by the AHU's supply fan, while still meeting airflow requests. The AHU is now much more responsive to demands, and can fill them quickly and efficiently. This has led to lower energy use, and thus reduced the operating costs for the entire building. This showed the potential for WCU's Facilities Management to apply a similar change to most, if not all of the other AHUs in the Health and Human Science building, and in other buildings across the campus. This paper provides an overview of the project-based learning courses within the School of Engineering and Technology, a summary of the needs, requirements, research, analysis, and findings of this capstone team project, as well as an assessment of several student outcomes.