Improving operation management performance of air conditioners in offices using data envelopment analysis

Abstract

Heating, ventilation, and air conditioning (HVAC) systems account for the bulk of a building's energy use, which means that potentially significant energy savings can be made by efficiently modifying how those systems are operated. Although several studies have demonstrated that optimizing the operation of HVAC equipment in combination with sensor readings can reduce potentially wasteful processes, such efforts are limited to buildings that have or can incorporate additional sensors. As an alternative approach, this paper aims to identify potentially wasted energy and provide suggested improvements for buildings that do not have installed sensors, which is important because such suggestions can extend the scope of energy reduction measures. More specifically, we hypothesized that comparing differences in user operations would make it possible to identify potentially wasteful operating times. Accordingly, we began our study by identifying target days and days for improvement using data envelopment analysis and then detected operational differences by comparing their operating times. Our new method was then applied to variable refrigerant flow systems in an office building as a case study. The obtained results showed that the potential for energy reduction was about 7.5%. These results, which helped determine the appropriate times for automatically shutting down each indoor unit, proved effective in implementing energy reduction measures. The novelty of this paper is that it clarified the energy waste that can be detected based on operating times, which is expected to lead to the development of additional options for energy reduction measures, thereby allowing building owners to implement more effective actions based on the sizes and conditions of their buildings.