Sensitivity analysis and optimization of building operations

Abstract

Operator decisions regarding daily and seasonal scheduling of systems' availability and setpoints play an important role in building performance. This paper reviews the key operational parameters of 14 office buildings in Ottawa, Canada. The results revealed that over 60% of the air handling units (AHUs) were not turned off outside of normal occupied hours, and most of them did not have an economizer cycle. The indoor temperature setpoints were between 20 and 24°C. Based on these insights, a building performance simulation (BPS)-based sensitivity analysis was conducted to better understand the energy and comfort performance implications of common operator decisions. Eight operational parameters were studied: AHU start and stop times, seasonal switchover to heating and cooling times, heating and cooling season temperature setpoints, and ventilation rate and mode (i.e., constant or occupancy-based). The results revealed that the AHU start and stop times and the ventilation rate are the most critical operational parameters examined in terms of affecting the energy and comfort performance of the buildings investigated. Subsequently, a mixed-integer genetic algorithm was applied to identify the optimal operational parameters among the set of eight operational parameters investigated for four different heating dominated climate zones, nine different occupancy and three different envelope scenarios. The relationships between the variables of these scenarios and the optimal operational parameters were examined.

Deriving sequences of operation for air handling units through building performance optimization

“…In a simulation-based investigation, Wang, Mathew, and Pang (2012) demonstrated that operational factors related to the control of AHUs of a medium-sized office building account for about 80% of the uncertainty in annual HVAC energy use. In another study, analysis of automation system data gathered from 14 office buildings revealed that most AHUs did not have a weekly schedule, a variable supply air temperature setpoint, nor a functional free-cooling mode (Gunay et al 2019a). In a simulation-based investigation, Zhang and Bannister (2013) between best practice and poor control could be as high as 50-90%.…”

“…Multi-zone variable air volume (VAV) air handling units are the most common HVAC system configuration for commercial buildings in North America (Taylor 2018). Operational parameters of AHUs such as supply air temperature setpoints, hours-of-operation, and free-cooling mode settings play an important role in the energy and comfort performance of commercial buildings (Gunay et al 2019a). For example, in a case study involving 12 AHUs in university buildings in Dayton, Ohio, Shea, Kissock, and Selvacanabady (2019) demonstrated 33% fan electricity savings by reducing the supply air pressure setpoints, a 35% reduction in energy use by tuning the availability schedules, and a 17% reduction in cooling energy by correcting the economizer settings.…”

A data‐driven modeling and analysis approach to test the resilience of green buildings to uncertainty in operation patterns

“…Gunay et al 37 conducted a sensitivity analysis of eight operational parameters of office buildings in Ottawa, Canada. The results revealed that the air handling units’ start and stop times and the ventilation rate have significant impacts on energy consumption and thermal comfort.…”

Analysis of active system operation optimization in office buildings

“…Usually, the complete building services and electricity systems are maintained by pure automation algorithms, i.e., on-off switch is made by facility management personnel or constant (0-24 o'clock) use of Heating, Ventilation and Air Conditioning (HVAC) systems [3]. Despite of the fact current modern office facilities are equipped with several kinds of Building Management Systems (BMSs) utilizing advanced applicable operation algorithms; these facilities are not utilized or even not programmed at the level of their full potential [4].…”