Experimental evaluation of occupancy-based energy-efficient climate control of VAV terminal units

Abstract

Results are presented from a nearly week-long experimental evaluation of a scalable control algorithm for a commercial building HVAC system based on real-time measurements of occupancy obtained from motion detectors. The control algorithm decides air flow rate and amount of reheat for each variable air volume terminal box based on real-time measurements of occupancy and space temperature. It is a rule-based controller, so the control computations are simple. The experiments showed that the proposed controller resulted in 37% energy savings over baseline on average without sacrificing indoor climate. In contrast to prior work that reports energy savings without a careful measure of the effect on indoor climate, it is verified that the controller indeed maintains indoor climate as well as the building's baseline controller does. This verification is performed from measurements of a host of environmental variables and analysis of before/after occupant survey results. A complete system required to retrofit existing buildings with the controller is presented, which includes a wireless sensor network and a software execution platform. Two useful observations from this work are: (i) considerable energy savings-along with compliance with ASHRAE ventilation standards-are possible with simple occupancy-based control algorithms that are easy to retrofit; and (ii) these savings are attained with binary occupancy measurements from motion detectors that do not provide occupancy-count measurements. Results also show that there is a large variation in energy savings from zone to zone and from day to day.

Evaluating the impact sequences of operation have on the implementation of occupant-centric controls

“…On the other hand, occupancy-centric control adjusts the indoor environment based on occupancy (i.e., presence/absence or occupant counts). For example, artificial lighting operation (e.g., [27] , [28] , [29] ) and HVAC equipment schedules and airflow setpoints (e.g., [30] , [31] , [32] , [33] , [34] , [35] ) can be altered based on the presence/absence of occupants or the number of occupants present, thus reducing lighting and conditioning loads if occupants are absent or the zones of interest are only partially occupied. Both types of OCC ultimately require a supervisory control program within the BAS to modulate dampers, valves, and/or other actuators to produce the desired equipment operation necessary to meet occupants’ needs as determined by OCC.…”

Performance Simulation and Analysis of Occupancy-Based Control for Office Buildings with Variable-Air-Volume Systems

“…Based on the MATLAB simulation for a single zone in three typical days (i.e., cold, hot, and mild), Goyal et al found HVAC energy savings of approximately 50% for that zone, relative to the baseline terminal control that had a minimum airflow rate fixed at 40% of the terminal box design flow rate. This rule-based OBC strategy was further tested in a campus building in Gainesville, FL [24]. The field test was performed on 12 fully actuated zones (i.e., each zone is served by a single terminal box) for six consecutive days in April.…”

An Air Terminal Device with a Changing Geometry to Improve Indoor Air Quality for VAV Ventilation Systems

“…To save energy, VAV systems regulate airflow according to the current needs in a ventilated zone [8,9]. When less air is needed, less energy is consumed by the system.…”

“…Energies 2020, 13, 4947; doi:10.3390/en13184947 www.mdpi.com/journal/energies Equation 1shows that VAV systems have energy-saving potential. However, when lowering the airflow, the system may not be able to remove all the contaminants [9] and may cause their accumulation within buildings, leading to dead zones [9]. The recommended parameters for systems with variable air flow, including the fresh air rate and criteria for the indoor environment (thermal, air quality, noise, light), are provided by standards EN 15251:2012 [17], ISO 7730 [18], and ANSI/ASHRAE-62.1 [19].…”