Performance of advanced control sequences in handling uncertainty in energy use and indoor environmental quality using uncertainty and sensitivity analysis for control components

Control sequences for air distribution and terminal systems in heating, ventilating, and air-conditioning (HVAC) aim to achieve a balance in the system outputs, i.e., maintain thermal comfort and indoor air quality (IAQ) with minimal energy use. ASHRAE Guideline 36 (G36) – High-Performance Sequences of Operation for HVAC Systems, is the result of ASHRAE research project 1455-RP intended to develop standardized sequences of operation to achieve more effective use of existing controls. This paper complements G36 by evaluating the influence of the uncertainty inherent in the control components (e.g. sensors and actuators) on the system outputs of a multiple zone variable air volume (VAV) system. The system outputs under study were zone air temperature, relative humidity, carbon dioxide (CO2) concentration, and site electricity use. To evaluate the effects of uncertainty in HVAC systems with advanced sequences of operation, this work applies a Monte Carlo uncertainty analysis to a detailed Modelica building energy model that has been programmed with G36 control sequences. Uncertainty models were integrated with the deterministic models of the building and the control sequence at small time scales to represent frequencies in which a real-world building automation system (BAS) samples its signals. The impact of uncertainty was quantified using annual simulations. Specification of the accuracy levels in the components of the control system were evaluated by the means of: 1) uncertainty analysis for low, medium, and high severities of accuracy in the components to identify relation between performance requirements and component accuracy, and 2) sensitivity analysis to identify the sensors and actuators where the impact of uncertainty on the system outputs is most influential.