Integrated Control of Multi-Zone Buildings with Ventilation and VRF systems in Cooling Mode

One common strategy for achieving reduced energy consumption and improved comfort in modern high-performance buildings involves the use of multiple interacting heating, cooling, and ventilation systems. Because tighter and more insulating building envelopes are often accompanied by a reduction in the capacity of the space conditioning systems, the limited control authority of these smaller systems raises the importance of understanding dynamics and control in this built environment. This paper explores the use of model-based strategies for analyzing and controlling the behavior of a representative building incorporating both a multi-zone VRF system and a ventilation system. The Modelica language facilitates the use of rapid prototyping and trade studies with three different ventilation systems - a fan-only system, an ERV system, and a DOAS - as well as the study of the performance of the building with each of these systems operating under closed-loop control. Analysis of the integrated system indicates that the subsystems interact dynamically, and that these dynamics must be considered during the design process. These three systems are evaluated over a 2 days of operation with realistic solar and weather inputs, and the DOAS system is found to consume 27% less energy than the fan-only system and 16% less energy than the ERV system over that time interval