Effects of Sensor Selection and Additional State Measurements on HVAC Predictive Control

Abstract

Research in passive Heating, Ventilation, and Air Conditioning (HVAC) systems has gained traction over the last few years. Although passive HVAC is not a new concept, advances in environment sensing, control methods, and hardware have made it a more viable method. Some difficulties still exist, such as optimal sensor placement and optimal control strategies. Sensor selection is an important aspect of HVAC design. The system can become difficult to control with incorrect placement of sensors, resulting in higher energy consumption, lower comfort levels, or poor air quality.
There are essentially three methods to determine the optimal sensor location: model-driven, data-driven, and simulation-driven. The model-driven methods use mathematical models to maximize the observability of the system but are mostly used for simplified simulated rooms. Data-driven methods often use clustering algorithms, or maximize metrics such as entropy or mutual information. These methods focus on estimating the indoor air temperature distribution. Simulation-driven methods use simulations to determine the airflow or temperature
fields, often with CFD. These are used to find local hot spots or locations for fast detection of contaminants. No research was found that used sensor data of additional building components besides of the indoor air temperature.
In this work, the sensors are selected based on model prediction accuracy and the overall control performance to determine the effect of addition state measurements. A model is constructed to simulate the building, together with an MPC and an extended Kalman filter for state estimation. These are combined to run the optimization and determine the control performance. The sensor set average of each measured state is considered the true temperature. For all possible sensor combinations, the error of the combination average w.r.t. the true temperature is assumed Gaussian. The fitted Gaussian error distributions are then used as measurement noise in the model. The building and control response is simulated
with the measurement error over multiple days. Two algorithms are implemented to find the optimal sensor set: a predictive method and greedy method. The results are compared to each other and both methods showed that the indoor air temperature measurements have the largest effect on performance. Measuring additional states only resulted in a small increase in performance.