Bridging the Gap Between Simulation and the Real World An Application to FDD

Energy simulation programs are increasingly used to assess the energy performance of buildings and heating, ventilation, and air conditioning (HVAC) systems during design. Faults during operation can lead to considerable increase in energy use and associated operating costs. In 2009, 13 of the most common energy faults in U.S. commercial buildings were thought to cause wastes of over $3.3 billion per year. Fault detection and diagnosis (FDD) tools can reduce some of these energy wastes. In the buildings industry there is still a disconnect between the design phase, commissioning, and operation. This work presents a process and a tool chain for model-based real-time automated FDD. It facilitates the introduction of FDD in building applications by allowing simulation models from the design stage to be reused during operation. Our tool chain uses models that comply with the Functional Mockup Interface (FMI) standard, a standard developed by 29 partners since 2008 that is supported by more than 40 simulations tools, including Modelica simulation environments and MATLAB. Engineers that use simulation tools compliant with the FMI standard (Blochwitz, 2011) can reuse their models for creating energy-aware FDD algorithms. This work presents and explains the general software architecture and FDD algorithm, which is based on a hybrid of various existing statistical algorithms: Bayesian updating, Unscented Kalman Filtering, and back-smoothing. We also demonstrate the algorithm to analyze simultaneous faults in a chiller plant.