Model-based design, digital delivery, and implementation of HVAC controls — Lessons learned from a building-scale application for AHUs and PLCs

The control logic implemented on building automation systems plays a crucial role for the operational performance of building energy systems. In industry practice, control sequences are developed using static considerations in single operation modes during the design phase, documented in textual and graphical documents, and manually translated in control code by executing contractors. These manual processes are highly work-intensive, and yet the actual performance of HVAC systems falls short of expectations (performance gap). While methods and tools for the model-based design of HVAC controls in Building Performance Simulations (BPS) are already available, the digital implementation of such controls on building controllers is a new feature. This study provides lessons learned from a full-scale, end-to-end application, from model-based HVAC control design to implementation on Programmable Logic Controllers (PLCs, IEC 61131-3). The workflow uses the BPS software IDA ICE and the IEC 61131-10 XML exchange format and is being used to redesign controls for two large air handling units in a factory building in Germany. A comparison of measured and simulated performance (controller, AHUs, thermal zones) for 1 full year in operation is used for performance gap analyses and fault detection. The revised control sequences enabled energy savings of 98 % heat and 62 % electricity compared to the initial operation. The experiences highlight the increased process efficiency of a model-based design-build-operate workflow compared to current industry practice. • Presentation of a toolchain for IEC 61131-3 code simulation using the IDA ICE simulation environment and digital implementation on PLCs using IEC 61131-10 XML. • Full-scale application: model-based control design, implementation, and operation of control sequences for air handling units in a factory building. • Comparison of measured and simulated data for 1 full year of operation confirms as-designed operation and enables fault detection. • Simulation-tested controls enabled savings of 98 % heat and 62 % electricity compared to baseline operation. • Analysis of regulatory framework outlines barriers and opportunities for model-based HVAC control design to improve process efficiency in industrial practice.