Design and experimental evaluation of energy-optimal control of air handling units

In this paper, we study the modeling and optimal control of air handling units (AHUs) that can be operated in different modes (active cooling, economizer, and active heating) to regulate the zone temperature within the desirable range. A simple control oriented model based on mass and energy balances is presented and validated against operational data. The energy-optimal control design for the AHU is decomposed into two layers: a supervisory layer and a local control layer. The supervisory layer determines a mix of setpoints and direct commands whereas the local control layer is responsible for maintaining the provided setpoints. The proposed two layer control architecture results in a robust and scalable architecture suited for practical implementation. An extensive simulation study is performed on a high-fidelity AHU model in EcosimPro (a multidomain modeling and simulation tool) to evaluate the energy saving potential across a wide range of operating conditions. The results show a strong dependency of energy savings on weather conditions, with an average saving potential of 17 % over conventional rule-based solutions. We also discuss the implementation details and the number of sensors required for the reliable implementation of the proposed approach. Finally, we conduct field experiments on a pilot plant to assess the energy saving potential and effectiveness of the proposed control strategy under real world conditions.