Optimal exergy control of building HVAC system

Exergy or availability is an accurate metric related to quality of energy and it is used to determine sustainability of an energy system. Exergy has been extensively used to evaluate efficiency of energy systems and energy conversion processes. An exergy model for a building is presented in this study. In this paper, exergy destruction, which indicates the loss of work potential, is formulated as a function of physical parameters of the building model and environment. To minimize exergy destruction in an Heating, Ventilation and Air-Conditioning (HVAC) system, we develop model predictive control (MPC) technique using the exergy model. Comparing to a traditional on-off controller for the building, the proposed exergy-based MPC (XMPC) reduces the exergy destruction and energy consumption up to 22% and 36%, respectively. Simulation results also indicate the advantage of XMPC over conventional energy-based MPC (EMPC). The results show that XMPC reduces exergy destruction by 4% compared to EMPC as well as saving 12% more energy.