Maintenance plan optimization in building retrofitting with interacting energy efficiency effects

This paper discusses a maintenance plan optimization problem for a building energy efficiency retrofitting project in which interactions exist among energy subsystems. The interactions between lighting and air conditioning systems are investigated. The coupled energy and reliability performances of a group of lighting units and a group of air conditioners, where items from the same group reveal similar energy and reliability performances, is modelled. The population and performance dynamics of the two groups is then formulated as a state-space model with coupled non-linear equations. Thereafter, the maintenance plan optimization problem is cast into an optimal control problem. The control objective is to maximize the overall energy savings and financial payback of the retrofitting project during a finite time period. Simulation results of a case study illustrate the effectiveness of the proposed approach.