Machine and production scheduling under electricity time varying prices

This paper presents two new mathematical models to reduce total energy consumption cost of a single machine manufacturing system. The problem consists of optimizing simultaneously the processing of the jobs and utilization of the machine, each machines state has its own energy consumption and the production shift is composed of a fix number of periods with different energy cost. The first model is an improved formulation of Shrouf et al. (2014) problem that considers a predetermined jobs sequence. Whereas, the second model studies production scheduling on machine and job levels, which proposes an optimal sequence for them by minimizing the occurrence number of each machines state, the optimal allocation of these states during the periods with less energy costs and jobs within the processing state. Finally, difference between these models are discussed based on several numerical examples.