Energy-conscious flow shop scheduling under time-of-use electricity tariffs

A time-indexed integer programming formulation is developed and used to identify manufacturing schedules that minimize electricity cost and the carbon footprint under time-of-use tariffs without compromising production throughput. The approach is demonstrated using a flow shop with 8 process steps operating on a typical summer day. Results suggest that shifting electricity usage from on-peak hours to mid-peak hours or off-peak hours, while reducing electricity cost may increase CO2 emissions in regions where the grid base load is met with electricity from coal-fired power plants. The trade-off between minimizing electricity cost and reducing CO2 emissions is shown via a Pareto frontier.