Allocation of Energy Consumption in a Contracted Manufacturing Company with a Flexible Job Shop Environment

Abstract

This paper researches the problem of allocating energy consumption in a contracted manufacturing company. The company accepts customers' manufacturing orders and generates a production schedule that minimizes the total energy consumption composed of processing, idle, and common energy consumption. The production environment is a flexible job shop, and each customer requests to fulfill the due date. A mixed-integer linear programming model developed explores the optimal solution that minimizes the total energy consumption while satisfying the due date constraint. As customers are sensitive to the energy consumption caused by their products' production, allocation of energy consumption among customers becomes a research issue. Among three components, the common energy consumption requires further study. The present study proposes three methods: proportional allocation, Shapley value, and unit time allocation. Numerical experiments were implemented under the condition of three customers, ten jobs, and seven machines. Results indicate that each method produced different allocations among customers. Proportional allocation roughly follows the solution of local optimization that considers each customer separately. Shapley value realized the same allocation between two customers with the same set of jobs. Unit time allocation depends on the schedule generated. It is not easy to estimate the allocation from the solution of local optimization under Shapley value and unit time allocation. The present study suggests adopting the most suitable allocation method based on these characteristics.