Energy-based storage assignment in a multi-aisle warehouse

An order picker performs repetitive tasks, which may result in fatigue, body pain, and injuries. Therefore, it is essential to approach the storage location assignment from an ergonomic standpoint as well. This study presents an energy consumption based optimization model for storage location assignment in an industrial warehouse that stores metal bars. Through a full factorial experiment, we study how product-location parameters like diameter, weight and location height influence time elements like pull and lift/lower time. Using this information, we predict the energy expenditure of pickers for each product-location combination. Then, we formulate an optimization model to decide the storage location assignment that effectively minimizes the total energy expenditure of pickers. The full factorial experiment shows that all the primary factors are significant. Moreover, computational experiments show that storage assignment based on energy optimization is significantly beneficial as compared to distance-based optimization. The energy expenditure decreases with increase in number of vertical levels. The model can predict the energy expenditure of order picker for different warehouse layout designs and help warehouse manager to decide slot height, number of storage locations, blocks and vertical levels. Finally, we derive insights for future research and practical applications based on our findings.