A life cycle assessment-based multi-objective optimization of the purchased, solar, and wind energy for the grocery, perishables, and general merchandise multi-facility distribution center network

Abstract

Walmart Inc., the U.S. and world’s largest grocery retailer, owns a perishables, grocery, and general merchandise distribution center network, which stores and distributes refrigerated and non-refrigerated food. Finding cost-effective strategies to implement solar and wind-powered electricity in their distribution centers was the central objective of this research. The study analyzed the tradeoffs and effects on costs and climate change impact related to the increase of renewable energy use in the distribution centers. The research combined the life cycle assessment and quantitative methods including the Monte Carlo uncertainty analysis and the multi-objective optimization. A life cycle assessment-based multi-objective optimization model was built to find cost-effective strategies to minimize fossil energy use and mitigate the impact of the Walmart Inc. distribution center network on climate change. The bi-objective and the triple-objective optimization included a number of combinations of minimal costs, non-renewable fossil energy use, and climate change impact criteria. The results of the multi-objective optimizations were Pareto-optimal solutions obtained by weighing the importance of chosen criteria from the baseline to the zero energy scenarios. A selection of the Pareto-optimal solutions included the good, the better, and the zero energy building scenarios. A better building was a Pareto-optimal set of buildings, which demonstrated superiority from the life cycle assessment perspective. The superiority of Pareto-optimal solutions was evaluated using the Monte Carlo pairwise comparison. The good distribution centers were characterized by the Pareto-optimal solutions between the baseline and the better distribution centers. Finally, the zero energy general merchandise distribution centers were mostly the Pareto-optimal solutions with a 100% share of solar energy. For the zero energy grocery and perishables distribution centers the solutions were a combination of solar and supplemental wind energy because refrigerated warehouses are more energy intensive. The study provided the benchmark results that may improve distribution centers and other buildings and a framework to test environmental and renewable energy policies in buildings.