Sensitivity of Potential Battery Electric Locomotive Energy Benefits to Freight Railway Operating Characteristics and Charging Strategies

Freight railroads are exploring alternative energy technologies such as battery electric locomotives (BELs). A BEL produces tractive effort from electricity stored in onboard batteries that are recharged at terminal stations, through regenerative braking, or both. To aid railroads in identifying the types of routes and train services benefiting most from BEL implementation, this paper investigates the sensitivity of BEL energy benefits to various parameters across multiple rail corridors. A simplified train energy model was developed to quantify BEL performance on four rail corridors in the United States. For each route, diesel energy consumption of conventional diesel-electric locomotives was compared with diesel consists supplemented with one BEL across a range of train weights, railcar resistances, battery efficiency, and battery capacity using the simplified model and a comprehensive train performance simulator. Both approaches indicated that BELs can achieve diesel savings from 0% to 40% depending on grade profile and terminal charging availability. Energy savings were more sensitive to changes in battery efficiency and train mass than to changes in train rolling resistance and battery capacity. Additional analysis of terminal charging strategies and charger power rates revealed a trade-off between battery size, charge rate, and life-cycle benefits. Although general trends were observed, BEL energy savings were highly variable between routes and should be analyzed on a case-by-case basis. Similarly, BEL implementations must carefully match battery capacity and charging strategy to operational needs instead of standardization across all routes. Further, favorable BEL implementation strategies were sensitive to technology pricing based on battery and charger development.