The first prototype of the new hybrid-electric locomotive is expected to be delivered in late 2023. Credit: Union Pacific.

US-based Union Pacific Railroad has struck a partnership with green technology firm ZTR for the development of new hybrid-electric locomotives.

The first prototype is scheduled for delivery by the end of next year.

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Five additional hybrid-electric locomotives are anticipated to be delivered in 2024.

These locomotives, which will work similarly to a plug-in hybrid car, can operate in multiple modes with various ways to charge the locomotive batteries such as wayside and onboard charging.

Union Pacific will replace one diesel locomotive, connected to an accessory or slug, with two locomotives, which are known as ‘mother-slug’ sets.

The slug unit will be transformed and installed with batteries, power electronics, and controls provided by ZTR.

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It will enable the hybrid-electric ‘mother-slug’ to run in single engine, battery charging, or electric-only modes.

The engineless slug helps increase traction motors available to the locomotive, as the new locomotives will be mainly used for yard operations.

Union Pacific started using ‘mother-slug’ sets with ZTR’s Nexsys control systems in 2017.

The new locomotives will be constructed at Union Pacific’s North Little Rock facility in Arkansas.

Union Pacific engineering and mechanical senior vice president Shane Keller said: “Adding hybrid-electric locomotives to our fleet is another important step for Union Pacific as we work to explore ‘drop-in’ technologies that modify current systems and reduce our carbon footprint.

“This pilot will help make our fleet more fuel efficient and further advance our commitment to reaching our sustainability goals, while testing the technology’s capability for expanded use across our locomotive fleet.”

Last month, Union Pacific launched a $600m green bond offering to facilitate investments for supporting decarbonisation.

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