Union Pacific Railroad and ZTR, a green technology company, announced a partnership to build hybrid-electric locomotives.
The locomotives will be built at Union Pacific’s North Little Rock, Arkansas, facility. The first prototype is expected to be delivered in late 2023, and five additional units are expected to arrive in 2024.
The locomotives work much like a plug-in hybrid car. They can operate in multiple modes with several ways to charge the locomotive batteries, including wayside and onboard charging.
Known as “mother-slug” sets, two locomotives are replaced with one diesel locomotive connected to an accessory or slug. In keeping with its sustainability commitments, Union Pacific converts older locomotives, typically with higher emissions.
The slug unit will be converted and equipped with batteries, power electronics and controls supplied by ZTR. This helps achieve fuel and maintenance savings and offers environmental benefits allowing the hybrid-electric “mother-slug” to operate in single engine, battery charging or electric-only modes.
As the new locomotives will be used chiefly for yard operations, the engineless slug increases traction motors available to the locomotive, boosting the pulling and braking power that is key for this work.
Union Pacific began rolling out “mother-slug” sets with ZTR’s Nexsys control systems in 2017. They currently operate in more than 65 yards systemwide.
Depending on the mode of operation, fuel savings and greenhouse gas emission reductions could total up to 80 percent.