GE unveiled a prototype hybrid locomotive at its Ecomagination event in Los Angeles last week. The 4,000 hp locomotive uses a set of sodium nickel chloride (Na-NiCl2) batteries to capture and store energy dissipated during dynamic braking, as well as an on-board fuel optimizer system.
The energy stored in the locomotive batteries will reduce fuel consumption and emissions by as much as 10% compared to most of the freight locomotives in use today. Railroads account for about 2.5% of national fuel usage in the US. In addition to reduced emissions, a hybrid will operate more efficiently in higher altitudes and up steep inclines.Locomotives are electric drive vehicles—the diesel engines function as gensets to power the electric traction motors. Locos use dynamic braking - traction motors ceasing to act as motors and becoming alternators - to decelerate or to maintain speed on a downhill grade. Typically, a resistor is used to dissipate the electric power (about 7,000 hp per locomotive) as heat produced by the electric motor during dynamic braking.
In the hybrid, the energy storage system (ESS) is connected to the main DC link through an electronic converter controlled by an energy management system and associated vehicle system controls. The ESS provides supplemental power to the traction motor along with the power from the genset, and receives power during regenerative braking.
The hybrid battery system for a locomotive has to provide both high energy and high power. GE’s hybrid prototype has a power/energy (P/E) ratio of about two. By contrast, the Toyota Camry hybrid has a P/E ratio of 19, the GE/Orion V prototype hybrid transit bus a P/E ratio of about five, and the Sprinter plug-in hybrid prototype with SAFT Li-ion batteries a P/E ratio of about seven, according to GE.
Before the GE hybrid locomotive is offered commercially, the engineering team will continue work and analysis on the batteries and control systems on-board the locomotive. Following lab testing, GE will produce pre-production units for customer field trials.
:: GE, Green Car Congress