A hybrid train is a locomotive, railcar or train that uses an onboard rechargeable energy storage system (RESS), placed between the power source (often a diesel engineprime mover) and the traction transmission system connected to the wheels. Since most diesel locomotives are diesel-electric, they have all the components of a series hybrid transmission except the storage battery, making this a relatively simple prospect.
Diesel electric locomotives may have most of what they need for regenerative braking since they might already use dynamic braking. This uses the traction motors as generators to absorb much of the train's energy, but without a way to store the generated electricity it is simply dumped into the atmosphere as heat with large rooftop resistor banks and cooling fans.
Using a storage system means that a non-fully electric train can use regenerative (as opposed to merely dynamic) braking, and even shut down the main power source whilst idling or stationary. Reducing energy consumption provides environmental benefits and economic savings. A smaller scale version of the concept is found in hybrid automobiles, such as the chevy volt.
In 1986, Czechoslovak locomotive manufacturer ČKD built a prototype hybrid shunting locomotive termed the DA 600. The locomotive was powered a 190-kW diesel engine and four electric motors, with a maximum overall power 360 kW powered from batteries. The batteries were recharged while the diesel engine was running, by regenerative braking or from external electric power.
After tests on the Railway test circuit Velim and some minor tweaks, the locomotive was lent to the Olomouc train depot and successfully operated there for ten years. Czechoslovak socialist economics failed to start mass production, mainly because of a lack of proper battery manufacturing capacities.
In May 2003, JR East started test runs using an "NE Train" ("New Energy") railcar, testing the system performance in cold regions.
The design had two 65-kilowatt fuel cells and six hydrogen tanks under the floor, with a lithium-ion battery on the roof. The test train was capable of 100 kilometres per hour (60 mph) with a range of 50–100 kilometres (30–60 mi) between hydrogen refills. Research was underway into the use of regenerative braking to recharge the test train's batteries, intending to increase the range further. JR had stated that it hoped to introduce the train into scheduled local service during the summer of 2007. Technology tested on this train was incorporated in the KiHa E200 diesel/battery railcars entering service in 2007.
During 2007, a modified Class 43 power car ran on the Great Central Railway and then as part of the Network Rail New Measurement Train (a 200-kilometre per hour track-recording train). The Hitachi developed system used a battery-assisted diesel-electric drive system; the hope being that it would demonstrate a cut in emissions by up to 50 percent and a reduction in fuel consumption costs of 20 percent. The modified locomotive, named Hayabusa, was semi-permanently attached to a converted passenger carriage containing the battery bank during the testing period.
In February 2009, it was announced that Hitachi, as preferred contractors for the Intercity Express Programme (IEP) would deploy hybrid technology on the self-powered variants of the IEP trains. These trains would be capable of 200 kilometres per hour. Some hybrid-trains would also be bi-modal, allowing power to be taken from overhead lines.
These diesel-electric hybrid trains are expected to cut emissions by up to 90 percent and to decrease fuel consumption by up to sixty percent, when compared to conventional diesel-powered locomotives. The "Green Goat" locomotives were intended to be used in marshalling yards.