Mehlman explains that batteries will take you typically half a mile to a mile and a half, which is farther than a super capacitor, but they are not quickly rechargeable.
“It’s typically a situation where you need a little more partial autonomy than a super capacitor to get across a little bit longer distance, maybe more than half a mile, but you’re not going to be able to recharge them so you’re going to have to be able to get back to a catenary or to an off-wire power to recharge them gradually to the rest of the network,” he says.
There have been some recent developments in batteries that allow even more autonomy, typically 20 to 30 kilowatt hours of power stored, which would allow you to reach two or three miles running on the battery, Mehlman says. At this time Alstom hasn’t developed a solution using this technology.
Of course all of these solutions come with an extra cost on the vehicle. “We think there’s a limit on what the extra cost on the vehicles of all these solutions should be. It’s basically if that extra cost significantly exceeds what the catenary cost would be for the system, then basically your hybrid propulsion system is not any more competitive,” Mehlman says.
He adds “You have to be careful that when you equip 20 tramways on a five-mile line with hybrid propulsion, if the cost equipping that hybrid propulsion is more than the cost of the catenaries that you would have to install on those trenches where you want the autonomy, then you’re tipping over on the wrong side. Your hybrid propulsion is becoming noncompetitive to installing catenaries even in areas where it’s difficult.”
“We have the catenary system to take electrical energy from. We call it dual power but some people also call it hybrid because it’s for the end customer; it’s not a big difference. It’s driving electric without any emissions; I think that is the key,” says Roman Porta, senior project manager for Bombardier.
Bombardier’s ALP-45DP locomotives have two power sources. One power source is the two diesel engines on the locomotive and the second source is electrical power from the catenary.
“The key point of that locomotive is the so called one-seat rides. So a typical scenario is if you start somewhere outside of a big city on a diesel locomotive, and then at a certain point or certain station from then on you have catenary and the engineer or operator just has to press a button and then it takes about two minutes until the locomotive changes the mode from diesel power to electric power or vice a versa,” explains Porta.
NJ Transit and Agence Metropolitaine de Transport (AMT) in Montreal have ordered these dual-powered locomotives. Because the DP locomotive is used in push-pull operation with double-deck coaches, it also has a pantograph and driver’s cab. Toenable “one-seat rides” — in other words travelling without changing trains —and to take passengers to their destination quickly, the ALP-45DP can reach a maximum speed of 160 km/h in diesel operation and maximum 201 km/h in electric operation.
With this type of technology, passengers are not aware of when the power source is switched. The cars have a full energy supply through the process. They may notice a slightly longer stop at a station. “Normally a stop is around 30 seconds and we need two minutes, but everything else is done from the locomotive,” Porta says.
According to Porta, this is the first locomotive that can travel under two systems, but for both systems it’s a full locomotive. “So it’s a full electric locomotive and a full diesel locomotive. We have regular electric locomotive as well as a regular diesel locomotive combined in one car body and the weight limits for North America,” Porta explains. “This is really a new product and it is possible because of our development of other components so everything went smaller and lighter and now it’s the first time the size and the weight was low enough that we could integrate that into one locomotive.”
Porta says, “When I look to North America or also to Europe I think environment will be very important in the future and to drive an electric system is the friendliest solution.”