Electric motor as practical addition to diesel engine
Alongside constant improvement of the diesel engine, development of alternative drive concepts for trucks and buses is a main thrust of the R&D activities of MAN Nutzfahrzeuge. The aim of these concepts is to cut pollutant/CO2 emissions and noise to a minimum and to achieve as sparing a use of fuels as possible.
In city buses with conventional drive systems almost one-third of the energy used for braking is converted into heat and goes unused. With a suitable storage system this brake energy could be saved and used again for the next acceleration.
On the way to a concept that combines minimum emissions with maximum economy MAN has developed diesel-hybrid drive. For this the diesel-electric drive concept has been combined with a high-performance electric storage unit. Integrated energy management controls the energy flows between storage unit and drive system. This leads to efficient system behaviour with a significant reduction in fuel consumption.
Another major advantage for local residents and passengers is that the bus leaves the bus-stop electrically, i.e. without annoying emissions (noise, exhaust gas).
The brake energy storage units used are the latest ultracapacitors (ultracaps). These have a much higher power density than other storage systems such as batteries or flywheels. Their ability to absorb power and their efficiency are higher too. In addition to all this they are reliable and easy to maintain.
