In principle, there are two energy efficiency effects obtainable through energy storage in diesel-electric vehicles:

• recovery and reuse of brake energy
• demand equalizing in order to operate diesel engine only at the operation point of highest efficiency

Various simulations of brake energy recovery on diesel-electric vehicles exist giving a quite heterogeneous picture. Anything between 10 and 35 % saving potential can be found in literature.

It is estimated that a saving potential between 10 and 15 % for regional service and up to 30 % for DMUs in some suburban networks with very frequent stops could be realistic.

DB Simulations of LIREX

The Research Center of Deutsche Bahn AG carried out simulations of the operation of the LIREX with energy storage, showing an energy saving potential of about 11% for a vehicle with storage fly-wheels compared with a similar vehicle without storage fly-wheels. As can be expected, the simulations showed that the use of storage flywheels in vehicles produced the greatest saving effects on routes with short distances between stops.

The simulation was carried out for the German line Magdeburg - Halberstadt - Thale having a total length of 87 km and 8 stations. It was based on operating mode 1 ("reduction of the fuel consumption by recovering the braking energy", cf. table 1). The simulations allowed for the power losses of the storage flywheel as well as the maximum available coefficient of adhesion between wheel and rail. The optimum driving style was assumed.

DB Simulations of Shunting Locomotive

Earlier calculations by the DB environmental center simulating a shunting locomotive with brake energy recovery yielded 14%. If in addition, an idle speed cut-off and fuel supply cut-off during slow down phases are assumed, energy consumption can be reduced by up to 35% compared to a reference vehicle.

Other estimates

Hentschel, Müller et al. (DaimlerChrysler / Adtranz) give a saving potential of 35 % for a suburban DMU. Even if this is too optimistic in a practical context, it hints at the huge theoretical saving potential offered by energy storage in diesel-electric vehicles.