Share of recoverable energy:

Share of recoverable energy heavily depends on speed and stopping pattern.

The following are typical values (referring to total energy demand) for different operation types

Main lines: 15%

Regional lines: 35 %

Suburban lines: 45%

Freight lines: 20%

The recovery rate actually reached in operation only exploits a part of this potential. This is due to several reasons:

• Efficiency of backwards power train: The recoverable energy can never be fully regenerated due to losses in backwards power train. Backwards efficiency is comparable to traction efficiency (~ 80%).
• Receptivity of catenary: The supply system may be „non-receptive“ because no other train is close enough to use it. In 16,7 Hz systems, non-receptive catenary is rare (cf. General criteria – barriers). Due to the 15 kV / 16 2/3 Hz system linked together nation-wide by a 110 kV supply grid, German DB has very good conditions for an effective use of recuperation. As a matter of fact, some experts claim that German trains use regenerative braking exclusively “under normal braking conditions”.
• Braking power: Many times the electric braking power is not sufficient and blended braking (cf. Description) is applied. Especially in freight operation, the electric brakes are usually insufficient for braking the entire train.

There is little (if any) quantitative data on these effects. The following table gives some estimates for 16,7 Hz systems:

Source: IZT

Since modern stock usually has the capacity to recover energy during braking, a big part of this potential is already exploited in today’s railway operation. Nevertheless, some potential is not exploited due to the following reasons:

• Some old electric stock is not equipped with regenerative braking.
• In some vehicles (especially locomotives) the choice of the brake is up to the driver.

The remaining potential is extremely dependent on the situation of an individual railway company but may be up to half of the above values, i.e. ~ 3 - 13%.