The regenerative brake or recuperation brake is a method to kinetic energy into storable electrical energy to convert, and make the vehicle slow down thereby. It is used z. B. in electric locomotives , railcars , trolleybuses , conveyor belts in mining and cable cars , in particular Erztransport- and material ropeways , electric cars , hybrid electric motor vehicles and passenger cars with Nitro-power storage and electric bicycles .
The regenerative brake works like any electrodynamic brake without wear. The braking effect is achieved by operating the traction motors as electrical generators . Such a regenerative brake is a special form of the electromotive brake . In contrast to the pure resistance brake from being kinetic energy regenerated electric energy is not converted into braking resistors into heat at the regenerative braking, but either in the drive transmission system fed back, or in a memory in the vehicle, such as a battery or supercapacitor , is stored. The braking effect in generator mode is limited according to the drive power of the motor.
Even in the early days of the electric railways, some locomotives were equipped with regenerative brakes, for example the SBB Ce 6/8 "Crocodile". When braking, the traction motors are switched to generators. In conventional AC locomotives and multiple units, the electricity produced is fed back to the transformer via complex circuits and fed into the catenary. With this technology, it was initially only possible to recover around five percent of the energy used, and the braking force was also weak and irregular.
Modern vehicles equipped with traction converters can make better use of braking energy. The locomotive's traction motors feed the converters with three-phase current . These in turn convert the energy into alternating current, which is stepped up and fed into the contact line. This circuit works in the entire speed range up to the full power of the traction motors and allows the recovery of around 25 to 30 percent of the energy required for the drive. Modern systems can recover up to 40% of the energy required for acceleration.
With three-phase railway systems, especially the northern Italian network from around 1902 to 1976, but also some mountain railways such as the Gornergratbahn near Zermatt , significantly higher feedback gains (around 50%) were achieved with a very reliable braking force with simple asynchronous motors (see history of the electric drive of rail vehicles ( Italy) ).
AC overhead line networks can normally always absorb the electricity produced by traction vehicles, as they can be fed back and the electricity can be used in the entire traction current network (only in the event of massive further disruptions, overloads and thus a power failure can occur, for example in Switzerland on June 22, 2005). If they are not capable of being fed back into the national grid, direct current grids are only capable of receiving them to a limited extent; the fed-in electricity can then only be used locally. If there is no consumer, for example a vehicle driving uphill, in the same feed section, braking current cannot be fed in either. Otherwise the overhead line voltage would rise in an impermissible manner. In order to enable intermediate storage of electrical energy in direct current networks, there are experiments, for example, with flywheels (Hanover tram network) or supercapacitors ( Warsaw tram ). Modern direct current and direct current capable multi-system locomotives have braking resistors so that the wear-free electric brakes can also be used in situations in which the electrical energy cannot be fed back.
Tram trains can be equipped with capacitors ( double-layer capacitors ) that store the braking energy on board so that it can be used the next time the train starts. There is also the option of setting up capacitor stations on the lines in order to be able to absorb the energy.
Cars with electric , hybrid or gyro drives are usually capable of regenerative braking. They feed braking energy back into their accumulators, into accumulators buffering supercapacitors or into a flywheel.
Also, electric bikes are isolated for regenerative braking capable.
In 2007, BMW launched the Efficient Dynamics u. a. introduced braking energy recovery for many of its gasoline and diesel vehicles. This is not a matter of recovery in the strict sense of the word, rather the on-board battery is charged, as far as possible, only when the vehicle is overrun ( engine brake ). This reduces the energy consumption of the generator and thus the fuel consumption when traveling.
In the Formula 1 is since the 2009 season, a variant of regenerative braking, the so-called kinetic energy recovery system used. Porsche has in racing cars GT3 R Hybrid (2010) 911 incorporates a regenerative braking in which the recovered energy in a flywheel accumulator is fed.
- Hans Streiff: Recovery of braking energy in rail transport (Part I) ( Memento from February 13, 2005 in the Internet Archive ) and (Part II). ( Memento from February 20, 2005 in the Internet Archive ) In: Homepage of the Swiss Railway Amateur Club Zurich (SEAK) , 1999.
- M. Khodaparastan, A. Mohamed: A study on super capacitor wayside connection for energy recuperation in electric rail systems . In: 2017 IEEE Power Energy Society General Meeting . July 2017, p. 1-5 , doi : 10.1109 / pesgm.2017.8273915 ( ieee.org [accessed February 15, 2018]).
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