# Regenerative braking and motion recovery: Engineering and integration

Catching power pulses that last just seconds

Source page: https://www.materialinsights.org/energy/e_regen_braking/rc-eng/

What this tab covers Engineering and operating integration: how tightly it is coupled to the host process, how steady the waste stream is, and how hard it is to retrofit.

Recovery is part of the drive or vehicle, so coupling risk is low. The real engineering problem is matching very short, spiky power pulses to a load or a store.

#### Process interdependence (coupling risk)
Favourable

If regeneration fails, friction brakes or braking resistors take over, so service continues. On DC metros and tramways the challenge is receptivity. Braking energy can only be reused if another train is drawing power nearby at that moment. Otherwise it is burnt in on-board resistors. Reversible substations solve this by sending the surplus back to the AC grid. Alstom says this also lets a new line be built with 20% fewer substations.^[3](https://www.alstom.com/press-releases-news/2025/6/capturing-wasted-energy-our-cities)
 Fewer substations on new line with Hesop 20%^[3](https://www.alstom.com/press-releases-news/2025/6/capturing-wasted-energy-our-cities)

#### Load factor and intermittency
Mixed

Braking pulses last seconds. A typical RTG lift lasts about 20 s, and the crane makes one move every 83 s on average. On a typical day an RTG drew 711 to 823 kWh, of which about 313 kWh on average was recoverable. Usefulness depends on duty. Busy metros, stop-start buses, high-rise lifts and port cranes gain most. Intercity trains and motorway driving gain least. Deutsche Bahn reports more than 1,500 GWh fed back into the grid as of the end of 2025, without saying over what period.^[2](https://www.deutschebahn.com/en/sustainability/measures/brake-energy-recovery)^[5](https://e-space.mmu.ac.uk/620872/9/Manuscript.word.pdf)
 RTG recoverable energy per day about 313 kWh^[5](https://e-space.mmu.ac.uk/620872/9/Manuscript.word.pdf) RTG share recoverable 50-57% on typical days^[5](https://e-space.mmu.ac.uk/620872/9/Manuscript.word.pdf) Deutsche Bahn energy fed back more than 1,500 GWh (reported end 2025; period not stated)^[2](https://www.deutschebahn.com/en/sustainability/measures/brake-energy-recovery)

#### Footprint and retrofit complexity
Favourable

In new EVs, trains and lifts regeneration is nearly free because the inverter can already run both ways. Retrofits cost more. Lifts need a regenerative drive in place of the resistor drive. Diesel RTG cranes need a battery, supercapacitor or flywheel because they have no grid to send power to. Metros need reversible substations. Gyrodrive was designed as a retrofit. In 2014 Go-Ahead ordered 500 units for London buses, to be fitted over two years.^[6](https://imeche.org/news/news-article/from-fast-lane-to-bus-lane)
 Gyrodrive order 500 systems for London buses (2014)^[6](https://imeche.org/news/news-article/from-fast-lane-to-bus-lane)

#### Sources

1. [Electricity is recycled at DB (brake energy recovery)](https://www.deutschebahn.com/en/sustainability/measures/brake-energy-recovery) Deutsche Bahn, 2026
2. [Capturing wasted energy in our cities (Hesop reversible substations) (company press release)](https://www.alstom.com/press-releases-news/2025/6/capturing-wasted-energy-our-cities) Alstom, 2025
3. [Analysis of energy usage for RTG cranes (Papaioannou et al.), Energy 125, accepted manuscript](https://e-space.mmu.ac.uk/620872/9/Manuscript.word.pdf) Elsevier (repository copy, Manchester Metropolitan University), 2017
4. [From fast lane to bus lane (GKN Gyrodrive order by Go-Ahead)](https://imeche.org/news/news-article/from-fast-lane-to-bus-lane) Institution of Mechanical Engineers, 2014

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_regen_braking/index.md)
- [Overview](https://www.materialinsights.org/energy/e_regen_braking/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_regen_braking/correlation/index.md)
- [Science and thermodynamics](https://www.materialinsights.org/energy/e_regen_braking/rc-sci/index.md)
- [Economics and contracts](https://www.materialinsights.org/energy/e_regen_braking/rc-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_regen_braking/rc-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_regen_braking/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_regen_braking/links/index.md)