Railway electrification and wireless power
Overhead wires and third rails for trains, and power sent without wires.
Transport · Electricity · No. 54
- Transport
- Form: Electricity
In 2025 a DARPA laser beamed over 800 W of power across 8.6 km of open air, with no wires at all.
Chart: Illustration: Railway electrification and wireless power
Where it comes from
Chart: Map of where it comes from
Substations along the track take grid power and feed it to an overhead wire or third rail. A pantograph presses against the wire, so an electric train never carries fuel.
Three things to know
- Optimised timetables let a metro reuse 95.5% of its braking energy, against 80.6% in normal running, in one modelled case.
- Some UK electrification schemes cost GBP 2-2.5 million per single-track km, against GBP 350,000-450,000 for overhead-line work in Switzerland and Germany.
- A battery swap takes about five minutes, but a swap station costs about 15 times as much as a fast charger.
The journey
- 1 GridFeeds traction substations along the line
- 2 SubstationSupplies the track, often 25 kV AC
- 3 Wire or railCatenary or third rail carries current
- 4 PantographRoof collector feeds the traction motors
- 5 BrakingMotors return energy to the line