Electric trains could provide a huge guaranteed market for renewables, but it will need some railway-specific power equipment. A British solar power company is working on technology that could enable railways all over the world to be powered by renewable energy.
Riding Sunbeams is the company behind a project of the same name that is already delivering power to trains on Network Rail’s Wessex route, which uses third-rail electrification, and in June 2020 it secured funding to develop equipment for the far more common overhead power lines. Both projects are supported by the Department for Transport’s ‘First Of A Kind’ (FOAK) scheme to boost innovation in rail, and the firm also hopes to have a role in electrifying the South Wales Metro.
Alex Byford, chief technology officer at Riding Sunbeams, explains that the initial Wessex route installation at Aldershot is quite small, at 37kW, but it “enables us to prove to Network Rail’s product assurance and safety teams that renewables could be integrated without causing any issues with the rail network”. A data logger at the site is gathering information about power quality, to ensure that the equipment will neither cause problems nor itself be damaged as a result of being connected to “quite a dirty supply” that suffers from harmonics, reactive power and voltage fluctuations.
The Wessex line operates at 750V DC, so it’s surprising to learn that the solar installation uses inverters to convert its DC output to AC. Byford says this is because Network Rail supplies the line from its own private distribution network at 33kV AC. Plugging directly into that enables the use of the same off-the-shelf inverters that are used by other solar sites to feed into the grid. It’s those inverters that are now going through the railway approval process.
Most of Britain’s electrified railway network uses overhead power lines at 25kV AC. The new Daybreak project will develop a power conversion device to meet this requirement. It’s needed because the railway’s electricity supply is single-phase, unlike the three-phase national power networks. Byford explains why this matters: “Single-phase electricity is normally used in domestic installations at 240V, whereas this is at 25kV, so the issue is that no equipment has really been designed to change the output of the renewables to that single-phase electricity.” As well as the lack of power conversion equipment at the right size and price, there’s also the challenge of operating in a railway environment.