Could UK trains be powered directly by solar energy? A recent report, Riding Sunbeams, suggests that up to 10% of the energy needed for the UK’s DC-powered routes could be provided by solar PV. Researchers calculated that using DC solar power rather than converting AC power from the grid could save rail companies £4.5m per year, according to Wired.
What is the proposal?
The report looks at the feasibility of connecting solar PV directly to electrified railways, bypassing the grid. The proposal is that small solar farms could be built alongside electrified rail tracks, providing around 10% of the electricity needed to power trains on those routes each year.
What are the benefits?
Even without public subsidy, the electricity produced by solar PV would be cheaper than grid-supplied electricity, based on current prices. Cost trends indicate that savings would only increase in future.
Electric trains run on 750V of DC electricity, while it is a happy coincidence that solar PV produces DC of between 600V and 800V and the peak generation tends to match peak train demand. The solar PV could be developed on land such as car park and train depot roofs, wasteland and similar sites alongside the rail track.
Using small-scale solar generation also chimes with the regularity of substations on track using DC supply; these tend to be every 3 kilomet whereas AC substations can be every 80km. Supply by private wire from solar farms is effective over distances of up to 2km, according to the Engineer.
What are the challenges?
There are some technical challenges that would have to be overcome in order for the concept to work effectively. In many areas, ‘third rail’ DC networks have been replaced with overhead AC networks, partly to improve safety. This means that the solar solution is only likely to be economically viable in areas retaining a DC supply, which tend to be urban areas where bridges and tunnels make overhead cables less practical.
Engineers would also need to find a way to make the solar power compatible with railway technology, including regenerative braking systems, the transmission of information through the third rail and managing how and when solar power is sent.
Scope for expansion
Internationally, the technology could prove valuable in sunny places around the equator, such as Asia, Latin America and the Middle East. In India, a booming railway sector could work hand-in-hand with a growing solar power industry to harness solar PV. Via a grid connection, 90% of the Delhi Metro is already powered by solar.
But the report also focuses on how solar PV could contribute to trains in the south of England, where it is claimed that 15% of commuter routes in Kent, Sussex and here in the South West could be powered in this way. This is certainly a story we’ll be keeping an eye on here at Zestec in Dorset – are solar-powered trains something you’d like to see?