A plan to lay solar panels down railway tracks like a carpet to generate electricity appears to have a number of flaws, the UK's Department for Transport has said.
Transport minister Baroness Vere said the idea, set to be trialled in Switzerland, was "interesting" but that it could be needlessly expensive and interfere with safety inspections.
The idea is being championed by Swiss start-up company Sun-Ways, which wants to install the panels near Buttes station in the west of the country, with a view to extending them to other parts of the network.
News reports about the idea were circulated widely on social media last month, although the company has yet to obtain sign-off from the country's Federal Office of Transport to go ahead with its trial.
But railway planners at the UK's department for transport appear to be less impressed with the proposals.
Responding to a parliamentary question about the technology Baroness Vere said her department had looked into the idea and found that putting the panels in a "safety critical location" like a railway would be "necessarily" more expensive than putting them elsewhere.
There would also be additional costs to maintaining the panels themselves in a "dusty, vibrating environment" like the middle of a live railway, she said.
Network Rail, the UK's infrastructure manager, is also concerned that covering part of the tracks would make visual inspections of the railway harder and so interfere with safety procedures, she revealed.
Sun-Ways co-founder Baptiste Danichert however told the Swissinfo.ch website that the technology could work.
"The biggest challenge is not technological. What is needed is a change of mentality in the railway sector, an area that’s usually not very open to innovation," he said.
His firm is not the only company looking at the idea, with Italy-based Greenrail and the UK-based Bankset Energy also exploring similar installations.
Sun-Ways says its panels are more durable than conventional ones, to take into account their positioning on a live railway. The company has also patented a removal system to make it easier to remove and replace panels as they need it. It has received backing EPFL, the Swiss federal technology institute in the city of Lausanne.
Asked about whether the UK had looked at a similar approach, rail minister Baroness Vere said: "Network Rail has had discussions with the Swiss Federal Railways and is aware of their strategic priorities, broadly aligning with its own.
"The proposed solar panel innovation is interesting, but an initial analysis suggests that the proposal underestimates the challenges of maintaining the solar panels in a dusty, vibrating environment.
"The business case has also not been proven, noting that the deployment of assets in a safety critical location is necessarily more expensive than using land away from the track.
"Finally, Network Rail is concerned that the installation would also conceal track fastenings making it more difficult to safely maintain the railway with Network Rail’s video track inspection system."
She said Network Rail was aiming for 100 per cent of its non-traction electricity to be from renewable sources by 2030 and "has committed to seek to reduce the carbon footprint of traction electricity consumption by directly purchasing renewable electricity from specific new renewable projects".
The minister added: "Network Rail is at an early stage in the process of reviewing options for feeding renewable electricity directly into the traction power supply.
"Through our First of a Kind scheme the Department for Transport has supported various projects looking at feeding renewable electricity into the railway. This includes providing £750,000 to Riding Sunbeams to develop and trial an innovative connection between renewable electricity generation and overhead electrification."
