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If you live south of London, chances are your train journey could soon be powered by solar energy. Well, sort of.

New research by Imperial College and green energy charity 10:10, has found that solar energy could supply ten per cent of the power needed to fuel the UK's DC-powered rail routes.


The report argues that this can be achieved at a cheaper rate than if the network were fuelled by normal electricity supplies as solar would bypass the national grid and avoid subsidiary costs.

According to the Riding Sunbeams report, 15 per cent of the train networks across Kent, East Sussex and West Sussex could be powered by track-connected solar PV arrays.

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On top of this, six per cent of the London Underground’s energy demand could also be supplied by solar-power. This is about half of the electricity used on the Piccadilly line. In the north of England, 20 per cent of the Merseyrail network in Liverpool could also be solar-powered. Rail networks closer to the equator could be completely supplied by solar PV arrays, the report explains.

"This study has concentrated on confirming that the power from a typical solar farm site could be matched with the patterns of train energy use," says Nathaniel Bottrell, an overseer of the project and a researcher at Imperial College. "The good news is that this is technically feasible and economically attractive."


By using direct current (DC) rail systems, the solar energy, which is also DC, would not need to be converted to and from alternating current (AC) systems, saving an estimated £4.5 million per year. "It just so happens that solar rays produce direct current (DC) electricity," says Leo Murray, director of 10:10. The railway needs 750 vaults of DC electricity, and solar comes in at between 600 and 800. "This is a very happy coincidence that solar energy produces the same type and same voltage the trains need," Murray says.

Riding Sunbeams

DC railway networks were some of the first to be built in the UK and have since been replaced with safer AC networks. In AC networks, the electricity cables are above the train rather than near the track, making them less dangerous. However, the compatibility of DC lines with solar rays means the study by Imperial College and 10:10 only focuses on DC traction networks for solar energy expansion.

"The fall in the cost of storage now make this proposal economically feasible," Bottrell says. Advances in storage technology mean that there is no energy waste from the solar rays. "There could be times when there is power available from the solar panels but no train close by to use it," adds Bottrell, as often the flow of energy has to be constant. This is solved by including a battery to store the energy and support the rail network during the evening or following the morning rush-hour.

"All of this equipment must be compatible with the railway systems, notably it must pass tests to prove it does not interfere with the things like the signalling system," says Bottrell. However, the report predicts these tests could be approved and effectively implemented in two to three years.



"There may not be a business case for implementing storage systems in the first place," Murray says. But installing storage systems down the network rail lines could be costly and will be something Network Rail needs to look into, he adds.


Phillip Thies, a senior lecturer of renewable energy at Exeter University agrees that business negotiations may prove the biggest complication for the idea. "The proposed method is to install them on land close to the power substations. This may have practical implications regarding availability of land and planning permits for large-scale solar arrays," he says. Nevertheless, he says the research provides a robust basis to explore potential investment in more detail.

However, in terms of vision, the UK may already be falling behind. India has the most ambitious target for implementing a solar-powered network, hoping to make 100 gigawatts of energy from solar PV generating capacity by 2022. "We have also seen news of something a bit similar in the Netherlands where the Dutch rail network is being powered by 100 per cent renewable energy," says Tim Green, director of the Energy Futures Lab at Imperial College London and lead on this project.

While the UK remains small-scale in vision, ultimately such proposals could be more significant for proving the economic advantages of solar. "It unlocks direct access to a major purchaser of energy in a way which enables subsidy-free solar energy to expand," Green says.