The UK has been searching for ways to directly supply the railway system through solar energy since some of the UK’s railway systems run on direct current (DC), which solar modules produce. Thus, there is no need to convert solar energy into alternating current. Now the pilot scheme of connecting solar power directly to rail networks has been launched. The researchers behind the project are hopeful that the technology could also be deployed in Liverpool, Manchester, and Glasgow.
The scheme is a collaboration between 10:10 Climate Action, a charity group, and Imperial College London, exploring the direct supply of solar energy to the railway since 2017. A social enterprise, Riding Sunbeams, has been launched, in the hopes of directly powering the electric traction system of the railway without first converting the power into an alternating current by inverters or a power grid.
Most of the earlier railways in the UK run on DC, while modern railways on AC, which is safer. Unlike DC cables, which are near the tracks, the cables of the AC railways were located above the trains. Hence, the risk is lower. However, only the DC-powered railway system can be supplied by solar energy directly.
Leo Murray, the project leader, explained that the voltage generated by solar energy is consistent with the voltage of the DC rail system, where the DC rail system voltage is 750 volts and the solar voltage is between 600 and 800 volts. Hence, the power supply can be directly supplied to the railway system, bypassing the electricity grid. Other than avoiding energy loss, the costs can also be reduced.
The researchers pointed out that the new scheme will not only reduce the cost of power transmission, but also reduce the energy loss of current caused by power transmission via the electricity grid. The previous research also pointed out that 10% of the energy required for powering UK’s DC-electrified railway networks could be provided by the solar traction power, which can save £4.5 million a year.
According to the report from Riding Sunbeams, solar power can account for 6% of the power supply of London Underground in the future, 20% of the Merseyrail network in Liverpool, England, and 15% of the commute routes in Kent, Sussex, and Wessex. However, the scheme is still in the testing phase. Currently, only 100 solar panels are installed at the Aldershot station on the Wessex route. The installed capacity is only 30KW, which can only supply enough power to the signals and street lights along the route.
This prompts the million-dollar question: how many solar panels are required to fully power a train? According to previous tests by the Austrian Federal Railways (ÖBB), they connected a railway system to a solar power system, which consists of 7,000 cubic meters of solar modules, with a capacity of 1,100 MWh annually. The solar power plant could power the train to travel from Salzburg to Vienna (about 2 hours 40 Minutes) for 200 trips.
Obviously, land availability and its planning permit will be major challenges for the UK in the future. The current practice in the UK is to install solar panels near the railway, then supply power to the train through dedicated substations and energy storage systems. However, the equipment must also be compatible with the railway system to avoid interference with railway signals.