Last year the mayor of London, Sadiq Khan, announced plans to make the city carbon neutral by 2050. A London Assembly measure in December called for that to be brought forward to 2030. Either way, the London authorities are setting themselves ambitious decarbonisation plans, including the roll-out of low emissions vehicles, a 2 gigawatt solar energy target, zero waste and an expansion of green space.
One of the biggest challenges will be transport. Transport for London (TfL) is the city’s biggest energy user, and any plan to decarbonise London will have to tackle its iconic subway system, the London Underground.
The Underground was the world’s first subterranean railway, opening its first line in 1863. It now includes over 250 miles of track over 11 lines, carrying some 1.3 billion passengers a year. It’s now complemented by an Overground network, and together they use 1.2 terrawatt hours of energy. So how are they going to make it carbon neutral?
The first step is to make the tube as energy efficient as possible, and work on that has been underway for a while. TfL began experimenting with regenerative braking in 2015, similar to the technology used in hybrid cars, and they estimate that capturing the energy of slowing trains can cut 5% of their energy use. This also generates less heat and dust, and cuts down on ventilation costs. Extensive Internet of Things connectivity is providing data to optimise train times and speeds, as well as cutting maintenance costs. Battery storage is also being installed at key points in the network to regulate electricity supply and prevent waste.
Energy effiency measures in stations include low energy lighting, and better escalators. Controversially for Londoners bred to stand on the right, escalators are 30% more efficient if people stand on both sides and nobody walks. This is yet to be implemented across the network, and I wouldn’t want to be in the city on the day that it is, but trials have shown that it reduces queuing too.
The tube generates a lot of heat from all that electrical equipment, friction, people, and commuter anger at people who stand on the left on the escalators. At the moment that excess heat goes into the walls, and the network relies on mechanical cooling systems. One possibility, being tested at the moment, is capturing this heat and using it to warm homes at the surface.
More efficient stations are helpful, but 83% of TfL’s energy use is in moving things around, and the biggest difference they can make is to switch to renewable energy. That’s hard to do at this kind of scale, and TfL have had to be creative. One solution is to buy energy as locally as possible, helping to reduce transmission losses. In November it put out a call to suppliers to try and shift to more local power. It’s partnering with local housing associations and companies to source energy for offices and stations, and of course it can generate its own.
Following 10:10’s pioneering research last year, TfL is looking into using trackside solar power. Obviously a lot of the network is underground, but large parts of it run overground too, and TfL often owns the trackside land and buildings. There is also talk of a ‘private wire’ supply from the regions, providing 15-20% of the tube’s power needs from a wind farm on the Thames Estuary.
A carbon neutral London Underground is a mammoth task, but one that could inspire other transport authorities to up their game and set more ambitious targets. If London can do it, at this scale and with all its ancient infrastructure, others can too.