Transport for London uses more electricity than anything else in the city. The Underground and Overground rail networks alone consume an astonishing 1.2 terawatt-hours each year, enough to power around 360,000 homes. Then there are buses, trams and an array of other infrastructure.
Sadiq Khan, the Mayor of London, has pledged to make the capital carbon neutral by 2050. It’s an ambitious target – and to succeed, TfL is going to need to come along for the ride. And work is already underway. Plans are ongoing to electrify London’s bus network and bring more electric vehicles to the city – including the electrification of all black cabs. But no project is bigger than making the Tube carbon neutral.
Professor Tim Green, director of the Energy Futures Lab at Imperial College London says it’s a chance for London to “show some leadership, learn by trying and become a beacon for how you do a low carbon transport system. TfL is attacking the problem from a number of different angles, says Alex Gilbert, senior energy strategy manager at TfL. “There’s a huge amount going on with commercial development and innovation, and we’re very keen to see how startups can assist us,” Gilbert adds.
Here are five ways the Tube is going green.
Trains coasting into stations
Every station on the Victoria line sits at the top of a very small hill. Going into each stop, the track rises very slightly, and then falls again as trains pull out to continue their journey. This gradient helps slow trains down, and means that drivers have less need to use their brakes, which are a big source of lost energy, and one of the main reasons the Underground gets so hot.
That system has been in place since the line was built in the 1960s, and newer trains are also equipped with regenerative braking systems that harvest some of that lost energy and supply it back to the train. “That’s a pretty well established technology,” says Green. “It’s got lots of advantages – you recover braking energy and reuse it, and it also reduces wear of the brake pads and dust in the tunnels so it leaves you with a cleaner tube as well.”
On top of this technology, which is being rolled out as older trains are replaced, TfL is also investigating where and when trains should start coasting into stations instead of braking to save even more energy. “It’s incredibly unsophisticated,” says Gilbert. “Just as you do in a car, you just lift off to save energy.”
Solar panels alongside tracks
TfL also has ambitious plans to generate its own power by placing solar panels on land that it owns alongside railway tracks, and other buildings that it owns. It is working with consultants to identify sites that might be suitable “It’s land that can’t be used for anything else, and the potential is huge,” says Gilbert. “We have such high power demands that we would like to take all of that ourselves.”
Green and colleagues at Imperial have been advocates of the idea of trackside solar, and published a report, Riding Sunbeams, which found that solar arrays could meet up to six per cent of the Underground’s energy demands. “One of the nice things about solar is you can buy it at almost any size,” says Green. “Every time you place a solar panel you buy a bit less energy from the grid, and you do that as much as you can because each bit is a win.”
Trackside solar has been talked about before, but has never been implemented. There are potential issues to overcome around maintaining access to the track for engineers, making sure that glare from solar panels doesn’t affect train drivers, and that electricity infrastructure doesn’t interfere with the signalling system.
Using excess Tube heat to warm London homes
Another first of its kind project is trying to use excess heat from the Tube to warm the houses of the very commuters that use it. Heat generated by braking trains and passengers currently just gets absorbed into the walls. “The clay around London’s tube tunnels gets incredibly hot,” says Gilbert.
Getting heat out of those spaces is tricky, and air conditioning uses up a lot of energy. “Cooling is a problem,” says Green. “What you really want to do is find someone who doesn’t have enough heat, and give them some of yours.”
A project is currently underway at Bunhill in Islington to use an existing ventilation shaft from the Northern Line to heat 1,000 homes during the winter. In summer, the process will be reversed, and cooler outdoor air will flow down into overheated stations.
Battery storage at key points
“We are very interested in battery storage but not in the sense of renewables,” says Gilbert. Instead, TfL plans to use batteries at key places in the network where lots of energy is being lost. To help, it’s creating maps of London’s entire transport infrastructure, highlighting places where heat and energy is coming out of the network.
“We’re overlaying so many maps on top of each other, there’s a lot going on,” says Gilbert. “It will give us great insight to know where we’ve got key losses.” Battery storage could also be used to shift demand – buying energy at cheaper times, or when renewable energy is freely available (on windy or sunny days, for example) and then using it at peak times when it costs more to buy power from the grid.
Private wind farms
“London Underground have choices over how they purchase their energy,” says Green. “They can purchase from a general supplier, and get a mixture of renewables, nuclear and fossil fuels,” or they can purchase from a carbon neutral supplier.”
As much as half of electricity costs come not from the generation of power, but in actually getting it from where it’s created to where it’s needed. TfL is thinking about cutting out the middleman by bypassing electricity companies and going straight to the source and buying power directly through power purchase agreements. “People don’t really get excited about this, but pound-for-pound it has the biggest potential,” says Gilbert.
A wind farm in the Thames estuary or further afield could be linked directly to London via what’s known as a private wire. This probably wouldn’t be a physical connection, but rather a virtual wire through which power from that source still flows through the national grid, but is exclusively used by TfL.
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