reat Western Railway (GWR) faces a dilemma common to rail network operators across the UK. An ageing diesel
fleet, much of which is still operating after 40 years’ service, requires increasingly expensive maintenance. There is also a need to decarbonise in line with government policy and stakeholder ESG demands. This makes electrification the most sustainable option for long-term infrastructure, but that entails significant investment and logistical implications. Full electrification involves high upfront costs
and long lead times on infrastructure completion for Overhead Lines Equipment – the masts and wires that deliver electricity to trains –making it difficult to justify for quieter lines and those in more remote areas where the rail system is a critical lifeline for local communities. These are lines that branch off electrified or non-electrified lines between stations. A fully-electric train cannot operate on these branch lines, currently. Once it leaves the main line, there is no electricity to power it – but the capital cost of electrifying these branch lines can be prohibitive. One alternative, replacing existing rolling
stock with new diesel engines, ultimately means investment in outdated technology, setting Net Zero ambitions back when, by contrast, electric trains are cheaper to purchase, operate, and to maintain. This led GWR to this test project, and to investigate the feasibility of fast-charge battery trains.
GWR, in collaboration with Network Rail and Nexos Group, embarked on a year-long trial to test fast-charging batteries and establish their viability as a solution to the problem of wholescale electrification across the GWR network, particularly the local branches where full-scale electrification of the infrastructure is unfeasible. A London Underground train was converted to
become the testbed, with batteries and a charging systemto power the train for a year-long pilot project over a five-mile return journey between West Ealing and Greenford. This line is normally served by diesel engines. The trial set out to establish whether battery-equipped trains could prove effective and how well fast-charging would work in daily operation.
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Fast-charge rails were installed within the normal running rails, avoiding the need for lengthy and costly engineering work or disruption to the line. These are a triple rail set, with a positive rail in the middle and negative rails on each side, meaning that they can power the train’s batteries regardless of the train’s orientation. Sensors fitted to the train and trackside prime
the fast-charge systemas the train approaches the platform, while contact shoes under the train drop into position to enable charging. These lowered charging shoes then ride up a short fast-charge rail approach ramp, making solid contact with the top of the rails. Once the sensors have confirmed that the train is in the correct position – with its charging shoes on the rails – lineside batteries begin to send current into the batteries on the train. The train batteries take the fast-charge
required. The charging shoes then retract, allowing the train to continue its journey. Once the train has left the platform, the lineside batteries resume receiving a trickle charge from the Grid. This is a safe solution, whereby the rails are only live during charging, when the train covers the line of track.
For a fast-charge system to work using a battery energy storage system (BESS), the choice of battery technology was critical. GWR required a battery or energy storage device or medium to deliver significant bursts of power, without impacting the Grid. Julian Fletcher, technology development manager at GWR explains: “The track side battery system has been a key aspect of the charging system. You’ve got to have that to make it work... charging continuously off the grid as a tiny trickle feed. And then, when the train turns up, you get a big boost of energy into the train. Without that, you would have to connect straight up to the Grid supply and, every time the train charges up, that would pull really hard on the local power supply.” BESS is an established power management technology with multiple
industrial applications, enabling the storage of energy – whether drawn fromthe Grid, fromon- site renewable energy assets, or a combination of both – for use when needed. It can reduce or mitigate the need for expensive or unfeasible Grid connection upgrades, buffering demand locally and discharging stored energy as required. DanielMcAteer, Nexos Group CEO, highlights
why Powerstar’s BESS technology, as an off the shelf already proven design, was the right fit for the GWR project. “It meant it was safe, agile, quick to deploy, and it builds resilience into the rail network,” he explained. The resilience that a BESS provides also offers
a further potential benefit for rail electrification, specifically in the case of a power outage. In the instance of Grid failure, overhead electrical lines will fail. However, a battery-powered electric train, with the combination of the onboard batteries and the lineside BESS with stored energy, may enable continued operation during such disruption, adding another layer of resilience to the network. In terms of the BESS functionality during this
GWR trial project, Fletcher notes: “The battery reliability has been excellent through this trial. We’ve been focusing a lot on the train itself, in the interface with the charging systemand, to some extent, the track side has been taken for granted. And it’s been reliable. It’s done what we hoped it would do – to sit there, charging up continuously from the Grid, dumping energy into the train every time we need it. Reliability has been great.”
While other battery-powered trains do exist, this GWR project is the first to demonstrate the potential – and prove the concept – of a BESS powered from a Grid feed to increase flexibility across the rail network, cost- effectively and efficiently. Fletcher notes the critical importance of
collaboration and advanced battery storage technology to the project’s success: “What’smade the project innovative is the involvement of all the parties together. You’ve got the track side energy system from Powerstar, and then you’ve got Network Rail overseeing the integration within the infrastructure, and what was Viva Rail – now GreatWestern Railway – looking after the train itself and the battery system. We need a supplier like Powerstar who had that agility to be able to
NexosPowerBESS
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