Plugging solar power into our railways

Source: RTM Jun/Jul 17

Dr Nathaniel Bottrell, research associate at Imperial College London (ICL), talks about the Renewable Traction Project, which is investigating the use of solar energy to power our rail network – especially in areas where the electricity grid has reached its limit.

Currently Network Rail is investing billions in electrifying the UK’s train lines. This, combined with increased renewable energy generation, means train travel could be significantly decarbonised by 2050. However, in many rural areas the electricity grid has reached its limit in both integrating distributed energy generation and supplying power to the train companies.

The Renewable Traction Project is our proposed solution. We are a collaboration bringing together experience and expertise from academia, industry and the non-governmental sector to tackle this issue. The partners in the project are Energy Futures Lab at ICL, 10:10, Turbo Power Systems and Community Energy South. 

Our idea is a deceptively easy-sounding premise: connect solar panels directly to the lines which provide electricity to trains. The idea is to bypass the electricity grid so the panels can provide power precisely when needed most. 

There is a huge business opportunity here. Space is normally the limiting factor for any company looking to generate power on site. For example, Jaguar Land Rover has the biggest rooftop solar PV array in Britain and even that can only supply 30% of its Staffordshire factory’s electricity demand. Network Rail has access to close to 18,000km of track, which is a lot of space. In 2015, it was estimated that installing solar PV on half of that could meet 40% of its annual traction power demand. 

We have been fortunate enough to have been given funding from Innovate UK’s ‘Energy Game Changers’ programme to understand the feasibility of such as system. If it proves feasible and successful it could have a wide impact, with commercial applications on electrified rail networks all over the world. This kind of system would open up thousands of new sites to small and medium-scale renewable developments by removing the need to connect to the grid. 

At the moment, our focus is on third rail systems. Although only used on about a third of the UK’s network, it has one major benefit: solar panels generally supply power around 750V DC, very close to that used by the third rail system. This allows us to focus on the engineering around integration of a direct power source and not worry about problems and losses introduced by converting to AC. Then we can tackle the extra issues overhead lines introduce. 

The challenges ahead 

This does not mean it will be straightforward. The third rail is an integral part of the signalling system and introducing power could lead to communications issues. We also need to address the issues around safety and integration of a secondary power source and managing how and when the solar power is being sent to the third rail. 

Failure to address the technical challenges identified may reduce the actual generation when compared with the expected or installed capacity. The worst case could result in suboptimal operation of equipment, which can have a huge impact, and a very real associated cost, on the operation of the rail network. 

Our work on technical integration will be one thing, but if we can prove financial sustainability of these systems it could also have an impact on the speed of electrification roll-out. Correctly addressed, these issues could also open new opportunities for distributed generation and encourage a new market in the UK. Connecting local generation to the traction supply will also help reduce the CO2 emissions of rail transport. 

Investment in, and building of, solar power schemes has been affected by changes in government policy but confidence is creeping back in through power purchase agreements (PPA). These long-term PPAs are between reliable industrial consumers who can commit to buying every unit of the power generated in a multi-decade contract. The problem is that there are a limited number of sites that are good for solar panels and have a long-term customer with high daytime energy use. This makes the Renewable Traction Project of particular interest for investors: our railways are pretty permanent, having been around for almost 200 years. 

Fundamental partnership working 

The project is a real mix of the technical and social elements of the problem. We’re not aiming to just create an ideal situation in a test environment. We want to know if this can work out there in the real world. This means it’s not just about plugging together huge pieces of kit but also understanding how all stakeholders can impact, and be impacted by, a successful implementation of the plan. 

To do this, the partnership we have built is key. We are very lucky to have brought on such a wide range of partners. At ICL we have experience with the underlying power electronics and electricity distribution off-grid, which will help us tackle many of the issues surrounding having large-scale solar installations in remote sites and unconnected to the National Grid. 

Turbo Power Systems complements this very well as it provides many of the systems on the UK’s trains related to electrical distribution and use. Its close working relationship with the train companies, Network Rail and the train manufacturers will make much of the integration a lot easier. 

Community Energy South and 10:10 both come from a different viewpoint. They will be working on establishing the financial model to support outside investment in new solar-generating capacity, and identifying promising pilot sites on the DC commuter network to prove the concept. 

The next steps 

At the moment, we are being open on where these pilot sites could be. We haven’t picked TOCs to target specifically; it is more about location and technologies used. Generally, though, anyone running electric trains on the DC network south of London would be ideal. There are also opportunities at the edges of the Tube network and we are looking at possibilities of working with TfL on that. London is not our only target though. Similar to the Tube, both Merseyrail in Liverpool and the Tyne and Wear Metro would be prime candidates for this project.

The team at 10:10 is also talking to solar developers and DC rail operators in overseas markets like India and California, and making plans for the innovation to be taken up as widely as possible. India has two big infrastructure targets – 2,000km of new rail electrification every year and 100GW of solar by 2020. These fit well with what we are doing as they are having issues with electrification and solar deployment due to inadequate distribution and transmission infrastructure at the moment. 

The project is still investigating the feasibility of the whole scheme and we hope to have that report out by the start of September. Assuming that the report finds that our plan is technically and commercially feasible, we hope to be connecting our first small solar farms to the rail network as soon as 2018. 

If we secure funding for a pilot stage, find viable sites and get agreement from the operators to support trials, we’ll be looking to raise investment for small new solar farms from a wide range of stakeholders in late 2018.

For more information


Nickk   17/07/2017 at 21:30

These suggestions all sound very plausible, but the reality of peak electricity demand is morning and evening rush hours in the winter, when homes also need light and heat. Solar will reduce the amount of gas or coal (yes, we still need that for peak loads when solar and wind are low) used over the year, but it won't stop distribution problems for the dark months. Get ready for power cuts (at least the bi-modes can keep going).

Andrew Gwilt   17/07/2017 at 22:54

I think its a great idea. I like the idea of how solar power can help to keep the electrified lines energised with more power being put into the railways and on the trains as electrification is becoming more of a better solution for the UK's railways. As well as trains that can operate on both electrified and non-electrified railway lines (Bi-Mode trains) either on AC/DC power and on Diesel power.

Redrows   11/08/2017 at 16:52

And what happens to excess energy generated or when available energy is inadequate, such as at night as Nickk highlighted? Inevitably such an approach would replace only a portion of mains grid supply, unless energy storage is used. At present that would probably make the concept unaffordable by any measure. However, in a few years, this could well change as storage technology advances, e.g vanadium redox flow. Availability of DER sites presents another obstacle, However, I suggest it is worth pursuing this feasibility project, at least to create a model for future examination.

Patrick   22/10/2017 at 11:23

Tricky to know what the best niche for this would be. Not many equatorial countries have electrified rail, although quite a few places without such dark winters as the UK do (e.g. parts of Turkey and Australia). Will be interesting to see what the feasibility study comes out with.

Add your comment

rail technology magazine tv

more videos >

latest rail news

View all News

rail industry focus

Versatile coating system enhances Indestructible Paint rail industry role

12/08/2020Versatile coating system enhances Indestructible Paint rail industry role

A highly versatile and robust epoxy coating s... more >
Network Rail partners with Cycling UK for new initiative

03/08/2020Network Rail partners with Cycling UK for new initiative

Network Rail and Cycling UK have launched a p... more >

editor's comment

23/01/2018Out with the old...

Despite a few disappointing policy announcements, especially for the electrification aficionados amongst us, 2017 was, like Darren Caplan writes on page 20, a year generally marked by positive news for the rail industry. We polished off the iconic Ordsall Chord (p32), hit some solid milestones on Thameslink (p40), progressed on ambitious rolling stock orders (p16), and finally started moving forward on HS2 (p14) ‒ paving the way for a New Year with brand-new infrastructrure to... read more >

last word

Encouraging youngsters to be safe on the railway

Encouraging youngsters to be safe on the railway

This summer, Arriva Group's CrossCountry and the Scout Association joined to launch a new partnership to promote rail safety among young people. Chris Leech MBE, business community manager at the TOC, gives RTM an update on the innovative scheme. Recognising that young people are more likely to take a risk trespassing on railway tracks, C... more > more last word articles >

'the sleepers' daily blog

On the right track, Sulzer is awarded RISAS accreditation for Nottingham Service Centre

29/06/2020On the right track, Sulzer is awarded RISAS accreditation for Nottingham Service Centre

Following an independent audit, Sulzer’s Nottingham Service Centre has been accepted as part of the rail industry supplier approval scheme (RISAS). The accreditation reinforces the high-quality standards that are maintained by Sulzer’s network of independent repair facilities across the UK and further afield in its global network. ... more >
read more blog posts from 'the sleeper' >


Andrew Haines, CE of Network Rail, tells BBC News his organisation could issue future rail franchises

24/06/2019Andrew Haines, CE of Network Rail, tells BBC News his organisation could issue future rail franchises

Andrew Haines, the Chief Executive of Network Rail, has told the Today programme on Radio 4's BBC’s flagship news programme that he wo... more >
Advancing the rail industry with management degree apprenticeships

08/05/2019Advancing the rail industry with management degree apprenticeships

In answering the pressing questions of how current and future generations of managers can provide solutions to high-profile infrastructure projec... more >
Women in rail - is the industry on the right track?

12/03/2019Women in rail - is the industry on the right track?

RTM sits down with Samantha Smith, sole female member of the TransPennine Route Upgrade Alliance Leadership Team, to find out more about encourag... more >
TfN Strategic Transport Plan: not just for transport's sake

22/01/2019TfN Strategic Transport Plan: not just for transport's sake

Peter Molyneux, Transport for the North’s (TfN’s) strategic roads director, has been leading on the development of the seven economic... more >