17.07.17
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
W: www.imperial.ac.uk