The environmental credentials of rail, compared to other forms of transport such as road and air, are already well publicised. But in order for such green policies to remain sustainable there is certainly scope for the UK rail network to benefit from new technology and the implementation of forward thinking to reduce environmental impact even further.
In recognition of this, South West Trains has recently completed a substantial £2.2 million investment into regenerative braking across more than 200 trains in its fleet. Although not the first operator in the UK to utilise this technology, South West Trains’ uptake is significant given its position as the UK’s biggest commuter rail franchise, with a network that covers south-west England and into London Waterloo. This programme forms part of a major £11 million investment within Stagecoach Group, South West Trains’ parent company, a part of its new sustainability strategy.Making the case
In terms of the reasoning behind the use of regenerative braking, over other types of energy saving solution, Christian Roth, engineering director at South West Trains, explains: “Regenerative braking actually offers a very good return on investment, which means we should see the initial outlay recouped in roughly a year’s time. Therefore there is a very strong business case for it. On top of this, regenerative braking helps to reduce energy consumption, which in turn translates into cost
savings, and the carbon footprint of the railway system in general.
“Aside from offering the best return rates, the other driver for choosing regenerative
braking over alternative types of modification or technology improvements is that these require a significantly higher investment on the infrastructure side. In comparison, South West Trains has implemented regenerative braking into the fleet without any additional investments or changes to the infrastructure.”
The programme itself was launched in late 2008, followed by the first modification
of trains approximately two years ago and subsequent introduction into the network. Prior to this though South West Trains carried out substantial engineering approval activities with Network Rail and London Underground, and necessary testing and trials. The installation of the technology onto the trains was completed in a staggered way during normal maintenance activities to ensure there was no reduction in fleet availability, and subsequent disruption, for passenger services. The regenerative braking system is now fitted to all of South West Trains’ modern trains, specifically the Class 458 and Siemens Desiro models, which make up around 60 per cent of the total fleet.Proven technology
Regenerative braking works by feeding the excess electrical energy produced by the traction motors in the train during braking back into the third-rail system, which then allows it to be drawn upon by other trains in close proximity. In the past when this energy was generated it was converted through a resistor bank into heat and lost to the atmosphere, in a technique known as rheostatic braking. The ability to therefore recycle this energy and use it to power other trains is clearly of benefit, but is reliant upon the receptivity of the lines and trains to this process. Over the years the advancement in power electronics has seen the receptivity of the railway grid to regenerative braking increase massively, particularly on AC networks, although the technology is also being used in trains running on DC networks.
It is estimated that the technology will save South West Trains 50 million kilowatt hours (kWh) of electricity annually, which is the equivalent of powering more than 11,500 UK homes for a year. The company is anticipating that energy consumption on the suburban network, where the first trials took place, will be reduced by up to 20 per cent, which also has certain cost implications.
“We also see that the closer you move into London, and other areas of high train density, the rate of energy you can save is higher than in some of the places on the network where a lower volume of trains are passing through,” notes Christian. Likewise there are considerable benefits in terms of maintenance requirements, with components such as brake pads seeing an extension in operational lifetime.Change in behaviour
Certainly the roll-out of the regenerative braking system is a significant step forward in improving the environmental performance of South West Trains, but such technologies are not always necessarily a means to an end on their own. Aware that other factors also play a role in delivering sustainable outcomes, Christian reveals how this investment is informing what comes next: “We have equipped 20 trains with electric energy metering, which enables us to compare the actual results with the predicted figures. Going forward we can then use this data to make decisions about further investments or changes in driver behaviours through retraining that can help to deliver even greater savings.”
On a wider level the programme represents a key element of Stagecoach Group’s five-year sustainability strategy to reduce the carbon emissions from its bus and rail operations across the UK and US. Running from the period of 2009-10 to 2013-14, the Group is targeting an overall reduction of around eight per cent in buildings carbon dioxide equivalent (CO2e) emissions and of three per cent in annual fleet transport CO2e emissions. Over the five-year period this plan is expected to save a total of nearly 150,000 tonnes of CO2e, whilst reducing the Group’s annual emissions by around 40,000 tonnes CO2e by 2014.
South West Trains
Tel: +44 (0) 845 6000 650