Urban light rail: How much energy does it really consume?

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In the last hundred years or so, we have made huge advances in transportation technologies. But with more than half the world’s population (and growing) now living in cities, coupled with the looming environmental crisis caused by our over dependence on fossil fuels, these urban transport systems need to meet ever-more stringent energy criteria in order not to further burden our already over-stretched natural environment.

Keeping rail cost-effective

Some statistics: global energy consumption is predicted to grow by 56% between 2010 and 2040, according to a recent UITP seminar on energy and light rail transport. By 2050, both urban transport energy consumption and emissions are expected to double. Such demand is not likely to lead to price decrease in coming years. Currently, energy represents 15 to 20% of the operation expenditures of a light rail network. If rail transport is to remain cost-effective, all options to save energy and avoid waste have to be explored and exploited.

But when it comes to measuring rail’s actual energy use and environmental impact, it’s not as clear-cut as it may seem. Urban rail systems are complex and the amount of energy they consume depends on a range of factors. Namely, though a new technology might yield improvements in one area, it might compromise other aspects of system performance. This means that it is often extremely difficult to assess the net benefits of introducing new energy saving technologies.

Focus on Duty Cycles

What is lacking is a standardised methodology of measurement for rail energy consumption. This is one of the key areas of study of a three-year European research project called OSIRIS, carried out by 17 European partners and co-funded by the Seventh Framework Programme.  The project aims to reduce overall light rail energy consumption, not just by focusing on vehicles used, but by examining all aspects of systems, from vehicles to infrastructure to operations.

For many transport modes, energy reduction strategies can be formulated at the vehicle level. New technologies can be introduced to a vehicle and the direct energy savings can be measured easily. However, this approach is not suitable for urban rail, where it is not enough to consider just the energy performance of one single vehicle; the energy associated with the interdependence between vehicles, with the infrastructure, as well as the influence of the mode of operation need to be considered, too.

Due to a lack of a harmonised way to measure energy consumption, well-intentioned operators are often at a loss when purchasing new vehicles. This increasingly vital information is often completely absent, and it is one of the problems the OSIRIS project wants to rectify. The Duty Cycle issue is an area where UITP members in particular have shown enormous interest.

Technological advances & the OSIRIS Project

Another issue that is worth raising is the fact that advancements in the past decade have allowed rail vehicles to increase their traction energy-efficiency. But these energy savings have been cancelled out with the addition of a number of comfort features such as energy-consuming air-conditioning, wifi and on-board equipment and infotainment. However this has allowed operators to modernise and improve their service and vehicles without further adding to consumption.

The OSIRIS project is also focused on the following technological advancements: innovative on-board energy storage solutions like li-on batteries, auxiliary converter to recover more braking energy, and heat recovery through innovative heat pump and smart grid studies.

The OSIRIS project is currently in its final stages and will come to an end in December 2014 when a conference will be held to present the study’s findings and recommendations.

In the run up to the UN Climate Summit in New York in September, UITP is also encouraging its members to demonstrate their own climate-friendly credentials by telling the UN what they’re doing to reduce the energy consumption of their transport operations and signing the UITP climate commitment Declaration.

OSIRIS is not the only EU energy-efficiency project in which UITP is involved. The project NODES – which UITP is coordinating – involves the construction of a Toolbox which will support European cities when building or upgrading their interchanges. One of the five topics in which tools are being developed is energy efficiency.

More information visit www.osirisrail.eu or contact caroline.hoogendoorn(at)uitp.org

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