The study builds on the previous COMET study on Energy Efficiency, which was conducted last year as metros experienced increasing energy costs driven up by the conflict in Ukraine. This study examined how members use recovered braking energy and reviewed the extent and use of energy storage systems amongst members, particularly to increase the efficiency of regenerative braking.
The data shows that the average share of traction energy obtained from regenerative braking is 27% across members, however there are notable differences between fleets and technologies. Key findings of the study cover areas of energy storage systems, relevant technologies, and benefits of using energy storage systems. The report includes several mini-case studies of metros who currently have or are in the advanced stages of implementation of energy storage systems for regenerative braking. These include examples from Washington WMATA, Ottawa OC Transpo, Seoul Metro, and Tokyo Metro.
The COVID-19 pandemic and the resultant economic downturns have had a steep impact on global energy production and supply chains. Inevitably COMET members, who are often one of the largest consumers of energy in their cities, were deeply affected by the energy crisis.
The study collected information from 32 metros, reviewing where metros procured their energy from and their trends in consumption, as well as benchmarking metros’ performance regarding energy efficiency and energy costs. The key objective of the study is to understand the impacts of energy crisis on metro operations, and the energy saving measures that have been successfully undertaken by members – which covers multiple areas such as lighting, HVAC, regenerative braking, escalators, driving modes and stabling, etc. An overview of pilot initiatives and technologies that are considered by metros in the future was also included in the report to explore further in future.
New Seoul Metro train with zero-speed regenerative braking
This research project examined metros’ practices when making the decision of whether to replace or refurbish ageing rolling stock. As annualised expenditure on rolling stock is typically about 20-25% of total operating costs, fleet investment decisions have significant impacts on overall metro costs. The focus of the study was to identify key factors and criteria in deciding to replace or refurbish rolling stock at end of nominal life, including the risks and opportunities of life extension beyond initial design life; to identify best practices in design, specification and planning of refurbishments; and to advise metros on appraisal and business case development process, parameters and assumptions.
Metros have been gaining increasingly significant benefits through refurbishment, and many metros (especially newer ones) are now undertaking or planning refurbishments to ageing fleets that are approaching or past their initial design lives. These refurbishment programmes are designed to extend initial design lives by as much as 15-20 years.
Cost saving opportunities of refurbishment
A key guiding principle is that refurbishment prolongs ‘more of the same’, as reliability following refurbishment tends to remain fairly similar. Therefore, only highly reliable fleets are usually worth refurbishing. A second principle is that most metros limit the extent of technology change attempted through refurbishment. So if significant upgrade is required, for example to enable unattended train operations, generally a new vehicle is preferred.
This case study has successfully assisted CoMET and Nova members in their decision-making. An Asian member needed to buy new trains when their 15-year-old line was extended and re-signalled. Findings from this report assisted with their decision to replace all the trains on the lines, instead of converting the older trains to work with newer signalling and then operating a mixed fleet. Conversely, Montréal STM used this research in support of a decision to refurbish their 40-year-old MR-73 cars and extend their life to 60 years. This is projected to save Quebec taxpayers nearly $500 million over the next 20 years. More information on Montréal’s decision can be found here.
Experts from 19 urban railways met to discuss energy saving strategies at a workshop hosted by TMB Barcelona. Fifteen CoMET and Nova metros and four suburban railway operators were represented at the workshop, which built on the CoMET 2012 ‘Energy Saving Strategies’ research project. Over two days, attendees investigated the measures taken by metros to improve energy efficiency and the factors affecting metro energy consumption; and sought to share good practice in management and procurement of energy. The workshop brought together energy experts from metros and railways, in a confidential environment to allow experts to share new ideas and take away evidence of successful practices and lessons learnt elsewhere. The workshop also helps build a network of peer contacts to enable ongoing collaboration between energy experts. In addition to brief energy introduction presentations from each participating operator, the workshop included detailed discussion of traction energy, non-traction energy, energy supply & monitoring, and carbon emissions; a presentation on the SEAM4US European research project, and technical visits to see Barcelona TMB’s high voltage substation.
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