Objectives & Work Streams - Environment - Translink
Objective l Technology l Euro 4 Engines l EGR l The Translink Approach l Targets
Objective
To use vehicles, fuel and technology which optimize the balance of efficient operations, output emissions and environmental impact, with regulatory compliance as a minimum standard.
New technology can play a key role in improving environmental performance. However, bus priority on roads and the efficient running of trains can also have a dramatic impact on our emissions performance. In addition, if journey times are reduced more people will be use bus and rail services.
As European exhaust emissions standards for large diesel engined vehicles progressed from Euro 0, through Euro 1, Euro 2 and Euro 3, significant decreases in the following pollutants were achieved:
- HC Hydrocarbons
- NOx Nitrogen Oxides
- PM10 Particulates
- CO Carbon Monoxide
These standards as applied to new vehicles achieved significant benefits for the environment including a major contribution to local air quality in towns and cities.
Translink further improved emission performances by specifying CRTs (Continuously Regenerative Traps), basically a combined oxidation catalyst and particulate trap to most Euro 2 and Euro 3 buses operating within Belfast City.
Moving from Euro 0 through to Euro 3 standards has meant an impact on fuel consumption as engines are reconfigured to achieve emission standards. Fuel consumption has also increased on public transport vehicles due to;
- Increases in weight due to
- Improved structural rigidity and crashworthiness
- Additional passenger facilities
- Increase in vehicle performance
All vehicles registered from October 2006 were required to meet ‘Euro 4’ standards and ‘Euro 5’ from October 2009, reducing exhaust emissions further.
The difference in exhaust emissions requirements between a Euro 3 and a Euro 4 engine is considerable; emissions of nitrogen oxides (NOx) are reduced from 5 to 3.5 g/kWh (30%), particulate (PM) emissions drop from 0.1 to 0.02 g/kWh (80%).
Engine manufacturers have 2 different technologies in order to achieve Euro 4; Selective Catalytic Reduction (SCR) and Exhaust Gas Recirculation (EGR).
SCR uses an additive, Aqueous Urea Solution that is injected into the exhaust gases before they pass through an SCR catalytic converter. In the catalytic converter, the nitrogen oxides are turned into harmless and naturally occurring nitrogen gas and water vapour. With Euro 4, the additive corresponds to about 4% of the amount of fuel, and for Euro 5 about 5%.
The use of SCR technology allows the engine to have improved fuel economy as compared to a similar Euro 3 specification engine.
EGR allows Euro 4 to be achieved without the use of Aqueous Urea Solution. Some of the exhaust gases are cooled and fed back into the engine to achieve a lower combustion temperature, this combined with high injection pressures provide lower levels of NOx and PM10.
The Translink Approach
Technology
Translink is specifying Euro 4 exhaust emissions requirements for all vehicle deliveries in 2007 and 2008. With each tender Translink retains an open mind with respect to exhaust emissions technologies. Projected fluid (fuel plus Aqueous Urea Solution) consumption is assessed over the projected life of the vehicle; many other factors are taken into account in selecting the preferred vehicle for a particular application.
Fuel choice – Bio Diesel
Translink has completed a bio diesel trial, at Coleraine, Ballymena and Omagh bus depots. The trial began in September 2006 with a 5% bio diesel / 95% DERV blend.
An advantage is that bio diesel is sourced from grown crops, e.g. rapeseed which is CO2 neutral (apart from the energy to grow, process and distribute), renewable, has no sulphur content and is biodegradable if spilt. There is a small cost advantage but this may be offset by poorer fuel consumption.
It is expected that the diesel fuel market in the UK generally will move to a 5%/95% Biodiesel blend during 2008.
Vehicle choice - Environmental Efficient Vehicles (EEV)
Translink has developed a project to introduce a number of more environmentally friendly vehicles into the Metro fleet for use in Belfast City Centre and for Coleraine.
The Coleraine based vehicles would be used mainly to service the Giants’ Causeway. This is both a trial of the current available technology and to demonstrate Translink’s commitment to reduce its impact on the environment.
The project aims are:
- Support a vision for public transport as the optimal choice for sustainable transport in Belfast and other urban areas in Northern Ireland.
- Compliance with / contribution to Belfast City Council’s Air Quality Action Plan.
- To demonstrate current EEV technology and determine if EEV’s are fit for purpose i.e. fulfils all performance and reliability demands in revenue service.
- To gain experience of operations and maintenance of EEV’s in advance of mandatory introduction including benchmarking results with other operators
- Study the perceptions of the public of this technology
There are many different types of EEV’s available; the preferred technical solution is a bio diesel / diesel – electric hybrid. The project budget is £1.5 million to purchase 7 buses - implementation will be dependant on funding approval.
- To achieve an average road fleet age of 8 years and retirement age of 12 years for coaches and 18 years for buses by 2013. This will significantly reduce exhaust emissions in terms of HC, NOx, CO and PM10.
- To optimise fuel efficiency of new road and rail vehicles by selecting appropriate engine ratings, engine technologies, transmissions and final driver ratios.
- To replace older passenger trains; older than 12 years with new trains by 2013 creating significant reduction in exhaust emissions and eliminating toilet emissions direct to track.
- Improving public transport fleet generally to assist via modal shift from private car to bus and rail.
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