The case for ‘clean’ buses

The threat of global warming together with growing congestion and pollution in European cities has now become a major, centre-stage issue of international concern.Today,many national Governments recognise the serious dangers for future generations if global temperatures continue rising at the present rate.Moreover, there is increasing pressure from the general public for cleaner, healthier air in our built-up areas to protect this generation and particularly the ones to follow.

The Kyoto conference on climate change concurred that Global greenhouse gas emissions, stabilised at 550 parts per million (ppm), could give the planet an 80% chance of keeping the global temperature rise to approx. 2°C.At this level it was believed that little environmental damage or change would occur.

More recent analysis concludes that a 400 ppm target is needed to provide an 80% chance of the 2°C shift. Clearly the situation has worsened. In fact, the original 550 ppm target now offers only a 20% -30% chance of containing global warming to a manageable 2°C rise.

The problem appears even more extreme for industrialised Western Europe, where a massive reduction (approx. 75%+) in greenhouse gases is needed to meet the 400 ppm target (predominately CO2, carbon dioxide). Moreover, estimates suggest that transport of all types is responsible for 25%-35% of the present emission levels.

Local authorities throughout the EU are now required to identify areas where the air quality is unsatisfactory and to put in place improvement programmes from 2005 onwards. The principal pollutants are Nitrus Oxide (NOX), Carbon Monoxide, Hydro-Carbons and Particulate matter. The British Government has added global warming (CO2) to its list of priorities and it is very likely that other European countries will follow suit.

Most of London’s inner city boroughs need ‘clean-up’ treatment and the pressure on London to take action has been significantly increased with its recent award of the 2012 Olympic games. In the UK alone, there are more than 120 poor air quality areas registered to date.

Even though all forms of transport are targeted to reduce green house gases and improve urban air quality, a fundamental first step should be the development of cleaner, more desirable public transport systems – buses, trams and trains. This then offers a discerning society of car owners an attractive alternative public travel option for journeys to city and town centres.

Some UK cities such as York, Bristol,Winchester and Bath are reducing inner city congestion by introducing highly successful Park & Ride facilities, where passengers leave their cars on the outskirts and take a dedicated, comfortable, frequent bus service into the centre at little cost.

London has created a congestion zone in its centre that costs private motorists £8.00 per day to enter. The effect on traffic has been significant and public transport journey times have improved by approx. 2 mph and public transport usage has increased. There are plans to extend the London zone in 2007 and other British cities are looking seriously at this option.

Clean-up options

The measurement method for emissions is ‘well to wheel’ – the emissions created by the energy from its source to its ultimate usage point. Electric trams, trolley buses and light rail systems do offer zero emission at point-of-use but they replenish their energy from the National Grid and these emissions must be added to calculate the true ‘well to wheel’ pollutant levels.

A comprehensive EU programme with diesel engine manufacturers has made significant strides in reducing air quality pollutants. Today’s Euro 3 buses are much cleaner and quieter than their ancestors.Average emissions from a pre 1980s diesel bus equates to ten or more modern units, however, NOX and CO2 emissions remain worryingly high.

The sustainable electric battery bus solution has long been a desirable public transport dream.At present, electric battery mini buses from 5.3m to 6.5m, carrying up to 25 passengers with top speeds of approx.35 kph (22mph), are being tried in France, Italy and Portugal. For example, Rome runs two operational routes across the city. Each mini bus works a four hour cycle before going off-route for battery charge or replacement. Battery charging, like trams, is also via the National Grid. These small units can positively influence public thinking about clean transport benefits, but they are not suitable replacements for the large bus network found in a typical European city.

During the last 40 years, battery manufacturers have striven to create longer lived, light but high powered batteries that could meet the operational demands of public buses. Manufacturers are now developing sophisticated options such as Nickel Metal Hydride, Lithium Ion and Zebra batteries that offer improved life and weight characteristics. These go part way to meeting operational needs but are very expensive compared to traditional lead acid units.

The lead acid battery, although heavy, has been improved too and its life cycle lengthened. Hence, it remains a favourite as good value for money, unless energy, weight and vehicle packaging issues are so critical that they justify the considerable additional costs.

The last 20 years has seen experiments in cleaner buses ranging from CNG and LPG fuel to alternative drive systems but a mainstream, affordable, operationally successful ‘clean bus’ has yet to be developed for public service vehicles. This said, electric drive development during the last decade does offer hope for interim and long term solutions.

A fuel cell bus evaluation programme currently operates in a number of key cities across Europe and elsewhere. These buses use hydrogen fuel and produce harmless water vapour emissions. The way hydrogen is produced will ultimately dictate the ‘well to wheel’ emission levels for this system.

Fuel cell buses could represent the long term future for the bus industry if the serious issues of price, fuel cell life and operational costs can be successfully solved and an infrastructure constructed to deliver hydrogen fuel economically in volume to its point of use. Expectations of success vary from five years by optimists to 20 years or longer. The road to commercial viability could be long not withstanding the current bus trials now taking place.

The shortcomings of the pure battery bus for mainstream operation coupled to the probable time required for affordable fuel cell vehicles has created the need for an interim product that can significantly improve emissions now; that fits operational needs; that can be afforded. Battery hybrid buses could fill this window of need.

Hybrid bus development has rapidly increased in the last seven years on both sides of the Atlantic.Although the USA has not signed up to the Kyoto accord, clean bus programmes have been encouraged, lead by CARB, the clean-bus authority of California. It has imposed a ‘clean-up’ programme with particular emphasis on severe reductions in air quality emissions, particularly NOX and particulates. Currently there are approx. 600 hybrid city buses operating in American cities.

Europe too has hybrid buses being tested in several countries including Italy, France and Germany. In the UK, Newcastle and Liverpool have active hybrid bus routes and London will take delivery of six hybrid units in the near future.

European hybrid activity and performance is presently being assessed. If bus operators find them reliable, the emission levels are significantly improved and passengers enjoy travelling on them, market demand will grow with the active encouragement and/or legislation from local authorities for cleaner urban bus transport.

A hybrid case study

In the late 1990s, The Wright Group based in Northern Ireland and a major UK bus manufacturer, began to explore alternative power sources. They concluded that electric drive power gave the best chance of developing a viable bus with very clean characteristics. It commenced with a pure battery bus. Whilst satisfactory for special applications, its range and refuelling time proved to be unsatisfactory for standard bus services operating 12-18 hours and travelling up to 250 miles a day.

As a first priority any new product Wrights’ develops must meet the fundamental operational needs of the market and its customers. Governments may help initially to launch new products but ultimately these must achieve a commercial viability to succeed.

The latest development, now in production, is a 10.2 – 10.8m electric hybrid city bus combining a 120kw electric drive, powerful lead acid batteries and a 16 valve Euro 4 diesel engine. It is specifically built for city and town stage carriage operation and sustains its driving power by continuous energy regeneration on board through regular stopping, including substantial regenerative breaking energy.

Where a conventional diesel bus produces 10-15 grams of NOX per kilometre, the Wright Electrocity hybrid emits approx. 3grams. For carbon monoxide gases, a similar reduction ratio is achieved while hydrocarbon emissions are barely measurable. Global warming issues are also addressed. Tests at Millbrook – the UK Government-approved testing centre – indicate a 30%+ reduction in CO2 emissions. Fuel consumption also improves significantly, since this is the primary method for reducing CO2.

The Electrocity hybrid has uniquely and significantly reduced air quality and hothouse gases in the same vehicle.Additionally, it can run in zero emission mode using only its batteries for 10-15 minutes in each hour of continuous operation. Its key operational features are:

Range 180-220 miles (290–350 kph)
Average speed 14 mph – (average UK cities = 7/10 mph: 11-16 kph)
Top speed 47 mph (75kph)
Acceleration 0 – 10 mph 3 seconds 0 – 30 mph 18 seconds
Carry capacity 50-57 passengers
Noise levels approx.68 decibels

In all other respects this is an ordinary city bus. It looks like a standard bus, carries a similar number of passengers for its class and complies fully with disability requirements.

Electrocity has undergone successful field tests for the past two years in Ballymena, London, Bristol, Bath, Leeds, Liverpool,York, Sheffield, Bradford, Swansea and Winchester. Some of these have been in-service tests carrying fare paying passengers who were asked to appraise its clean air credentials and ride qualities. The prototype has successfully tested more than 25000 miles.

On board surveys showed that in addition to the overwhelming approval of the clean bus concept, passengers were equally impressed with the quietness, smoothness and general comfort the bus offered throughout its journey – improved ride characteristics they seek from all public transport vehicles. Drivers also found Electrocity a comfortable and less stressful experience when compared to conventional diesel buses.

Local authorities are looking with serious intent at ‘clean bus’ development such as the Electrocity as an important ingredient in plans to comply with European legislation for cleaner cities and towns. No less importantly, the general public are increasingly demanding that their city and town centres once more become pleasant, uncluttered and healthy places in which to live, work and to visit.

Wrights’ now plan to develop a comprehensive range of ultra low emission hybrid buses for home and export markets.