Repowering buses can bring big benefits, says John Lewis
Cascaded down through fleets and relocated from busy city centres to quieter rural districts, buses can have a long shelf life.
A possible cause of early termination however is the power source they use; Euro 3, Euro 4 and even Euro 5 diesels may be viewed as increasingly unacceptable by local authorities worried about the impact NOx and particulate emissions are having on the environment. Those pollutants
can contain un-burnt hydrocarbons and carbon monoxide.
So does that mean that whole swathes of single and double-deckers will have to be scrapped? Not necessarily – one option could be to remove that old, polluting and uneconomical diesel engine and replace it with something younger, cleaner and potentially more efficient.
That something could be a fully-electric drivetrain, suggests Magtec. As well as supplying such drivetrains on an OE basis – to Optare for example – the Yorkshire-based company can install them in existing buses as a retrofit.
Simon Buckley, Magtec Programme Manager, said: “We estimate that operators should see a payback in five years. We’ve done work in the USA and Africa as well as in the UK, including sight-seeing double-deckers in operation in York. We’ve repowered hybrids as well as diesels.”
Benefits of the retrofit include zero tailpipe emissions with annual environmental savings of 535kg of NOx and 33 tonnes of CO2, so far as a city bus is concerned, says the firm.
With no diesel engine or conventional gearbox, maintenance costs are down by as much as two-thirds according to Magtec. Switching from diesel to electricity should result in a yearly fuel expenditure saving of roughly £20,000, it calculates. “The latest 300kWh batteries we’re using can offer a range of between 160 to 180 miles on a single charge,” Simon continued. “It takes six hours to recharge the battery pack and typically that will be done overnight.”[wlm_nonmember][…]
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Heavy lifting
The conversion involves removing 2,100kg of engine and gearbox and replacing them with 1,900kg of battery packs, electric motors and solid state converters. Installing the new drivetrain can take between one and two weeks. Much depends on whether Magtec already has a design for the vehicle being converted, and it may have to order certain key components and wait for them to arrive. “Remember that we’re talking about a major alteration that will extend the vehicle’s life,” Simon remarked. “We’re stripping everything out and putting something completely new in.”
Various approaches to acquisition are available, including leasing. “You could, for example, lease the battery pack from five to seven years,” he said.
Grants for switching to environmentally-friendly modes of propulsion are available from time to time depending on whereabouts in the UK a fleet is based. The overall cost of repowering would be lower, Simon argues, if the Bus Service Operators Grant (BSOG) did not in his view unfairly favour diesel buses. He would like to see BSOG undergo a radical readjustment so that environmentally-friendly zero emissions buses are clearly favoured over their diesel counterparts.
Electric buses operate more quietly than their diesel equivalents, although that of course can be a double-edged sword given that cyclists and pedestrians appear to use their ears (which may of course be blocked by headphones) as much as their eyes. It may make sense to fit some sort of targeted noise generation system so that vulnerable road users are made aware that a battery-powered bus is heading their way – and can respond accordingly.
Brigade Electronics has been busy developing a device that generates a warning sound targeted at whoever is in danger. It will not be heard elsewhere in the vicinity, thereby minimising the risk of noise pollution.
Diesel do nicely
Some fleets are simply opting to replace their existing diesels with more recent ones. Last December saw Cummins announce an initiative which involves swapping older engines for a Euro 5 four-cylinder B4.5 or six-cylinder B6.7 diesel. A key aim is to enable older pre-Euro 6 buses to continue operating in London once the ULEZ (Ultra Low Emission Zone) takes effect in April, 2019.
Exchange the Euro 4 engine in a 2007-registered bus for a Euro 5 engine and you cut particulate emissions by nearly 90% and NOx by 50%, says Cummins. “Our repower package can incorporate smart features such as Cummins Stop/Start,” said Ashley Watton, Cummins Director, On-Highway Business Europe. Cummins calculates that switching a Euro 5 bus to Euro 6 can cut annual fuel costs by between £1,500 and £2,500. Carbon dioxide emissions could fall by between four and six tonnes annually, it adds. A 1962 AEC Routemaster run on heritage routes in London has undergone a Cummins repower, meets Euro 6, and is certified as Low Carbon because it achieves 9.5mpg.
Not that operators are necessarily obliged to pension off their existing diesels in favour of a younger diesel or battery power. They could opt to have a hybrid diesel-electric package installed instead. That is the route recommended by Greenford, London-based Vantage Power. It offers the B320 Hybrid Retrofit System. It employs a 4.5-litre diesel to keep the lithium-ion battery pack topped up which, in turn, drives the 210kW electric motor. The package allows the bus to travel up to 4km without having to use the diesel engine.
Installing the B320 involves pulling out the existing engine and gearbox and connecting the new system to the vehicle’s electronics, hydraulics and pneumatics, which remain in place. The exercise takes around 40 man hours and is designed to cut fuel usage by roughly 40%, with a simultaneous fall in CO2, NOx, particulates and other pollutants.
The cost of the whole exercise is likely to be around one-fifth to a quarter of the price of a brand new hybrid bus. It gives the recipient vehicle a few more years of life and should ensure that it does not fall foul of tightening emissions regulations.
Both Arriva and RATP Dev have had buses converted and Rob Tarrant, Engineering Technical Manager at RATP Dev London, is impressed: “The package can be removed quickly for maintenance purposes and gives 10-year-old diesel buses a new lease of life,” he said. “In my view every bus in London will be either pure electric or hybrid by 2025.”
Some operators are heading in the opposite direction however, replacing their hybrid systems with standalone diesels because they have experienced reliability problems with the former. The mainstream media has of course been littered with reports that the hybrid New Bus for London (now not quite so new) has been plagued with faults.
Yanked out
In the USA, New York’s MTA (Metropolitan Transportation Authority) announced as long ago as 2013 that it was proposing to remove all the hybrid technology from around a quarter of its buses and install new diesel engines instead. Contemporary media reports said that it was finding that the electric traction motors fitted to the hybrids were burning out prematurely, and was worried about the future cost of replacing them once the five year warranty on the vehicles expired.
Closer to home, a high-profile north of England fleet operator – which has asked not to be named – has had all of the hybrid equipment taken out of 10 of its buses but retained their diesel engines. The hybrid element has been replaced by either an EcoLife or Ecomat ZF gearbox, with the work carried out by Morpeth, Northumberland-based Loansdean Hill.
“The hybrids had serious reliability issues and we were finding it very difficult to keep them on the road,” said the operator’s Chief Engineer. “We were having problems with everything from the sensors and the cooling pumps to the generators and the batteries themselves. If we were lucky the vehicle would manage to limp back to the garage. If we weren’t then we would have to either repair it at the roadside or recover it to our workshop.”
The glitches were covered by a five-year warranty on the vehicles, although this did not of course shield the fleet from the embarrassment of having buses break down with passengers on board. “That warranty was coming to an end however,” he said. “We could have purchased an extended one, but we concluded that removing the hybrid kits, putting in automatic gearboxes and going back to diesel would be cheaper. We’d already had battery packs replaced and we were worried about the likely cost of replacing them yet again once the vehicles were out of warranty,” he added. “The cost of doing so would have been eye-watering.
“The re-engineered buses are now back in service and we’re having no trouble whatsoever with them,” he said. “We don’t see them in the workshop other than for routine inspections and maintenance. We’re now able to put all 10 of them on the road simultaneously and that never happened previously. We understand that a couple of other operators have had similar work done and for much the same reasons.”
Ditching the hybrid approach does of course have implications for tailpipe emissions and fuel economy, but in the operator’s understandable opinion that does not outweigh the cost and inconvenience of having vehicles off the road.
It should of course be stressed that in both cases the hybrid packages that were removed were older systems and that the battery leasing arrangements now being offered by some suppliers should ensure that fleets are insulated from the unpleasant financial shock of having to replace a battery pack. Newly installed systems put together by companies that have learned from previous mistakes should hopefully not give anything like the same level of trouble; Vantage Power’s B320 retrofit unit seems to have been particularly well-received.
The five new articulated Mercedes-Benz Citaro hybrids, using technology recently unveiled by the manufacturer and going into service in Germany with Stuttgarter Strassenbahnen AG, represent a prime example of vehicles with what looks like a well-designed OE hybrid system. Expected to deliver a fuel saving of up to 8.5%, it makes extensive use of volume components that have already proved themselves in other Mercedes-Benz models – the additionally-required cooler for the motor and inverter is used in Mercedes-Benz trucks for example – which should help ensure reliability and durability.
All of the parts should last for the Citaro’s life says Mercedes-Benz, and volume production should help keep the price down. “The objective with the Citaro hybrid is to make the diesel engine even more economical while optimising the degree of electrification for maximum overall economic efficiency,” said Rudiger Kappel, Sales Manager at Mercedes-Benz Buses Germany.
No pain, no gain
It should also be emphasised that ripping out hybrid technology and going diesel (or fully electric or gas for that matter) is not necessarily a pain-free exercise. Environmentally friendly arrangements will have to be put into place to dispose of all the components that will have to be scrapped – especially the batteries.
Kevan Browne, UK Communications Director at Cummins, said: “You will have to take that into account. If you are proposing to retain the existing engine, then bear in mind that it will have been calibrated for operation in conjunction with the hybrid kit that has been removed.”
Nor are there all that many specialist engineering companies in a position to take on the work: “Removing a hybrid system and putting in a new diesel is a project we’ve been looking at, but we’ve not concluded it yet,” said Michael Kerslake, Director of Paul Clark Services. “We are of course aware that battery packs are extremely expensive and that it’s cheaper to change an engine.”
A ZF Services partner for the past year or so, the Royal Wootton Bassett Wiltshire-based business can carry out major component changes on buses, repair key items such as gearboxes and engines, undertake contract maintenance and provide seven-days-a-week supervisor and technician workshop cover for bus and coach operators who need to cope with the impact of staff holidays, short or long-term illness or recruitment issues.
No matter on what basis they are employed, more and more technicians will have to be trained to work on buses operating on alternative sources of power; while cutting NOx and particulates is vitally important, cutting your carbon footprint also still matters given continued concerns over global warming.
“Reducing CO2 is absolutely critical when you look at the way the world is,” said Simon. “Yet many people are still blind to that fact; and that worries me.”[/wlm_ismember]
