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updated 24/4/14

Some years ago, Sir Peter Hendy, Transport for London's Commissioner, said there's nothing wrong with trolleybuses, clean, quiet and fast, just that the need for overhead wires had to be proved. Since then there's been many moves to bring greener buses to the streets, even if the impetus has not been operators or authorities like TfL but politicians answering growing concerns about climate change and air quality. Trolleybuses are of course very green and efficient, so why haven't there been many more? Why do reports barely mention them? Why is there an aversion to their consideration? Why are overhead wires seen as an almost total barrier to wider implementation? And do the alternative technologies mean trolleybuses are becoming out dated? The aversion to wires is something that's assumed to be a public distaste by planners, many of whom, when concerned with the urban fabric, have spent their lives getting rid of phone and power lines. There is little real evidence that the public is really so concerned, but to understand the way future city transport is being developed does warrant an examination of prevailing mindsets. It has been said that hybrid buses have been born of diesel bus designers and while the take up has doubtless been an alliance between the existing industry and politicians keen to show green credentials, the technology would likely have evolved anyway. It has at least been admitted as a temporary stop gap in the great scheme of things on the ladder to zero emissions. Hybrids, even if they behaved as intended rather than as they do in harsh real world conditions, still emit CO2 and more dangerously, carcinogenic micro particulates. They are not like-for-like competitors to trolleybuses.
One of Salzburgs Metro style Solaris 18m artics on new wiring to the Arena. Ashley Bruce

What then, are the technological threats to trolleybuses? There are only two, but with many variations possible. Fuel cells and batteries depend on how they are fuelled or charged, with no guarantees that where the electricity comes from is clean. The same argument is used against trolleybuses with rather more vehemence, as a reason, together with an obsession to do away with wires, to justify finding new technologies almost for their own sake. Of course, neither fuel cells or batteries are new and have needed considerable development to come close to being viable alternatives to wiring city streets. But the mindset of those creating the ecology of green bus thinking has to fit certain criteria. Once asked why the World Bank was funding fuel cell bus demonstrations in Brazil when trolleybuses already fitted the required bill, a senior transport researcher paused, thought, and said "you don't understand how these things work", meaning progress is seen as encouraging fledgling technologies with funding to private industry that can't be justified if the technology is mature. Overhead wires provide an easy target for those who want to create new industrial opportunities although, to be fair, the European Bank for Reconstruction and Development has funded many trolleybus systems in East Europe and the World Bank did finance the Quito system. Nonetheless, trolleybuses are branded as old fashioned and wireless alternatives are the coming thing, even if their zero emissions are likely to cost more to achieve. Quite how much more is difficult to discover with can-do, short termist and positive spin obscuring objective comparisons. With bus producers, electrical infrastructure companies and PR minded operators all vying to promote their latest model, newest systems and greenest initiatives, all of which promise a better tomorrow, there are vested interests intent on not disclosing deal breaking problems. If some details, longevity comes to mind, might be hard to state but inherent costs, even physical limits will have to be faced. So who and what are the contenders?
BC Transit 1017 a New Flyer Industries H40LFR fuel cell hybrid built for the 2010 Winter Olympics and now withdrawn. Dennis Tseng

Fuel cells
Fuel cell buses, usually with units by Ballard or UTC, have been trialled since 1998 often in connection with exhibitions or as heavily subsidised demonstrations, with a peak of trials in 2005. There is common consensus that commercialisation is some way off, probably after 2030. The worlds largest fleet, at Whistler in Canada, has stopped operating due to cost. 26 fuel cell buses across 5 European cities at a cost 26 million euros under the CHIC project had aimed to achieve full commercialisation by 2015 but reliability (less than the target 85% availability), infrastructure and capital costs continue to be said to need considerable improvement. Chinese fuel cell buses have failed because poor air quality has damaged the cells. The complexity of the well to wheel process, namely electricity generation to produce hydrogen that is compressed and transferred to the bus for reconversion back into electricity is an inherent barrier to efficiency and commercialization, even if the much lauded 'only' by-product, pure water, plays well to public attention. The complexity, however, requires considerably more maintenance than any other zero emission technology. Daimler, Van Hool and the now defunct APTS Phileas have been the main players in Europe while New Flyer in North America has produced a 60 foot prototype for 22 months of tests since the withdrawal of the Whistler fleet. Manufacturers hope to deploy 500 fuel cell buses by 2020, under a letter of understanding with operators that include London, although there is no indication of where funding would come from. With the technology called mature by protagonists, public subsidy may not be as forthcoming as previously. There have also been demonstrations of hydrogen internal combustion engined buses by MAN under the EUs HyFLEET:CUTE project which finished in 2009. The comparative calorific poverty of hydrogen will most likely mean no further development of H2-ICE buses.
Wangxiang EV bus chassis, using Ener1 batteries, a joint venture based in Hangzhou, with a full service range of 60 miles.Wangxiang

The last decade has seen a proliferation of battery buses, starting with midi buses and developing with induction charging systems. There are now full size 18m battery bus prototypes and many different charging designs. The options also include battery swapping, ultracapacitors, roof and underbody collectors, zinc-air cells, iron-phosphate batteries and induction charging. A goal that would make battery buses comparable with trolleybuses would be a range ability of 350km a day with equal passenger capacity and equal cost over a 25 year life. No battery bus is yet capable of such performance on any of the three criteria, although protagonists might argue that things are getting close. The discussion is again made difficult with the fog of spin; for instance, industry leader BYD of China claims 3 hour charging when experience finds over 5 hours is necessary to give a range of 250km. BYD shares fell by 40% at the end of 2014, thought to be because their order book had been cut. Company claims had been made of 4000 battery bus sales per year in China alone when manufacturing capacity was only half that figure. Other sources (Businesswire) state total BYD bus production is 1300. World trolleybus production is around 1000 units a year which may increase because of new Chinese commitment to the mode. There are no commercial battery buses according to Forbes, but IDTechEX, a research company that refuses to include trolleybuses as pure electric buses, claims a world market of $10billion for 'all' types of electric bus (Including minibuses, hybrids and school buses etc.).
The BYD Lancaster 60' artic prototype demonstrated to LA Metro Orange Line. LA Times

BYD uses many lithium iron phosphate batteries in its buses to achieve all day running with long overnight charging. The penalty is the weight of the batteries, 3-5 tons according to Bombardier, that reduces passenger capacity, and lower energy density (~60%) but a longer cycle life. The cost of a 60ft (18m) BYD artic is $1.2 million, 50% greater than an equivalent CNG bus (or trolleybus). The battery life is claimed to be 12 years, although most other battery bus manufacturers would only claim half of that and experience with battery trolleybuses in Rome showed a battery life of only 3-4 years. Proterra, a leading US battery bus manufacturer, guarantees their Lithium Titante fast charge batteries for only 3 years. The replacement cost of battery packs every 3-4 years is equal to the capital cost of the vehicle over a trolleybus lifetime, so doubling their cost. The extremes of battery bus deployment range from the simple approach of piling many batteries into the bus (BYD, Rheinbahn etc.) to ultracapacitor buses that recharge at nearly every stop (Shanghai). Both extremes, and those in between, risk the bus becoming stranded and so have to build-in operational distances of around 60% of their maximum ranges. Recharging regimes needing more than seconds are being regarded by operators as likely to cause timekeeping havoc. Air conditioning and heating also limit battery buses, catastrophically in the case of Shanghai's ultracapacitor buses, where the problem contributed to their withdrawal.
Geneva's TOSA Hess charging at the Palexpo terminus in 2014. ABB

None of this has stopped demonstration schemes going ahead. TOSA (Trolleybus Optimisation Systeme Alimentation) in Geneva uses a 18.7m Hess with 133 passenger capacity that aims to equal trolleybus service performance using lithium titante batteries and 'flash' charging of 400 kW in 15 seconds every 1.5-2km and a full 3-4 minutes charge at termini. LTO batteries have a lower energy density than Li-ion, but can be fast charged. The proof of concept is a 1.8km route between Geneva airport and the Palexpo that is scheduled to take 3 minutes. An overhead collector, which appears to need very accurate alignment of the bus, deploys in one or two seconds as doors open. Conflict would arise if two buses arrive at a charge point at the same time. No data has been found about capacities, 1st year operations or cost, although TPG Geneva is said to be installing a 'regular' TOSA line 'somewhere around 2017' according manufacturer press releases. The US Federal Transit Administration has pointed out the very high power transfer as having overcharge and fire hazards. Meanwhile, according to ABB, the test line operated for 18 months at certain times until the end of 2014. No evaluation of cost benefit or results have been publically released.
The induction pick-up beneath Braunschweig Solaris Urbino BS VG1401. Braunschweiger Verkehrs-GmbH

An example of induction charging, that seemingly gets rid of all visible charging mechanisms apart from a large road plate, is the Braunschweig research project using Bombardier's Primove system. With half the charging power of TOSA and a need for considerable ground works and cooling, there are safety issues from electromagnetic interference and questions of efficiency. The route is the fourth Primove demonstration, but the first to replace conventional buses. The Circular M19 is 12km long, has a 10 minute headway, 25 stops, two 30 second charge stations and one 11 minute terminus charge stop. There's also a 15 minute charge pad at the depot. One 12m Solaris Urbino started testing a year ago with two 18m Solaris artics arriving in December 2014. A 2.9 million euro subsidy from the German Federal Ministry of Transport, together with equal local funds pays for the trial. The six diesel buses that currently carry 6000 people a day may be entirely replaced by 2016 if the initial experiment is judged a success. Costs again appear critical with the addition of an expensive infrastructure that doesn't appear to be entirely necessary and which could prove problematic in established city centres where existing underground services would need moving to avoid magnetic contamination. Other battery bus schemes use smaller buses on short, lightly loaded routes where exotic charging machinery isn't necessary. But battery replacement costs remain the Achilles heel.
Two of 38 Youngman 12m e-BRT buses at charge points in Jinhua.

Ultracapacitors, with 5-10% the capacity of Li-Ion batteries, but very fast charge and >10000 cycle life have proved cost effective in trolleybuses as efficient stores of regenerated power from braking, resulting in 20% reductions in energy consumption. The TOSA system has added them to reduce battery size to 40kWh. Ultracapacitors have also been tried as the primary power source, mainly in Shanghai where three routes partly use them. The latest developments see a combination with battery characteristics to reduce weight (1.6~0.6 tons) and increase range (4km~10km). Operational limitations have stopped widespread use but trolleybus manufacturer Youngman has just built 38 'e-BRT' 12m buses for Jinhua, a city of 5 million without trolleybuses. The '3rd generation Carbon nano lithium-ion superbatteries', made by Youngman, provide a top speed of 70km/h, a range of 50km and a 10 minute charge time. 140 million euros have been invested in the Youngman plant to build all-electric buses but little is yet known about costs or reliability of the new system. Youngman has also just built 18m articulated trolleybus versions of the same model for Beijing.

Zero emissions
Carrying around a power supply is never going to be as efficient as drawing it from overhead wires but there is now considerable momentum to do away with the 'visual intrusion'. Much of what will happen depends on commitment to save lives lost through street air quality and real understanding of the gravity of man-made climate change.
Libroduct testing on a Lusanne NAW trolleybus, 2014. Kummler+MatterKummler+Matter

There is an option that might mean a greater trolleybus revival that plays into the need for battery charging and less overhead. Kummler+Matter, the overhead wiring supplier, has spent a number of years working with a specialist software company, DIaLOGIKa, to come up with LibroDuct, a system that can repole trolleybuses with considerable sophistication and precision. Using 3D imaging from two cameras, GPS and winged trolley heads, booms are guided with real time control that 'sees' the wires while 'knowing' where on any route the trolleybus is. The process is automatic and can happen while moving. An adapted Lausanne NAW trolleybus with the system and servo motors added to the trolleybase has been successfully tested during summer 2014. The system has the potential to avoid building complex overhead junctions and saving considerable costs as well as removing 'intrusion'. If London were ever to implement full electrification of 5 minute frequency bus routes - those that coincide with the worst air pollution - then a fourth generation trolleybus technology with auto re-poling and superbatteries might be the only practical answer. Of course, a future just around the corner is also the history of fuel cell and battery buses! Meanwhile, wires remain essential.

Ashley Bruce, 3/2015.
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updated 24/4/14