The Trolleybus System

The Trolleybus System. An underestimated energy efficient and non-carbonising transit solution A proven zero-emission electric vehicle technology for public transit The paper “Towards a sustainable energy future”, issued by the International Energy Agency (IEA) in 2008, is explaining: “In the longer term, new technologies will be needed to de- carbonise transport. Advanced biofuels, hydrogen fuel cells and electric vehicles are all possible options. Today, it is hard to tell which technology or combination of technologies will prevail. They all require much more R&D before they become ready for mass deployment. To achieve a 50% CO2 reduction by 2050, one or more of these technologies must be deployed on a large scale by mid-century. This underlines the urgent need to partner with industry to accelerate R&D advances.” From the technical point of view the electric vehicle technology is the most advanced of these three technologies and is – for certain purposes - ready for mass deployment. Nowadays, for railbound transit systems the electric propulsion is state-of-the-art. Since decades, tramways, metros, interurban trains and other railbound urban transport systems are driven by electric motors. In view of this fact, it is surprising that the mass deployment of the electrical drive for rubber- tired transit systems has not yet taken place until today (Figure 1). Thereby, one can draw on the long-time tested and reliable “zero-emission” Trolleybus System, which exists since 1882.

One of the core advantages of the electrical drive is the remarkably low energy consumption. One main reason is, that from the thermal point of view, electric motors generally work more efficient than combustion engines. In addition to that electric propulsion provides the option to regenerate about 30% of the braking energy by sending it back to the catenary or by onboard storage in ultra-capacitors and using the stored energy for acceleration after the stop. By this, electric driven systems have an about 50% lower specific energy consumption compared with fuel motor driven systems (Figure 2). Modern Trolleybus Systems offer a wide range of strengths:  High transport capacity  5 to 10 times cheaper and shorter timescales for planning, decisions and construction than LRT Systems  Less than 50% of operational cost of LRT Systems  Capability to operate on ordinary road surface and no need for rails or dedicated roadbeds  An obviously higher torque compared with diesel or gas buses  No idling motor energy losses (e.g. at bus stops or at traffic signals)  Better overall performance and less vibration (none whilst idling!) which results in jerk- free acceleration and faster, more comfortable, smoother and hence more attractive journey experiences for passengers  Improved climbing ability (up to 12%) because of rubber tyres and also high acceleration capability on gradients  Lowest possible noise levels inside the vehicles and almost no noise irritations for residents

1  Zero exhaust emission on site. Especially no carbon dioxide emissions by the vehicles. Even when the electricity is sourced from fossil fuel there is still a reduction in global air pollution! (Figure 3)  Independency of the development of the mineral oil situation  Reduced vehicle maintenance thanks to low vibration  Long life timescale of the vehicles (up to 20 years) and of the infrastructure (up to 60 years) as well as the opportunity for an economic mid-life refurbishment  The external costs are very low compared with Diesel Bus and Light Rail Systems  Proven and very reliably technology with less risks  Experienced and innovative industry  The presence of the catenary is a high “easy to find factor” and acts as a continuous advertisement for the system  The catenary – as "rails in the sky" - provides confidence that the transport will be here today and tomorrow (rail bonus) too, thereby encouraging businesses to make investments in the served corridors and attracting more passengers. This can generate higher profits on the market One of the reasons why more cities are not investing in electric rubber-tired transit systems is the still insufficient situation of the energy storage technology. The only way to obtain sufficient electrical energy for a full days' work is by making that energy available wherever the vehicles are. The only proven viable way to achieve is through the installation of an overhead wire power supply system. The additional costs of such systems as well as the fact that often decision makers dislike overhead wires are arguments enough to abandon electric bus systems. To avoid such short-sighted decisions awareness of the advantages of modern trolleybus systems has to be increased to get more financial and argumentative support by politicians and governments to disrobe the old-fashioned image of the trolleybus and start a revival by putting new systems in place. At the same time, to increase flexibility and to reduce investment and operation costs of Trolleybus Systems political initiatives have also to been taken to encourage the industry to accelerate the development of the energy storage technology.

Trolleybuses worldwide The Trolleybus System is well known all over the world. About 40’000 vehicles are being operated in about 350 cities, in countries as different as Russia, Ecuador, New Zealand, Czech Republic, China, Greece etc (Figure 4). The prototype, invented in 1882 by the German engineer Werner von Siemens, looked like a hackney carriage, but was already powered by an electric motor. Around 1930, the age of the modern trolleybus system began when reliable overhead contact systems were introduced. Beginning from this day, this principle has constantly been optimised and developed further. Worldwide the number of Trolleybus Systems is growing - but still very slowly. In the former Soviet Union countries trolleybuses are widespread used. Also in South America important networks are operated. During the last years some new systems have been opened, e.g. in Merida and Barquisimeto (Venezuela) or Castellón (Spain), re-opened (e.g. Rome) or extended, e.g. in Lyon (France), Salzburg (Austria) and Bratislava (Slovakia). New networks are being proposed, e.g. for Valenciennes (France) and Leipzig (Germany). A lot of existing systems have renewed their trolleybus fleets.

2 Moscow has the biggest trolleybus operator of the world with more than 1200 electric vehicles in operation. Landskrona in Sweden is the smallest operator and owns 3 trolleybuses. With 13 Trolleybus Systems, Switzerland has the worldwide highest rate of trolleybus operators per million inhabitants.

An economic solution for high frequented routes Often the trolleybus is compared to the diesel bus, which is stated to be more flexible, more reliable and cheaper. The first and the second argument must be negated in the meantime. The technical development has increased the reliability of the infrastructure to zero-failure, the electrical traction causes less failures than the diesel engine due to less moving parts. Unlike Diesel Bus Systems the Trolleybus System needs investments for a current supply system with substations and an overhead contact wire system. The infrastructure of a Trolleybus Systems can be realised five to seven times cheaper than the infrastructure of a comparable Light Rail System whose time to market, the timescale for planning and construction, is up to 5 times longer than for Trolleybus Systems. The trolleybus industry is a quasi-monopoly with less competition and high prices. Furthermore, in Western Europe, high labour costs are additionally increasing the prices for the infrastructure. These are the main reasons that investment in a Trolleybus System is about 70% higher than for an ordinary Diesel Bus System, even though the prices for the vehicles have been fallen in the last years. Market development and common tenders lead to more attractive prices. The difference of the annual vehicle capital costs for the Trolleybus and the Diesel Bus Systems can be brought down to 6 until 17% (Figure 5) because trolleybuses as a rule have a longer life time (about 20 years) than diesel buses (about 10 to 12 years). Capital and maintenance costs of the infrastructure are predominantly fixed costs. The more heavy the trolleybus service is (short headways, articulated vehicles) the lower the cost difference between Diesel and Trolleybus System will be. Even though the initial investment in Trolleybus Systems is higher, LCC can become lower than for diesel buses and of course lower than for LRT Systems. At the moment a great uncertainty exists about the development of availability and price of the crude oil. This is the main weakness of the Diesel Bus and also of the Gas Bus System. The higher the price and the uncertainty about the availability of diesel fuel (and also for natural gas) the better the situation for the Trolleybus System will become.

More passengers and revenues by Trolleybus Systems There are circumstantial evidences, that Trolleybus Systems are perceived more attractively of the market than Diesel Bus Systems:  By the overhead contact wire system the Trolleybus and with that Public Transport in general has a permanent visual presence in the public area (analogous to railbound systems)  The permanent visibility makes it much easier for the customers to detect and access the public transport modes  By this better perceptibility, trolleybuses are much less involved in accidents than diesel buses. In Switzerland the price for the third-party insurance of trolleybuses is half as high as those of diesel buses.

3 By this increased attractiveness more passengers can be generated. In Arnhem (Netherlands) the ridership increased in the order of 15% on routes converted to trolleybus service. In Salzburg (Austria) ridership increased up to 16% by a five year plan which included extensions of trolleybus routes and converting a diesel bus route to electric operation. Increases in ridership have also been noted in the USA, for instance in Seattle and San Francisco. In Zurich, on trolleybus routes 31 and 32 new 25 m long double articulated trolleybuses (Figure 6) have provably increased the image of the Trolleybus System as a whole and the ridership by 8% during the first six months of operation.

Concerning external costs the Trolleybus System is in the pole position In the Public Transport field the external costs should play an important role and find their expression in the national economic consideration by the general public. The following external effects obviously speak for the Trolleybus System, also compared with LRT Systems:  Energy consumption  Output of climate gases  Atmospheric pollutions  Noise irritation of passengers and third parties  Frequency and severity of accidents In the national economic calculation the position of the Trolleybus System considerably improves opposite to the Diesel Bus System.

High reliability of modern Trolleybus Systems Despite of the quasi-monopoly situation of the trolleybus industry the technology is innovative and remarkably reliable. The reason is the fact that trolleybus manufacturers can benefit from the development and experiences of the diesel bus manufacturers (car body, axles etc.) and of the electric railway industry (control equipment, motors etc.). Modern design outside and inside the vehicles and low floor at the entrances are state-of- the-art as well as air conditioning, kneeling and boarding ramps for passengers with mobility restrictions (Figure 7). Modern vehicles also offer ABS and TCS as well as automatic hill holding and allow powerful running up to a maximum speed of 70 km/h. Based on the experience with Light Rail technology modern electric trolleybus equipments for 600 or 750 V DC are very reliable, not least because trolleybus motors have fewer moving parts than diesel motors. In contrast to railbound vehicles the current collector system makes trolleybuses flexible enough to drive the vehicles with a lateral offset of up to 4 m from the optimum lane to avoid obstacles. The trolleybus current collectors can be equipped with pneumatic quick lowering and locking of the poles and automatic wiring. In the case of a “dewirement” the poles are automatically caught and locked. Modern trolleybuses are equipped with either a low power fossil fuel engine or batteries to operate away from the catenary, perhaps at reduced speed. These secondary power systems can also be used in the depots, giving the ability to access every part of the facility without having to provide wiring. Modern trolleybuses are equipped with chopper or inverter control equipment which are focused on the reduction of the energy loss during the acceleration phase. Both systems

4 offer smooth running and braking of the vehicles, considerable electricity savings and little maintenance of the control equipment. Regenerative braking is possible. Trolleybus equipments with voltage inverters have maintenance-free AC motors of small dimension and closed construction. During the braking phase the electric motor works as generator and the electric current can be fed back to the overhead system and utilised by other trolleybuses accelerating at the same moment. A further way is the storage of the braking energy. The actual technology is such that batteries (lead-acid or nickel metal hydride/NiMH type) tend to be the most favoured option, although trials using flywheels and ultra-capacitors have also taken place. Unfortunately reliability, durability, weight and costs of batteries are not satisfying and have (when life-expired) environmental limitations. Therefore alternative energy storage options have been developed. One of these is the ultra-capacitor (super cap) onboard the vehicle or in a substation. A super cap is an electrochemical capacitor that has an unusually high energy density when compared to common capacitors. Apparently ultra-capacitors offer the promise of high power rates, light weight and long life at a reasonable cost. Up to 35% of the electricity can be reclaimed in this way. Trials with ultra-capacitors are currently underway in China, Europe and the USA. A batch of appropriately equipped trolleybuses has been placed into experimental service in Shanghai (Figure 8). The onboard super caps are charged at several stops via a short catenary section. The trolleybuses can operate about 1 km without an overhead wire power supply system. After this trip the super caps have to be recharged. Modern and innovative overhead contact system solutions provide a high reliability of the current supply system. The state-of-the-art switches allow running with full speed of up to 70 km/h with almost no risk of dewirement. The switches can be automatically controlled by the vehicles.

Can Hybrid Buses replace the Trolleybuses? Today, hybrid buses are only competitive with diesel buses by public hand subsidies because they are about 30% more expensive than the conventional variant. Hybrid buses cannot compensate the higher initial costs while operating. The construction principle of hybrid buses is not only complex but causes also high costs: Li- ion batteries for commercial vehicles – given that they are available on the market - are still hardly to pay by customers at present. To avoid such problems manufacturers are hoping to be able to replace the diesel engine by a hydrogen fuel cell in the future or to make natural gas-hybrid concepts ready for series production. Further developments of efficient storage technologies will give new opportunities for combinations of electric drive and diesel, gas or fuel-cell drive concepts, so called hybrid bus systems. The manufacturers promise up to 25 per cent less fuel consumption but this cannot be reached in practice yet. One is common to all current hybrid developments: They can decrease the problem of the CO2 emission but they do not solve it. Alternative propulsion systems without greenhouse gas emissions can be realized only on the basis of hydrogen as fuel for internal combustion engines or as a source of energy for hydrogen fuel cells. Until these technologies will be marketable and the required infrastructures built up - nobody knows exactly when this will be - the Trolleybus System next to the electrified Railway Systems remain for a wide range of tasks as the "climate friendliest" public urban means of transportation. Nevertheless the “Hybrid Hype” could offer a wide range for modular solutions (Figure 9) beginning from diesel buses with minimised power fossil fuel engines for feeder bus routes up to “pure race” trolleybus vehicles which are able to operate in the city “completely wireless” thanks to a light weight and powerful super-capacitor.

5 The Trolleybus as affordable Light Rail As Light Rail Systems consume more energy and squeak in curves, the Diesel Buses are noisy and produce fumes and particles, even with modern filter technology, none of the existing technologies can compete with the Trolleybus System in terms of emission and reliability. The Trolleybus System provides all the benefits of the Light Rail Transit (LRT) System, especially the same urban-friendly advantages, combined with the flexibility of Diesel or Gas Bus Systems and lies therefore ideally between the LRT and Bus Rapid Systems (BRT) adding the ecologic quality of LRT systems to the economic advantages of BRT systems. Light rail trains can be up to 90 m long when running in mixed traffic areas. For non-guided diesel or gas buses and also for trolleybuses the maximum vehicle length is limited to 25 m. Thanks to the small compact electric motors such long vehicles can be economically equipped with a two axle drive which allows to climb hills with ease. This two axle drive concept can also be used in single articulated 18 m or 20 m long trolleybus vehicles to increase the adhesion for hill climbing or obtaining better driving conditions on snow-covered streets. With a capacity of up to 200 passengers per vehicle the low-floor bi-articulated trolleybuses definitively close the gap between Light Rail and Diesel Bus Systems. The 25 m long vehicles can operate on regular streets and on separated lanes (Figure 10) as well as in tunnels. Thus, even for cities with at least 40 to 50’000 inhabitants which are planning to extend an existing or to build a new Light Rail System, or introduce a new mass transport system, the Trolleybus System is a recommendable alternative. The same applies to cities where diesel buses have to be renewed or the ecological situation is worse and passenger demands force higher capacity a Trolleybus System can play the role of an affordable Light Rail System.

Conclusions 1. The Trolleybus System is the most advanced energy efficient, non-carbonising and long-time tested rubber-tired electric vehicle solution and is – for many purposes - ready for mass deployment. 2. By the overhead contact wire system the Trolleybus System has a permanent visibility in the public area (analogous to railbound systems). By this increased perceptibility more passengers in the order of 15% and more revenues can be generated. 3. In consideration of the required investments into the overhead wire system Trolleybus Systems work economically with high capacity vehicles and at short headways, i.e. on high frequented routes. Thus life cycle costs (LCC) can become lower than for diesel buses and of course lower than for LRT Systems. 4. Despite of the quasi-monopoly situation of the trolleybus industry the technology is innovative and remarkably reliable. 5. Hybrid buses can decrease the problem of the CO2 emission but they do not solve it. Until alternative propulsion systems without greenhouse gas emissions can be realized - nobody knows exactly when this will be - the Trolleybus System next to the electrified Railway Systems remain for a wide range of tasks as the "climate friendliest" public urban means of transportation. 6. The Trolleybus System can provide 90% of the benefits of a Light Rail System for 15 to 20% of its price. Thus for cities with at least 40 to 50’000 inhabitants the Trolleybus System is a recommendable alternative to Light Rail Systems.