Monday, September 8, 2008
Trolleybuses - The future of electric vehicles
2 Trolleybuses in Kiev.
Trolleybuses are electric buses that are powered by overhead wires, along which they travel. In terms of urban transport they are classified between tramways (light rail) with fixed tracks and independent diesel buses.
Invented 1882 in Berlin, they have been used since all over the world.
They have become somewhat rare in North America over the last decades (still in use in San Francisco, Edmonton, Vancouver) but are heavily used in most European countries, China and especially in the countries of the former Sovietunion, totalling 350 large cities.
However, in the last decade they have become increasingly popular again, with existing systems expanded and 37 new systems have opened. How to explain this trend reversal?
Trolleybuses have all the advantages of an electric vehicle: being green due to zero emissions, noiseless and very energy efficient operation.
The only emissions come from rubber wear of the tires, noise output is less than the average street level and the electric engine enables the bus to climb hills more rapidly, recover brake energy (as in the new car hybrids) and accelerate and brake more quickly than combustion-based engines, therefore they are ideal for inner city stop-and-go traffic.
Disadvantages compared to diesel buses are a fixed route (required by the overhead wire), however the wire allows for a certain flexibility, ie. to change lane if blocked, and higher construction costs for the overhead system - but not necessarily when comparing the whole system, since electric vehicles have much lower maintenance costs.
Advantages to trains are obvious - no costly construction of dedicated tracks needed.
Drawing of a trolley bus showing its flexible attachment to power lines.
The motivation for the trolley bus revival comes from the desire to enhance public transport and at the same time looking at costs for the comparable systems (train, fossil fuel-based buses).
Oil price levels have been rising in leaps and bounds. The environmental impact of pollution from carbohydrate combustion in terms of health care costs is increasingly considered. Also countries which have ratified the Kyoto protocol and have to reduce greenhouse gases, are obliged (and indeed, under great pressure) to implement measures to reduce emissions, or offset them by payments to 'greener' countries. Of all developed countries, the United States is the only one not to ratify it and Canada, while having ratified, does not respect it under its current administration.
I looked at three different studies that compare trolley bus systems to diesel bus and trains:
A UK study found that trolley buses are cheaper to operate than any other forms of public transport - note that a litre of fuel there costs around CAN$2.50 (August 2008).
An report about the Edmonton system gives actual costs $0.60/km for diesel bus as compared to $0.90/km for trolley bus. It further adds that as its trolley buses operate in the city core and therefore have more stop & go traffic (which decreases combustion engine energy usage alot) and also travel less kilometres than the diesel buses, which makes cost/km go down, the trolley buses might actually be cheaper. When including health care costs of pollution they arrive at $2.46/km for diesel bus (not even counting negative effects on the quality of life: noise pollution, being sick and or economic effects following thereof) and conclude the trolley bus a clear winner.
This Vancouver study shows that their trolley bus system consumes only half the energy/km than their diesel buses fleet. They emphasize also that the comparison is unfair against the trolley bus, since they operate on inner city routes with frequent stops and should therefore be rated even better.
In Quebec there are no trolley buses at the moment, but the very cheap electricity of the province (and trolley buses are 80% energy-efficient, while conventional engines are only 25%) give ideal conditions for it.
The cost of construction is one disadvantage over existing diesel bus fleets, but when comparing to light rail train or metro lines it is extremely cheap:
A trolley bus overhead system costs $0.75-1M/km, while light rail train costs $17M/km (double that with building the train stations) as found in this study. The new Montreal metro extension to Laval cost $150M/km, CBC reported on its website. The tram system proposed in the 2008 Transportation Plan of Montreal will cost $260M for the 20km downtown loop, costing $13M/km. Another article from Radio-Canada quotes its cost at $50M/km.
To give an idea, the cost of this recent metro extension is probably in the same order of magnitude of converting the bus fleet of the whole Island of Montreal to trolley buses. It also would not be far from the cost of the total of three proposed tramways that would cover only a small downtown area and could be implemented far more quickly.
There are developments to overcome the disadvantage of being bound to wires. Several cities are experimenting with trolley buses, that can for a shorter or longer distance go off the wire, running battery-powered. Shanghai (China) is forefront by experimenting with supercapacitors that are quickly recharged in stations, so no more wires needed. The government of China is subsidizing petrol prices in addition to being heavily dependent on oil imports and they therefore has a strong incentive to rapidly deploy alternative technologies.
From polls and petitions (Vancouver, Edmonton, ...) it can be seen clearly that people living in these cities are opposed to plans of shutting down existing trolley bus systems and would like to see primarily expansions of those systems over any other form of public transport.
The individual electric car is still very much in the future and has unresolved problems such as: relatively short range, very expensive batteries (and where will all the materials for them come from, if everyone wants to buy one?), delays to unknown reasons, fake 'safety concerns' (the car industry lobbying? the cowardice of our politicians not to be able to take a responsible decision?) and not enough electricity being available to replace the fossil fuels used as of now.
Collective electric transport in the form of a trolley bus used in medium to large cities does not expose the above problems.