Wednesday, March 04, 2009

Fast opportunity charging electric buses

ILLUSTRATION - The ancestor of fast opportunity charging electric buses, the Gyrobus from Oerlikon corporation, was used in Switzerland in the early 1950s. The electrical energy gained during the 70 seconds recharges every 2 km accumulated in a flywheel. This illustration is the cover page of the former Science and Mechanics magazine of April 1954.

As we have seen in my note on the depletion of global resources (March 3, 2009), the sustainable development of people transportation goes through public transit systems much more developed than today.

The all-electric vehicles are ideal for the quality of life (no pollution and little noise). Already metros, trams and trolley buses are operating in several cities. But the bus remains a very important component of urban public transport. We see more and more battery electric buses make their appearance, such as the small fleet of electric minibuses set up in old Quebec City in 2008, but their range is limited to approximately 100 km (60 miles) due to the cost and weight of batteries.

With the advent of fast charging fast lithium titanate batteries, since 2007, it is now possible to have fast opportunity charging electric buses. These buses will fill up with electricity at regular intervals along their way by means of a retractable pantograph making momentary contact with the overhead conductor of a fast charging station, for about one minute every 5 km (3.1 miles), or 25 seconds every 2 kilometers (1.25 miles).

The advantage is that opportunity charging does not need overhead cables all over the streets, as in the trolley buses, or rails like tramways. The cost of infrastructure is thus reduced, as well as the cost of batteries, since a range of about 20 km is sufficient. A system of opportunity charging electric buses also offers more flexibility since you can easily change the itinerary. This is not the case for trams or trolley buses, which must follow their predetermined itinerary all the way to be supplied with electricity.

If we want to increase the transit capacity of buses and approach the capacity of tramways, we need only to drive the buses in dedicated lanes, not available to other vehicles. This is the busway concept, becoming increasingly popular as cheaper than the tram. The city of Nantes in France, among others, installed a very popular line in November 2006. Most busways today use articulated buses (120 passengers) running on diesel or natural gas. The next logical step would be fast opportunity charging electric Busways.

The principle of fast opportunity charging is not new. It was tried in Switzerland in the early 1950s with the Gyrobus, built by the company Oerlikon (illustration at the beginning of this post). At that time, there was obviously no long lasting and fast charging batteries. The energy storage system used was a flywheel set in rotation at a speed of 3,000 rpm.

Furthermore, the Swiss company Numexia is currently developing autonomous small electric vehicles with fast opportunity charging for public transit without drivers (recharges in 5 seconds to regularly spaced stations). The system will be installed in Switzerland, at the site of École Polytechnique Fédérale de Lausanne in 2010 and will serve a distance of 4.6 km (2.9 miles). It will use 30 small vehicles and 15 non contact fast charging stations. This innovative transportation system was introduced in the program Nouvo at the television channel TSR in Switzerland.

In California, Proterra company just introduced in February 2009 its all electric bus EcoRide BE35 (shown below) that can travel 50 km to 60 km on a recharge of its lithium titanate battery from Altairnano. The battery can be recharged in less than 10 minutes through a high power charger also sold by Proterra. The bus is also available in plug-in hybrid version, giving it the same range as a traditional diesel bus. It is a very interesting intermediate step before the actual fast on the way opportunity charging electric buses.

For further reading on this topic, you can explore the website developped by Roger Bedell.

1 comment: