A trolleybus in Zurich showing the extensive overhead wiring.
contact on the underside of the vehicle connected with the plate, taking a fast boost charge. The plate is harmless to others on the road when not in use. More recently, Bombardier, well known in Europe for trains and trams, has introduced its Primove induction charging system of wiring laid beneath the road surface at busy bus stops and at each end of the route. Vehicles can take a fast charge whenever they are stationary for a minute or more. The Primove system can be used in any other vehicles equipped to take a fast charge. It works rather like road tolling, with users charged for the amount of energy consumed at the end of each month. Wrightbus, the innovative bus manufacturer based in Northern Ireland, is leading a consortium that will deliver eight all-electric midibuses to Milton Keynes in England later this year. The buses will use inductive charging by Conductix-Wampfler, a U.S. company that supplies automated guidance systems for vehicles in factories. William Wright, still leading the company’s projects on alternative fuels at the age of 85, has some very interesting views on batteries. His company is currently using lithium-ion, which is in short supply. As demand increases and prices rise, he believes the solution may well be sodium-ion. Sodium-ion is readily available and works better at lower temperatures.
BUSRide
At $300,000, the all-electric midibus is nearly twice the price of its diesel equivalent. However, electricity is much less expensive than the European price of diesel. Wright predicts net fuel cost savings of up to $18,000 per year. Buses operating solely on batteries have been running in Europe for several years, recharging only at a depot at the end of the day. They tend to be small vehicles used on precinct work in historic town centers with narrow streets. Their problem has always been limited range, especially if the batteries also have to power the HVAC. With that said, battery technology is improving and we are starting to see
larger vehicles with greater range capabilities. Greater range requires a greater number of batteries, however, which can restrict the number of passengers so as not to exceed maximum legal axle weight limits. A small number of trial contracts have been signed for full-size transit buses, principally with Chinese manufacturers like BYD, and with Foton which has an assembly plant in Spain. The British bus builder Optare has been offering all-electric versions of its Solo and Versa midibuses for four or five years. Deputy CEO Glenn Saint has been closely involved in the development. He believes that plug-in recharging is much less expensive and easier to install than either conductive or inductive systems. Saint is not an advocate of compressed natural gas as a fuel for buses. He believes it is much more efficient to convert gas to electricity. EMT, the principal operator in Madrid, Spain, has a number of hybrid buses which use a CNG-fueled thermal engine. These give very clean emissions but are quite complicated, with all the hybrid equipment plus gas storage tanks. In the medium to longer term, electricity may well be the answer. Further developments are inevitable, and it will take time to refine systems so that they become thoroughly reliable and achieve the required operating range. BR Doug Jack is with Transport Resources in the United Kingdom.
Alexander Dennis hybrid double-deck buses in Reading, England. They are color branded for different routes.
May 2013
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