An overview of alternative fuels in Europe
By Doug Jack
As I visit manufacturers the subject of alternative fuels and drive systems is always on the agenda. Heavy taxes on diesel in Europe make the fuel considerably higher priced than in North America. Still, operators acutely aware of fuel economy generally prefer to stay with diesel because of its ready availability.
With stark warnings from green lobbies about fossil fuels running out, it is simply not acceptable to say that fuel will not run out in one’s own generation, a problem for future generations. This is why manufacturers are trying to think ahead. They do not want to wake up one day and find their investments in diesel engines rendered obsolete by electric motors.
Currently, diesel engines in the European Union must have emission limits that comply with the Euro 5 standard. Euro 6 goes into effect January 2014, which is broadly similar to EPA 2010. Several manufacturers have announced Euro 6 engines already.
Hybrid sales low
Sales of hybrid buses in Europe are still relatively low, but with the higher price of diesel in Europe, the payback period for hybrid buses is becoming more realistic. Normally government funding makes up the difference between a standard diesel vehicle and the hybrid unit. Volvo has sold its in-house ISAM hybrid system in more than a dozen European countries. However, the leader, in volume terms, is Alexander Dennis with BAE Systems, almost wholly in the United Kingdom, but with some units soon to enter service in Spain.
With Allison, Eaton, Siemens and Vossloh Kiepe also offering hybrid systems there is plenty of competition in the European market. BAE Systems also is working on stop-start technology. Buses fueled by compressed natural gas (CNG) have been around in Europe for many years. At one time they held a very significant advantage over diesel buses because of their lower emissions.
CNG buses popular
That gap has almost closed but CNG buses remain popular in some countries, usually for political reasons. There are drawbacks, not least the weight of the gas tanks on the roof of the vehicle. They increase its unladed weight, and therefore can restrict the total number of passengers. On the other hand while enforcement authorities in some countries frequently check coaches and their gross weight, they have probably never taken a loaded city bus to the nearest weighbridge.
Although the consumption of gas is about 1.6 times that of diesel per mile, its normal tax rate is much lower. Sometimes, the gas utilities will pay for the installation of refuelling facilities at a depot, recovering that cost in the price of the gas supplied. Liquefied petroleum gas (LPG) buses are less common in Europe, mainly because LPG is a bi-product of refinery processes. MAN was the last European manufacturer to offer an LPG engine large enough to power a bus, but ceased production due to the cost to build.
LNG a no go
Solbus, a small Polish manufacturer, showed a full-floor city bus powered by liquefied natural gas at Hanover in 2008. The gas tank was little larger than the fuel tanks on a diesel bus, and sat neatly above the Cummins ISLG engine at the rear of the vehicle. It did not catch on probably because the only LNG refuelling facility in Poland was at the Solbus factory.
Biogas a win-win
Demand is on the rise for buses that run on biogas, principally from Sweden and Norway. The Swedes describe it as a “win-win” fuel because they can produce it from renewable resources such as sewage, slaughterhouse waste and surplus food and more easily dispose of the residue from the process.
For more than 20 years Scania in Sweden has developed engines that can run on ethanol, another fuel produced from renewable resources such as sugar cane, beets, sellulose and other feedstocks. Sweden produces from the unwanted sap in trees felled by the forestry industry.
Ethanol fuel tanks are half again as large as diesel tanks to provide the same range. Ethanol requires an additive to improve ignition, as well as special lubricants because engines run hotter. Napier University in Edinburgh has developed butanol made from two bi-products of the distillation of whisky. It blends with petrol, diesel or ethanol. Although not yet in volume production, the raw materials are readily available.
Prototype liquid hydrogen buses by MAN entered service at Munich Airport and a small fleet later when on trial in Berlin, but stopped any further development in 2009 after difficulties modifying a supercharged 12-litre engine to produce sufficient power and torque, and problems with backfiring and an overheating exhaust manifold.
The technology for fuel cell hybrid buses is making steady progress. Mercedes-Benz has developed the third generation now on extended trial in Hamburg. Others are in service in Switzerland and Italy.
With fuel cell stacks becoming more efficient, the number of hydrogen storage tanks has dropped from the previous nine to seven on the latest generation. The price of fuel cells has probably fallen by half in the last two years, and there are confident predictions of a similar fall over the next two years. Even so, there is a long way to go before they can become commercially viable.
All-electric buses still popular
All-electric trolleybuses have operated in Europe for years and have recently enjoyed a revival in Italy. These modern, conventionally styled buses draw current from overhead wires. In Switzerland, the electricity from hydropower, make the trolleys truly zero-emission vehicles. Most models have a small diesel engine to power the generators so they can run off-wire off their normal route and circulate within depots.
In the Swiss city of Zurich trams and trolleybuses tend to operate almost all services. In its last order for bi-articulated vehicles with Hess, VBZ, the Zurich operator, specified super capacitors instead of diesel generators. These have sufficient energy to power the vehicle for up to one mile off wire.
Until now the only vehicles powered solely by batteries have been small buses. The problem has always been the limited range of the batteries. New techniques allow vehicles a fast charge at each end of their route. Usually a charging station built into the surface of the road activates only when the bus parks above it. As these technologies become more refined it may well be possible to build larger battery-powered buses with sufficient range for a full day’s service.
The IAA in September in Hanover, Germany is the next major commercial vehicle exhibition in Europe. The latest examples of at least some of these technologies are bound to be on display.
BIO: Doug Jack is with Transport Resources in the United Kingdom.