Modified diesel engine.

To use the E95 blend in the diesel engine, Scania raised the compression ratio from 18:1 to 28:1, added larger fuel injection nozzles, and altered the injection timing.

Different gaskets and filters are required, as well as larger fuel tanks—the engines burn 65% to 70% more ethanol than diesel.

The intervals between oil changes is halved, and more scheduled maintenance is required.

Scania has fifteen years of operational data with its ethanol buses, developed in cooperation with Stockholm Public Transport. The company has delivered about 600 ethanol buses so far, with substantive emissions results.

Scania calculates that since 1990, use of the ethanol buses in Stockholm has:

• Reduced CO₂ by 120,000 tonnes

• Reduced NO_x by 900 tonnes

• Reduced PM by 25 tonnes

Scania is now developing its third generation ethanol engine, planned to be introduced in 2007. Ethanol buses are now on operating trials in several cities outside Sweden: Madrid, Spain; La Spezia, Italy; and Slupsk, Poland.

Scania acknowledges the ability of diesel engines to burn biodiesel—specifically rapeseed methyl ester (RME)— without any modifications at all, but believes that the farming capacity is insufficient for the huge need foreseen for the transport industry. Scania sanctions its modern diesel engines running on any blend of biodiesel up to 100%.

The Scania hybrid. Scania is developing a prototype hybrid designed to work with engines burning diesel, ethanol, RME or natural gas. A motor generator provides traction assistance and supports regenerative braking. Ultracapacitors store the energy.

Scania estimates potential fuel savings of 25% or more, with correspondingly lower emissions as estimates that the technology could be market-ready in five years’ time.

Resources:

• Ethanol buses: Experiences and Prospects for Sustainable Urban Transport