Volvo has received its first order for buses that operate on both biogas (biomethane) and diesel, for 11 buses from Vårgårdabuss in Sweden, for putting in service in July 2011. It involves the Volvo 8500 intercity bus model.
Using diesel technology increases environmental efficiency compared with current gas-operated buses, Volvo notes.
A diesel engine is 30-40% more efficient than current gas-operated engines. In a time when we must reduce society’s total energy consumption, higher utilization of the diesel-engine technology is an important development.—Edward Jobson, Environment Director at Volvo Buses
Volvo is also testing methane/diesel heavy-duty trucks as well. (Earlier post.)
AB Volvo is participating in a demonstration project for methane/diesel technology using buses for regional traffic and trucks. Current diesel engines will be used, but up to 70% of the fuel is biogas or natural gas. The Swedish Energy Agency is contributing nearly SEK 24 million (US$3.6 million) to the project.
With respect to the buses, a common diesel bus will be used, on which gas tanks will be mounted on the roof and equipment that injects the gas into the engine to create an optimal mixture of air and fuel.
The diesel engine functions as usual, but only a small amount of common diesel or bio-diesel will be continuously injected into the cylinders. The diesel’s task is to function as a type of ignition for the gas, which is the primary fuel. The engine can operate as usual on only diesel if the gas tank is empty.
The gas will be stored in the tanks in a gaseous state, as with current gas-operated buses and refilled in exactly the same manner from the same filling stations.