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Scania to Test E95 Diesel Hybrid Buses in Stockholm

In collaboration with Storstockholms Lokaltrafik (SL), the regional public transport company in Stockholm, Scania will carry out large-scale testing of series hybrid electric buses. The tests will begin during 2008 and run for at least one year. A prototype is expected to be completed in May 2007.

A Scania E95 ethanol-fueled diesel engine will serve as the genset for the electric motor that propels the bus. (Earlier post.) The motor also serves as a generator for regenerative braking; the resulting energy is stored in ultracapacitors.

To optimize the diesel engine for its E95 ethanol blend (95% ethanol with 5% ignition improver), 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 Swedish Energy Agency is supporting Scania’s hybrid technology and is contributing more than SEK 16 million (US$2.3 million) for the development of the city buses. The Scania hybrid drive offers fuel savings of 25% or more, according to the company.

Carbon dioxide emissions from traffic can be reduced by lowering fuel consumption and transitioning to renewable vehicle fuels.

Scania combines reduced fuel consumption with renewable fuel in its hybrid technology. This technology is expected to save at least 25 percent fuel. The engine—a high-efficiency diesel engine—is powered by ethanol, a renewable fuel. The technology is robust and dimensioned to last for the normal service life of the bus. We regard this as an optimal combination for city traffic, with its constant stopping and acceleration.

In a longer perspective, innovations such as hybrid drive will help us to meet stricter environmental targets for city traffic. Even today, however, we can take a major step towards lowering the environmental impact of public transport by operating on such renewable fuels as ethanol and rapeseed methyl ester (RME).

—Hasse Johansson, Head of Research and Development at Scania

Between 1970 and 2000 Scania halved fuel consumption per tonne-kilometer for truck haulage. The company’s goal is to halve fuel consumption once again by 2020.



What does "ignition improver" mean? Is it MTBE? A Diesel based Fuel? Does the engine still run a Diesel cycle?


Most likely ether.


?? Do I understand this correctly: compression-ignition of ethanol? What's the advantage of diesel or bio-diesel?


Energy density


the ignition improver is usually Beraid or Avocet.


Yes, ethanol can be used in diesel engines, using a normal diesel cycle. E95 has been researched in the past for this use, though it hasn't caught on since you need to use a lot more fuel to get the same amount of work done (the energy content of ethanol per unit volume is waaay lower than diesel). Ordinarily, if you want to go the biofuel route for diesels, biodiesel is the best at the moment. But, Sweden has really been pushing ethanol, so I presume they're just using what's available.

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