Alcohol Fueled Heavy Duty Vehicles Using Clean, High Efficiency Engines

Ethanol and methanol derived from a variety of sources could make a substantial contribution to replacing oil-derived transportation fuels and reducing greenhouse gas emissions. Particularly important are next generation, low carbon biofuels derived from agricultural, forestry, municipal and industrial waste by biochemical or thermochemical processes including plasma gasification, as well as specially grown biomass such as switchgrass. Ethanol, methanol or mixtures of these fuels can be used in turbocharged direct injection spark ignition engines which are as or more efficient than diesel engines and also provide advantages of lower cost, lower emissions and higher power. The strong knock suppression resulting from direct alcohol injection enables engine operation with power densities of up to three times that which can be provided by diesel engines. A representative power density is 200 hp/liter. The introduction of these engines in heavy duty vehicles could be relatively rapid because of the need to replace present heavy duty diesel engines in order to meet more stringent air pollution regulations and relatively modest fueling infrastructure requirements. During the initial market introduction phase the fuel could be presently produced ethanol. In addition, these engines could be operated as flexible fuel engines to allow use of gasoline as the main fuel when alcohol fuel is not available or it is more economically attractive to use gasoline. The flexible fuel engines could use a secondary tank of independently controlled direct ethanol injection to prevent knock and allow operation primarily on gasoline without compromising performance. Depending on the application the amount of alcohol from this second tank would be around 15-20 % of gasoline use for prolonged high torque operation long haul trucks with gasoline alone in the main tank. It would be less than 3% for a typical non long haul truck operation drive cycle. The high power density turbocharged operation enabled by the knock suppression from direct alcohol injection could allow super engine downsizing where, for example, a 5 liter spark ignition engine could be used to provide the same power as a diesel engine with an 11 liter displacement and possibly a 15 liter diesel engine. High power density, alcohol fueled heavy-duty vehicle engines could be used for both long and short haul trucks, buses and off road vehicles. Dedicated ethanol operation could be particularly attractive for farm vehicles. High power density alcohol fueled engines can also be attractive for light duty vehicles.