University of Wisconsin Wins FutureTruck Competition

emmons writes: "The University of Wisconsin has won this year's FutureTruck Competition by reducing the greenhouse gas index of a Ford Explorer by 50% and increasing over-the-road fuel economy by 45%. The modified Explorer uses an aluminum/steel hybrid frame, a titanium exhaust system and sports a hybrid bio-diesel/electric engine. I saw the vehicle on campus a few months ago and got to talk to some of the team members- it's really quite impressive."

Comments

Faulty logic

[Spamalamadingdong]

Diesel has a greater density than gasoline, and thus that is why Diesel engines are more efficient than gasoline engines.

Um, no. If all you did was substitute a fuel with more energy/gallon (such as gasoline for propane), you will get more miles per gallon even at the same efficiency. Greater energy density of the fuel does not make an engine more efficient. You might also want to look at this paper, where it states:

Burning natural gas and propane gives less carbon dioxide and more water vapour per energy unit than burning gasoline or diesel fuel. Carbon dioxide is the most important greenhouse gas. International agreements to reduce carbon dioxide have been signed /39/. The emission of greenhouse gases is dependent on both the efficiency of the whole chain and fuel chemistry. Evaluations of energy consumption and greenhouse gases should be carried out over the whole fuel chain including production, distribution and utilisation (life cycle analysis, LCA).

One argument heard in promoting natural gas as an automotive fuel is that natural gas reduces carbon dioxide emissions compared to conventional hydrocarbon fuels. This is most cases true when substituting gasoline with natural gas.

The situation is different for heavy-duty vehicles. The thermal efficiency of the Otto cycle is lower than that of the diesel cycle, and therefore the energy consumption of a heavyduty spark-ignited natural gas or propane engine is higher compared to the diesel engine.

The fact is that diesel engines running on typical fuels use higher compression ratios than Otto-cycle engines, and higher compression means greater efficiency. The diesel also runs without a throttle, eliminating throttling losses at partial power and further increasing efficiency; engine torque is modulated by reducing the fuel without changing the airflow, which cannot be done in an Otto-cycle engine because the engine will misfire when the mixture gets too lean.

If you run an Otto-cycle engine exclusively on propane rather than gasoline, and increase the compression to suit the fuel, you will get higher efficiency and lower CO2 emissions than the gasoline version... but at 5 pounds of propane per gallon vs. 6.2 pounds/gallon of gasoline, you are still going to get fewer miles per gallon.