Study Examines Best Combination of Fuels and Powertrains, Reports GM

Hydrogen viewed as best long-term fuel replacement for gasoline.

Published: 23-Mar-2001

DETROIT, March 21 /PRNewswire/ -- A comprehensive study, released today, gives high marks to gasoline-derived fuels and fuel cell vehicles as the cleanest and most efficient combination of fuel and propulsion systems for the near term. Additionally, the study found that hydrogen-powered fuel cell vehicles are the best long-term solution, while diesel hybrids also scored well in the report.

When discussing vehicle emissions and fuel efficiency, attention is typically focused solely on the vehicle. However, for a true reading of what really matters for the environment -- how much energy is used and what emissions it creates -- it is critical to look at the complete picture: from the time the fuel is first taken from the ground, produced, refined, manufactured, transported, and stored, until it actually powers a vehicle. This approach is known as a total system or "well-to-wheels" analysis.

General Motors Corp. conducted the study with Argonne National Laboratory and energy partners, BP, ExxonMobil and Shell. What emerged is the most definitive well-to-wheels analysis to date.

The study examined gasoline and diesel internal combustion engines, fuel cells, and hybrids, all in a common platform -- a Chevrolet Silverado pickup -- and studied a variety of fuel types from a North American perspective. The Silverado was chosen because it is a popular vehicle that, with modest improvements in fuel economy, can deliver large overall gains in fuel saved and total greenhouse gas emissions reduced.

Researchers then set out to determine what is the cleanest -- in terms of greenhouse gas emissions -- and most efficient combination of fuel type and propulsion system.

"We believe this will become the definitive study and reference point for the industry and for government decision-makers," said Dennis R. Minano, GM vice president, environment and energy, and chief environmental officer. "The study compares apples to apples in a far more comprehensive manner than any previous study."

The study findings support GM's view: Petroleum-based gasoline and diesel are excellent fuels in the near-term, and a gasoline-like fuel is the best bridging strategy to a hydrogen economy for fuel cell vehicles. GM plans for this gasoline-derived fuel to work in both its fuel cell and conventional vehicles.

Hydrogen, made renewably, is the end goal, as it is clearly the best long- term, clean fuel. But these results reinforce GM's philosophy that there is no need to create a costly and temporary infrastructure for fuels such as methanol or compressed natural gas (CNG) to reach a hydrogen economy.

"This study provides a strong basis for thoughtful decision-making on fuels and powertrains," said Greg Ruselowski, director of finance, planning and infrastructure for GM's Global Alternative Propulsion Center. "This work supports GM's goal of developing advanced vehicles for mass commercialization and it reinforces what GM is doing in fuels and fuel cell research."

Key findings in the study are:

* Fuel cell vehicles powered by clean gasoline offer higher efficiency and lower emissions when compared with the other powertrains examined in the study.

* A diesel hybrid electric vehicle (HEV) -- using a clean, reformulated diesel fuel -- scored very high among the non-fuel cell vehicle fuel/vehicle combinations, in terms of efficiency and carbon dioxide emissions. Overall, diesel powertrains had high well-to-wheels marks, scoring even higher than gasoline hybrids.

* Fuel cell vehicles powered by hydrogen offer the greatest long-term potential.

* Methanol used in fuel cells and compressed natural gas internal combustion engines offered no advantages over clean gasoline in well-to-wheels efficiency.

* As expected, renewable fuels such as ethanol from cellulose gave by far the lowest greenhouse emissions.

Researchers considered 75 fuel pathways and 15 vehicle pathways -- the path from well-to-wheels -- and chose 27 for complete analysis. Fuel types included: low sulfur, clean gasoline-type fuels; low sulfur diesel; low sulfur naphtha; and methanol, liquid hydrogen and gaseous hydrogen from non North American natural gas.

Argonne National Laboratory, a recognized leader in well-to-wheels modeling, conducted the "well-to-tank" portion of the study with significant input from BP, ExxonMobil and Shell. For this study, Argonne used a model known as GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation), considered the industry standard in U.S. emissions and energy use modeling.

The "tank-to-wheels" portion of the study was performed at General Motors, using a proprietary computer model that was validated for conventional, hybrid and fuel cell powertrains. The vehicles were computer-tested, using the EPA Urban and Highway Driving Cycle. A total of 15 fuel/vehicle combinations were analyzed. Since some of the fuels can reach the vehicle by multiple pathways, 27 pathways were analyzed on a well-to-wheels basis.

Ruselowski said the next areas for investigation include expanding the study to include other emissions such as oxides of nitrogen, hydrocarbons and particulates, as well as examining more real world issues like cost and packaging. Expanding the study to focus on Europe is another area for future study.

"We plan to use this collaborative analysis as a baseline that will be updated as we learn about future technology improvements," Ruselowski said.

General Motors (NYSE: GM), the world's largest vehicle manufacturer, designs, builds and markets cars and trucks worldwide. In 1999, GM earned $5.6 billion on sales of $176.6 billion. It employs about 395,000 people globally. For more information about GM's environmental progress in the areas of products, plants and partnerships please visit .

SOURCE General Motors Corporation

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