May 22, 2002

“Well-to-wheel” fuel study released

Brussels, Belgium. – General Motors, with input from various energy companies and a leading independent research institute, presented initial results yesterday from a comprehensive study assessing the effect of greenhouse gas emissions at a leading fuels conference.

The study, released at the Hart World Fuel Conference, assessed fuel sources, processing techniques and propulsion systems. A total of 36 fuel pathways and 18 propulsion concepts examined for the 2010 timeframe, from conventional engines to advanced concepts, were analyzed under European driving conditions. (The study assessed energy efficiency and greenhouse gas emissions, but not costs.)

Experts examined the complete chain, from the production of fuels from their basic feedstock components to the actual consumption of the fuel in the car, what scientists call “well-to-wheel” analysis.

Ludwig Bolkow Systemtechnik (LBST), a research institute in Ottobrunn, Germany (near Munich) acted as a scientific advisor and consultant. BP, ExxonMobil, Shell and TotalFinaElf energy companies provided additional data and analysis.

A principal finding of the study was that fuel cell vehicles using hydrogen produced from natural gas could be attractive in terms of well-to-wheel gas emission depending on the source of the natural gas. However, optimum results are realized when renewable energies such as biomass or wind power are used to produce the hydrogen. (For purposes of this study, biomass is fuel generated from trees, sugar beets and oil seeds and did not include garbage.)

This project is a sequel to the North American Well-to-Wheels study published by GM, BP, ExxonMobil, Shell and Argonne National Labs last year analyzing the impact of energy sources and alternative propulsion systems in North America. In that study, a Chevrolet Silverado pickup was used as a reference vehicle.

That study reached similar conclusions and is now regarded as a reference work in worldwide discussions on transport-related greenhouse gas emissions and energy consumption. In the new study, the original methodology was applied in a European context for both fuel and vehicle.

“We based our additional research work, which took over a year, on the Opel Zafira minivan, European driving conditions, and our understanding of the European energy supply situation,” explained Raj Choudhury, project manager for the study at a GM research center in Mainz-Kastel, Germany. The vehicle data for the European study was compiled by GM scientist, Trudy Weber: “The Zafira proved to be the ideal reference vehicle, since it already exists with gasoline, diesel, compressed natural gas (CNG) and fuel cell propulsion systems. We forecasted the powertrain system characteristics for the 2010 time frame and imposed the constraint that all 18 vehicle variants examined be able to meet the same set of stringent, customer-based performance criteria over the European drive cycle (EDC).

“For the first time, this provided us with a realistic and comparable basis for energy use and net greenhouse gas emissions in a European context,” Weber said. On the fuel side, a variety of different pathways were considered. They can be put into four basic groups, based on their source of feedstock: crude oil, natural gas, electricity – from both traditional power stations and renewable sources – and biomass.

Results to emerge from the study included:

  • On a well-to-wheel greenhouse gas emissions basis, the best use for natural gas was to reform it to obtain hydrogen for use in hydrogen fuel cell vehicles.

  • To a lesser extent, natural gas offered improvements relative to conventional gasoline and diesel systems when used to fuel compressed natural gas vehicles.
  • The use of hydrogen from natural gas in internal combustion engines actually produces poorer well-to-wheel results than do conventional gasoline engines.
  • When natural gas was used to produce methanol for an on-board reformer fuel cell vehicle, no well-to-wheel benefits were seen relative to conventional gasoline or diesel internal combustion engine vehicles or gasoline reformer fuel cell vehicles.

“The best alternative, however, is to produce hydrogen from renewably generated electricity – e.g. wind power – and use it in a fuel cell. This will essentially eliminate well-to-wheel greenhouse gas emissions,” says Dr. Erhard Schubert, Co-director of GM’s Fuel Cell Activities.

The complete study will be concluded and published this summer. The focus for the GM team now turns to addressing commercialization challenges faced by fuel cell vehicles and the hydrogen infrastructure, including cost and availability issues.

“It’s clear fuel cells have much more promise than any other propulsion option, especially if renewable energy is used in the production of hydrogen as a suitable infrastructure becomes available,” says GM Vice President Larry Burns, responsible for research & development and planning at General Motors. “That is why we intend to do everything we can to produce a fuel cell car that is both affordable for the customer and economically viable for us by the end of this decade.”

GM has more than 400 scientists and engineers working globally on fuel cell propulsion systems and their commercialization with research facilities in Honeoye Falls, NY; Mainz-Kastel, Germany and Warren, Michigan.

Connect with