Finding 5-8. Solar-based hydrogen does not appear viable even with currently envisioned cost decreases in photovoltaic cells and in electrolyzers.

Finding 5-9. Most of the hydrogen supply chain pathways would release significantly less carbon dioxide into the atmosphere than would gasoline used in hybrid electric vehicles. Only coal-based nonsequestered production and grid-based electrolysis are comparable to gasoline in this respect. The higher efficiency of fuel cell vehicles compensates for the high carbon dioxide content of the fossil fuels.

Finding 5-10. The technology advances envisioned by the committee would not significantly reduce the carbon dioxide emissions from fossil fuels, absent sequestration.

Finding 5-11. Carbon dioxide emissions could be brought down to near zero with biomass, with electrolysis depending exclusively on wind turbines or photovoltaics, with nuclear energy, or with the successful sequestration of carbon dioxide from the production of hydrogen from fossil fuels. Carbon dioxide emissions could be made negative if the hydrogen was produced from biomass and the carbon dioxide from production was separated and sequestered.

Finding 5-12. With current technologies, hydrogen vehicles would not significantly increase the “well-to-wheels” energy efficiency significantly beyond the increase available with gasoline hybrid electric vehicles. Well-to-wheels energy efficiency would be increased with the possible future technologies, and so all of the hydrogen technologies would use less energy per mile driven than would the conventional gasoline-fueled passenger vehicle. Fuel cell vehicles that derive their hydrogen from natural gas, coal, or nuclear-based technologies would be more energy-efficient than hybrid electric vehicles would, but even these technologies would not substantially reduce energy use per mile driven. Only the system that uses 100 percent of its electricity from wind turbines and solar power would sharply reduce well-to-wheels energy use, in this case down to near zero.