Tuesday, November 22, 2005

Protons vs. Electrons

My posting last Friday on hydrogen cars for China generated a thought-provoking comment suggesting that advances in battery technology would foreclose the opportunity that hydrogen fuel cells are chasing, at least in automobiles. When you consider developments such as next-generation Lithium-ion batteries that promise to cost less, recharge faster, and last longer than current hybrid car batteries, the threat to fuel cells could be considerable. After all, fuel cells and hydrogen are only one path with the potential to improve vehicle efficiency, reduce oil dependence, and lower greenhouse gas emissions. Hydrogen has no monopoly on these outcomes.

When the first hybrid cars appeared in the late 1990s, they raised the bar against which hydrogen fuel cells would have to compete, in three important areas:

  • They provided energy efficiency improvements nearly as large as those promised by fuel cells.
  • They reduced greenhouse gas emissions by almost as much as fuel cells, when the emissions associated with producing, storing and transporting hydrogen from natural gas--the primary current source--were included.
  • They delivered these benefits at a substantially lower cost than fuel cells, even based on optimistic forecasts of fuel cell manufacturing cost reductions.

The prospect of plug-in hybrids raises the bar even higher, bearing in mind that neither plug hybrids nor fuel cell cars are yet in mass production. Plug-in hybrids would leverage the fuel consumption and emissions of an internal combustion engine by recharging with grid-based electricity, rather than just recycling braking energy, as conventional hybrids such as the Prius do. With improved batteries, the all-electric range of plug hybrids could be significant, and their cost premium over conventional hybrids modest.

As promising as this technology sounds, it's premature to write off the hydrogen fuel cell, because a device with no moving parts ought to have an inherent advantage over even a highly-advanced internal combustion engine. However, better batteries and the rapidly accumulating real-world experience generated by hundreds of thousands of production hybrid cars could keep pushing fuel cells over the horizon for some time.

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