Posted by: paul | January 17, 2009

Why Fuel Cell Vehicles?

Because hydrogen fuel cell vehicles offer the single best option to dramatically reduce carbon dioxide contributions from automobiles.

That is a bold statement. And although I’ve supported hydrogen for stationary and small portable applications for years, only in the past twelve months have I really understood how critically important hydrogen is to reducing green house emissions from automobiles.

Dr. C. E. (Sandy) Thomas, of H2Gen Innovations, developed a model that convinced me.This model compares projected greenhouse gas emissions throughout the 21st century for a transition to four different vehicle options: gasoline-electric hybrids (e.g., Toyota Prius), gasoline plug-in electric hybrids (e.g., Chevy Volt), ethanol plug-in electric hybrids (e.g., the Volt using ethanol for the gasoline), and fuel-cell vehicles (e.g., Honda Clarity FCX). The graph below summarizes Thomas’s results. It clearly shows that fuel cell vehicles offer the only option to significantly reduce greenhouse gas emissions below 1990 levels:

Greenhouse Gas Emissions for Various Vehicle Types

Greenhouse Gas Emissions for Various Vehicle Types

I recommend reading Dr. Thomas’s full paper. It is quite readable if you are conversant in greenhouse gas and new vehicle concerns. You can also watch a webinar of Dr. Thomas presenting his paper at the National Hydrogen Association’s website.

Of course, if the model’s assumptions are wrong, then the results are wrong. So, since learning of Dr. Thomas’s results, I’ve been seeking evidence to either support or discredit his assumptions and results.  So far, I haven’t found anything to discredit his model, but I have found some that corroborate it, although indirectly.

Dr. Thomas’s model is the only one I have seen that incorporates a gradual transition from current automobiles to the replacement technology. His is also one of the few to consider the current electric supply and realistically introduce more renewables and nuclear power over time. For comparison, consider the results from a model Dr. Mark Jacobson of Stanford University has developed:

Rankings of Vehicle and Energy Source Combinations

Rankings of Vehicle and Energy Source Combinations

Jacobson’s model looks at a wide range of socio-economic factors. Furthermore, Jacobson compares different renewable energy sources, while Thomas combines all renewable and nuclear sources. But most importantly, Jacobson looks only at 100% renewable solutions. He completely ignores the reality of the current grid and the fact that, at best, we face a long, slow transition to a grid powered largely by renewables. In fact, our current grid is so coal-dependent that electric vehicles today result in higher CO2 emissions than similar gasoline vehicles! As a result of considering only 100% renewably sourced energy, Jacobson’s results place battery electric vehicles powered by wind power as the best option. Fuel cell vehicles powered by wind come in a close second. Within the article, Jacobson points out that he did not perform calculations for fuel cell vehicles using the other renewable sources, but one could easily do so using a simple conversion, since their impact differs from batteries by a constant factor. In other words, right next to each battery solution in Jacobson’s graph, there is a similar fuel cell solution. So Jacobson’s model tells us that in an ideal, 100% renewable scenario, battery-powered vehicles are slightly better than fuel cell vehicles for any given resource. (This is because charging and discharging a battery is about three times more efficient than producing hydrogen though electrolysis and using it in a fuel cell.) He leaves it to the reader to recognize that in a more realistic scenario, fuel cells will fare better.

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Responses

  1. […] Why Fuel Cell Vehicles? Browse Monthly Archives February 2009 January 2009 […]

  2. […] CO2. The CO2 impact of battery cars is vastly higher than that of hydrogen cars today and will continue to be so for the forseeable future. This is primarily due to the amount of coal we use to generate electricity and the fact that hydrogen can be efficiently created from natural gas.  See Why Fuel Cell Vehicles. […]


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