Hydrogen math
Today, powering fuel cells with hydrogen can create more greenhouse gasses than powering directly from fossil fuels, because hydrogen is most often made using traditional gas- or coal-fired electricity. Today, renewable sources produce only 2% of the world’s electricity. Consider the math for a PEM based fuel cell car:
Burning coal to generate one megawatt-hour of electricity produces about 2100 pounds of carbon dioxide. Using that electricity to make hydrogen would yield enough fuel for a fuel-cell [PEM] car to travel about 1,000 miles. But driving those 1,000 miles in a gasoline-powered car that gets 40 miles per gallon would produce just 485 pounds of carbon dioxide.
From “Hell and Hydrogen”, David Talbot, Technology Review, March/April 2007
Of course, most cars today do not get 40 mpg, either…The point is, fuel-flexible SOFCs using traditional fuels like natural gas make less CO2 than hydrogen-burning PEMs (PEMs cannot operate easily from hydrocarbons since CO poisons them). When you factor in the losses due to hydrogen generation alone, not including storage in tanks, the true efficiency of PEMs is reduced to less than 10%. SOFCs reach over 40% efficiency with natural gas. Of course, SOFCs can operate from hydrogen as well. Fuel cells hold the promise of world-saving, pollution-free, reliable, electricity – when clean, efficient hydrogen generation becomes a reality. Below are some links to various hydrogen generation technologies.