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| Joined: | Mon Nov 21st, 2005 |
| Location: | California USA |
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Obviously refining hydrogen from fossil fuel isn’t going to solve any energy shortages. Distilling hydrogen from biomass is equally problematic; it has the same problems all biofuels have – there isn’t enough land or water on earth to yield anywhere near the quantities of energy necessary to replace petroleum (read “Will Biodiesel Replace Crude Oil,” for a chart showing the relationship between land consumption and biofuel production). Moreover, if you are going to refine hydrogen from biofuel crops that truly make economic sense to grow, such as sugar cane, why not just burn the ethanol directly and save the energy losses from the conversion process?
Theoretically, electrolyzing hydrogen from renewable electricity and water is a way for hydrogen to make economic and ecological good sense. But this analysis neglects to consider where the electricity will come from, and more importantly, the significant conversion losses incurred when electricity is electrolysed into hydrogen. The hydrogen resulting from a process of electrolysis will have at best about 65% of the energy that was in the electricity used to make it.
If electrolysed hydrogen is then used to power a fuel cell automobile, the absurdity of its practicality becomes very clear. A fuel cell is necessary to turn the hydrogen back into electricity, and the electrical output of the fuel cell is at best only about 65% of the energy that was in the hydrogen used to make it. The compounding problem here – electricity from the grid made hydrogen via electrolysis at a 65% efficiency (best case), then hydrogen processed through a fuel cell made electricity at a 65% efficiency (best case) – means the electric motor providing traction for your fuel cell car will only be able to use about 40% of the electrical energy drawn from the grid for that purpose. Read “The 100% Electric Car,” for an in-depth explanation of conversion losses using fuel cell cars.