Environmentalists have touted hydrogen as the panacea for world energy challenges for decades, and as is common with populist environmentalist causes, their focus on hydrogen has caused more harm than good. This isn’t the first time thoughtful critics inside and outside the environmentalist movement have called the hydrogen future a hoax, but unfortunately the hydrogen zealots still aren’t listening.
First of all, hydrogen isn’t a primary fuel. It has to be produced from something else, either from electricity via electrolysis, or refined from fossil fuel, or distilled from biomass. In all these cases, using the source fuel directly would be far more efficient than converting this energy into hydrogen.
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.
By contrast, a simple onboard battery can be charged and discharged at greater than 90% efficiency – a plug-in hybrid, available today, will use grid electricity twice as efficiently as a fuel cell car. Furthermore, fuel cells cost $4,000 per kilowatt (a kilowatt is about 1.3 horsepower), they use expensive materials, they degrade quickly, they take several minutes to start, they can’t tolerate cold, and vibration makes their membranes rupture. Meanwhile, batteries are cheap and getting cheaper. If you’ve got cheap renewable electricity, there are better ways to exploit that electricity than by producing hydrogen.
Let’s not forget that nobody’s figured out how to store hydrogen. It is the lightest substance in the universe, so storing a meaningful amount of hydrogen requires pressurization up to 10,000 PSI. Even under these densities, the hydrogen equivalent of only a few gallons of gasoline could be carried on an automobile since otherwise the pressure vessel would weigh far too much. A natural gas vehicle, by contrast, requires the gas to be stored at only 300 PSI, a vast difference. The tanks, fittings and hoses to safely store usable amounts of pressurized hydrogen haven’t been invented yet. Maybe someday hydrogen can be stored via cryogenics, or in metal substrates using nanotechnology. Don’t hold your breath.
Will scientists figure out someday how to store hydrogen in practical, economical ways? Will they ever figure out how to build cheap, safe and durable fuel cells? The answer to these questions is yes, but probably not before they figure out how to develop ultra-capacitors or cheap batteries with extremely high energy densities.
The biggest problem with hydrogen is the opportunity cost of spending billions of dollars in research on this technology and lobbying for this technology when so many alternatives exist. Use more efficiently exploited feedstocks for hydrogen to power ultra-efficient clean diesel cars, serial hybrid cars, and battery powered cars. These technologies are here now, and they are being neglected. Hoax is not too strong a word to describe the environmentalist fixation on hydrogen, a technology that will be eclipsed by better solutions long before it ever becomes practical.