An incredible amount of mythology still surrounds hydrogen as a clean energy source.
Episode Summary:
Hydrogen is widely touted as an important route to a carbon neutral future. The amount of disinformation and sheer ignorance about hydrogen however, is significant, and persistent, despite efforts by the scientific and engineering press to educate the public about what hydrogen can, and can’t do and the switch from fossil fuels as energy sources. Jim Anderton explains the five key things everyone should know about hydrogen.
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Transcript of this week’s show:
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Hydrogen. Next to wind and solar, hydrogen is the most talked about alternate energy source in popular culture today. It’s been used as a rocket fuel for over half a century, and in fuel cells to generate electricity for spacecraft too, and more recently in limited production autos from companies like Honda and Toyota. But what we know about it? We know it’s lighter than air, and when used for energy, emits no carbon dioxide. But that’s about it. And because of this, the mass media is filled with misinformation, distortion and plenty of fear, uncertainty and doubt about what hydrogen is and what it can do as a future energy source. There doesn’t need to be this kind of confusion. Here the five key things that everyone should know about hydrogen to make informed choices about future energy policy come election time.
1. Hydrogen is not a natural resource. Petroleum is the result of millions of years of plant life, compressed underground with incredible pressure by geologic forces. The carbon that makes up oil, coal and natural gas started as a CO2 in Earth’s atmosphere, taken up by plants in a system powered by sunlight, photosynthesis. Hydrogen does not exist in usable quantities on the earth. Hydrogen atoms are reactive, and they bind to other elements in millions of different chemical compounds. The hydrogen we want for energy purposes, hydrogen gas, H2, has to be made, using industrial processes. As a commercial gas, it’s most often made by removing it from carbon atoms, typically from natural gas in a process that itself has emissions implications. It can be made by splitting it from oxygen by electrolysis of the familiar water molecule, H2O. This also requires energy, although it’s emissions free.
2. Hydrogen is not a fuel. Turning hydrogen gas into electricity in a fuel cell, or heat in a combustion process, involves a reacting it with oxygen in the air to turn it to water, H2O. The energy required to split the hydrogen from the oxygen in water in the first place by way of electrolysis is energy we get back when we reunite the hydrogen and oxygen in the fuel-cell. Hydrogen is like a battery. It is an energy storage medium, but is not an energy source in itself.
3. Because no chemical or industrial process is 100% efficient, including production of hydrogen gas, we never get as much energy out of hydrogen fuel cells as it took to make the hydrogen in the first place. You chemical engineers out there know this as bond disassociation energy. Conceptually it’s a little like gravitational potential energy, except that the energy costs associated with hydrogen gas production, processing, compression, distribution and reaction in the fuel-cell makes it a lot less efficient than the falling weights in a grandfather clock.
4. Hydrogen is expensive. How expensive? About three times the price of natural gas per unit of energy. That’s understandable, given how concentrated an energy source petroleum is after millions of years of compression in the earth’s crust, but at street level, even if we could produce enough to pipe it into every home, it’s highly unlikely that fuelling homes and businesses at three times the current price is feasible.
5. Hydrogen is difficult to handle. That H2 molecules small, incredibly small, so small that it wants to diffuse through the walls of storage tanks and piping on the molecular level, making long-term storage difficult. As a gas, to hold enough of it to be practical, storage tanks may operate at pressures as high as 10,000 psi. As a liquid, it has to be chilled to -250°C. Those giant rockets that we see covered with frost on the launch pad? They are huge thermos bottles. It’s not all bad however. It’s lighter than air, so it tends to diffuse up and away if a leak occurs, and contrary to popular belief, it’s not especially flammable. It doesn’t explode, but burns with a soft blue flame. But it will never be as easy to store and distribute as those big molecule hydrocarbons like natural gas.
So what does all this mean? Is hydrogen pointless? Well, no, especially as better catalysts and more efficient ways of producing the gas develop. But the key is choosing the right form of energy used to make the hydrogen the first place. If it’s from electricity, that hydrogen gas is just another form of battery, and battery enthusiasts claim that it’s easier to just cut out the middleman and use the electricity by way of batteries directly. The possible ace in the hole for hydrogen? Nuclear energy. Nuclear not only produces clean electricity, it also creates a vast amounts of process heat, which could be used in steam reforming processes to strip hydrogen from carbon-based fuels. The question is, will any of this happen before battery technology becomes cheap, effective and ubiquitous? I have my doubts.
