Source: Cycle World
Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)Hydrogen power for bikes seems like a great idea. The only product of reacting hydrogen with oxygen is water, so regulated emissions are zero. If you like the sound of internal combustion engines, they make the same sound on hydrogen as on gasoline. If you prefer the hum of electric motors, run high-purity hydrogen through a fuel cell to produce electricity and go that way.First problem is, there’s no hydrogen on Earth in a free, chemically uncombined state. If, as many assume, there will soon be gobs of extra electric power from wind and solar, we can use some to electrolyze hydrogen from water. Trouble is, to liberate hydrogen this way, we have to put in more energy than we can later realize from either burning the hydrogen or using it to make electricity in a fuel cell. What this tells us is that hydrogen is not a fuel. It is an energy carrier.Carrying liquid hydrocarbon fuel—gasoline—on a bike is straightforward: We go to the gas pump and fill our 7–10 pound steel gas tank with it.NASA engineers used to say, “Hydrogen is huge.” If we compress the hydrogen that we’ve electrolyzed from water to 10,000 psi, it takes six times the volume of the pressurized gas to equal the energy in one volume of gasoline or other liquid hydrocarbon fuel. That means to functionally replace 4 gallons of gasoline with hydrogen at 10,000 psi, we must carry 24 gallons of hydrogen. That is why images of hydrogen-powered bikes of the future look like tourers with what appear to be side bags and top trunk but are actually packed with long slender pressure tanks.Related: Hydrogen Suzuki EvolvesTanks for storing hydrogen need to hold six times the volume to be equal to gasoline. (Kawasaki/)When I Googled the weights of such pressure tanks I found that volume-for-volume they weigh about nine times what gasoline tanks weigh.OK, but didn’t NASA reduce the volume of hydrogen required on the space shuttle a lot by liquefying it and carrying it at atmospheric pressure? It did, but to compress and refrigerate hydrogen to the liquid state at minus 410 degrees Fahrenheit uses energy equal to about 40 percent of what’s in the hydrogen to begin with.Yeah, but isn’t there some kind of catalyst that can separate oxygen and hydrogen from water at next to no energy cost?Catalysts can speed up or slow down chemical reactions but they are not a substitute for energy. If such a cat existed, we could just put it in the exhaust from our hydrogen-burning piston engine or fuel cell, it would separate the hydrogen and oxygen, and we could run that back to the intake and ride forever. Perpetual motion.Hydrogen differs considerably from gasoline vapor. Accidentally released hydrogen in an enclosed space rises, accumulating at the ceiling. Gasoline vapor, being heavier than air, settles to the floor. The ignition energy threshold for hydrogen is much lower than that of gasoline vapor, and hydrogen’s ignitable mixture limits are wider.We don’t give much thought to the safety hazards presented by gasoline, but where possible, above-ground parking structures have no walls, allowing vapor from any gasoline leakage to be carried away. The same applies to hydrogen. A general rule for storage and handling of compressed gases is to locate it outdoors (like gas stations).Related: Kawasaki Demonstrates Hydrogen PrototypeKawasaki has demonstrated its hydrogen-powered sport-tourer recently. (Kawasaki/)Equipment for transferring high-pressure hydrogen to vehicles will be more expensive than present-day gas pumps because assuring adequate and highly reliable sealing of the refueling coupler will not be trivial. The word “aerospace” comes to mind.The trucking industry has shown interest in hydrogen, probably because refueling is expected to be much quicker than battery charging, and because hydrogen and its tankage are much lighter than battery energy storage. Trucking is highly competitive, so every pound carried that is not payload is revenue lost. Advocates of battery trucking are not generous with numbers, but estimates run from 6,000 to 15,000 pounds of battery to be carried. Hence hydrogen’s appeal.Before the present focus on electrification, there was much interest in a future “hydrogen economy” (Google “Rocky Mountain Institute, hydrogen economy”). Reviving that concept will require the confidence of large investors in its profitability. Cross your fingers on that one.The bottom line? Remember the cheerful GI phrase: “If we had some ham, we could have ham and eggs. If we had some eggs.” Hydrogen as an energy carrier for transportation faces similar problems:There is no free hydrogen.There is no hydrogen infrastructure to supply it to consumers.
Full Text:
Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)
Hydrogen power for bikes seems like a great idea. The only product of reacting hydrogen with oxygen is water, so regulated emissions are zero. If you like the sound of internal combustion engines, they make the same sound on hydrogen as on gasoline. If you prefer the hum of electric motors, run high-purity hydrogen through a fuel cell to produce electricity and go that way.
First problem is, there’s no hydrogen on Earth in a free, chemically uncombined state. If, as many assume, there will soon be gobs of extra electric power from wind and solar, we can use some to electrolyze hydrogen from water. Trouble is, to liberate hydrogen this way, we have to put in more energy than we can later realize from either burning the hydrogen or using it to make electricity in a fuel cell. What this tells us is that hydrogen is not a fuel. It is an energy carrier.
Carrying liquid hydrocarbon fuel—gasoline—on a bike is straightforward: We go to the gas pump and fill our 7–10 pound steel gas tank with it.
NASA engineers used to say, “Hydrogen is huge.” If we compress the hydrogen that we’ve electrolyzed from water to 10,000 psi, it takes six times the volume of the pressurized gas to equal the energy in one volume of gasoline or other liquid hydrocarbon fuel. That means to functionally replace 4 gallons of gasoline with hydrogen at 10,000 psi, we must carry 24 gallons of hydrogen. That is why images of hydrogen-powered bikes of the future look like tourers with what appear to be side bags and top trunk but are actually packed with long slender pressure tanks.
Related: Hydrogen Suzuki Evolves
Tanks for storing hydrogen need to hold six times the volume to be equal to gasoline. (Kawasaki/)
When I Googled the weights of such pressure tanks I found that volume-for-volume they weigh about nine times what gasoline tanks weigh.
OK, but didn’t NASA reduce the volume of hydrogen required on the space shuttle a lot by liquefying it and carrying it at atmospheric pressure? It did, but to compress and refrigerate hydrogen to the liquid state at minus 410 degrees Fahrenheit uses energy equal to about 40 percent of what’s in the hydrogen to begin with.
Yeah, but isn’t there some kind of catalyst that can separate oxygen and hydrogen from water at next to no energy cost?
Catalysts can speed up or slow down chemical reactions but they are not a substitute for energy. If such a cat existed, we could just put it in the exhaust from our hydrogen-burning piston engine or fuel cell, it would separate the hydrogen and oxygen, and we could run that back to the intake and ride forever. Perpetual motion.
Hydrogen differs considerably from gasoline vapor. Accidentally released hydrogen in an enclosed space rises, accumulating at the ceiling. Gasoline vapor, being heavier than air, settles to the floor. The ignition energy threshold for hydrogen is much lower than that of gasoline vapor, and hydrogen’s ignitable mixture limits are wider.
We don’t give much thought to the safety hazards presented by gasoline, but where possible, above-ground parking structures have no walls, allowing vapor from any gasoline leakage to be carried away. The same applies to hydrogen. A general rule for storage and handling of compressed gases is to locate it outdoors (like gas stations).
Related: Kawasaki Demonstrates Hydrogen Prototype
Kawasaki has demonstrated its hydrogen-powered sport-tourer recently. (Kawasaki/)
Equipment for transferring high-pressure hydrogen to vehicles will be more expensive than present-day gas pumps because assuring adequate and highly reliable sealing of the refueling coupler will not be trivial. The word “aerospace” comes to mind.
The trucking industry has shown interest in hydrogen, probably because refueling is expected to be much quicker than battery charging, and because hydrogen and its tankage are much lighter than battery energy storage. Trucking is highly competitive, so every pound carried that is not payload is revenue lost. Advocates of battery trucking are not generous with numbers, but estimates run from 6,000 to 15,000 pounds of battery to be carried. Hence hydrogen’s appeal.
Before the present focus on electrification, there was much interest in a future “hydrogen economy” (Google “Rocky Mountain Institute, hydrogen economy”). Reviving that concept will require the confidence of large investors in its profitability. Cross your fingers on that one.
The bottom line? Remember the cheerful GI phrase: “If we had some ham, we could have ham and eggs. If we had some eggs.” Hydrogen as an energy carrier for transportation faces similar problems:
There is no free hydrogen.There is no hydrogen infrastructure to supply it to consumers.
