In this edition of CleanTech Talk, Paul Martin and I discuss Michael Liebreich’s hydrogen ladder. Paul is a working chemical process engineer, and has spent his career building prototypes of biofuel, hydrogen, and chemical processing plants as part of scaling them to full, modularized production systems for clients. Paul’s piece in CleanTechnica on why hydrogen is not suitable as a replacement for natural gas in buildings is a must read.
Liebreich is an entrepreneur, founder of what has become Bloomberg New Energy Finance (BNEF), chairman on multiple boards, has engineering and business degrees, and represented the UK on their skiing team in 1992. He’s had a rich and interesting life, but for the purposes of this pair of podcasts and attendant articles, it’s his iteratively improving hydrogen ladder Paul Martin and I are focusing on.
Regular readers of CleanTechnica will know that I have been assessing hydrogen’s place in the decarbonized economy in the areas of transportation, oil refining, and industry, among others. Paul and I share a strong opinion that “blue” hydrogen, which is sourced from fossil fuels with 10-30 times the mass of CO2 which is theoretically going to be sequestered or used, is a fossil-fuel industry lobbying effort and not a viable climate solution.
Listeners are recommended to keep the hydrogen ladder in front of them as Paul and I talk through aspects of it.
We start with a discussion of one of Paul’s frequently used hashtags, #hopium, which he defines as the drug that is made out of our own hope to overcome our faculties and divert government money to things which aren’t useful. We agree that the fossil fuel industry are masters of PR when it comes to giving false hope to governments and individuals that we can just vacuum CO2 out of the air or out of smokestacks after emitting it, rather than the reality that we leave most fossil fuels unburned and unused.
Paul steps through existing hydrogen production, pointing out that of the 120 million tons used annually today, less than 0.1% could be considered green hydrogen, intentionally cracked from water using renewably generated electricity. All hydrogen today is actually black, at least 30% blacker per unit of energy than the fossil fuel it was made from. For coal, up to 30 kg of CO2 is created for every kg of hydrogen, with one data point suggesting a proposal in Australia to make hydrogen from low-grade coal with 35 kg of CO2 for each kg of hydrogen. For natural gas, it’s up to 10 kg, but there is also methane leakage with its 86x worse than CO2 on 20 years global warming potential. Creation of hydrogen from natural includes an almost equal amount of GHGs in methane leakage, which is typically not counted in the emissions.
We continue with a discussion of ground transportation, where there is no place for hydrogen, in our opinion. Paul draws out the efficiency versus effectiveness argument first. Gasoline isn’t efficient, as perhaps 15% turns into useful energy, but it is effective due to being cheap, easily poured into gas tanks, and easily transported.
Hydrogen is neither efficient or effective for ground transportation. The misleading truths that are used for #hopium are that it’s the most common element in the universe and has excellent energy density for its mass.
The first truth is not helpful, as all hydrogen available to us is tightly chemically coupled with other substances, whether that is fossil fuels or water. It takes a lot of energy to break those bonds.
The second truth is not helpful either. Hydrogen, as the lightest element and lightest gas, has very poor energy density by volume, regardless of whether you compress it to 700 atmospheres, a little over 10,000 pounds per square inch, or chill it to 24 degrees above absolute zero to liquify it. As a gas, it has less than a third the energy density by volume of methane, and as a superchilled liquid, its energy density by volume is only 75% better.
Paul points out that the Toyota Mirai vs Tesla Model 3, otherwise comparable cars, is illustrative in that the Mirai weighs as much as the Tesla, even though it only carries 5.6 kilograms of hydrogen. The tanks weigh hundreds of kilograms. A standard hydrogen cylinder weighs 65 kg and only delivers 0.6 kg of hydrogen, a problem that transportation uses have to overcome with expensive thin-walled aluminum tanks wrapped in carbon fiber. It’s also worth noting that hydrogen cars have less interior and luggage room due to the hydrogen storage and fuel cell component space requirements.
Paul points out the lost mechanical energy of compression. He calculated once that the energy used to compress 5 kg of hydrogen to 700 atmospheres was equivalent to the kinetic potential energy of suspending the car 500 meters in the air, ready to drop. That energy is lost. If superchilled hydrogen were used instead, 40% of the energy in the hydrogen would have to be used to chill it.
The final devil in the details is thermal management. Hydrogen is an interesting gas in that unlike many other gases, it gets warmer as it expands. Anyone used to compressed air cans know that the jet of air comes out cold, but an equivalent jet of hydrogen would come out hot. Even though compressed hydrogen isn’t liquified, in other words, it has to be chilled in its tanks before being pumped into cars, another loss of energy.
This all leads to the common myth that hydrogen cars are quick and convenient to refuel. The reality is shown by Toyota’s entry in the 24-hour enduro Super Taikyu Series in Japan’s Shizuoka Prefecture. They prepped a racing Corolla with a hydrogen combustion engine. It had four huge carbon-fiber tanks in the area where you would normally have back seats. They brought four tractor trailers full of equipment to fuel the car. The car had to spend four hours of the 24 hours of the race refueling. Ineffective, inefficient, and with startling infrastructure requirements.
As Paul says, the devil isn’t hiding in the details, he’s waving his pitchfork in plain sight of anyone willing to see him.
We move on to agreeing in general that hydrogen might have a direct play in long-haul shipping, or at least hasn’t proven itself uncompetitive in that space. I recently assessed Maersk’s methanol drivetrain dual-fuel ships announcement, and 40-day journeys with thousands of tons of fuel are a very hard problem to crack. Maersk has proposed a green methanol manufacturing facility capable of producing enough synthetic green methanol annually to cover half of one trip for one of the eight ships.
For the rest of the first half of the podcast, aviation is in our sights. Paul and I agree that short- and medium-haul aviation — basically all air trips within the boundaries of most continents — are going to be battery electric. Hydrogen has no advantages for those ranges.
And we agree that long-haul aviation is another hard problem. I went deep on long-haul aviation’s global warming contributions and challenges recently, so had the concerns at top of mind. First was the problem of direct carbon dioxide emissions of course, but aviation also has contrail and nitrous oxides emissions problems.
Contrails are water vapor, effectively clouds. Due to the altitude of especially night-flying high-altitude planes, they keep more heat in than they reflect. That’s something that can partially be managed by changing operations, reducing altitude and night-time operations, but there are economic reasons why planes fly high and at night that need to be addressed with economic incentives.
Nitrous oxides are trickier. Any fuel burned in oxygen produces nitrous oxides with a bunch of the nitrogen from the air, which is, after all, 78% nitrogen. Nitrogen combined with oxygen in the form of N20, nitrous oxide or laughing gas, has a global warming potential of 265 times that of CO2, and persists in the atmosphere a long time.
Another form of nitrous oxide, NO2 or nitrous dioxide, is the chemical precursor to smog, causing asthma and other heart lung problems. For those following along, yes, if you have a natural gas stove or furnace in your home, it’s also putting NO2 into your home’s air along with carbon monoxide, which you need a detector for if you don’t have it. All the more reason to electrify to induction stove tops and heat pumps as your appliances age out.
Paul’s perspective is that hydrogen for long-haul aviation has multiple problems. The first is that it can’t be stored as a pressurized gas in airplanes due to the increasing loss of atmospheric pressure and bulk as planes ascend to 30,000 ft. The second is that even chilled, it’s much less dense by volume than kerosene, so it would have to be stored in the fuselage. The third is that fuel cells are bulky for energy output of sufficient electricity, so would also have to be within the fuselage, and fuel cells give off a lot of heat. So that means either jets lose a fair amount of passenger and luggage storage, or get a lot bigger and heavier, even before the cooling and venting requirements for the fuel cell heat. That makes the economics of jet travel problematic, which might be just fine, as it arguably should be more expensive than it is.
However, this means that it would be hydrogen jet engines that would be used if hydrogen were to be used directly as a fuel. And burning hydrogen in a jet engine will produce a lot of water vapor, hence the same contrails, and nitrous oxides, hence the high global warming potential. Hydrogen would only deal with two-thirds of the problem.
Paul and I agree that biofuels for hard-to-service transportation modes such as long-haul shipping and aviation, along with operational changes and reduced use, are likely the best we can do until we achieve a battery as much better than lithium-ion as lithium-ion is than lead acid, and that took a century.
But we’ve had biofuels certified for aviation use since 2011, and they just aren’t being used. They are more expensive, despite being much lower CO2 emissions cradle-to-grave than kerosene. Once again, negative externalities have to be priced.
The next half of the podcast discussion gets into places where hydrogen actually has a place in the sun, but makes it clear that hydrogen is actually a decarbonization problem, not a decarbonization solution.