Warming Thoughts© #10, “Hydrogen Hype, or Hope?” Part 2
More Hydrogen and the complexity of actually using it.
Summary of my views: There has been tremendous investment into bringing down the capital cost of hydrogen producing electrolysis, which is necessary but not sufficient for the creation of a “Hydrogen Economy”. The fundamental physical properties of hydrogen; difficult to compress and difficult/impossible to liquify at scale plus its propensity to leak will stop widescale adoption of hydrogen as a fuel. Green hydrogen production from electrolyzers driven by renewable energy will expand but the greatest growth will probably be in carbon capture from plants producing hydrogen by the traditional steam methane reforming process driving the same industrial processes as currently exist. New uses for hydrogen and hydrogen fuel cells will expand, but slowly.
There are too many transitions required and too much energy is lost in the process of producing, transporting, and using hydrogen for hydrogen to fulfill its hype. There will also be a lot of resistance from AHJ’s (authorities having jurisdiction) in this case fire marshals and building codes concerned about fires and explosions. An additional concern is finally rising; the potential (there is very little research, just hints) for highly harmful effects of hydrogen leakage on both global warming and ozone depletion---and leak it will.
Physical Issues:
In the first essay we discussed hydrogen’s low energy density and the need for energy consuming compression to make it reasonably transportable. Just to review some facts, about Hydrogen: Melting Point: 13.99 K (-259.16C, -434.49 F), Boiling Point: 20.27K (-252.88C, -423.18F). Put another way, at 20 degrees Celsius above absolute zero hydrogen turns to liquid, at 6 degrees colder it freezes, but even then, its density is less than 10% that of water. These temperatures are insanely cold and require massive amounts of energy. That’s why we have highly compressed hydrogen and not liquid hydrogen, and we don’t ship large quantities, unlike liquified natural gas where around 400 million tons were shipped worldwide in 2022.
How fast a molecule moves is a function of its weight, and hydrogen is the lightest element, so it bounces off surrounding walls 3x faster than natural gas, hence it is hard to pressurize and will escape through any crack. As a last fun fact, when it bounces off steel, it sometimes doesn’t, penetrating deep into the crystal structure and make the steel brittle and subject to cracking. For more fun, hydrogen embrittlement occurs as well as in Iron, Nickel, Titanium and Cobalt and their alloys. So, nothing about hydrogen is easy, least of all just trying to plug it in as a replacement for natural gas piped to millions of homes. There are only 1,600 miles of hydrogen pipeline in the US, and most of them are very short runs from dedicated producer to end-user(s) vs. 2 million miles of natural gas pipelines.
Transition One: How We Make Hydrogen.
Currently we primarily use steam methane reforming (SMR), combining hot steam and methane to produce what is called grey hydrogen. The goal and excitement surrounding hydrogen is based on “green” hydrogen, using renewable powered electrolysis to split H2O into Hydrogen and Oxygen using electricity. Hydrogen produced by electrolysis, whether the electricity is clean or dirty represents less than 5% of hydrogen production, so this is a massive transition. Complicating this transition is the intermittency problem. The vast majority of hydrogen usage, for the production of ammonia, for oil refining, or chemical manufacturing is based on continuous processes with the hydrogen production plant in immediate proximity and dedicated to the enduser. Creating hydrogen only when the wind blows or the sun shines dramatically increases the need to expensive storage, causing further complications in this, the direct hydrogen use, “easiest transition”. At least for these usages, there is no major process change, the hydrogen source is the change, the processes are the same.
Blue hydrogen, where the SMR process is retrofitted to capture the CO2 emitted, is likely to dominate and is a major driver in the creation of CO2 pipelines for collection and disposal, particularly in petrochemical hubs like Houston. But why bother with capturing and burying CO2 when you can make hydrogen without CO2 with an electrolyzer? As usual the answer is energy—and capital. Electrolyzers require more energy, need electricity and not heat, and currently cost a lot, plus there is an extensive installed base of everything except electrolyzers. Will the existing plants still be more economical when outfitted with CO2 capture is not clear. The ability of electrolyzers to scale up to meet existing demand, let alone massive new demand is unclear. Most likely, new uses for hydrogen, and new builds will gravitate around hydrolysis and not SMR, but there will also be significant blue hydrogen production from hydrocarbons where renewable electricity isn’t available since the world really does need more hydrogen—for ammonia.
Since I have mentioned blue, green and grey hydrogen, I have to digress to hydrogen production “colors”. Seriously, there is:
· Green Hydrogen—renewable powered, produced from water electrolysis
· Blue Hydrogen—produced from fossil fuels with CO2 capture
· Grey Hydrogen—Natural gas via Steam methane reforming (SMR)
· Black or Brown Hydrogen—from Coal via gassification
· Purple/Pink Hydrogen—Nuclear powered electrolysis
· Turquoise Hydrogen—Thermal splitting of methane producing solid carbon
· Yellow Hydrogen—hydrolysis powered by general grid power
· White Hydrogen—Produced as a byproduct of an industrial reaction
That should tell you there are some real issues with hydrogen and its green, clean image; seriously-- Pink, Turquoise? The colors that most matter, including for subsidies are Green Hydrogen which is hydrogen produced from water via an electrolyzer that uses renewable electricity as discussed above, and Blue Hydrogen which is SMR with capture and permanent geological sequestration of the CO2.
I got an email yesterday hyping a hydrogen conference and it cited 3 GW of hydrogen electrolysis announcements (for to be built over some number of years ahead) as a reason to rush to the conference, again following the rule that every measure in anything promotional is going to distort what is really going on to make things seem better. What is 3 GW of hydrogen? In this case it means that 3 GW of electricity will go into making hydrogen from electrolysis. Which will produce?
It takes 39 kilowatt hours at 100% efficiency and assuming rather optimistically 80% efficiency, that is almost 50 KWH/kg (no compression included). But wait, the dimension above was GW, not GWH, and lets convert that to KWH, so let’s multiply by 8760 hours in a year, and round down to 8000 since 90% uptime would be excellent: 8000x 3,000,000,000/1,000= a big number/50KW/kg and then divided by 1,000 to get tons, and the answer is 480,000 tons, .8% of current production.
In fairness it is early days, and the same negativity could have been applied to solar panels. But electrical production from solar panels is a thin film phenomena with the active layer and required materials extremely thin. With hydrogen production you are dealing with moving and converting massive quantities of materials. The cost curves are very different.
Transition Two: Hydrogen for process heating.
The world uses a lot of heat to drive industrial processes ranging from petrochemical production to smelting iron ore, to melting silica to create glass, to driving off the CO2 from limestone to create cement clinker. Most of this heat is from natural gas or oil, and in some cases coal. Hydrogen burns very hot and doesn’t produce CO2. But it’s never so simple, and here I quote from an article in a Royal Society of Chemistry Article:
“Combustion seems likely to be a major pathway given that it requires only incremental technological change. The use of hydrogen is not however without side-effects and the widely claimed benefit that only water is released as a by-product is only accurate when it is used in fuel cells. The burning of hydrogen can lead to the thermal formation of nitrogen oxides (NOx – the sum of NO + NO 2) via a mechanism that also applies to the combustion of fossil fuels. NO2 is a key air pollutant that is harmful in its own right and is a precursor to other pollutants of concern such as fine particulate matter and ozone. Minimising NOx as a by-product from hydrogen boilers and engines is possible through control of combustion conditions, but this can lead to reduced power output and performance. After-treatment and removal of NOx is possible, but this increases cost and complexity in appliances. Combustion applications therefore require optimisation and potentially lower hydrogen-specific emissions standards if the greatest air quality benefits are to derive from a growth in hydrogen use.”
Hydrogen is not a drop-in replacement, or an adjustment of the burner tip valve like when you change your grill from propane to natural gas, but a complex engineering challenge that must be adapted, designed and tested for every installation. The natural question is why use hydrogen at all? Use electricity instead and avoid the energy wasted in making hydrogen. The problem is that while you can use electric resistance heating to achieve very high temperatures, the materials to do so are expensive, usually refined carbon or, more commonly, platinum group metals. You simply can’t do large scale high temperature electric heating due material constraints, but I do think we are not doing enough research on the topic.
Transition Three: Hydrogen for boiling water and space heating
Yes, you can safely add 10-15% hydrogen to a natural gas distribution system and most heaters will function perfectly, but since we are supposedly shutting down all natural gas production, what good would that do? As to using hydrogen directly, as pointed out, the pipes will become brittle, the burners won’t work, and since hydrogen burns at an absurdly wide range of mixtures with air, lots of things will go up in smoke—greatly aiding the environmental subset dedicated to reducing the number of people on the planet.
What about heat pumps, why hydrogen at all, and why can’t you use heat pumps for high temperature heating? Unfortunately, while heat pumps are about as close to a free lunch as thermodynamics allow, there are no miracles and it is very hard to extract enough energy from air to raise temperatures dramatically, and you also run into freezing and condensation problems with the remaining air. The limit for specialized heat pumps is around 160C. Enough to boil water for some heating, not for power generation, marginal for district heating, and definitely not for large scale high temperature process heat.
So yes, assuming we somehow solve the problems of electrical transmission and distribution, heat pumps will fill a distributed heating role—hydrogen won’t. Too hard to distribute and too dangerous for residential situations—and firemen (and women). There is a niche application for hydrogen however in certain industrial and commercial situations assuming you can get hydrogen to the site. Fuel cells convert hydrogen to electricity and then they do just produce water. They also produce heat since the process is only around 60% efficient, and they can be more even efficient in very high temperature cells. That heat, can be used for heating—if you happen to need it.
Transition Four: Fuel cell vehicles.
This was going to be the big one. It’s not going to happen. With one or two off-road exceptions. The argument for hydrogen fuel cell vehicles was powerful; quick refilling, longer distances, electric drive trains and lighter weight. Yes, fuel cells were expensive, but they keep getting cheaper and nothing drives down costs like car scale production went the argument. PEM fuel cells which are the most practical for vehicles require rare metals and it is unclear whether there are enough at any price to allow widespread adoption.
Then you have safety. Hydrogen catches fire when mixed with air at anywhere between 5% and 75%, perhaps the widest range of any flammable material. It also burns so fast that it essentially explodes. How happy are you going to be going through the Lincoln Tunnel surrounded by vehicles with 5-10,000 psi hydrogen tanks. Strange things happen in crashes, most of them bad. We can’t keep car charging plugs in working order, how exactly are we going to manage millions of 5,000 PSI hydrogen refill connections safely? Hydrogen, the arguments go, is so light it dissipates very rapidly. Me, I’ll take my chances on gasoline. We are pretty good at fighting gasoline fires, less so for battery fires, which at least are localized, and hydrogen—well it burns out quickly, really quickly and dissipates rapidly so outside is less of a problem. 500,000,000 hydrogen powered vehicles in tunnels and garages—what could go wrong?
Then there is the issue of hydrogen distribution and production to fuel the vehicles. A hydrogen tanker, something I really don’t (and won’t since they are banned) want to see in a tunnel next to me, can’t carry nearly as much energy as a petroleum tanker. The magic of electrolysis allows you to make hydrogen locally at the filling station and at least one major gas station owner has a contract with an electrolyzer manufacture to do just that. But, and there is always a but, you are going to need 30-50% more electricity to drive electrolyzers and produce high pressure hydrogen to put in car tanks than is required for electric car charging—and we don’t have enough power to get to even highway gas stations to support electric car charging.
The real issue is efficiency. Why, to quote Lindsay Leveen, “make sawdust from fine furniture”. The round-trip efficiency of battery storage approaches 90%, so start with 100 KWH and end up with 90 KWH driving your electric motor. For the hydrolyzer/fuel cell system if you start at 100 KWH of electricity, you will have 75 KWH, less around a 7.5% loss for compression coming from the pump. Put that remaining 70 KWH of hydrogen into the fuel cell vehicle, and then extract 60% of the energy to net 42 KWH, wasting almost 60% of the electricity along the way. We don’t have that much clean energy to waste.
Trucks we were told definitely require fuel cells and hydrogen tanks, but Tesla’s electric truck is already showing batteries are possible for the shorter haul segment of the market. A 25% improvement in batteries, which I think is probable and even the long-haul segment becomes possible. Yes, there will be more downtime for charging. Yes, the power demands of a truck stop will be astounding, but still much less than that of a hydrogen truck stop.
So where do I see fuel cell vehicles succeeding? Farm vehicles and tractors. Batteries are heavy; most battery powered vehicles are 30-50% heavier than their gasoline or fuel cell equivalents. Heavy tractors compress the soil. A typical tractor has 6 sets of wheels and tires for different conditions with the widest being for preparing the soil for planting so it isn’t compacted. During planting and harvesting, tractors and harvesters are often at work 20 hours a day. You don’t have the time for recharging. So, if and when the legislators decide that diesel must go, as they have in California in another attempt to wipe out the farming sector—and any economic activity in the state, then hydrogen must rise.
Transition Five: Aviation
Yes Airbus has shown designs for hydrogen powered planes. Yes, you can use hydrogen to drive a jet engine and yes real money is being invested. But please do a search for hydrogen powered aircraft designs, they are radically different because hydrogen is not a volumetrically dense fuel, hence bigger volume and almost certainly more air resistance requiring more energy. It’s a race between working fusion power reactors and hydrogen power aircraft for which will take the longest to arrive, and the best hopes for fusion are still always 30 years in the future. I’m betting on fusion. Sustainable aviation fuel, probably made with extra hydrogen from electrolyzers and/or offsetting emissions from CO2 direct air capture are much more likely. We have refined the design and safety of aircraft for 100 years and hydrogen power will require a complete redesign.
In our next thrill packed episode, I want to tackle moving large quantities of hydrogen and powering the shipping sector, using ammonia, methanol, and dimethyl ether and discuss hydrogen energy storage.