Hydrogen Fuel: An Overview, and Potential for Green Energy

Hydrogen Fuel: Is it Fantastically Green Energy or Just Ridiculous?

By Christina De La Rocha

There is a lot of talk lately about renewable fuels and the role they could play in getting us to net zero greenhouse gas emissions to the atmosphere. The idea behind renewable fuels is that burning them or using them in fuel cells doesn’t add a net amount of carbon dioxide, or other greenhouse gases, to the atmosphere. Also, their production should be sustainable—meaning that it doesn’t wreak environmental havoc—and carbon neutral.

Alas, in reality, most renewable fuels fail to meet these standards. But our latest hopes are pinned on hydrogen fuel, which, in the currently rare instance when it’s produced from water using renewable electricity (instead of from fossil fuels using non–renewable energy) is carbon neutral and sustainable. But hydrogen fuel is explosively flammable and challenging to store and transport, making it currently less efficient and more expensive than fossil fuels like natural gas.

However, if we were to use it strategically to store excess wind and solar energy for those times when it’s dark and windless, hydrogen fuel could play a critical role in getting us to net zero greenhouse gas emissions and keeping us there, helping us to stop making global warming worse before it’s too late.

Renewable Fuels

Today, most of what is termed renewable fuel are biofuels, produced mainly from maize (corn), wheat, sugar beets, sugar cane, molasses, vegetable oils, animal fat, and plant and animal waste. In principle, at least, the carbon dioxide they release when burned is carbon dioxide that the biofuel crop (or animal feed crop) recently removed from the air.

If what you return is what those plants just took out, that’s no net addition of carbon dioxide to the atmosphere and, presumably, a win for not further accelerating global warming. But a lot of food that could be feeding people goes into making biofuels.

Likewise, biofuel crops also take up land that could be used to grow food or given back to nature at a time when nature is running out of habitat. Biofuel crops are also intensively farmed with lots of decidedly environmentally unfriendly fertilizers and petrochemical pesticides. And they’re planted, maintained, and harvested using massive machinery that runs on fossil fuels and compacts the soils.

That makes biofuels neither carbon neutral nor a good answer to the environmental and global warming crises we’re facing. Biofuels are more of a way for corporate farming ventures to make money. They also enable the rest of us to keep doing the same old things we’ve been doing that are ruining the climate and the environment, only now we can pat ourselves on the back for feeling like we’re being so ecological about it.

But what about hydrogen as a renewable fuel? Could it fit the bill, producing no greenhouse gases and requiring no petrochemicals or fossil fuels and doing no environmental harm during its use or production? The short answer is yes and no. Because there are several different ways to produce hydrogen and several different ways to use it as a fuel. And not all of those ways are carbon neutral and sustainable, not by a long shot.

Semi-Trailer labelled with and carrying Hydrogen Fuel

When we talk about hydrogen fuel, we mean H2. This gaseous material consists of molecules that are two hydrogen atoms bonded together. Breaking this bond during the process of oxidation—to stick an oxygen atom in between the two hydrogens, essentially—releases heat and energy that we can use. We can do this in fuel cells that turn this energy from H2 oxidation directly into electricity. Or we can use hydrogen fuel as a replacement for natural gas, using the heat produced to cook, heat water, or turn turbines in powerplants that produce electricity.

What is so great about hydrogen fuel is that when you oxidize it, either in a fuel cell of via combustion, the waste product produced is not carbon dioxide. It’s… water. And doesn’t that just sound like good, clean fun? Honestly, doesn’t that just sound like how environmental angels generate their electricity and heat their homes?

But life, of course—not to mention energy production—is never quite that simple.

Natural Gas

One of the dreams for hydrogen fuel is that it could replace natural gas.

At 97%, at least for the refined stuff we tend to use, natural gas is mostly methane gas (CH4). The last 3% of the stuff that makes up natural gas is a mixture of gases like carbon dioxide (CO2), nitrogen (N2), hydrogen sulfide (H2S), and helium (He) that didn’t get weeded out during the refinement process.

That may not sound particularly natural to you, but what’s natural about natural gas is that it’s mined out of the Earth, not synthesized in a lab or factory. The biological and geological process that produce crude oil, also produce natural gas, such that crude oil down in the ground has a lot of natural gas dissolved into it.

Although sometimes that gas has already bubbled out down in the ground and, as it has moved toward the surface, has gotten trapped in pockets under impermeable layers of rock or sediment. We can tap these gas reservoirs directly to obtain natural gas. We also collect the natural gas that bubbles out of crude oil as it’s pumped to the surface.

This brings us to one big natural gas (in addition to the fact that burning it produces carbon dioxide): Methane—which is leaked to the atmosphere in great amounts when we mine and refine fossil fuels—is a powerful greenhouse gas.

Much stronger than carbon dioxide on a molecule per molecule basis, methane’s only saving grace is that it’s more reactive than carbon dioxide and therefore has a much shorter lifetime in the atmosphere, and so it has less time to trap heat, thereby warming climate. If you were to release a ton of methane to the atmosphere, over the next 20 years it would do something like 100 times more greenhouse warming than a ton of carbon dioxide. But over the next 100 years, which would see most of the methane oxidize away, it would be only 28 times more warming.

Either way, though, yikes! Both the production and combustion of natural gas are powerful drivers of global warming. Bring on the hydrogen, please!

Replacing Natural Gas with Hydrogen

Environmentalists—and investors—have many dreams for using hydrogen in place of fossil fuels. This can be as a literal replacement, like swapping hydrogen fuel in for natural gas in gas–fired powerplants or—if you’re really dreaming—in stoves and ovens.

Not only could this make investors lots of money, if done right, in the short term, we could just keep doing the things we’re doing right now exactly the same way we’re doing them, just using a truly renewable, carbon neutral fuel instead of an environmentally and climatically catastrophic fossil fuel. This could help keep our power levels up while we build up the infrastructure we need to generate all of our electricity via wind and solar power and change all of our heating systems to heat pumps that run on electricity.

But the devil really always is in the details.

For starters, to help us reach net zero greenhouse gas emissions to the atmosphere, the hydrogen fuel we use as a replacement for fossil fuels couldn’t be made out of a fossil fuel. It would have to be produced renewably. That sounds like a no brainer, but right now almost all of the hydrogen fuel we produce is made from fossil fuels. So, while burning it doesn’t produce greenhouse gas, producing it most certainly does, and that’s not helpful at all.

Secondly, we can’t just swap in hydrogen fuel for natural gas. We have to retrofit old natural gas–fired powerplants first, fitting them with pipes and burners suitable for hydrogen fuel. We also have to build new H2–capable gas–fired powerplants. Both of these things are expensive and time consuming and the political will is lacking to undertake this fast enough to matter (see, for example, the current German plan, far scaled back from the far more expensive original one, and yet still not entirely feasible).

What’s true in powerplants is also true at home. We can’t just switch to burning hydrogen in your stove, oven, and boiler. They also need to be fitted with new burners… and that’s if we were able to supply these applicances with a steady, piped in supply of hydrogen fuel. But hydrogen fuel, voluminous and explosive (see: the Hindenburg disaster), is expensive and difficult to transport. The entire network of pipes we’re currently use for natural gas, would not work for hydrogen fuel, but would have to be replaced.

Hydrogen pipelines
Countries are beginning to build up hydrogen infrastructure, including pipelines suitable for transporting hydrogen long distances, for example, between hydrogen production plants and industries that need to use hydrogen as fuel.

But why can’t we just use natural gas burners and natural gas pipes with hydrogen fuel? Firstly, burning hydrogen creates a hotter flame than natural gas (and also propane, which some people use in stoves). Burning hydrogen would melt burners made for natural gas or propane.

Meanwhile, to get the same amount of energy out of hydrogen as natural gas, you have to burn a larger volume of it, because it is volumetrically less energy dense than natural gas. That means that the pipes and valves delivering hydrogen gas to the burners need to have a larger diameter, otherwise you can’t deliver hydrogen fuel fast enough to the burners.

Hydrogen gas is also leakier than natural gas, which is not a great feature for either safety or efficiency, since leaks make explosions both possible and probable.

All of that means that we can’t just adopt the current network of natural gas pipes and burners for hydrogen. Again, we’d have to swap out the burners in powerplants and stoves and replace the entire network of pipes delivering natural gas around town.

This need for different pipes is pretty much the death knell for dreams of switching over to burning hydrogen for heating and cooking in our homes and small businesses.

No investor or group of investors, even with government backing, is going to spend the hundreds of billions if not trillions to replace the networks of gas pipes in our cities and towns that we’ve built up over the last seventy years. Even if the cost were not a non–starter, it would take decades to accomplish the change. But that’s the same amount of time it will takes up to build up enough solar and wind power to replace the power we currently generate via natural gas.

In other words, why bother kitting ourselves out to burn hydrogen if it’s not going to help us wean ourselves off fossil fuels faster than wind and solar will manage it on their own?

What’s far more likely to happen in the coming years is that the companies who currently own and maintain these networks of natural gas pipes (and make their profit by doing so) will have to write the gas pipes off as we phase out natural gas.

Don’t believe for a moment, though, that these companies will be happy to “strand” these assets worth many billions of dollars. They will fight the phase out of natural gas, via marketing, lobbying, and propaganda, as hard as they can. And part of those efforts will be spent to convince you that hydrogen is always environmentally friendly, even when it has been made from a fossil fuel. So don’t fall for it!

But as much as we’ll never be piping hydrogen fuel into our homes for heating and cooking, converting natural gas–fired powerplants over to hydrogen and replacing coal–fired powerplants with newly built, hydrogen capable powerplants is something that is already slowly starting to happen, because building the infrastructure to supply a small number of powerplants with hydrogen fuel is far more feasible than building up a new network of pipes that has to connect up millions of small buildings.

There are companies, governments, investors, and environmentalists who see a strong role for hydrogen fueled powerplants in moving us toward net zero greenhouse gas emissions to the atmosphere.

How Fuel Cells Work

So far so 20th century with this talk of burning fuel in powerplants to generate electricity. The future is where fuel cells come in. They represent a considerably more portable way to produce power out of hydrogen fuel. We’re already testing out how to use hydrogen fuel cells to power ships, cars, trucks, drones, and maybe even airplanes.

Yet, at this point, most of us don’t understand by what magic can we put hydrogen into a fuel cell to get electricity out. Although, of course, it isn’t magic at all. It’s chemistry.

As with combustion, using hydrogen in a fuel cell involves oxidizing the fuel, just not so fast and uncontrollably that it bursts into flames. If burning hydrogen in air releases heat that can be used to turn turbines, thereby generating electricity, a hydrogen fuel cell converts the chemical energy of this oxidation of hydrogen by oxygen directly into electrical energy. Fuel cells do this oxidation in a more controlled manner by using catalysts that bind hydrogen and oxygen atoms together to form water, producing electricity and heat in the process.

H2 fuel cell
Sketch of a hydrogen fuel cell whereby hydrogen flowing in provides hydrogen ions and electrons that combine with oxygen ions to form water, producing electricity as part of the process.

This happens through the combined operation of three adjacent sections, the anode, the electrolyte layer, and the cathode. In an H2 fuel cell, the anode is where a catalyst breaks the hydrogen–hydrogen bond of H2 to liberate hydrogen ions (H+) along with negatively charged electrons. The electrolyte layer then brings the H+ ions toward the cathode, where H+ and electrons react with O2 to produce water and energy.

In addition to producing water as a waste product instead of carbon dioxide, hydrogen fuel cells more efficiently convert fuel to energy than combustion does, clocking in at converting 40–60% of the energy in the fuel to power compared to the 25–35% that internal combustion engines manage. As time goes by and we develop better fuel cells, they should get even more efficient. Fuel cells should also become smaller and less expensive than they are now. So, on this end of things, we’re doing well.

How Do We Produce H2?

At the moment, the problems with hydrogen are all upstream of our use of hydrogen, namely with the production, storage, and transport of it.

At the moment, hydrogen production is anything but green. Almost all of the H2 we use is produced by “steam reforming” natural gas, meaning that all of the hydrogen fuel we’re using right now is a fossil fuel. Oxidizing it to release energy may not directly produce carbon dioxide, but producing it requires mining fossil fuels out of the ground. That means leaking a lot of methane to the atmosphere. It also means producing a lot of crude oil and natural gas that are also going to get used, releasing a lot of carbon dioxide to the atmosphere. So, that’s not a win for climate or the environment.

This is really important to realize. None of the hydrogen fuel that is produced from natural gas—which is that hydrogen that is marketed under the cute terms blue hydrogen and grey hydrogen—is renewable, sustainable, or carbon neutral. None of this fossil fuel based hydrogen will help us reach net zero greenhouse gas emissions to the atmosphere. This fossil fuel hydrogen is a way for investors and petroleum companies to keep making money and it’s a license to keep mining hydrocarbons out of the ground rather than leave these billions of dollars in assets stranded there.

For hydrogen to help us reach net–zero carbon emissions, what we have to do is start scaling up the production of H2 from water via electrolysis and make sure that this production is powered by renewably produced electricity.

Here now, finally, is where hydrogen fuel starts to get actually interesting.

Electrolysis of water to produce O2 and H2 is something you might have watched in a high school biology or chemistry class. You start with a container of water that you’ve added ions to, in the form of something like salt or baking soda.

You run a current of electricity through the water by putting, for instance, the anode and cathode electrodes of a battery into water. On the anode, you’ll be producing O2 and on the cathode, you’ll be producing H2, which then bubble up toward the surface of the water. To collect the hydrogen gas, you just have to place a collection vessel above the cathode.

The systems that will produce H2 in the future will be far more sophisticated versions of this basic premise. All you need is water, some salt, and some electricity, preferably generated renewably via wind turbines or solar arrays. Now we’re getting close to the production of hydrogen fuel not adding any greenhouse gases to the atmosphere at all.

The Upsides and Downsides of Producing H2 With Renewable Energy

But all is not yet bliss. You may already be wondering if producing hydrogen fuel via electrolysis actually makes sense, even if it doesn’t release carbon dioxide or methane to the atmosphere. Because it means using renewable electricity to produce H2 that we then burn or use in fuel cells to… produce renewable electricity.… with losses of energy at every step.

This is a problem. The energy you get out of hydrogen produced via electrolysis of water is less than half of the energy that you used to power the electrolysis. That great loss makes using hydrogen at the moment, less energy efficient than using fossil fuels… and that’s even before you factor in the additional losses involved in converting the hydrogen fuel into ammonia (which takes up less space and isn’t prone to catching on fire or exploding) for storage and shipping. Because of this, renewably produced hydrogen fuel—known as green hydrogen—is more expensive than fossil fuels and thus unpalatable to consumers and businesses.

Of course, you could argue that by not causing climate change, green hydrogen is ultimately cheaper than fossil fuels, but that’s a bitter pill for the consumers of electricity to swallow. And it’s one that we should not be expected to swallow on our own!

Worse, even, is that the inefficiency of hydrogen production via electrolysis makes producing renewable hydrogen fuel a profligate use of renewable energy. We’re already not producing enough renewable electricity to keep the lights on, run heat pumps and air conditioners, fuel electric stoves and ovens, run factories powered by electricity, fuel standard electric vehicles, store data in the cloud, play with generative AI, and mine and use cryptocurrencies.

But All Hope Is Not Lost for Hydrogen

So, then, why bother with hydrogen at all? While improvements in technology and infrastructure will eventually bring the price of hydrogen fuel down, it will always be less efficient to convert electricity to hydrogen fuel that we use to produce electricity than it would be just to use that electricity in the first place. And yet, there are situations in which using renewably produced hydrogen fuel makes a lot of sense.

One big problem we have with producing energy with solar and wind is that you can only do this when it’s sunny and/or windy. But sometimes you need electricity when it’s dark and windless. Germans have a great expression for such times—because of course German has an expression for this—kalte Dunkelflaute. This literally means the cold, dark doldrums, and those are exactly the times when electricity demand will be high—because people will be running heat pumps to heat their homes and they will have the lights on—but wind farms and solar arrays will not be generating any power.

When we’re in the midst of the kalte Dunkelflaute, we need a backup system that provides what can be peak amounts of electricity. Sure, we could do that with batteries, if we’ve got enough of them and all the raw materials it takes to create them. But we could also do it with hydrogen fuel.

Because the flip side of cold, dark doldrums are super sunny summer days with a nice, stif breeze. People won’t be using much power, because they won’t have the lights on and it’s not cold enough to have the heat on and maybe it’s not hot enough for people to be running air conditioning. Right now, during these times, wind turbines get shut off to stop them from pouring energy into the grid.

In the future, solar arrays will be blocked from pouring energy into the grid. Why? Because pouring more energy into the grid than people are using causes instabilities and surges that blow fuses, start fires, and damage electronic equipment.

But do you know what we could be doing instead of turning off wind turbines and dissipating the energy from solar arrays? We could be using this excess renewable energy to produce hydrogen fuel via the electrolysis of water. This might be an inefficient use of renewable electricity, but that renewable electricity would either be going to waste or wouldn’t be being produced in the first place. Producing renewable hydrogen fuel when we’ve got renewable energy to spare is great way to capture that excess energy and save it for later.

It would be even better if we produced this hydrogen fuel where it will be used to fill fuel cells or burned to produce heat or electricity. This would minimize the need to transport this hydrogen around, saving us both money and energy. For instance, if we made renewable hydrogen out of water at a hydrogen fired powerplant, we could then use the hydrogen to generate electricity during the darkness of winter, or on windless summer nights.

The Big Message

The TL;DR in all of this is that dreams of converting all our cars, domestic heating systems, home appliances, and powerplants to run on renewably produced hydrogen fuel instead of fossil fuels are misguided. But there is a huge role for truly renewably produced hydrogen fuel to play in the coming decades as we wean ourselves off of fossil fuels and move on over to a zero carbon emissions economy.

We just have to be strategic about using excess solar and wind power during sunny and windy times to produce hydrogen fuel that we then convert back into electricity during those dark and windless times when solar and wind can’t meet our needs for electricity. It will also make sense to use hydrogen fuel cells in things like large ships and long haul trucks which can’t hold batteries with enough capacity for their journeys.

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