Why hydrogen can’t solve our climate change problems

One of the conversation points that I often encounter in the debate around climate change and the move to net zero/energy independence is the role that could be played by hydrogen. Like many of the other aspects of this debate, it is poorly understood, particularly among the press and policymakers. 

What is hydrogen ? Chemically, it is the simplest and most plentiful element in the universe, having one proton and one electron. It’s thought that, along with a small number of other light elements, hydrogen was created in the aftermath of the Big Bang. Heavier elements with larger numbers of protons and neutrons are created when stars explode or merge. 

There are three hydrogen isotopes. The most common is sometimes referred to by an alternate name, “protium”. A small proportion – roughly 0.01% – of hydrogen atoms have a neutron (“deuterium”) and even more rarely there’s a second neutron (“tritium”), which is radioactive. 

 

Hydrogen is highly chemically reactive. It burns with minimal provocation, reacting with oxygen in the air to produce a molecule with two hydrogen atoms and one oxygen atom – H2O – well known simply as water. For this reason it generally does not exist as a gaseous element on earth; it is often found bound up in molecules with other elements. Alongside oxygen, it can be found bound to carbon (producing many complex forms known as hydrocarbons) or both carbon and oxygen (again, in many complex forms known as carbohydrates).

Over billions of years, plant and animal life has evolved in a complementary way around the properties of these three elements, alongside much smaller quantities of other elements – sodium, calcium, potassium, iron, zinc, copper and so on. Plants produce energy required to sustain themselves and grow through photosynthesis, using carbon dioxide and water as a source of carbon, oxygen and hydrogen to produce complex hydrocarbons and carbohydrates, releasing oxygen into the air as a byproduct. In turn, mammals, including humans, breathe in the oxygen, and consume hydrocarbons/carbohydrates, releasing carbon dioxide as a byproduct. The input energy for all of these processes comes from the sun. Dead plants and animals serve as a store of hydrocarbons. Over geological time, pressure and heat transform the dead material into coal, oil and natural gas.The energy in the fuels we burn today originally arrived on earth from sunlight millions of years ago.

Bringing us back to the present, it’s important to understand that hydrogen is not a source of geologically stored energy in the way that fossil fuel is. We have to produce using chemical processes to separate it from other elements.. Almost all hydrogen gas today is made by heating up natural gas to the point where the carbon within it splits off, in a chemical process called “steam reforming” which is around 70-85% efficient. Of the remaining supply, most of it comes from electrolysis of water – splitting the oxygen away using electricity. This is about 70-80% efficient.

The reason why most hydrogen comes from natural gas rather than electrolysis is simple – cost. A unit of electricity costs around 3 or 4 times that of a unit of natural gas. In addition, most of our electricity is already produced by burning gas, oil or coal, discarding a large proportion of the input energy. Generating hydrogen from natural gas skips the middle man. 

By now, one of the several major problems with hydrogen should now be apparent. If you produce it from gas, there is no benefit; you’re wasting at least 20% of the energy in the conversion process and still emitting all the carbon you would have emitted if you had simply burned the gas. If you produce it from electricity, it can never be cheaper than the electricity that was used to produce it.

I’ve heard it argued that renewables can be used to create the electricity to power the electrolysis. That is, of course, true. But there is a significant opportunity cost as the electricity used to produce the hydrogen could have been sold on the grid. If you’re able to produce renewable electricity cheaply and at scale, then going through the extra step to convert it to gas is only justified for applications where electric power is deficient.

There are theoretical approaches that may become viable in the future. One way to produce hydrogen is to build gas-cooled nuclear reactors that can run at very high temperatures, typically around 750 degrees C. This is high enough to split the hydrogen gas from water. After producing hydrogen, the coolant is still hot enough to produce steam, which can power a turbine to generate electricity in a combined cycle. This technology is not theoretical but it has not yet been done at scale. 

Even if we overcome the issues of hydrogen’s high cost of production, there are still other issues to consider. 

I often hear hydrogen proposed as the future of zero-carbon transportation. Hydrogen powered vehicles are, outwardly, very attractive. A hydrogen-fuelled car avoids most of the disadvantages of a battery electric car. There’s no need for a heavy battery, and the tank can be filled within a few minutes. The range will match that of a petrol car, and it doesn’t drop in cold weather. You don’t need the exotic metals such as cobalt for the battery.

But this technology brings a few disadvantages of its own. A big one is efficiency; hydrogen fuel cells are about 50% efficient, compared to electric vehicle batteries which are around 80-90% efficient depending on the temperature. After you’ve paid for the fact that your hydrogen car needs almost twice the amount of energy poured into its tank to travel the same distance as a BEV, you also need to pay the significant capital and recurring costs to get the hydrogen to the places where it is needed. Transporting hydrogen is extremely expensive; you have to liquefy it (another 30% of the energy lost) physically move it (requiring trucks and drivers to operate them %) and you need the equipment to store and pump it for customers. 

The benefits that hydrogen can provide for transportation come at a very high cost. While battery electric vehicles have a number of disadvantages, these are offset by other factors. Wide deployment of electric vehicles will create challenges for grid operators, but charging electric vehicles slowly and overnight at home or on business premises means that it is likely that wholesale replacement of the grid can be avoided. EV batteries can be repurposed for energy storage, and BEVs can be used to power households and businesses during peak times. None of these benefits are available from hydrogen. Batteries are not likely to work well for heavy haulage, but that is a problem that might be better solved by thinking about how we manage heavy transportation in general.

What about home heating ? On face value, it seems like a no-brainer. Swap your boiler out for one that burns hydrogen instead of natural gas, and you’re carbon free without having to replace your central heating. 

But, as with transportation, the devil is in the details.  Firstly, it should be obvious that you can’t send hydrogen and natural gas down the same pipeline – there are no currently available technologies for combining and then splitting them at either end. That means that you need to isolate sections of the network and ensure that every premises connected is ready to switch over at the same time. With tens of millions of gas-connected premises across Ireland and the UK, that is a significant logistical nightmare and will likely require expensive construction of additional trunk gas pipework, as well as all the boilers, cookers and other appliances fitted to it. Retrofitting the gas network to hydrogen is self-evidently a decades-long project.

In addition, you cannot simply push hydrogen through existing natural gas networks. As a small element, it tends to embrittle metals, leading to leaks. The networks will therefore require retrofitting with pipework that is not susceptible to this problem.

For these and other reasons, it’s my opinion that hydrogen only makes sense for certain niche applications. For transportation, battery vehicles work well for the vast majority of use cases. The latest electric cars currently on the market can add 200 miles of range within around 20 minutes. Right here in Belfast, we’re using battery electric buses in the city, and Translink plans to electrify the entire Foyle bus network. Batteries fall down for long range, heavy haulage or construction equipment. Gas combustion is likely to make more sense in those cases. 

For home heating, insulation and heat pumps are likely to be the way forward. This is a huge logistical task too. Heat pumps require expert knowledge and complex configuration to work correctly, and full and effective insulation of properties is also essential. However the final outcome will be more sustainable and more environmentally friendly than if we follow the foolhardly path of trying to build out hydrogen everywhere. 

So, given all of these reasons, why is there so much lobbying going on; why are UK government ministers pushing so hard for hydrogen ? I’m not a fan of conspiracy theories, but I can’t help wondering who actually benefits from a push towards hydrogen. There are companies, in particular Japanese car manufacturers, who have invested so heavily in hydrogen that they don’t want to face up to the fact that they made a bad call. And, of course, the oil and gas industry benefits from selling natural gas as an easy bridge to hydrogen, perhaps hoping that by the time everyone discovers that making the gas is hard and expensive, we’ll have spent too much money to turn back.

To conclude, hydrogen looks like a simple solution to the complex problems of how we can make our energy and economies carbon-free. However, in practice, it introduces a series of difficult to solve problems of its own. It certainly has applications where high energy density is required such as aviation, or heavy haulage. Beyond this, most of the problems we have can be solved more easily with electricity and batteries.

 


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