Directly Using Seawater for Green Hydrogen Could Be the Breakthrough of the Century

Direct electrolysis of saltwater is the real deal for green hydrogen 6 photos
Photo: Image by bearfotos and macrovector on Freepik
Most of hydrogen is sourced today from methane in natural gasCheap Sun energy is feasible for green hydrogenGreen hydrogen requires too much energyFor now, direct electrolysis of saltwater is a lab-breakthroughHydrogen cost for cars is much higher than batteries
Sourcing clean hydrogen from water (H2O) only needs splitting the two atoms of hydrogen from the oxygen one. It turns out this is far from a simple task. It’s an energy-intensive process and we still haven’t figured out how to make it economically feasible. But now, researchers from the University of Adelaide may be onto something here.
You already know that a number of carmakers out there – I know you’re all thinking right now of Toyota, right? – are pouring a lot of money into the research and development of fuel cell technology. Which is praised as a battery-killer technology, especially by the oil industry. Which also bets billions on it.

Without question, replacing fossil fuels with abundant pollution-free hydrogen is by all means the right choice. Sadly, this transition isn’t happening fast enough because hydrogen tech isn’t a simple task at all. I could brag about Big Oil using this delay to its advantage to keep doing business as usual, but this isn’t the point now.

Sourcing hydrogen from water is huge energy intensive

The fact is sourcing hydrogen from water isn’t efficient enough today to economically make sense. At least on a large scale. Let’s see some numbers:

- the daily average consumption of a person’s primary energy is estimated at around 60 kWh

- 1 kg (2.2 lbs) of hydrogen has a theoretical usable energy of more than 30 kWh, so we need 2 kg (4.4 lbs) of hydrogen to satisfy the energy hunger of each person on the planet each day

- there are already 8 billion people on the planet, so simple math reveals that the industry has to produce at least 16 million tons of hydrogen each day

Most of hydrogen is sourced today from methane in natural gas
Photo: Image by macrovector on Freepik
Splitting water by electrolysis requires a lot of energy. Today’s industrial-scale technical solutions are up to 70% efficiency, but in real life that percentage is closer to 50%. It simply means that, in order to obtain 1 kg (2.2 lbs) of hydrogen from water electrolysis, you need double the amount of electricity that you can use from that kilogram of hydrogen.

Would you still loan someone 100 bucks when you know for sure he will give you back only half of that? This is what investing in hydrogen looks like today. Of course, we should take into account the huge savings related to the lack of pollution, but for now, the economy isn’t working this way.

So the best-case scenario is we have to use daily around 1,000 TWh of electricity for water electrolysis to source the green hydrogen needed to cover the energy demand of the Earth’s population, which is around 500 TWh daily.

Well, each day the Sun hits the Earth with 2.5 million TWh. The one thousand Terawatt hour we need for water splitting is less than 0.05% of the daily Sun’s energy. We could fetch that amount by investing a lot more in solar panels, and also in wind turbines.

Cheap Sun energy is feasible for green hydrogen
Photo: Image by Pexels from Pixabay
This raises an interesting question: why don’t we simply use the renewables to produce that 500 TWh daily that we need? Glad you ask, but, again, it’s not the time, nor the place for this very interesting question. We are trying to figure out how to solve the hydrogen issue, remember? Please focus on this, otherwise, you risk concluding that hydrogen makes no sense

More energy, please. Much more!

In order to source 1 kg (2.2 lbs) of hydrogen, you need around 10-11 liters of deionized water, although, in real life, these values are more like 15-16 liters because of the low efficiency of nowadays industrial electrolyzers. But let’s be optimistic, for now.

In order to produce 16 million tons of hydrogen each day, we need at least 160 million tons of deionized water. Two-thirds of Earth is covered by water, and the total mass of the oceans is estimated at 1.35 x 1,018 metric tons. So there’s plenty of water to use for electrolysis. Or is it?

The devil is in the details: the water for electrolysis must be deionized water, while the water in the oceans is salted. First, we need a process called desalination to get freshwater, which then goes through filtering, reverse osmosis, and deionization process.

The bottom line is only highly purified water can go into electrolyzers for hydrogen to be made. And turning 1 ton of salt water from the ocean into purified water requires a lot of energy, at least 10-20 kWh, depending on the efficiency of industrial plants.

Green hydrogen requires too much energy
Photo: Image by Roman from Pixabay
That’s why most of the electrolyzers around the world use freshwater from rivers and lakes. Unfortunately, this increases the scarcity of limited freshwater resources, so this tends to become an environmental risk. By the way, better efficiency requires rare and expensive metals, like platinum or iridium – and this is much worse than the batteries’ lithium conundrum.

There’s no need for math anymore, as I’m sure you already have an idea about the vast amounts of energy needed to make hydrogen out of salt water. So finally we can now better understand why the findings of researchers from the University of Adelaide and Tianjin University are so important.

It’s really a game-changer idea. In the lab

They managed to bypass the need for desalination and all the other processes by creating a direct electrolyzer for salt water, with similar performance to a typical electrolyzer operating in high-purity water. In their words, they provide “a solution to directly utilize seawater without pre-treatment systems and alkali addition.

In the lab, they managed to split saltwater from the ocean using a non-precious and cheap catalyst, like a cobalt oxide with chromium oxide on its surface. The team claims the efficiency was nearly 100%, but we’ll have to wait and see the results after they will scale up this new type of electrolyzer.

Researchers from the University of Adelaide in Australia and Tianjin University in China are not the first to find a way for direct electrolysis of seawater. But their approach is, for the moment, the best one to be universally compatible with varying compositions of seawater depending on location.

For now, direct electrolysis of saltwater is a lab\-breakthrough
Photo: Image by Roman from Pixabay
As we know, lab research takes some years until an economically viable model can attract investors. The testing phase and developing and monitoring pilot projects also require a few years. So this “lab breakthrough” could become reality somewhere at the end of this decade, while global deployment can be expected only after 2030.

So, as promising and exciting as this news seems for the companies in the hydrogen business, the best approach is to wait and see. After all, the same applies to solid-state batteries, a promising tech that doesn’t pay off yet.

We should all take these breakthrough novelties with a grain of salt. One from the ocean’s saltwater is more proper for our case here.
If you liked the article, please follow us:  Google News icon Google News Youtube Instagram
About the author: Oraan Marc
Oraan Marc profile photo

After graduating college with an automotive degree, Oraan went for a journalism career. 15 years went by and another switch turned him from a petrolhead into an electrohead, so watch his profile for insight into green tech, EVs of all kinds and alternative propulsion systems.
Full profile


Would you like AUTOEVOLUTION to send you notifications?

You will only receive our top stories