Gigawatt upon gigawatt of green hydrogen capacity is being planned across Europe, Asia, and Australia. According to proponents of the technology, green hydrogen - the kind produced through electrolysis powered by solar, wind, and other renewable energy sources - is the best way to decarbonize heavy polluter industries. There is much talk about the falling costs of solar and wind and how they will make green hydrogen viable very soon. What nobody seems to want to talk about is water. Electrolysis is the process of breaking down water into its constituent elements - hydrogen and oxygen - using an electric current. The process is performed in an installation called an electrolyzer. When hydrogen advocates talk about the bright future of the technology, they focus on the costs associated with the electricity needed for the electrolysis. But electrolysis, besides electricity, needs water.
Tons of water - literally.
One industry source told Oilprice that the production of one ton of hydrogen through electrolysis required an average of nine tons of water. But to get these nine tons of water, it would not be enough to just divert a nearby river. The water that the electrolyzer breaks down into constituent elements needs to be purified
The process of water purification, for its part, is rather wasteful. According to the same source, water treatment systems typically require some two tons of impure water to produce one ton of purified water. In other words, one ton of hydrogen actually needs not nine but 18 tons of water. Accounting for losses, the ratio is closer to 20 tons of water for every 1 ton of hydrogen.
Speaking of water purification, organic chemists explain that the simplest way to do this is by distilling it. This method is cheap because it only needs electricity, but it is not fast. Regarding the electricity cost, distilling a liter of water requires 2.58 megajoules of energy, which translates into 0.717 kWh, on average.
This doesn't look like much at first glance, but let's see how things look on a larger scale. Germany is the country with the most ambitious plans for green hydrogen. The cost of electricity for non-household users in Germany was an average of $0.19 (0.16 euro) per kWh as of last year. At a power consumption rate of 0.717 kWh, the distillation of a liter of water, then, would cost $0.14 (0.1147 euro). For a ton of water, that would be $135.14 (114.72 euro).
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However, electrolysis needs as much as 18 tons of water - not accounting for losses during the process - to produce one ton of hydrogen. That means that the cost of water purification for the production of a ton of hydrogen would be $2,432 (2,065 euro). This is based on the assumption that the water would be purified using the cheapest method available. There are other - much faster - methods, but they are also costlier, involving ion exchange resins or molecular sieves.
Other alternatives to distillation, according to chemists, are unreliable at this point.
So, providing the right kind of water for hydrolysis costs money, and while $2,400 per ton of hydrogen may not sound like much, the cost of purifying water is not the only water-related expense in the technology that seeks to make hydrogen from renewable sources. Besides being pure, the water to be fed into an electrolyzer has to be transported to it.
Transporting tons upon tons of water to the site of an electrolyzer means more expenses for the logistics.
To cut these, it would make sense to pick a site where water is abundant, such as by a river or the sea, or, alternatively, close to a water treatment facility. This puts a limit on the choice of locations suitable for large-scale electrolyzers. But since an electrolyzer, to be green, needs to be powered by renewable energy, it would also need to be in proximity to a solar or a wind farm. These, as we know, cannot be built just anywhere; solar farms are most cost-effective in places with a lot of sunshine, and wind farms perform best in places where there is sufficient wind.
Needless to say, these places are not, as a rule, close to waterways, except offshore wind, which seems perfect for the production of green hydrogen. Unfortunately, offshore wind is also the costliest form of the three renewable sources - solar, onshore wind, and offshore wind - normally mentioned in the context of green hydrogen production. According to Rystad Energy, the capital costs of an offshore farm are twice as high as those of its onshore counterpart and four times as high as the costs of a comparable solar installation.
Not all costs associated with the production of hydrogen from renewable energy sources are the costs of those renewable energy sources. Water is the commodity that the process needs, and it is a little odd that nobody seems willing to discuss the costs of water, including the European Commission's Green Deal Team.
Perhaps the cost of water supply, storage, and purification is negligible compared with other costs that need to be addressed first. Yet it is an actual cost that should be added to the total when estimating how far the technology of producing hydrogen from renewable electricity has progressed and how viable it has become.
For now, experts appear to be unanimous that it is not viable - not without significant government support.
By Irina Slav for Oilprice.com
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Irina is a writer for Oilprice.com with over a decade of experience writing on the oil and gas industry. More
Comments
The thing most people forget is that Hydrogen is not a source of energy, it is a medium by which energy can be stored. Whatever energy you put into getting the Hydrogen, you will not be able to get an equal or greater amount out. So the energy to get it must be produced from something. To go to a carbon free process and to also kill two birds with one stone, my idea would be to utilize "geologic hotspots" like iceland or Hawaii to generate the electricity, then use it to produce hydrogen which could be liquified and transported to generators located in spots where there is a need for the purified water which would result when the hydrogen was "burned " and combined with oxygen to produce potable water or even safe water for crop irrigation. Thus clean hydrogen, clean water, increase arable land for food production. in Any event, good article, hope my comment helps.
As an example of how public rejection may happen: We may remember how a movie called China Reaction at the same time with serious Long Island accidents turned out. Even no one died, the media presented it as Hiroshima's kind of event. This (together with lack of political will to solve nuclear waste placement) practically killed the future of nuclear power in the US. The opinion was enforced following the Chernobyl catastrophe and Fukushima nuclear accident (blaming Tsunami victims on nuclear power was creative). There is also opposition to renewables, which emphasizes the failed projects and doesn't stick with facts. This will not change public opinion, but failed projects, high energy bill, and a few large scale blackouts can.
To purify water in large quantities, it takes about 30% VR 70% purify waters that comes out of the process.. that is 300 liters of every 700 liters purified. It's alot.. but not as dramatic as described in this article.
I smaller quantities, it tent to touch the 50%-50% mark waste of water to purified..
Wouldn't it make more sense to use the same renewable source to power water purification?
Best regards!
Ivan
To John's comment: I think also that our fresh water is to precious to us like that but maybe the sea water. What do you do with the salt waste?
I'm more a fan of the nuclear (thorium) solution and agree with Pekka that the public distaste is an emotional reaction to a danger not based in facts. When the US Oak Ridge Labs developed nuclear power they pursued two paths, one was uranium and the other thorium. Uranium was chosen because it could be used also to make weapons. The thorium path which was recommended by the director was discarded. But they had a thorium reactor running alongside a uranium reactor. The thorium has many virtues that would serve us well as the climate debate escalates.
Than you for the article,
Phil
1. If water is purified by osmosis or filtration the "waste" water is returned to the lake , sea or stream so it is not lost.
2. the ratios you mention apply to sea water or highly saline groundwater, they are much lower for clean fresh water
3. If water is purified by distillation then there is almost zero waste water. The water flowing into the system is equal to the steam flowing out so you are double counting the water usage.
Then there is the question of scale. If the conversion efficiency is 60%.i.e. some combustion applications will be 90% efficient, fuel cells 60% and combustion in engines 40% average 60%. Then at 120 MJ/kg we will deliver 72 MJ of energy delivered per kg of hydrogen. (72 GJ/tonne of water)
The US currently uses about 100 Quadrillion BTUs of energy, about 2/3 rds of which is lost up the the exhaust pipe, cooling tower etc. so energy services require about 35 billion GJ
In a fully electrified economy, pretty much all travel under 200 miles will be powered by catenaries or batteries and the combination of solar, wind hydro and nuclear with some batteries and demand response will mean that very little electricity will be stored as hydrogen and reconverted. In my view it will be around 5% but lets assume it is 15%.
That means the US needs 15% of 35 billion GJ = 5.2 billion GJ from hydrogen at 72 GJ/tonne of hydrogen that is around 75 m tonnes of hydrogen or 700 m tonnes of water. That sounds like a huge amount, but a 1 GW nuclear plant uses about 15-20m tonnes of water per year in its cooling towers. So the entire US hydrogen system needs about as much water as 1/3rd of the US nuclear fleet
Energy can only be conserved and transferred, never created. If we are using electricity to turn water into hydrogen, there is energy losses associated with that process. Lets hypothetically say 5% (It's likely to be way, way worse, I just don't have the numbers)
So, we put 1GwH of electricity into our green hydrogen machine, and we get 0.95GwH of hydrogen out. Then we are supposed to run ex coal fired power plants on this, which typically have an efficiency of ~40%
So in the end, in this ideal situation. We've used 1GwH of electricity to create 0.38GwH of electricity. We are already losing 62% of the electricity that we started with, before transmission. Obviously we could justify the loss by using hydro, or solar or wind, but surely it would make more sense to just route the electricity they create directly to the grid, before losing 2/3 of it, for no reason. You would be able to power the same town with less than half the input energy needed just to create the hydrogen that eventually powered it. I'm sure if we did the actual math here it would work out that IRL you could power a town with about 1/4 of the renewable energy that would be need to be used to make green hydrogen to be used in existing power plants.
Even if the power plant here was 100% efficient, and you only lost 5% from conversion. It would still make more sense to capture the 5% you'd lose from conversion, by just not converting it. And it would remove all the costs involved in storing and transporting water, gas, running a second power plant etc. And, we are starting with energy in the form we actually want it in. Why do we want to change it 10 times and eventually end up back in the form in started in.