2 myths and an open question about water and Power-to-X
Water is the main ingredient in green hydrogen, so the types and water sources used impact the business case and sustainability of Power-to-X projects. Here’s what you need to consider as green hydrogen goes for scale.
Today, almost all hydrogen is produced from fossil fuels. Only a tiny fraction – 0.1% – is green hydrogen made using water electrolysis and renewable energy, according to the International Energy Agency (IEA).
But many analysts predict green hydrogen will soon reach scale. And when that happens, water will get increased attention in the business case for Power-to-X developers.
That fact is reflected in the types of questions we get more and more at Ramboll: “How do you source water for Power-to-X sustainably, effectively, and at the lowest cost?” are one of the most common.
That’s what we would like to answer in this article – and perhaps debunk a myth or two along the way:
Myth 1: Water should guide where you place a hydrogen facility
Contrary to popular belief, water access does not need to be the main criteria for when and where to place hydrogen facilities.
Barring edge cases, like wind parks in very arid regions, you will likely have access to some water. But it will likely not be groundwater or potable (drinking) water. This is a good thing!
The reason that you may not want to use these water sources is to avoid competing with the supply needed for households and agricultural use. That is a legitimate concern with the scale of announced hydrogen projects we are seeing now – according to the International Renewable Energy Agency (IRENA), a 1 GW hydrogen facility requires the same amount of water as a city of 70,000 people.
There are many different potential water sources for hydrogen projects. In many cases, effluent or contaminated water is preferable to groundwater or potable water.
Water sources for hydrogen production
- Surface water: One of the largest sources of water is surface water. Surface water includes rivers, lakes and reservoirs.
- Groundwater: Groundwater can exist in both bedrock and overlying geology depending on local conditions.
- Potable water: Potable water is drinking water. Potable water is typically treated and distributed by a water utility for domestic and industrial use.
- Sea water: Sea water is an abundant coastal resource. Sea water is any salt water extracted from coastal or estuarine regions.
- Effluent: Effluent is a liquid waste discharged into a water body. Effluent water can come from municipal or industrial sources.
Above all, the right water source depends on a number of factors. Cost is one, but sustainability is also tremendously important. Which brings us to the next myth:
Myth 2: Only clean water can be used
The ideal location for a Power-to-X facility is where there is a water supply that is reliable and not subject to competitive use. Seawater ticks both those boxes. And so does impaired groundwater or treated wastewater effluent.
In fact, because the water has to be extremely clean when it enters the electrolyser, you can actually choose less clean sources; the water has to be meticulously pre-treated in any case, so whether it is more or less contaminated to begin with matters less.
Take seawater: Of all water types, it requires the most extensive treatment and energy before it can be used, because higher pressures are needed to remove salt from the water (which would otherwise damage the delicate electrolysers). But even so, purifying the sea water will only require 0.15% of the total energy required to run a Power-to-X facility. While that has a price, extraction and transport costs for seawater are extremely low, making up for it.
This also means that for most projects the water type has no meaningful impact on the production cost for green hydrogen. But understanding local water conditions is key to select the most sustainable and reliable sources, so developers should prioritise these assessments in the early project stages.
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Because Power-to-X is an emerging industry, there are also some questions we still don’t know the answer to. Namely:
Who will treat the water?
Traditionally, the offering from water utilities has been limited more or less to potable water. But with Power-to-X, an entirely new market emerges for other types of water, including water from other, less clean sources.
It may be attractive for Power-to-X developers to do water treatment ‘in-house’, so to speak, as they are then able to control supply. But – if regulation allows, and that will vary from country to country – new suppliers could also emerge as demand for wastewater effluent and sea water increases.
And in the other direction, sector coupling offers a potential secondary revenue stream, because electrolysis generates oxygen and heat as by-products. Providing oxygen to industry or wastewater treatment plants or excess heat to district heating could improve the business case of specific projects.
How much water does it take to produce green hydrogen?
To produce 1 kg green hydrogen, 9 kg water is needed for the electrolysis process.
The water must be rid of impurities, like salts and organic matter. The reason is that as the water is split into hydrogen and oxygen in the process, these impurities remain, which will wear out the electrolysers over time.
Prioritise detailed assessment of water resources early in the project
Hydrogen project developers should carry out a detailed assessment of local water resources in the very early stages of their project.
The assessment should include water availability and cost, the impact of the project on local water resources, ecology and other local water users over the lifecycle of the project.
Developers should further engage with stakeholders to identify and develop strategic synergies, such as sharing new water infrastructure, recycling treated effluent or using contaminated groundwater, and/or finding uses for waste heat from hydrogen production, and electrolytic oxygen.
We're here to help you solve these water challenges
Early water management planning will ensure smooth sailing throughout your hydrogen project.
With more than 50 years of experience in water, wastewater treatment, and designing and implementing energy solutions, we combine key disciplines to best consult you and your organisation in successful and profitable hydrogen projects.
Over the years, we have built successful partnerships to pioneer innovations and we continue to do so in advancing Power-to-X and green hydrogen.
Want to know more?
Patrick J. Campbell
Director, Water and Wastewater Treatment, Americas
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