THERE IS NO GREEN WITHOUT BLUE: WATER’S ROLE IN CLEAN ENERGY TRANSITION

By Mrs. Verónica García Molina Global Marketing Leader – Industrial Water & Energy DuPont Water Solutions

The need for water to generate energy is getting a lot of attention, particularly given the growing interest in green hydrogen’s potential for the continued decarbonization of numerous industries.

The water-energy nexus, with the inextricable linkage between the two, has long existed. With green hydrogen, the novelty between water and energy resides in the combination of the amount of “new” water needed and the timeline—by when that water is going to be needed. The obvious next question we need to ask ourselves is where is that water going to come from, particularly in regions already facing water scarcity.

A key component of the production of green hydrogen is the electrolyser, which electrically splits the water molecules into hydrogen and oxygen gas. Within an electrolyser, ultrapure water is needed as the feed stream and, if the production site accounts for cooling towers, additional water will be needed.

Even though fit-for-purpose qualities of water are needed for the feed stream feeding the electrolyser and for the cooling towers, the reality is that technology exists to treat almost any type of raw water (river water, seawater, wastewater, etc..) to meet the required quality of water for each process.

According to a variety of sources, in order to produce 1kg of hydrogen, 9 to 13 Litres of ultrapure water (UPW) are needed and depending on the source of water used, the real water needs can vary quite significantly. For example, to produce 1 L of Ultrapure Water, 3.3 L of Seawater are needed. This amount gets reduced by a half, i.e., 1.5 L if the source water is wastewater or surface water.

Intuitively, and given the global water scarcity situation, the potential water sources often considered for green hydrogen are seawater desalination and wastewater. An interesting figure, provided by Newborough and Cooley

(Fuel Cells Bulletin, December 2021) indicates that if today, all the energy provided by fossil sources would be replaced by green hydrogen, the water needs would be 0.000006% of the total seawater available and 10 times lower than the global wastewater production. According to this, we’ve got the water availability to fulfil the needs for green hydrogen and equally, as stated earlier, the technology is readily available.

That said, which water source should be selected, seawater or wastewater?

The advantage of seawater desalination is that it represents a very large supply relative to the estimated demand from green hydrogen, provided that the location is in a coastal area. The key “con” however is the relatively high capital and operating expenses.

Regarding, wastewater, from a municipal or industrial origin, the main advantage is the cost compared to seawater desalination, both from a capital and operational expenses. The key disadvantage is on the other hand related to the smaller supply. Another potential disadvantage of the wastewater option relies on the fact that this water source is becoming more and more a “precious” resource, and thus, competing needs for the same water may arise in the coming future which may compromise its availability for Green Hydrogen.

The rise of information technology and with that the semicon industry is a great testimonial how the water industry tackled a large need for ultrapure water. From that perspective, green hydrogen is not that different. We need to make sure to manage that need in the most sustainable way though, given the different water sources and the technology available.