Green hydrogen may be one of the keys to sustainably meeting our future energy needs, but one often overlooked aspect of effective electrolysis and hydrogen production is water purity. Patrick Buzzell, director of product management at Evoqua Water Technologies, discusses the vital role that water purity plays in improving green hydrogen production, while minimizing operational costs.
Widespread interest in green hydrogen production is seeing some existing mining and oil and gas companies pivot, alongside a large number of small-scale startups. For the uninitiated, green hydrogen is hydrogen gas made via electrolysis using solely renewable energy sources. It means that no CO2 emissions are generated in its production – exactly what humanity needs for the energy transition.
Currently, green hydrogen is just 0.1% of global hydrogen production, but it is expected to grow substantially. Given the role it may play in the energy economy and the investment it is currently attracting, awareness of the components of its production process are critical to its future success. Water treatment is one of these components and its importance within the electrolysis process is critical. For those looking to lead the green hydrogen revolution, the importance of water quality in maximizing efficiency and minimizing operational expenditure cannot be overstated.
Water Quality Challenges
While a focus on the technology and effective use and implementation of renewable energy in green hydrogen production is a central focus for many, water treatment is in some cases considered peripheral – an afterthought. But what are the consequences of this approach?
For starters, without appropriate water treatment to achieve high levels of water purity, the electrolysis process is detrimental to electrolyzers and inefficient. This is of particular importance when your production costs directly govern green hydrogen delivered as price/kgH2. Secondly, impure water will contain a high level of contaminants that will degrade the electrolyzer, leading to higher life cycle repair and replacement costs. Thirdly, there will be additional, undesirable byproducts to the electrolysis process, which will contaminate the hydrogen.
Monitoring & Ultrapure Water
For operators, ongoing and continuous monitoring of water purity is essential. Testing for known contaminants and organics will highlight quality issues before they become problematic. The conductivity of water, for example, is a good gauge to see the level of total dissolved solids removal, therefore, one monitor for suitability in electrolysis. That being said, water quality requirements will evolve and understanding monitoring limitations within operational conditions is critical.
The two primary types of electrolysis used for hydrogen production are alkaline electrolysis and polymer electrolyte membrane (PEM) electrolysis. High purity water is required for both methods. However, recirculation polishing in the PEM process requires higher treatment volume and purity levels. The alkaline method requires a lower deionization level compared to PEM processes.
The Answer: EDI and UV Solutions
At Evoqua, we have over 100 years of proven experience in water treatment and remain at the forefront of treatment technologies. As a relatively new industry, that has the opportunity to play a significant role in the future of energy production, we are excited to be working with – and providing solutions for – green hydrogen projects and companies. So, what are the best water treatment options for green hydrogen plants?
To produce ultrahigh purity water, we recommend electrodeionization (EDI) and ultraviolet (UV) systems. Why?
Well, at first EDI may seem like a more expensive option when compared to ion exchange tanks or single use resin, but it is far more cost-efficient in the long term with extremely low OPEX that negates the initial capital cost. It also has an upper-temperature limit that would be detrimental to ion exchange resins. EDI offers continuous operation and regeneration for minimal downtime and peace of mind.
This chemical-free process meets the performance and efficiency of the other options, making it an ideal on-site solution with far lower maintenance and operational requirements. When compared to mixed bed deionizers (MBDI), our EDI Ionpure® systems offer annual cost savings as high as 77%. They are also far more cost-efficient than rental units too, offering up to 84% OPEX annual savings.
Ultraviolet (UV) is also a highly effective chemical-free treatment process. High performance UV systems eliminate total organic carbon (TOC) to help reach the quality and level of water purity required. Removal of ions and organics is essential to keep electrolyzers working at optimum efficiency and to remain unfouled.
The Evoqua ATG™ UV VT system series, which has been designed for superior TOC reduction in ultrahigh purity water processes, exposes the water to 185nm wavelength UV light. This process creates a short-lived hydroxyl radical which breaks down TOCs into carbon dioxide for significantly improved ultrahigh purity water quality. With fewer lamps and longer lamp life, the VT series helps to reduce capital and operational expenditure.
With high purity water such a critical ingredient in the production of green hydrogen, it’s time to shine the spotlight on water treatment. Put simply, if the quality of water isn’t right, the production process won’t be operating at maximum efficiency. Getting it right will help increase output, extend the life of production equipment and, ultimately, improve the levelized cost of green hydrogen. Looking ahead, if production is to ramp up to meet ambitious generation targets, water treatment can’t be overlooked.
 IEA (2019), The Future of Hydrogen, IEA, Paris https://www.iea.org/reports/the-future-of-hydrogen, License: CCBY4.0
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