Purified water is crucial to ensure an efficient and reliable electrolysis process when producing green hydrogen. Here Derek Mcintyre at Veolia Water Technologies UK (VWT UK) looks at the benefits of green hydrogen, the damage untreated feed water can cause to electrolysers and how VWT UK can help guarantee a highly purified water supply.
Understanding green hydrogen
Despite hydrogen having no colour, the gas is subdivided into different colour categories providing information of how it was produced and the energy sources used. We explain these colours below:
- Green Hydrogen: Produced by an electrolyser using energy from a "green" source (eg wind turbines).
- Blue Hydrogen: Produced by steam reforming from natural gas and steam.
- Black and Brown Hydrogen: Produced by using coal or lignite.
- Grey Hydrogen: Produced from natural gas or methane using steam methane reformation.
- Pink (or Purple or Red) Hydrogen: Produced by an electrolyser using nuclear power.
- Yellow Hydrogen: Produced by an electrolyser using solar power.
Green Hydrogen is produced when water molecules are split into oxygen and hydrogen molecules by the electrolyser. After this process, the oxygen is vented out into the atmosphere whilst the hydrogen is safely stored as fuel for later use. When burned as a fuel, hydrogen produces no greenhouse gases - only water molecules.
At present, only 0.1% of hydrogen is renewably produced but interest is growing rapidly. With the push to reduce greenhouse gas emissions and issues with the supply of fossil fuels green hydrogen production is ramping up.
The importance of purified water
The feed water for green hydrogen production must be purified before it is fed to the electrolyser. If the incorrect purity of water is used the electrolyser could become fouled or degraded and its output become compromised. VWT has the purification technologies available for the following sources:
- Mains water (whatever the source)
- Surface water
- Rain water
Finding the right pre-treatment technology
Typically, the purified water for generating hydrogen gas via electrolysis is produced by reverse osmosis (RO), which is then ‘polished’ with mixed bed ion exchange cylinders or continuous electrodeionisation (CEDI). However, it is crucial that the pre-treatment of the feed water is correct to prevent the RO and CEDI from fouling after a short period of operation. There are a number of pre-treatment technologies available:
- Particle filtration
- Water softeners
- Organic scavengers
- Granulated activated carbon (GAC) filters
- Antiscalant dosing
- Degassing systems (particularly relevant if a CEDI is fitted)
The required pre-treatment processes are determined by the amount of total dissolved solids (TDS) in the water, organic material, particulate matter, chlorine and carbon dioxide. At VWT we have extensive experience of analysing feed water and selecting the ideal pre-treatment. We are then able to ensure maximum operational lifespan and reliability of the water purification system downstream.
Add value through digital tools
In addition to this, VWT offers Hubgrade, a digital tool designed to address operational issues and optimise performance. Scalable for use and able to be installed on existing Veolia and non-Veolia water treatment equipment, Hubgrade can alert operators on the quality of feed water to ensure the desired purity is provided.
Remote monitoring is also an option with Hubgrade. This allows remote operators to check the operation of the purified water system and pretreatment at all times. It also allows VWT service engineers to assess the performance of the plant and diagnose problems remotely. This can be useful if the electrolyser and water treatment is located on an unmanned offshore wind turbine.
As the market for green hydrogen continues to grow, with industries increasingly turning to more sustainable fossil fuel alternatives, the quality of feed water will be a vital component. By opting to work with a water treatment specialist such as VWT, we can provide a range of solutions and digital monitoring to guarantee a consistent supply of highly purified feed water to ensure a reliable and efficient electrolysis process. With business units across the world we are ready to support you from start up through to scale up nationally and globally.
For more information on Veolia Water Technologies’ range of water treatment solutions, please visit: https://campaign.veoliawatertechnologies.co.uk/hydrogen-generation
About the Author
Derek has 30 years experience of business development on water purification and waste water treatment at ELGA and Veolia. Derek is a Chartered Engineer and has been involved in developing markets for ELGA and Veolia products for much of his career.