The energy water nexus: balancing water needs for hydrogen production
As the clean hydrogen industry grows, we must fully investigate its water requirements to ensure developing the industry aligns across energy and water security, as well as wider equity and environment needs.
The journey toward a zero emissions future relies on the development of a wide range of renewable energy resources. While solar, wind, and hydropower offer excellent grid-scale performance, hydrogen has a critical role to play as a replacement for fossil fuels in otherwise hard to abate applications.
The clean hydrogen industry is still in its infancy with very few production facilities operating beyond demonstration stage. But it is paramount we move quickly to understand the potential impacts it will have as the industry scales. We must fully investigate its water requirements to ensure developing the hydrogen industry aligns across energy and water security, as well as wider equity and environment needs.
This ‘energy water nexus’ is essential to planning for our sustainable future. The Australian Government’s Department of Climate Change, Energy, the Environment and Water (DCCEEW) and the Australian Hydrogen Council (AHC), identified the need to support the development of a technical study on water use for hydrogen. With their collaborative support, we undertook a technical assessment and prepared the Water for Hydrogen Technical Paper on the water needs for the development of the hydrogen industry. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) then supported the report by undertaking a technical review.
We assessed water usage for a range of hydrogen production and hydrogen carrier conversion processes. We also examined water quality and quantity requirements throughout the hydrogen value chain, including opportunities for process water recycling and reuse to enable any potential water savings. Below we have summarised some of the report’s highlights and key takeaways for understanding the energy water nexus.
Water requirements are highly variable
When analysing the entire hydrogen value chain, water requirements can vary substantially. Water source quality, water treatment method, climatic conditions, the hydrogen production method, the cooling method, and the hydrogen carrier conversion process all impact on the final calculation of litres of water per kilogram of fuel produced.
For example, water requirements are generally higher in the production of green hydrogen than blue, due to both feedstock water consumption and cooling water consumption and losses. There is also a higher water requirement when carrier conversion to liquid ammonia or liquid hydrogen is performed.
We have offered deep analysis of the various requirements, but it’s important to understand how this variability will suit different locations and needs on a case-by-case basis.
Planning for a sustainable future requires a holistic approach to the mitigation of environmental and social impacts throughout the food energy water nexus.
Cooling water requirements vary significantly
One further distinction on water requirement variability is in cooling water requirements, which contributes a significant proportion of the water usage in the hydrogen value chain. We assessed three different cooling methods – once-through, evaporative, and air cooling – and saw that each may be suited to certain location and climatic conditions.
For example, evaporative cooling has a high-water requirement and high consumption rate due to losses in evaporation. This is well suited to a wide range of conditions but can lead to greater water losses in dry climate regions than in wetter areas. Meanwhile, air cooling does not use water, which may suit certain conditions and locations best, but it is more expensive to implement and requires more energy input.
Water consumption is comparable to fossil fuels
When comparing hydrogen fuel cell electric vehicles (FCEV) and fossil fuel combustion engines (diesel and petrol) for passenger applications based on fuel usage per 100km travelled, we found water consumption for green hydrogen process with an evaporative water-cooled system to be comparable to that of fossil fuels.
For heavier vehicles such as buses, the results indicate that for air cooling or evaporative cooling in a wet climate zone, water use is comparable to diesel. However, if evaporative cooling is used in dry climate zones, the water consumption for green and blue hydrogen may be higher.
Advanced recycled water is the ideal water source
We assessed six raw water sources – surface, ground, recycled, advanced recycled, brackish, and seawater – and found that where available, advanced recycled water is the most preferable for use in hydrogen production. This source requires the lowest level of treatment and associated water and energy consumption to produce the feedstock and cooling water.
In order of preference, this is followed by surface, ground, brackish, recycled class A, and seawater. Seawater has the highest water use with the least recyclable water availability, with waste streams from the treatment process too saline for reuse.
Where possible, manufactured water sources such as those from wastewater treatment plants and desalinated seawater will provide the most sustainable supplies with the least impact on existing water use, delivering the best levels of community acceptance.
Holistic thinking is required
It’s important for all decision makers to not consider the results of this technical study in isolation. Planning for a sustainable future requires a holistic approach to the mitigation of environmental and social impacts throughout the food energy water nexus. We must ensure the hydrogen value chain is aligned with wider efforts to secure water supply and manage water sources sustainably.
As the hydrogen industry moves from demonstration to commercial scale development, the details of this study will be refined as more real-world information gives us more data for analysis. Technology advancement in hydrogen production and carrier conversion will continue with a focus on improving operating fundamentals such as optimum temperature, longevity of efficiency, and water quality characteristics. This is expected to deliver water requirement savings compared to the mature technologies assessed in this study, providing better future outcomes for the industry, community, and environment.
Hydrogen has a critical role to play in our sustainable energy future, and understanding the water supply needs of this future industry is fundamental to meeting the demands of our National Hydrogen Strategy. As we map out the path ahead for hydrogen, The Water for Hydrogen technical study is a valuable resource for the industry, providing insight into the assessment and requirements of water for a range of hydrogen production.
Download the report here
