How much water is needed to develop hydrogen energy?

In the context of "dual carbon", clean hydrogen has risen rapidly in recent years. It is understood that hydrogen energy is of great significance for breaking through the bottleneck of emission reduction in typical "difficult emission reduction fields" such as steel, chemical industry, and transportation.

However, with the acceleration of the global development of the hydrogen energy industry, the issue of water for hydrogen production has also attracted attention. On December 10, the Global Report on Water for Hydrogen Production, co-authored by the International Renewable Energy Agency (IRENA) and Bluerisk, was officially released during the 28th Conference of the Parties to the United Nations Framework Convention on Climate Change (COP28). This is the world's first report to systematically analyze the issue of water for hydrogen production, and provides important suggestions for the sustainable development of the hydrogen energy industry, which has entered the fast lane of development, from the perspective of "water resources".

Hydrogen is growing rapidly, and the demand for water is rising

It is understood that although hydrogen energy production currently accounts for only a small part of the world's total industrial water demand, as a dark horse in the field of clean alternative energy, if hydrogen energy is expected to develop rapidly in the next few decades, its demand for water resources will naturally rise accordingly.

At present, all hydrogen production methods require the use of water, and the water used for hydrogen production is mainly concentrated in the two processes of hydrogen production and cooling.

Luo Tianyi, a partner at Weilan Consulting, said: "In the hydrogen production process, hydrogen production technology consumes three parts: one is the physical or chemical reaction process of hydrogen production, the second is the use of water for cooling, and the third is the use of water for all blue hydrogen technologies. ”

According to reports, green hydrogen is generally through photovoltaic, Wind power and other renewable energy water electrolysis to produce hydrogen;Grey hydrogen is produced from natural gas, which requires water vapor and methane reforming together (SMR)Brown hydrogen uses coal as raw material to produce hydrogen through gasification, and water is needed to prepare coal-water slurry;Blue hydrogen is based on gray hydrogen and brown hydrogen with carbon capture, storage and utilization technology (CCUS) is added to reduce carbon dioxide emissions into the atmosphere, and after these hydrogen production systems are added to CCUS, water consumption will increase greatly, mainly for two reasons, the first is the system efficiency because the energy consumption of CCUS becomes low, and the second is because CCUS itself has a large amount of cooling demand, and it is removing impurities, adsorption, etc., each step requires the use of water.

In cooling, the more efficient the system, the less waste heat is generated by energy loss, and thus the less water is required for cooling.

Green hydrogen is known to be the most water-efficient of all clean hydrogen technologies. On average, proton exchange membrane (PEM) electrolysis of water has the lowest water consumption intensity, consuming approximately 17.5 litres of water per kilogram of hydrogen produced. Alkaline electrolysis is a close second, with a water consumption intensity of around 22.3 litres per kilogram. In comparison, the water consumption of blue hydrogen based on steam methane reforming (SMR-CCUS) technology is about 32.2 L/kg, while the blue hydrogen based on autothermal reforming (ATR-CCUS) is about 24.2 L/kg.

Coal gasification is currently the largest water consumption of any available hydrogen production technology, with an average water withdrawal intensity of about 50 L/kg and a water consumption intensity of 31 L/kg, which is about twice that of PEM. If equipped with CCUS, its water intensity will increase by about 60%, to 80.2 litres and 49.4 litres per kilogram. For example, a coal-to-hydrogen plant with an annual production capacity of 237,000 tonnes of hydrogen and CCUS would draw about 19 million cubic metres of water per year, enough to support the city's residential water needs for half a year or a 1 GW thermal power plant for more than a year.

Hydrogen production may increase the risk of local water stress

The reality is that the energy industry is the "water giant" in the industrial sector. With the intensification of climate change, the frequency and intensity of extreme weather increases, the uncertainty of precipitation increases, and cases of forced closure or production reduction of energy facilities due to water scarcity are frequently reported around the world, and the "water-energy" relationship is becoming more and more tense.

Based on the World Resources Institute's (WRI) Global Watercourse Risk Map (Aqueduct), the report assesses the water stress situation in the locations of green and blue hydrogen projects (already operating or planned) around the world.

For example, the Gulf Cooperation Council countries lack fresh water resources and can only meet the current demand for grey hydrogen through desalination and cooling. Luo Tianyi said that the Gulf countries have plans to build the region into a "hydrogen export center", with an annual output of more than 30 million tons by 2040, including 10 million blue hydrogen and 20 million green hydrogen. This also greatly increases the cost of desalination for the local hydrogen production industry and the environmental risks of seawater halogenation.

Another example is the intensification of droughts caused by climate change in Europe, which is affecting the energy sector more frequently. Many of the planned hydrogen production projects are located in places where water is already scarce, and the "water-energy" conflict is likely to escalate further in the next decade.

Ute Collier, Acting Director of the Centre for Knowledge, Policy and Finance at IRENA, said: "Some of the current hydrogen production methods that try to address greenhouse gas emissions actually increase the risk of local water stress, reinforcing the fact that green hydrogen is the best option to help achieve the global 1.5C goal. ”

According to the report, at present, the annual scale of fresh water extracted from global hydrogen production is 2.2 billion cubic meters, accounting for 0.6% of the total water withdrawal in the energy sector. Among them, grey hydrogen production accounts for about 59% of the global hydrogen production water withdrawal, and brown hydrogen accounts for 40%. By 2040, global freshwater withdrawals for hydrogen production could increase by more than 230% to 7.3 billion cubic meters, and reach 12.1 billion cubic meters by 2050, a nearly six-fold increase. The hydrogen industry's share of total freshwater withdrawals in the energy sector could rise from 0.6% today to 2.4% in 2040.

At the global level, the hydrogen industry is not yet a major water user, but if you focus on the specific location of hydrogen production sites, the "water-energy" conflict may be very serious.

The report found that more than 35% of the world's green and blue hydrogen production capacity (operating and planned) is currently located in areas with high water stress. For example, 99% of hydrogen production capacity in India by 2040 may be located in areas with extreme water stress, and China, the European Union, the United States and other G20 countries are also facing varying degrees of water stress, which will lay a hidden danger for hydrogen production projects to be sustainable in the future. Therefore, planning the development of hydrogen energy must comprehensively consider the actual situation of local water resources from a longer time frame and multiple dimensions.

For every 1% increase in electrolysis efficiency, water consumption of green hydrogen can be reduced by about 2%

It is worth noting that how to incorporate "water" as a key production factor into the early, medium and late planning in a more timely and appropriate manner when developing hydrogen energy will be an important breakthrough point to realize the coordinated development of water and energy, and will also become the key to unlocking a sustainable future for the earth.

In key areas of the hydrogen energy industry where water resources are scarce, green hydrogen should undoubtedly be a priority development option to reduce the impact on the local ecological environment and its own production risks.

In recent years, China has been actively deploying the hydrogen energy industry. In the Medium and Long-Term Plan for the Development of the Hydrogen Energy Industry (2021-2035) released in early 2022, China has made it clear that hydrogen energy is the key direction for the development of strategic emerging industries, and it is a new growth point for building a green and low-carbon industrial system and creating industrial transformation and upgrading. According to the data, China's hydrogen industry is expected to reach 1 billion yuan ($134 billion) by 2025.

Through simulation, the report found that with the improvement of green hydrogen production technology, the water consumption of green hydrogen can be reduced by about 2% for every 1% increase in electrolysis efficiency.

It is understood that about 63% of China's hydrogen energy is brown hydrogen, which has high carbon emissions and water consumption. The Yellow River Basin is one of the most important hydrogen producing regions in China, with 70% of the basin's coal-chemical plants located in water-stressed or extremely stressed areas.

In China's Yellow River Basin, if coal-to-hydrogen production is replaced by "water vapor and methane reforming technology + CCUS", alkaline electrolysis or a mixture of the two, then by 2030, the Yellow River Basin can reduce water consumption and increase hydrogen production. For example, switching from brown to blue hydrogen increases hydrogen production by 11%, reducing total extracted water by 18% and water consumption by 15%, while switching from brown to green hydrogen increases hydrogen production by 11%, extracts water by 28% and consumes water by 20%.