The push toward sustainability is leading to converting from reliance on hydrocarbons to hydrogen for applications in such sectors as chemical, cement, industrial steel production and transportation. Hydrogen is now produced by a number of pathways with the main one still relying on methane reforming which uses natural gas. 

Global demand for hydrogen for all applications is anticipated to grow from an annual requirement of 100 million metric tons per year in 2020 to approximately 530 million metric tons by 2050. With this accelerated growth in the need for hydrogen, there is an incentive to find ways to increase the production of green hydrogen from electrolysis of water, which only accounts currently for 2% of global hydrogen production. 

The energy needed to manufacture green hydrogen is available from renewable sources such as solar and wind energy. But optimizing the generation of energy from both sources still needs to be done. A previous TLT article¹ discusses a new approach for harvesting solar energy using a non-reciprocal solar thermophotovoltaic system. Theoretically, analysis shows that this system can direct all incoming solar energy for use as electricity up to the theoretical thermodynamic efficiency limit of 93.3%. 

Dr. Lorenzo Rosa, principal investigator at Carnegie Institution for Science in Stanford, Calif., says, “Our interest in hydrogen originates from research on how the chemical industry can implement climate mitigation procedures to reduce the dependency on fossil fuels in energy intensive processes such as the synthesis of ammonia.”  

For a hydrogen economy to be successful, figuring out how to deploy this material globally is necessary. Rosa says, “To deploy green hydrogen on a large scale globally, land and water resources must be available. Land is needed to permit the installation of solar cells, wind turbines and electrolysis facilities to produce green hydrogen. This must be done without detracting from land needed for agriculture. Another factor to be considered is the continuing growth globally of human population also will reduce the availability of potential land for green hydrogen production.” 

Water usage represents a difficult challenge to overcome due to the increase in demand coupled with the decline in available water and the increase in pollution. Rosa says, “While demand for water to be used in electrolysis is approximately less than 1.5% of the demand for water for agriculture, constraints found in specific locations may limit availability.” 

Past studies on how a hydrogen economy can be devised have relied on global assessments of land and water availability. This does not furnish an accurate analysis of the steps needed globally for producing and using green hydrogen efficiently. Rosa and his colleagues have now conducted a study to provide more details on a country level about the supply and demand for hydrogen to determine the future for a global hydrogen economy. 

Country-by-country assessment 
The researchers started their analysis by determining the hydrogen demand in 2020 and 2050 for each country. They found that hydrogen demand for the top 35 countries per capita will increase seven times from 2020 compared to 2050. Rosa says, “We determined this figure by evaluating changes in demand for seven sectors (methanol, ammonia, light industry, cement, refineries, transport and steel) that have significant requirements for hydrogen. Hydrogen demand will not increase in all sectors as refineries will see an 80% decrease while significant increases will be found for the chemical and transportation sectors.” 

Each country’s land and water resources were then examined by the researchers. In conducting a detailed land analysis for each country, calculations were made to determine what percentage was occupied by agriculture, artificial surfaces and forests. The remaining land was then determined to be available for installing renewable energy structures (solar and wind turbine farms). 

Rosa says, “In considering water availability, agricultural, industrial, ecosystems and municipal usage represent the major uses. Water needed for hydrogen production accounts for less than 3% of the total.” 

Evaluation of each country’s ability to use land and water resources to produce hydrogen led the researchers to conclude that not every country can meet its own needs. Rosa says, “We found that countries located in the North African and Middle East regions are ones that already are dealing with water shortages and do not have the ability to produce their own hydrogen. This means that some countries with superior water resources will need to be net exporters of hydrogen as demand ramps up.” 

In projecting hydrogen demand in 2050, the researchers determined the level of land and water scarcity that will occur due to hydrogen production. As shown in Figure 1, this analysis was conducted assuming 100%, 10% and 5% coverage for the use of solar and onshore wind power on land. The water analysis involves determining the added stress in using this available resource for hydrogen production based on relying on 100%, 10% and 5% of the available supply in each country. The net result is that countries were organized based on whether they will incur scarcity for land and/or water or neither resource. 


Figure 1. A global study determines the challenge for converting to a hydrogen economy. As part of the analysis, the potential land and water scarcity found for all major countries is shown at 5%, 10% and 100% coverage. Figure courtesy of The Carnegie Institution for Science.

The move toward a hydrogen economy is in process, but this research points out the challenges that will be faced by each country in meeting its needs. Rosa says, “We intend to build on this analysis by examining land and water resources for hydrogen production and use in each country on a plant-by-plant basis.” 

Additional information can be found in a recent article² or by contacting Rosa at lrosa@carnegiescience.edu.

REFERENCES
1. Canter, N. (2023), “New approach for harvesting solar energy,” TLT, 79 (1), pp. 12-13. Available here. 
2. Tonelli, D., Rosa, L., Gabrielli, P., Caldeira, K., Parente, A. and Contino, F. (2023), “Global land and water limits to electrolytic hydrogen production using wind and solar resources,” Nature Communications, 14, Article Number 5532.