Researcher Quantifies Water Requirements for Transitional Hydrogen Economy; A Significant Impact on A Critical Resource
A researcher at the University of Texas has provided the first analysis of the water intensity of a transitional hydrogen economy. Michael Webber, Associate Director at the Center for International Energy and Environmental Policy at the University of Texas at Austin, quantified the direct and indirect water requirements to annually manufacture 60 billion kg of hydrogen partly by thermoelectrically powered electrolysis.
While the hydrogen economy is expected to be in full swing around 2050 (according to a 2004 report by the National Research Council [NRC]), a transitional hydrogen economy could occur in about 30 years, around 2037.
The analysis, which is published in the open-access journal Environmental Research Letters, determines that up to 143 billion gallons of water would be directly consumed as a feedstock, with a total consumption including evaporation of cooling water at power plants of 0.5–1.7 trillion gallons annually.
Total water withdrawals for thermoelectric cooling (most of which is not consumed) are expected to increase by 27–97% from 195,000 million gallons/day used today by the thermoelectric power sector to generate about 90% of the electricity in the US. The amount of the increase depends primarily on the aggregate efficiency of electrolyzers that will be in place and the portion of hydrogen that is produced by thermoelectrically powered electrolysis.
On a per unit basis, thermoelectric power generation for electrolysis will on average withdraw approximately 1,100 gallons of cooling water and will consume 27 gallons of water as a feedstock and coolant for every kilogram of hydrogen that is produced using an electrolyzer that has an efficiency of 75%.
...if the hydrogen economy includes thermoelectrically or hydroelectrically powered electrolysis as a prominent source of hydrogen, then we can expect significant increases in water withdrawals and consumption for fuel production over today’s use of gasoline. Given that water withdrawals have remained steady for decades, these increases in water use represent a significant potential impact on a critical resource.
If minimizing the impact of water resources is a priority and electrolysis becomes a widespread method of hydrogen production, it is likely that the power for electrolytic hydrogen production will have to come from non-thermoelectric, non-hydroelectric and non-irrigated renewable sources. Consequently, almost all the new electricity generating capacity for hydrogen production would need to be from hydrogen production pathways that do not use much water (such as wind or solar), or effective water-free cooling methods (e.g. air cooling) will need to be developed and widely deployed.
Webber, Michael E. “The water intensity of the transitional hydrogen economy.” Environmental Research Letters, 2 (2007) 034007