[ water treatment ]
1 . Geography 2 . Standardization 3 . Sustainability
To gain access to cheap renewable energy , green hydrogen facilities will be located in arid or coastal environments where freshwater is either scarce or not available at all , and where seawater is the only available water resource .
Seawater is a relatively uniform type of water with similar qualities across different geographies , which allows for a high degree of standardization . To drive down the cost of green hydrogen , standardization can become an important tool , and the use of seawater rather than local water sources of variable quality could enable this for the water treatment system .
As a green technology , there is also a strong focus on not relying on drinking water resources , and use of seawater is a way to avoid this .
Freshwater versus seawater
When comparing the use of seawater with lowsalinity freshwater resources like groundwater , river water , or wastewater effluent , two of the main differences are : 1 . Water footprint 2 . Energy consumption
Seawater is more water intensive than freshwater . To produce 1 m ³ of ultrapure water for electrolysis you need around 1.5 m ³ of freshwater , but up to 2.5 m ³ of seawater . This also means that where the use of freshwater will generate around 500 L of wastewater for every m ³ of ultrapure water , seawater will generate around 1,500 L for every m ³ of ultrapure water . For seawater , the wastewater will be a brine solution that must be discharged safely . In comparison , the wastewater from freshwater plants can be more readily handled in a wastewater treatment plant .
A second concern is the energy consumption of turning seawater into ultrapure water . Depending on the desalination technology , desalination generally requires 5 – 10 kWh of electricity for every m ³ of ultrapure water , sometimes even more , compared to 2 – 3 kWh of electricity for freshwater . However , this should be seen in comparison with the overall energy consumption
Hydrogen Tech World | Issue 16 | June 2024 21