[ water treatment ] making maintenance simpler . Scaling is a challenge for both technologies , and they need a similar level of pretreatment to operate well . Once established , servicing typically occurs annually . Regarding ability to follow the varying production of the electrolyzer , both systems operate best under constant conditions , but SWRO systems are better suited for frequent starts and stops . However , thermal systems are better able to handle fluctuations in the feed water quality and temperature .
The size of water treatment plants varies depending on the model and brand , but rough estimates can be made and compared for relevant electrolyzer sizes such as 10 and 100 MW . Generally , thermal systems tend to be slightly larger than RO systems . A thermal system for 10 and 100 MW will have footprints of up to 6 m ² and 25 m ², respectively . In comparison , SWRO systems for the same capacities typically have footprints around 2 m ² and 10 m ², respectively .
As for energy consumption , a SWRO system needs around 3 – 5 kWh of electrical energy to produce 1 m ³ of product water . A VC system needs approxiately 6 – 12 kWh of electrical energy to produce 1 m ³
of product water . For other thermal desalination technologies , such as VD , 2 – 6 kWh of electrical energy and 100 – 200 kWh of thermal energy are typically required . Notably , the thermal input for these systems could to some extent be covered by the waste heat from the electrolyzers .
Capital costs are always difficult to assess directly . However , in the desalination industry , SWRO are generally found to have a lower CAPEX compared to thermal systems . This may be especially true for the smaller systems well suited for green hydrogen applications . In this range there are many available SWRO systems on the market ensuring high competitiveness on price . In comparison , thermal systems have mainly been used in niche applications and are therefore not available in the same volume . Thus , expect higher capital costs per m ³ of water for a thermal desalination system .
Summary
Due to different drivers , seawater as a main water source for green hydrogen is likely to grow in the future . It will require more water and use more energy than systems based on freshwater , but the
Hydrogen Tech World | Issue 16 | June 2024 25