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چکیده
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Green hydrogen production as a seasonal storage is a crucial component of the sustainable energy transition. However, the water demand for the electrolysis process and cooling purposes is often overlooked. This paper designs, models, and optimises the water requirements of a green hydrogen chain deployed as a seasonal energy storage mechanism in a renewable energy system. Accordingly, a comprehensive analysis of the water requirements for green hydrogen production is conducted, considering four primary water sources: seawater, brackish water, surface water, and groundwater. Coarse screen, conventional clarifier, lamella clarifier, dissolved air flotation, multimedia filter, reverse osmosis desalination, and electro-deionisation are considered for water purification. A detailed treatment system, composed of the above processes, is considered for each water source separately to meet electrolysis and cooling quality requirements. Then, the relevant mathematical models are developed for the water treatment system and integrated into the hydrogen system. The size of water purification processes, electrolyser, hydrogen compressor, high-pressure tank, fuel cell, and electrical equipment (wind turbines, photovoltaic panels, battery storage, and diesel generator) are optimally determined to supply the electric power demand of a real case study within a whole-year planning horizon. Results of simulations indicate that treating seawater, brackish water, groundwater, and surface water for electrolysis requires, in turn, 7.384, 4.553, 2.365, and 2.454 kWh of energy per cubic metre of water with treatment ratios of 33.5%, 36.3%, 56.8%, and 52.9%, respectively. Adding water treatment raises green hydrogen system costs by about 2.5–3.5%. Non-cost factors, including water availability, intake-conveyance costs, withdrawal limits, brine disposal, and social acceptance, can also significantly affect site viability and must be considered. Scaling from pilot to real large-scale systems can exacerbate these challenges and lead to non-linear or step-wise increases in infrastructure needs, permitting complexity, disposal pathways, and supply chain constraints. These results provide a quantitative basis for future research by integrating water-related constraints into green hydrogen techno-economic assessments.
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