The Potential of Seawater Electrolysis in Solid Oxide Electrolyzers in Central Eastern Europe

Due to the need to protect freshwater resources and guarantee the continuity of supply to residents, use of seawater or saline water for the process of electrolysis and electric energy seems to be a promising idea. As one example of inland seas - the Baltic Sea, presents significant potential for the development of a hydrogen economy. Of particular relevance is the possibility of using wind energy to produce low-emission hydrogen, as well as the usage of seawater as substrate for electrolysis. This review focuses on the opportunities and challenges of hydrogen production in the zone of the Baltic Sea, especially in Poland. The work tackles technological, environmental, and economic aspects. The Polish economic zone of the Baltic Sea, covering an area of approximately 30,533 km² [1], is particularly attractive for the development of offshore wind farms due to favourable wind conditions ( an average wind speed at 100 m fluctuates between 8 and 10 m/s [2]). According to the study by Polish Wind Energy Association the potential of Polish offshore wind energy is estimated at 33 GW which translates to 130 TWh per year [3]. With this annual production it would be possible to reduce emissions of Polish energy sector by approximately 102 million CO 2 tonnes annually. Poland ranks scarcely 24 th in terms of renewable freshwater resources per capita according to the report of the Central Statistical Office [5]. This situation forces the economy to seek water sources that will not negatively impact the lives of residents and will not increase the risk of a water crisis in Poland [5]. Taking into account the relatively small resources of fresh water in the country, it seems advisable to use waters of Baltic Sea. The direct electrolysis process of seawater is an innovative approach to hydrogen production, eliminating the need for pre-desalination. In the context of technical challenges, attention should be paid to the problem of electrode corrosion caused by the presence of chlorides, the formation of by-products (mainly chlorine) and the effect of variable salinity on the process efficiency [6]. Despite being one of the most polluted seas, the Baltic Sea can be a water source for hydrogen production. Before electrolysis, impurities such as salt, organic matter, heavy metals, microplastics, and phosphorus and nitrogen compounds must be removed. The Baltic Sea is the least salty sea in the world, with an average salinity of 7.5‰, varying by location. Low salinity reduces ionic conductivity, increases energy demand, and lowers electrolysis efficiency. Additionally, contaminants can damage catalysts and electrodes, raising operational costs. The presence of chloride ions may also accelerate electrode degradation. The previously mentioned impurities may poison the catalysts and cause degradation of the electrodes, which will limit the long-term stability of electrolyser. Chloride ions present in water compete with hydroxide ions in the oxidation reaction. The presence of these contaminants will result in higher operating costs because more frequent maintenance will be necessary [6]. Integration of water desalination technology, renewable energy and electrolysis can play a significant role in the decarbonization process. The development of brine produced during reverse osmosis creates additional opportunities to obtain key elements [10]. This approach is environmentally friendly due to the use of zero-emission energy and contributes to the implementation of a circular economy. The challenge and subject of research remains the development of electrode materials of solid oxide electrolysis resistant to degradation caused by chlorides and deposited hydroxides. ACKNOWLEGMENT RenewStart for Hydrogen Technologies project is part of the European Climate Initiative (EUKI) of the German Federal Ministry for Economic Affairs and Climate Action (BMWK). References [1] Exclusive economic zone of Poland n.d. https://en.wikipedia.org/wiki/Exclusive_economic_zone_of_Poland (accessed February 12, 2025). [2] What is the wind potential of the Baltic Sea? 2023. https://globenergia.pl/jaki-jest-potencjal-wiatrowy-baltyku/ (accessed February 12, 2025). [3] The potential of offshore wind energy in Poland. 2022. [4] Principles_for_the_update_of_Energy_Policy_of_Poland_until_2040_EPP2040 2022. [5] GUS report. Https://WwwGovPl/Web/Susza/Najnowszy-Raport-Gus--Polska-Na-24-Miejscu-w-Unii-Europejskiej-Pod-Wzgledem-Odnawialnych-Zasobow-Wody-Slodkiej 2021. https://www.gov.pl/web/susza/najnowszy-raport-gus--polska-na-24-miejscu-w-unii-europejskiej-pod-wzgledem-odnawialnych-zasobow-wody-slodkiej (accessed February 12, 2025). [6] Yu H, Wan J, Goodsite M, Jin H. 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