Alkaline Water Electrolysis: A Review on Technological Progress, Market Dynamics, and Environmental Implications

Year 2025, Volume: 1 Issue: 2, 39 - 60, 30.11.2025

Alperen Çankaya , Ahmed Emin Kılıç , Yüksel Kaplan

Abstract

As global climate change continues to change rapidly, the development of sustainable and environmentally friendly energy technologies that can replace fossil fuels has become one of the top priorities in energy policy and research. Renewable energy sources such as geothermal, wind, and solar energy play a critical role in low-emission energy production; however, due to structural limitations such as intermittency and dependence on weather conditions, they cannot alone provide a continuous and reliable energy supply. In this context, hydrogen energy stands out as a strategic energy carrier that offers a solution to the intermittent nature of renewable energy sources, thanks to its high energy density, broad potential for use across different sectors, and long-term energy storage capacity. Green hydrogen, in particular, is of critical importance in terms of converting and storing excess renewable electricity production for reuse when needed. This eliminates the temporal mismatch between energy production and consumption, minimizing the carbon footprint of energy systems. Among current hydrogen production methods, alkaline water electrolysis (AWE) stands out due to its commercial maturity, relatively low investment and operating costs, stable operating performance, and ability to adapt to variable renewable energy inputs. Considering this, current developments in alkaline electrolyzer technologies are systematically examined in terms of principles, components and materials, performance optimization approaches, market dynamics, techno-economic assessments, and environmental and sustainable dimensions.

Keywords

Hydrogen Production , Carbon Emission Reduction , Alkaline Electrolyzer , Sustainability , Green Hydrogen

Alkali Su Elektrolizi: Teknolojik Gelişmeler, Piyasa Dinamikleri ve Çevresel Etkiler Üzerine Bir İnceleme

Abstract

Küresel iklim değişikliği hızla değişmeye devam ederken, fosil yakıtların yerini alabilecek sürdürülebilir ve çevre dostu enerji teknolojilerinin geliştirilmesi, enerji politikası ve araştırmalarında en önemli önceliklerden biri haline gelmiştir. Jeotermal, rüzgar ve güneş enerjisi gibi yenilenebilir enerji kaynakları, düşük emisyonlu enerji üretiminde kritik bir rol oynamaktadır; ancak kesintili üretim ve hava koşullarına bağlılık gibi yapısal sınırlamalar nedeniyle, tek başlarına sürekli ve güvenilir bir enerji arzı sağlayamamaktadırlar. Bu bağlamda, hidrojen enerjisi, yüksek enerji yoğunluğu, farklı sektörlerde geniş kullanım potansiyeli ve uzun vadeli enerji depolama kapasitesi sayesinde yenilenebilir enerji kaynaklarının kesintili yapısına bir çözüm sunan stratejik bir enerji taşıyıcısı olarak öne çıkmaktadır. Özellikle yeşil hidrojen, ihtiyaç duyulduğunda yeniden kullanılmak üzere fazla yenilenebilir elektrik üretiminin dönüştürülmesi ve depolanması açısından kritik öneme sahiptir. Bu, enerji üretimi ve tüketimi arasındaki zaman uyumsuzluğunu ortadan kaldırarak enerji sistemlerinin karbon ayak izini en aza indirir. Mevcut hidrojen üretim yöntemleri arasında, alkali su elektrolizi (AWE), ticari olgunluğu, nispeten düşük yatırım ve işletme maliyetleri, istikrarlı işletme performansı ve değişken yenilenebilir enerji girdilerine uyum sağlama yeteneği nedeniyle öne çıkmaktadır. Bu bağlamda, alkali elektrolizör teknolojilerindeki güncel gelişmeler, prensipler, bileşenler ve malzemeler, performans optimizasyon yaklaşımları, pazar dinamikleri, tekno-ekonomik değerlendirmeler, çevresel ve sürdürülebilirlik boyutları açısından sistematik olarak incelenmektedir.

Keywords

Alkali Elektrolizör , Yeşil Hidrojen , Hidrojen Üretimi , Karbon Emisyon Azaltılması , Sürdürülebilirlik

References

• [1] Global Hydrogen Review 2025, Paris. [Online]. Available: https://www.iea.org/reports/global-energy-review-2025, Accessed: Mar. 2025.
• [2] C. M. S. Kumar et al., “Solar energy: A promising renewable source for meeting energy demand in Indian agriculture applications,” Sustainable Energy Technologies and Assessments, vol. 55, 102905, 2023.
• [3] H. Khurshid, B. S. Mohammed, A. M. Al-Yacouby, M. S. Liew, and N. A. W. A. Zawawi, “Analysis of hybrid offshore renewable energy sources for power generation: A literature review of hybrid solar, wind, and waves energy systems,” Developments in the Built Environment, vol. 19, 100497, 2024.
• [4] Q. Shao and H. W. Lo, “Advancing renewable energy technologies in remote areas: Exploring key success factors and interdependencies for sustainable wind energy development,” Sustainable Energy Technologies and Assessments, vol. 79, 104367, 2025.
• [5] S. Serag, A. Echchelh, and B. Morrone, “Hydroelectric and hydrogen storage systems for electric energy produced from renewable energy sources,” Energy Engineering: Journal of the Association of Energy Engineers, vol. 121, no. 10, p. 2719, 2024.
• [6] N. A. Pambudi and I. R. Nanda, “Understanding knowledge, perception, and acceptance of geothermal energy among Indonesian students: Implications for sustainable renewable energy initiatives,” Sustainable Energy Technologies and Assessments, vol. 79, 104357, 2025.
• [7] F. Ceglia, E. Marrasso, C. Roselli, and M. Sasso, “Energy and environmental assessment of a biomass-based renewable energy community including photovoltaic and hydroelectric systems,” Energy, vol. 282, 128348, 2023.
• [8] M. Bianchi and I. F. Fernandez, “A systematic methodology to assess local economic impacts of ocean renewable energy projects: Application to a tidal energy farm,” Renewable Energy, vol. 221, 119853, 2024.
• [9] A. Alanazi, “Evaluating the feasibility of wave energy converters for renewable energy expansion in Saudi Arabia,” Results in Engineering, vol. 25, 103956, 2025.
• [10] L. Mulky et al., “An overview of hydrogen storage technologies – Key challenges and opportunities,” Materials Chemistry and Physics, vol. 325, 129710, 2024.
• [11] C. Tarhan and M. A. Çil, “A study on hydrogen, the clean energy of the future: Hydrogen storage methods,” Journal of Energy Storage, vol. 40, 102676, 2021.
• [12] B. Oussmou, S. Sigue, and S. Abderafi, “Review of green hydrogen production technologies, to choose the optimal process of electrolysis–renewable energy,” Renewable and Sustainable Energy Reviews, vol. 225, 116205, 2026.
• [13] S. Bhardwaj and A. Jayant, “Advancements in electrolysis technologies: Exploring the potential of oxyhydrogen as a clean energy source,” Fuel, vol. 389, 134522, 2025.
• [14] K. J. Yoon, S. Lee, S. Y. Park, and N. Q. Minh, “Advances in high-temperature solid oxide electrolysis technology for clean hydrogen and chemical production: materials, cells, stacks, systems and economics,” Progress in Materials Science, Art. no. 101520, 2025.
• [15] S. G. Nnabuife et al., “Integration of renewable energy sources in tandem with electrolysis: A technology review for green hydrogen production,” International Journal of Hydrogen Energy, vol. 107, pp. 218–240, 2025.
• [16] M. Chatenet et al., “Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments,” Chemical Society Reviews, vol. 51, no. 11, pp. 4583–4762, 2022.
• [17] J. Chi and H. Yu, “Water electrolysis based on renewable energy for hydrogen production,” Chinese Journal of Catalysis, vol. 39, no. 3, pp. 390–394, 2018.
• [18] M. El-Shafie, “Hydrogen production by water electrolysis technologies: A review,” Results in Engineering, vol. 20, Art. no. 101426, 2023.
• [19] IRENA, Green Hydrogen Cost Reduction: Scaling Up Electrolysers to Meet the 1.5 °C Climate Goal. International Renewable Energy Agency, Abu Dhabi, ISBN: 978-92-9260-295-6, 2020. [Online]. Available: https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2020/Dec/IRENA_Green_hydrogen_cost_2020.pdf, Accessed: Oct. 2025.
• [20] S. S. Kumar and H. Lim, “An overview of water electrolysis technologies for green hydrogen production,” Energy Reports, vol. 8, pp. 13793–13813, 2022.
• [21] N. Sezer, S. Bayhan, U. Fesli, and A. Sanfilippo, “A comprehensive review of the state-of-the-art of proton exchange membrane water electrolysis,” Materials Science for Energy Technologies, vol. 8, pp. 44–65, 2025.
• [22] S. Palmas et al., “Anion exchange membrane: A valuable perspective in emerging technologies of low temperature water electrolysis,” Current Opinion in Electrochemistry, vol. 37, Art. no. 101178, 2023.
• [23] X. Wu, Y. Chen, and Y. Ma, “Research progress of solid oxide electrolysis cell system: dynamic modeling and control,” Renewable and Sustainable Energy Reviews, vol. 225, 116166, 2026.
• [24] Y. Du et al., “The development of solid oxide electrolysis cells: Critical materials, technologies and prospects,” Journal of Power Sources, vol. 607, Art. no. 234608, 2024.
• [25] S. Sebbahi et al., “A comprehensive review of recent advances in alkaline water electrolysis for hydrogen production,” International Journal of Hydrogen Energy, vol. 82, pp. 583–599, 2024.
• [26] Y. Zheng, Y. Jiao, A. Vasileff, and S. Z. Qiao, “The hydrogen evolution reaction in alkaline solution: from theory, single crystal models, to practical electrocatalysts,” Angewandte Chemie International Edition, vol. 57, no. 26, pp. 7568–7579, 2018.
• [27] J. Wang, F. Xu, H. Jin, Y. Chen, and Y. Wang, “Non-noble metal-based carbon composites in hydrogen evolution reaction: Fundamentals to applications,” Advanced Materials, vol. 29, no. 14, Art. no. 1605838, 2017.
• [28] T. Reier, H. N. Nong, D. Teschner, R. Schlögl, and P. Strasser, “Electrocatalytic oxygen evolution reaction in acidic environments – Reaction mechanisms and catalysts,” Advanced Energy Materials, vol. 7, no. 1, Art. no. 1601275, 2017.
• [29] E. Liu et al., “Unifying the hydrogen evolution and oxidation reactions kinetics in base by identifying the catalytic roles of hydroxyl-water-cation adducts,” Journal of the American Chemical Society, vol. 141, no. 7, pp. 3232–3239, 2019.
• [30] H. Tüysüz, “Alkaline water electrolysis for green hydrogen production,” Accounts of Chemical Research, vol. 57, no. 4, pp. 558–567, 2024.
• [31] E. Fabbri, A. Habereder, K. Waltar, R. Kötz, and T. J. Schmidt, “Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction,” Catalysis Science & Technology, vol. 4, no. 11, pp. 3800–3821, 2014.
• [32] X. Zhang and A. Bieberle-Hütter, “Modeling and simulations in photoelectrochemical water oxidation: from single level to multiscale modeling,” ChemSusChem, vol. 9, no. 11, pp. 1223–1242, 2016.
• [33] J. K. Nørskov et al., “Origin of the overpotential for oxygen reduction at a fuel-cell cathode,” The Journal of Physical Chemistry B, vol. 108, no. 46, pp. 17886–17892, 2004.
• [34] J. Rossmeisl, Z. W. Qu, H. Zhu, G. J. Kroes, and J. K. Nørskov, “Electrolysis of water on oxide surfaces,” Journal of Electroanalytical Chemistry, vol. 607, no. 1–2, pp. 83–89, 2007.
• [35] N. Zhang and Y. Chai, “Lattice oxygen redox chemistry in solid-state electrocatalysts for water oxidation,” Energy & Environmental Science, vol. 14, no. 9, pp. 4647–4671, 2021.
• [36] Z. F. Huang et al., “Chemical and structural origin of lattice oxygen oxidation in Co–Zn oxyhydroxide oxygen evolution electrocatalysts,” Nature Energy, vol. 4, no. 4, pp. 329–338, 2019.
• [37] Z. Y. Yu et al., “Clean and affordable hydrogen fuel from alkaline water splitting: past, recent progress, and future prospects,” Advanced Materials, vol. 33, no. 31, Art. no. 2007100, 2021.
• [38] N. Guillet and P. Millet, “Alkaline water electrolysis,” in Hydrogen Production: Electrolysis, pp. 117–166, 2015.
• [39] J. Hou and M. Yang, Green Hydrogen Production by Water Electrolysis. Taylor & Francis, 2024, p. 362.
• [40] B. Lee et al., “Integrative techno-economic and environmental assessment for green H₂ production by alkaline water electrolysis based on experimental data,” Journal of Environmental Chemical Engineering, vol. 9, no. 6, Art. no. 106349, 2021.
• [41] L. Deng et al., “Bubble evolution dynamics in alkaline water electrolysis,” eScience, Art. no. 100353, 2024.
• [42] F. Gambou, D. Guilbert, M. Zasadzinski, and H. Rafaralahy, “A comprehensive survey of alkaline electrolyzer modeling: electrical domain and specific electrolyte conductivity,” Energies, vol. 15, no. 9, Art. no. 3452, 2022.
• [43] M. Bodner, A. Hofer, and V. Hacker, “H₂ generation from alkaline electrolyzer,” Wiley Interdisciplinary Reviews: Energy and Environment, vol. 4, no. 4, pp. 365–381, 2015.
• [44] A. S. Emam, M. O. Hamdan, B. A. Abu-Nabah, and E. Elnajjar, “A review on recent trends, challenges, and innovations in alkaline water electrolysis,” International Journal of Hydrogen Energy, vol. 64, pp. 599–625, 2024.
• [45] S. Dash, A. Singh, S. K. Surapraraju, and S. K. Natarajan, “Advances in green hydrogen production through alkaline water electrolysis: A comprehensive review,” International Journal of Hydrogen Energy, vol. 83, pp. 614–629, 2024.
• [46] B. V. Tilak, A. C. Ramamurthy, and B. E. Conway, “High performance electrode materials for the hydrogen evolution reaction from alkaline media,” Proceedings of the Indian Academy of Sciences – Chemical Sciences, vol. 97, no. 3, 1986, pp. 359–393. New Delhi: Springer India.
• [47] Y. Zhang et al., “High-efficiency and stable alloyed nickel-based electrodes for hydrogen evolution by seawater splitting,” Journal of Alloys and Compounds, vol. 732, pp. 248–256, 2018.
• [48] S. R. Ede and Z. Luo, “Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review,” Journal of Materials Chemistry A, vol. 9, no. 36, pp. 20131–20163, 2021.
• [49] D. Zhou et al., “Recent advances in non-precious metal-based electrodes for alkaline water electrolysis,” ChemNanoMat, vol. 6, no. 3, pp. 336–355, 2020.
• [50] D. M. F. Santos, C. A. C. Sequeira, D. Macciò, A. Saccone, and J. L. Figueiredo, “Platinum–rare earth electrodes for hydrogen evolution in alkaline water electrolysis,” International Journal of Hydrogen Energy, vol. 38, no. 8, pp. 3137–3145, 2013.
• [51] T. Tang et al., “Synergistic electrocatalysts for alkaline hydrogen oxidation and evolution reactions,” Advanced Functional Materials, vol. 32, no. 2, Art. no. 2107479, 2022.
• [52] R. R. Raja Sulaiman, W. Y. Wong, and K. S. Loh, “Recent developments on transition metal-based electrocatalysts for application in anion exchange membrane water electrolysis,” International Journal of Energy Research, vol. 46, no. 3, pp. 2241–2276, 2022.
• [53] Y. Li et al., “Progress on the design of electrocatalysts for large-current hydrogen production by tuning thermodynamic and kinetic factors,” Advanced Functional Materials, vol. 34, no. 28, Art. no. 2316296, 2024.
• [54] H. Michishita et al., “Cathodic performance of La₀.₆Sr₀.₄CoO₃ perovskite oxide for platinum-free alkaline water electrolysis cell,” Journal of the Electrochemical Society, vol. 155, no. 9, p. B969, 2008.
• [55] D. D. Matienzo, T. Kutlusoy, S. Divanis, C. Di Bari, and E. Instuli, “Benchmarking perovskite electrocatalysts’ OER activity as candidate materials for industrial alkaline water electrolysis,” Catalysts, vol. 10, no. 12, Art. no. 1387, 2020.
• [56] F. Ganci et al., “Nanostructured Ni based anode and cathode for alkaline water electrolyzers,” Energies, vol. 12, no. 19, Art. no. 3669, 2019.
• [57] F. Ganci, S. Lombardo, C. Sunseri, and R. Inguanta, “Nanostructured electrodes for hydrogen production in alkaline electrolyzer,” Renewable Energy, vol. 123, pp. 117–124, 2018.
• [58] X. Li, X. Hao, A. Abudula, and G. Guan, “Nanostructured catalysts for electrochemical water splitting: current state and prospects,” Journal of Materials Chemistry A, vol. 4, no. 31, pp. 11973–12000, 2016.
• [59] A. Kong et al., “Robust Pt/TiO₂/Ni(OH)₂ nanosheet arrays enable outstanding performance for high current density alkaline water electrolysis,” Applied Catalysis B: Environmental, vol. 316, Art. no. 121654, 2022.
• [60] C. Liu, F. Yang, A. Schechter, and L. Feng, “Recent progress of Ni-based catalysts for methanol electrooxidation reaction in alkaline media,” Advanced Sensor and Energy Materials, vol. 2, no. 2, Art. no. 100055, 2023.
• [61] J. Brauns and T. Turek, “Alkaline water electrolysis powered by renewable energy: A review,” Processes, vol. 8, no. 2, Art. no. 248, 2020.
• [62] F. Gambou, D. Guilbert, M. Zasadzinski, and H. Rafaralahy, “A comprehensive survey of alkaline electrolyzer modeling: electrical domain and specific electrolyte conductivity,” Energies, vol. 15, no. 9, Art. no. 3452, 2022.
• [63] F. Razmjooei et al., “Elucidating the performance limitations of alkaline electrolyte membrane electrolysis: dominance of anion concentration in membrane electrode assembly,” ChemElectroChem, vol. 7, no. 19, pp. 3951–3960, 2020.
• [64] A. Alashkar, A. H. Alami, and M. Mahmoud, “Advancements in electrolyzer materials for green hydrogen production,” 2025.
• [65] C. A. C. Sequeira, D. P. Cardoso, L. Amaral, B. Šljukić, and D. M. F. Santos, “Corrosion-resistant materials for alkaline water electrolyzers,” Corrosion, vol. 76, no. 12, pp. 1155–1176, 2020.
• [66] K. Zeng and D. Zhang, “Recent progress in alkaline water electrolysis for hydrogen production and applications,” Progress in Energy and Combustion Science, vol. 36, no. 3, pp. 307–326, 2010.
• [67] K. Scott, Ed., Electrochemical Methods for Hydrogen Production. Royal Society of Chemistry, 2019, pp. 28–58.
• [68] M. F. Ali et al., “Zirconia toughened alumina-based separator membrane for advanced alkaline water electrolyzer,” Polymers, vol. 14, no. 6, Art. no. 1173, 2022.
• [69] M. Paidar, V. Fateev, and K. Bouzek, “Membrane electrolysis — History, current status and perspective,” Electrochimica Acta, vol. 209, pp. 737–756, 2016.
• [70] D. Henkensmeier et al., “Separators and membranes for advanced alkaline water electrolysis,” Chemical Reviews, vol. 124, no. 10, pp. 6393–6443, 2024.
• [71] Y. S. K. De Silva, P. H. Middleton, and M. L. Kolhe, “Performance comparison of mono-polar and bi-polar configurations of alkaline electrolysis stack through 3-D modelling and experimental fabrication,” Renewable Energy, vol. 149, pp. 760–772, 2020.
• [72] R. Phillips and C. W. Dunnill, “Zero gap alkaline electrolysis cell design for renewable energy storage as hydrogen gas,” RSC Advances, vol. 6, no. 102, pp. 100643–100651, 2016.
• [73] J. W. Haverkort and H. Rajaei, “Voltage losses in zero-gap alkaline water electrolysis,” Journal of Power Sources, vol. 497, Art. no. 229864, 2021.
• [74] M. T. De Groot, J. Kraakman, and R. L. G. Barros, “Optimal operating parameters for advanced alkaline water electrolysis,” International Journal of Hydrogen Energy, vol. 47, no. 82, pp. 34773–34783, 2022.
• [75] Z. Ren, J. Wang, Z. Yu, C. Zhang, S. Gao, and P. Wang, “Experimental studies and modeling of a 250-kW alkaline water electrolyzer for hydrogen production,” Journal of Power Sources, vol. 544, Art. no. 231886, 2022.
• [76] Z. Abdin, C. J. Webb, and E. M. Gray, “Modelling and simulation of an alkaline electrolyser cell,” Energy, vol. 138, pp. 316–331, 2017.
• [77] V. V. Solovey et al., “Development of high pressure membraneless alkaline electrolyzer,” International Journal of Hydrogen Energy, vol. 47, no. 11, pp. 6975–6985, 2022.
• [78] C. Valderrama, “High-temperature electrolysis,” in Encyclopedia of Membranes (pp. 1–3). Berlin, Heidelberg: Springer, 2015.
• [79] N. P. Sakkas, F. Gillung, K. Thummar, R. Abang, and L. Röntzsch, “Advanced pressurized alkaline water electrolysis at high temperatures up to 130 °C,” International Journal of Hydrogen Energy, vol. 149, Art. no. 150075, 2025.
• [80] F. Xiao et al., “Aligned porous nickel electrodes fabricated via ice templating with submicron particles for hydrogen evolution in alkaline water electrolysis,” Journal of Power Sources, vol. 556, Art. no. 232441, 2023.
• [81] Y. Chen, J. Liu, and L. Feng, “Transient analysis of a green hydrogen production and storage system using alkaline electrolyzer,” Fuel, vol. 324, Art. no. 124752, 2022.
• [82] L. Yang et al., “Recent progress of enhanced bubble separation in alkaline water electrolyzer,” 2023.
• [83] K. C. Sandeep et al., “Experimental studies and modeling of advanced alkaline water electrolyser with porous nickel electrodes for hydrogen production,” International Journal of Hydrogen Energy, vol. 42, no. 17, pp. 12094–12103, 2017.
• [84] M. M. Bakker and D. A. Vermaas, “Gas bubble removal in alkaline water electrolysis with utilization of pressure swings,” Electrochimica Acta, vol. 319, pp. 148–157, 2019.
• [85] V. Kienzlen, D. Haaf, and W. Schnurnberger, “Location of hydrogen gas evolution on perforated plate electrodes in zero gap cells,” International Journal of Hydrogen Energy, vol. 19, no. 9, pp. 729–732, 1994.
• [86] S. Ding et al., “Analysis of the effect of characteristic parameters and operating conditions on exergy efficiency of alkaline water electrolyzer,” Journal of Power Sources, vol. 537, Art. no. 231532, 2022.
• [87] M. Dreoni et al., “Alkaline electrolysis CFD modeling and application: A novel expression for a volume fraction-dependent current density,” in Proceedings of the 37th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS), Rhodes, Greece, vol. 30, Jun. 2024.
• [88] D. L. Martinho and T. Berning, “A conceptual approach to reduce the product gas crossover in alkaline electrolyzers,” Membranes, vol. 15, no. 7, Art. no. 206, 2025.
• [89] P. Trinke et al., “Hydrogen crossover in PEM and alkaline water electrolysis: mechanisms, direct comparison and mitigation strategies,” Journal of The Electrochemical Society, vol. 165, no. 7, p. F502, 2018.
• [90] R. L. G. Barros, J. T. Kraakman, C. Sebregts, J. van der Schaaf, and M. T. de Groot, “Impact of an electrode–diaphragm gap on diffusive hydrogen crossover in alkaline water electrolysis,” International Journal of Hydrogen Energy, vol. 49, pp. 886–896, 2024.
• [91] X. Luo et al., “Porous PVA skin-covered thin Zirfon-type separator as a new approach boosting high-rate alkaline water electrolysis beyond 1000 hours’ lifespan,” eScience, vol. 4, no. 6, Art. no. 100290, 2024.
• [92] H. Gao et al., “High-performance composite membranes: embedding yttria-stabilized zirconia in polyphenylene sulfide fabric for enhanced alkaline water electrolysis efficiency,” Small, vol. 21, no. 1, Art. no. 2407008, 2025.
• [93] S. Kim et al., “Highly selective porous separator with thin skin layer for alkaline water electrolysis,” Journal of Power Sources, vol. 524, Art. no. 231059, 2022.
• [94] H. I. In Lee et al., “The synthesis of a Zirfon-type porous separator with reduced gas crossover for alkaline electrolyzer,” International Journal of Energy Research, vol. 44, no. 3, pp. 1875–1885, 2020.
• [95] M. F. Ali et al., “Zirconia toughened alumina-based separator membrane for advanced alkaline water electrolyzer,” Polymers, vol. 14, no. 6, Art. no. 1173, 2022.
• [96] J. Rodríguez and E. Amores, “CFD modeling and experimental validation of an alkaline water electrolysis cell for hydrogen production,” Processes, vol. 8, no. 12, Art. no. 1634, 2020.
• [97] L. Xue, S. Song, W. Chen, B. Liu, and X. Wang, “Enhancing efficiency in alkaline electrolysis cells: optimizing flow channels through multiphase computational fluid dynamics modeling,” Energies, vol. 17, no. 2, Art. no. 448, 2024.
• [98] Y. C. Jiang et al., “Holistic dynamic modeling and simulation of alkaline water electrolysis systems based on heat current method,” Energies, vol. 17, no. 23, Art. no. 6202, 2024.
• [99] W. Zhao, M. R. Nielsen, M. Kjær, F. Iov, and S. M. Nielsen, “Grid integration of a 500 kW alkaline electrolyzer system for harmonic analysis and robust control,” e-Prime – Advances in Electrical Engineering, Electronics and Energy, vol. 5, Art. no. 100217, 2023.
• [100] M. O. Qays, I. Ahmad, D. Habibi, A. Aziz, and T. Mahmoud, “System strength shortfall challenges for renewable energy-based power systems: A review,” Renewable and Sustainable Energy Reviews, vol. 183, Art. no. 113447, 2023.
• [101] H. Lee et al., “Outlook of industrial-scale green hydrogen production via a hybrid system of alkaline water electrolysis and energy storage system based on seasonal solar radiation,” Journal of Cleaner Production, vol. 377, Art. no. 134210, 2022.
• [102] U. Remme, Global Hydrogen Review 2024. IEA: Paris, France, 2024.
• [103] C. Gulli, B. Heid, J. Noffsinger, M. Waardenburg, and M. Wilthaner, Global Energy Perspective 2023: Hydrogen Outlook. McKinsey Energy Solutions, Jan. 10, 2024. [Online]. Available: https://www.mckinsey.com/industries/oil-and-gas/our-insights/global-energy-perspective-2023-hydrogen-outlook, Accessed: Oct. 2025.
• [104] European Commission, Commission Delegated Regulation (EU) 2023/1184 (RFNBO additionality/temporal/geographical correlation), Feb. 10, 2023. [Online]. Available: https://energy.ec.europa.eu/publications/renewable-hydrogen-delegated-acts_en
• [105] European Parliamentary Research Service (EPRS), “Decarbonised gases and hydrogen package: low-carbon hydrogen definition (≈ 3.38 kg CO₂e/kg H₂),” May 6, 2025; see also EWI (2024) explainer. [Online]. Available: https://www.europarl.europa.eu/thinktank/; https://www.ewi.uni-koeln.de/en/news/what-is-low-carbon-hydrogen/, Accessed: Oct. 2025.
• [106] European Commission, “A Hydrogen Strategy for a Climate-Neutral Europe,” COM(2020) 301, Jul. 8, 2020. [Online]. Available: https://energy.ec.europa.eu/system/files/2020-07/hydrogen_strategy.pdf
• [107] European Commission, REPowerEU Plan (hydrogen targets: 10 Mt domestic + 10 Mt imports by 2030), May 18, 2022. [Online]. Available: https://commission.europa.eu/strategy-and-policy/priorities-2019-2024/repowereu_en
• [108] T.C. Enerji ve Tabii Kaynaklar Bakanlığı, “Türkiye Ulusal Hidrojen Teknolojisi Stratejisi ve Yol Haritası,” n.d. [Online]. Available: https://enerji.gov.tr/duyuru-detay?id=20316
• [109] UAE Government, “National Hydrogen Strategy 2031,” n.d. [Online]. Available: https://u.ae/en/about-the-uae/strategies-initiatives-and-awards/strategies-plans-and-visions/environment-and-energy/national-hydrogen-strategy
• [110] Sultanate of Oman, Ministry of Energy and Minerals, “Hydrogen Oman (Hydrom) targets,” n.d. [Online]. Available: https://hydrom.om/Media/Pdf/Oman-Green-Hydrogen-Strategy-2024.pdf
• [111] Air Products / ACWA Power / NEOM, “NEOM Green Hydrogen project (≈ 600 t/day),” 2023–2024. [Online]. Available: https://www.airproducts.com/energy-transition/neom-green-hydrogen-complex; https://acwapower.com/en/projects/neom-green-hydrogen-project, Accessed: Oct. 2025.
• [112] D. Kronkalns, L. Zemite, L. Jansons, and A. Backurs, “Pursuing Opportunity: A Multi-Dimensional Analysis of Green Hydrogen Production Technologies,” Latvian Journal of Physics and Technical Sciences, vol. 62, no. 5, pp. 87–108, 2025.
• [113] F. Rosner et al., “Green steel: design and cost analysis of hydrogen-based direct iron reduction,” Energy & Environmental Science, vol. 16, no. 10, pp. 4121–4134, 2023.
• [114] Ö. Özgün, I. Dirba, O. Gutfleisch, Y. Ma, and D. Raabe, “Green ironmaking at higher H₂ pressure: reduction kinetics and microstructure formation during hydrogen-based direct reduction of hematite pellets,” Journal of Sustainable Metallurgy, vol. 10, no. 3, pp. 1127–1140, 2024.
• [115] G. He, D. S. Mallapragada, A. Bose, C. F. Heuberger, and E. Gençer, “Hydrogen supply chain planning with flexible transmission and storage scheduling,” IEEE Transactions on Sustainable Energy, vol. 12, no. 3, pp. 1730–1740, 2021.
• [116] A. Król, M. Gajec, J. Holewa-Rataj, E. Kukulska-Zając, and M. Rataj, “Hydrogen purification technologies in the context of its utilization,” Energies, vol. 17, no. 15, Art. no. 3794, 2024.
• [117] S. R. Naqvi, S. A. A. Taqvi, W. H. Chen, and D. Juchelková, “Techno economic analysis for advanced methods of green hydrogen production,” Current Opinion in Green and Sustainable Chemistry, vol. 48, Art. no. 100939, 2024.
• [118] Q. He et al., “Supercapacitor-isolated water electrolysis for renewable energy storage,” Chemical Engineering Journal, vol. 495, Art. no. 153461, 2024.
• [119] M. Holst, S. Aschbrenner, T. Smolinka, C. Voglstätter, and G. Grimm, “Cost forecast for low-temperature electrolysis – Technology driven bottom-up prognosis for PEM and alkaline water electrolysis systems,” Fraunhofer Institute for Solar Energy Systems ISE: Freiburg, Germany, 2021, p. 79.
• [120] A. Buttler and H. Spliethoff, “Current status of water electrolysis for energy storage, grid balancing and sector coupling via power-to-gas and power-to-liquids: A review,” Renewable and Sustainable Energy Reviews, vol. 82, pp. 2440–2454, 2018.
• [121] N. Saravanan and G. Nagarajan, “An experimental investigation of hydrogen-enriched air induction in a diesel engine system,” International Journal of Hydrogen Energy, vol. 33, no. 6, pp. 1769–1775, 2008.
• [122] N. Saravanan and G. Nagarajan, “Performance and emission studies on port injection of hydrogen with varied flow rates with diesel as an ignition source,” Applied Energy, vol. 87, no. 7, pp. 2218–2229, 2010.
• [123] ISO, ISO 8178-1: Reciprocating internal combustion engines — Exhaust emission measurement — Part 1: Test-bed measurement systems of gaseous and particulate emissions, 2017.
• [124] Q. Hassan, A. Z. Sameen, H. M. Salman, and M. Jaszczur, “Large-scale green hydrogen production via alkaline water electrolysis using solar and wind energy,” International Journal of Hydrogen Energy, vol. 48, no. 88, pp. 34299–34315, 2023.
• [125] Y. Xia, H. Cheng, H. He, and W. Wei, “Efficiency and consistency enhancement for alkaline electrolyzers driven by renewable energy sources,” Communications Engineering, vol. 2, no. 1, Art. no. 22, 2023.
• [126] O. Aguirre, M. David, O. Camacho, and C. Ocampo-Martinez, “Hydrogen production through electrolyzers as a key player in multi-energy systems,” in Energy Systems Integration for Multi-Energy Systems: From Operation to Planning in the Green Energy Context, Cham: Springer Nature Switzerland, 2025, pp.343–360.
• [127] C. Huang, Y. Zong, S. You, and C. Træholt, “Economic model predictive control for multi-energy system considering hydrogen-thermal-electric dynamics and waste heat recovery of MW-level alkaline electrolyzer,” Energy Conversion and Management, vol. 265, Art. no. 115697, 2022.
• [128] C. Huang, Y. Zong, S. You, and C. Træholt, “Optimal operation of multi-energy system integrated with an alkaline electrolyzer dynamic power-to-hydrogen & heat (P2H2) model,” EnerarXiv, vol. 19, pp. 1–6, 2022.
• [129] J. Wang, J. Wen, J. Wang, B. Yang, and L. Jiang, “Water electrolyzer operation scheduling for green hydrogen production: A review,” Renewable and Sustainable Energy Reviews, vol. 203, Art. no. 114779, 2024.
• [130] J. Gu et al., “Experimental studies on dynamic performance of 250-kW alkaline electrolytic system,” Journal of Power Sources, vol. 592, Art. no. 233920, 2024.
• [131] R. Cozzolino and G. Bella, “A review of electrolyzer-based systems providing grid ancillary services: current status, market, challenges and future directions,” Frontiers in Energy Research, vol. 12, Art. no. 1358333, 2024.
• [132] R. Jain, K. Nagasawa, S. Veda, and S. Sprik, “Grid ancillary services using electrolyzer-based power-to-gas systems with increasing renewable penetration,” e-Prime – Advances in Electrical Engineering, Electronics and Energy, vol. 6, Art. no. 100308, 2023.
• [133] S. Shanian and O. Savadogo, “Techno economic analysis of electrolytic hydrogen production by alkaline and PEM electrolyzers using MCDM methods,” Discover Energy, vol. 4, no. 1, Art. no. 23, 2024.
• [134] H. Song, Y. Kim, and H. Yang, “Design and optimization of an alkaline electrolysis system for small-scale hydropower integration,” Energies, vol. 17, no. 1,Art.no.20,2023.
• [135] U.S. Energy Information Administration. [Online]. Available: https://www.eia.gov/outlooks/aeo/electricity_generation/pdf/AEO2023_LCOE_report.pdf, Accessed: Oct. 2025.
• [136] B. Hurtubia and E. Sauma, “Economic and environmental analysis of hydrogen production when complementing renewable energy generation with grid electricity,” Applied Energy, vol. 304, Art. no. 117739, 2021.
• [137] IMARC Group, Potassium Hydroxide (KOH) Pricing Trends, Forecast and Market Analysis. [Online]. Available: https://www.imarcgroup.com/potassium-hydroxide-pricing-report, Accessed: Oct. 2025.
• [138] S. Krishnan et al., “Present and future cost of alkaline and PEM electrolyser stacks,” International Journal of Hydrogen Energy, vol. 48, no. 83, pp. 32313–32330, 2023.
• [139] Y. M. Acevedo, J. H. Prosser, J. M. Huya-Kouadio, K. R. McNamara, and B. D. James, Hydrogen Production Cost with Alkaline Electrolysis (No. DOE-SA-09629-1). Strategic Analysis, Inc., Arlington, VA, USA, 2023, 24 p.
• [140] International Energy Agency, The Future of Hydrogen: Seizing Today’s Opportunities. Paris: IEA, 2022. [Online]. Available: https://www.iea.org/reports/the-future-of-hydrogen, Accessed: Oct. 2025.
• [141] A. Mayyas and M. Mann, “Manufacturing competitiveness analysis for hydrogen refueling stations and electrolyzers,” DOE Hydrogen Fuel Cells Program, 2018.
• [142] J. Proost, “State-of-the-art CAPEX data for water electrolysers, and their impact on renewable hydrogen price settings,” International Journal of Hydrogen Energy, vol. 44, no. 9, pp. 4406–4413, 2019.
• [143] S. M. Saba, M. Müller, M. Robinius, and D. Stolten, “The investment costs of electrolysis – A comparison of cost studies from the past 30 years,” International Journal of Hydrogen Energy, vol. 43, no. 3, pp. 1209–1223, 2018.
• [144] Clean Hydrogen Partnership, Levelised Cost of Hydrogen (LCOH) Calculator Manual. European Hydrogen Observatory, 2024. [Online]. Available: https://observatory.clean-hydrogen.europa.eu/sites/default/files/2024-06/Manual%20-%20Levelised%20Cost%20of%20Hydrogen%20%28LCOH%29%20Calculator.pdf
• [145] M. R. Shaner, H. A. Atwater, N. S. Lewis, and E. W. McFarland, “A comparative technoeconomic analysis of renewable hydrogen production using solar energy,” Energy & Environmental Science, vol. 9, no. 7, pp. 2354–2371, 2016.
• [146] M. Yu, K. Wang, and H. Vredenburg, “Insights into low-carbon hydrogen production methods: green, blue and aqua hydrogen,” International Journal of Hydrogen Energy, vol. 46, no. 41, pp. 21261–21273, 2021.
• [147] R. S. El-Emam and I. Khamis, “International collaboration in the IAEA nuclear hydrogen production program for benchmarking of HEEP,” International Journal of Hydrogen Energy, vol. 42, no. 6, pp. 3566–3571, 2017.
• [148] H. Ozcan, R. S. El-Emam, S. Celik, and B. A. Horri, “Recent advances, challenges, and prospects of electrochemical water-splitting technologies for net-zero transition,” Cleaner Chemical Engineering, vol. 8, Art. no. 100115, 2023.
• [149] P. Zhu, M. Mae, and R. Matsuhashi, “Techno-economic analysis of grid-connected hydrogen production via water electrolysis,” Energies, vol. 17, no. 7, Art. no. 1653, 2024.
• [150] A. Al-Sharafi, A. Z. Sahin, T. Ayar, and B. S. Yilbas, “Techno-economic analysis and optimization of solar and wind energy systems for power generation and hydrogen production in Saudi Arabia,” Renewable and Sustainable Energy Reviews, vol. 69, pp. 33–49, 2017.
• [151] D. Kumar, C. Zhang, E. Holubnyak, and S. Demirkesen, “Integrated assessment of levelized costs of hydrogen production: evaluating renewable and fossil pathways with emission costs and tax incentives,” International Journal of Hydrogen Energy, vol. 95, pp. 389–401, 2024.
• [152] R. M. Habour, K. Y. Benyounis, and J. G. Carton, “Green hydrogen production from renewable sources for export,” International Journal of Hydrogen Energy, vol. 128, pp. 760–770, 2025.
• [153] Y. Tang and Y. Li, “Comparative analysis of the levelized cost of hydrogen production from fossil energy and renewable energy in China,” Energy for Sustainable Development, vol. 83, Art. no. 101588, 2024.
• [154] F. Hönig, G. D. Rupakula, D. Duque-Gonzalez, M. Ebert, and U. Blum, “Enhancing the levelized cost of hydrogen with the usage of the byproduct oxygen in a wastewater treatment plant,” Energies, vol. 16, no. 12, Art. no. 4829, 2023.
• [155] E. Curcio, “Techno-economic analysis of hydrogen production: costs, policies, and scalability in the transition to net-zero,” International Journal of Hydrogen Energy, vol. 128, pp. 473–487, 2025.
• [156] H. V. Ghadim, R. Canessa, J. Haas, and R. Peer, “Electrolyzer cost projections compared to actual market costs: a critical analysis,” in 2023 IEEE PES Innovative Smart Grid Technologies – Asia (ISGT Asia), Nov. 2023, pp. 1–5. IEEE.
• [157] E. Vartiainen et al., “True cost of solar hydrogen – Levelised cost of hydrogen in Europe 2021–2050,” in Proceedings of the 38th European Photovoltaic Solar Energy Conference and Exhibition, 2021, pp. 1601–1607, ISBN: 3-936338-78-7.
• [158] K. Gandhi, H. Apostoleris, and S. Sgouridis, “Catching the hydrogen train: economics-driven green hydrogen adoption potential in the United Arab Emirates,” International Journal of Hydrogen Energy, vol. 47, no. 53, pp. 22285–22301, 2022.
• [159] N. Gerloff, “Comparative Life-Cycle-Assessment analysis of three major water electrolysis technologies while applying various energy scenarios for a greener hydrogen production,” Journal of Energy Storage, vol. 43, Art. no. 102759, 2021.
• [160] A. C. Hoppe and C. Minke, “Reducing environmental impacts of water electrolysis systems by reuse and recycling: Life cycle assessment of a 5 MW alkaline water electrolysis plant,” Energies, vol. 18, no. 4, Art. no. 796, 2025.
• [161] J. C. Koj, P. Zapp, C. Wieland, K. Görner, and W. Kuckshinrichs, “Life cycle environmental impacts and costs of water electrolysis technologies for green hydrogen production in the future,” Energy, Sustainability and Society, vol. 14, no. 1, Art. no. 64, 2024.
• [162] M. David, C. Ocampo-Martínez, and R. Sánchez-Peña, “Advances in alkaline water electrolyzers: a review,” Journal of Energy Storage, vol. 23, pp. 392–403, 2019.
• [163] W. Ajeeb, P. Baptista, and R. C. Neto, “Life cycle analysis of hydrogen production by different alkaline electrolyser technologies sourced with renewable energy,” Energy Conversion and Management, vol. 316, Art. no. 118840, 2024.
• [164] S. G. Simoes et al., “Water availability and water usage solutions for electrolysis in hydrogen production,” Journal of Cleaner Production, vol. 315, Art. no. 128124, 2021.
• [165] Y. Li et al., “Improving the efficiency of seawater desalination and hydrogen production: challenges, strategies, and the future of seawater electrolysis,” Desalination, vol. 609, Art. no. 118882, 2025.
• [166] International Energy Agency (IEA), Global Hydrogen Review 2021. Paris: IEA,2021. [Online]. Available: https://iea.blob.core.windows.net/assets/3a2ed84c-9ea0-458c-9421-d166a9510bc0/GlobalHydrogenReview2021.pdf1adad