Abstract
<title>Abstract</title> <p>Freshwater scarcity limits green hydrogen production in arid regions like the Middle East and North Africa (MENA), despite high solar potential. This study compares two atmospheric-moisture-based systems: a Direct Air Electrolyzer (DAE) using a hygroscopic H₂SO₄ electrolyte in a porous sponge, and a hybrid dehumidifier–alkaline electrolyzer (DH-AE) that condenses ambient moisture via vapor-compression refrigeration. Both are designed for Cairo's worst-case relative humidity (RH = 38.19%). The four-module DAE sizing is anchored to a platinum-referenced electrochemical ceiling (1.686 V per module, 87.8% energy efficiency, 97.3% electrolysis efficiency). For the SS‑904L stainless-steel prototype employed herein, an electrode-material correction (80–140 mV penalty) yields a realistic operating band of 1.766–1.826 V and an energy efficiency of 81.1–83.9%, which brackets the measured prototype range of 1.82–1.95 V. The DH‑AE achieves equivalent output at 68.5% overall efficiency. Thermal simulations (ANSYS) confirm safe operation of SS‑904L electrodes within the iso-corrosion envelope. A closed-loop control framework (humidity/temperature sensing, PID current regulation, SCADA) is proposed and validated in simulation, enabling autonomous operation. Techno-economic analysis for 50–1,000 kg·day⁻¹ shows a benchmark levelized cost of hydrogen (LCOH) of 4.7 USD·kg⁻¹ for the DAE at 1,000 kg·day⁻¹. When full maintenance, electrolyte replenishment, and long-term degradation are included, the fully loaded LCOH rises to approximately 5.8 USD·kg⁻¹—yet this remains roughly 15% lower than the comparable DH‑AE estimate. Prototype implementations are presented. Overall, atmospheric-moisture-based electrolysis offers a viable, decentralized, water-independent pathway for green hydrogen in arid environments.</p>