E. Greenbaum
GTA, Inc.,
United States
Keywords: underwater electrolytic hydrogen production, offshore wind and nuclear energy integration, safety and reliability of underwater hydrogen systems, techno-economic analysis of underwater hydrogen storage
Summary:
Underwater electrolytic hydrogen production offers compelling safety, reliability, and techno-economic advantages over conventional above-surface or platform-based systems. In this presentation, we describe a modular, megawatt-scale underwater hydrogen production and storage architecture powered by either offshore wind turbines or nuclear reactors. This approach integrates mature materials (polyethylene, nickel, and steel) with pressure-balanced electrolysis and storage subsystems designed for underwater operation. The result is a highly safe and resilient system that minimizes explosion risk, eliminates oxygen-related hazards, and ensures hydrogen generation independent of atmospheric or meteorological events. From a safety perspective, underwater hydrogen generation and storage fundamentally alter the risk landscape associated with hydrogen. By operating in a fully submerged environment at hydrostatic pressures commensurate with hydrogen pressure, the system precludes the formation of explosive gas mixtures with air, achieving intrinsic safety without active ventilation or containment. The electrolyzer and storage assemblies are immersed in a non-flammable, thermally stable aqueous medium that provides passive cooling and immediate dissipation of any gas leaks. The absence of surface electrical infrastructure—high-voltage AC inversion, transformers, and exposed cabling—significantly reduces arc-flash and fire hazards. Furthermore, the underwater architecture is inherently resistant to hurricanes, floods, and wildfires, and offers natural electromagnetic-pulse (EMP) and physical protection. From a reliability standpoint, underwater electrolyzers leverage stable pressure and temperature conditions, minimal diurnal cycling, and negligible corrosion from atmospheric oxygen and seawater. Integration of high-voltage DC (HVDC) output from offshore wind turbines or the DC bus of nuclear electricity allows direct power delivery without the conversion losses associated with AC inversion and step-up/step-down transformers. This direct-current topology improves round-trip efficiency and enhances fault tolerance. Distributed modular electrolyzer arrays—each on the order of 250 kW—can be selectively activated through intelligent switchgear to optimize current density and load matching, maintaining high utilization factors. Hydrogen storage in pressure-tolerant polyethylene or composite pipelines at depth further eliminates moving mechanical parts, reducing maintenance and O&M costs relative to surface cryogenic or compressed-gas systems. From a techno-economic perspective, the underwater configuration reduces capital and operational expenditures through (i) elimination of offshore platforms, (ii) simplified DC cabling and switchgear, and (iii) the use of commodity materials rather than iridium- or titanium-intensive PEM electrolyzers. Levelized cost of hydrogen (LCOH) analyses, based on discounted-cash-flow formulations, indicate that underwater alkaline systems can achieve production costs below $2 kg⁻¹ H₂ when powered by day-ahead, below-average hourly electricity prices. The proposed technology represents a convergence of marine engineering, electrochemistry, and renewable-energy integration that can enable secure, grid-independent hydrogen generation for coastal industrial hubs, ammonia synthesis, and long-duration energy storage (LDES). The presentation will include system schematics, comparative safety analyses versus terrestrial plants, and preliminary techno-economic metrics validated through prototype testing. Collectively, the results demonstrate that underwater megawatt-class hydrogen production and storage offer an inherently safe, reliable, and economically scalable pathway for global clean-hydrogen deployment. A TRL-4 GTA prototype was validated at NREL under the H₂@Scale CRADA program. GTA is the recipient, and Parabellum Strategic Group LLC the provider, of a 2025 DOE-funded techno-economic analysis voucher award managed by EnergyWerx.