(296b) Solar Thermoelectrochemical Hydrogen Production Using Reversible High Temperature Electrolysis

Water electrolysis requires energy to enable endothermic electrochemical reactions. High-temperature solid-oxide electrolysis takes place at a high temperature of ~750°C, and there is a large amount of total energy, for instance, the energy for steam formation can be provided by thermal energy instead of electricity. Concentrated solar-thermal thus offers a unique approach, enabling H2 production using solid oxide electrolysis cells (SOEC).

This presentation introduces our project, newly awarded by the DOE Solar Energy Technologies Office (SETO) and hosted at NASA's Katherine Johnson Independent Verification and Validation Facility (NASA IV&V) at Fairmont, West Virginia, and our project's collaborating industry teams in solar energy conversion, electrolysis, and green hydrogen utilization in automotive and space technology. This project focuses on designing, building, integrating, evaluating, and optimizing an energy conversion system consisting of SOEC with solar concentrator thermal Energy Storage (TES) to generate green hydrogen for solar fuel production. A parabolic trough solar concentrator, coupled with TES, is integrated with steam generators to produce hot steam > 750 °C to feed into the SOEC. First-of-its-kind modular designed & reversible SOEC/Solid oxide fuel cells (SOFC), ready for electricity generation using natural gas and its mixture with H2, will be designed and integrated with both solar concentrators and solar photovoltaic. Under the electrolysis mode, the magnitude of electrolysis current density has a significant impact on hydrogen production. While the percentage of the thermal energy input remains constant at ~ 20% for steam generation, the absolute amount of steam and the thermal/solar energy needed for steam generation is proportional to the increased hydrogen production. The advantage of the SOEC coupled with Solar thermal energy is more pronounced when operating at a higher current density. While the state-of-the-art commercial SOECs are typically operated at the current density of 0.5-0.75A/cm2, and the DOE 2026 technology target has been set as 1.2 A/cm2 @1.3V, the designed reversible SOEC through this project further integrates the stacks consisting of cells with atomic layer deposition (ALD) of effective catalysts and conductors to boost electrolysis current density to >1.5A/cm2 @<1.2V. The designed 25 KW SOEC system, powered by 100% solar energy, will produce a minimum of 15 Kg of H2 per day, which is sufficient for cruising one H2 fuel cell electric vehicle for ~900 miles. The present work further depicts a perspective ALD coating layer that could be implanted into SOFC and lead to its electrolysis current density of ~5A/cm2, which is an order of magnitude higher than that of the state-of-the-art.

This project will demonstrate the technology's uniqueness and outlook of integrating solar thermal systems with reversible solid oxide cells for versatile applications in emerging H2 and electric vehicles, urban air mobility, aviation, AI data centers, and space technology, including space life support.