Techno-economic evaluation of an integrated solar still and solid oxide electrolysis cell system for hydrogen production from brine water

Hydrogen production from salt water using solar energy has led to renewable desalination and electrolysis technologies. In this paper, a technical and economic study of an innovative combined solar still system (results experimentally) with a solid oxide electrolysis cell system (results simulated with COMSOL) is carried out. Experimental results of a solar still (SS) device under desert climate conditions from November 25 to December 2, 2024 were presented for different scenarios such as solar tracking effects, active versus passive operation, seawater depth, and thermal insulation. The distilled water produced by the SS was subsequently used as feed to the solid oxide electrolysis cell system (SOEC), which was modeled and simulated in COMSOL Multiphysics to evaluate hydrogen production under different operating voltages and temperatures. The results of the SS system with solar tracking and full insulation achieved a 355% increase (4.1 liters per day) in freshwater yield compared to a conventional SS (0.9 liters per day), with a freshwater production cost of $0.031384 per liter. In system SOEC-SS, 7 scenarios based on the purchase price of electricity in different countries from 0.05 to 0.2 USD/kWh were examined. The levelized cost of hydrogen (LCOH) is approximately 9.13 and 14.38 USD/kg of hydrogen produced, respectively, for electricity purchase prices of 0.05 and 0.20 USD/kWh from the grid. The results further show that when the electricity demand of the combined SOEC–SS system is supplied entirely by a PV–battery hybrid plant (SOEC+SS+PV+battery), the LCOH is about 12.43 USD/kg of hydrogen produced.