Synthetic fuel production from renewable energy, water, and anthropogenic carbon resources offers a promising alternative to fossil fuels by reducing the consumption of nonrenewable resources and greenhouse gas emissions. This article presents a case study of a solar-based methanol plant that derives hydrogen and carbon dioxide material inputs from seawater on an offshore artificial island. Photovoltaic cells generate electricity for an electrolytic cation exchange membrane (E-CEM) reactor that simultaneously produces hydrogen and carbon dioxide, with freshwater for electrolysis via seawater reverse osmosis. Carbon dioxide hydrogenation in a low-pressure isothermal cascade-type reactor system produces methanol as a liquid fuel product. Thermodynamic assessment of the integrated system indicates solar-to-methanol energy and exergy conversion efficiencies of 1.5% and 1.3%, respectively, with the most significant losses occurring in the offshore concentrator photovoltaic (CPV) and E-CEM reactor unit.