A perspective on practical solar to carbon monoxide production devices with economic evaluation

Solar-chemical production is one of the most promising options for producing valuable chemicals from greenhouse gases. An economically attractive and industrially applicable solar-chemical production device not only requires catalyst and/or reactor design, but also auxiliary unit process design, process integration, and optimization. Herein, we report a state-of-the-art monolithic solar-chemical production device having 8.03% solar to CO conversion efficiency and 0.77 to 31.9% CO₂ one path conversion. Since the monolithic device directly couples a photovoltaic cell and a CO₂ electrolyzer, the power loss due to a current converter can be avoided. According to the solar-chemical production device, a comprehensive process design accounting for CO₂ to CO conversion, unreacted CO₂ separation, and recycling structure is provided. The process model shows good agreement with experimental data for CO₂ conversion in the electrolyzer. A process level techno-economic evaluation and a comprehensive review are also presented to highlight the current state and the economic feasibility of the developed device. Thereafter, we provide a sensitivity analysis in terms of CO₂ conversion, membrane cost, solar to chemical efficiency, and current density necessary for economically profitable CO production. The equivalent CO sales cost from a 4 MW production plant is estimated to be $10.9 per kg and the corresponding carbon tax compensating for the price gap of the current market price is $6.6 per kg CO₂. The sensitivity analysis demonstrates that >80 mA cm^-2 current density or 22% CO₂ conversion is desirable to effectively compete with the conventional CO production process.