Whither solar fuels?

Solar fuels are a long-term permanent solution to renewable fuel technologies to reduce foreign oil imports and carbon dioxide emissions. Although promising in laboratory and pilot scale, they possess inherent technical and economic challenges that hinder large-scale implementation. This work examines critical issues for four solar fuel technologies: solar-powered electrolysis, photoelectrochemical (PEC) systems, solar biomass gasification, and solar thermochemical cycles. Also identified are areas of chemical and materials engineering research that are essential to cost-competitive solar fuels production.

► Solar fuels technologies cannot compete with the current prices of oil and natural gas.
► The result of solar fuels R&D should be a liquid fuel petroleum substitute.
► Photoelectrochemical systems R&D should focus on water splitting to make H2 versus CO2 reduction.
► Solar-driven water electrolysis is today a scalable technology.
► Solar biomass gasification is the most competitive technology versus steam methane reforming for syngas synthesis.