A solar-driven biogas reforming reactor for enhanced hydrogen production based on cascaded-optimized thermal matching

Under the global imperative for carbon-neutral fuels, solar-driven biogas reforming stands out. However, its efficiency is fundamentally constrained by the geometric incompatibility between conventional two-dimensional (2D) reactor channels and the non-uniform heat flux of parabolic dish collector (PDC), leading to significant irreversible losses and inadequate gas residence time in high-temperature channels. To overcome this, this study proposes a three-dimensional (3D) solar-driven reactor based on cascaded-optimized thermal matching. This innovative architecture dynamically aligns the gradient solar thermal input with the reaction's endothermic requirements through a 3D channels layout. A comparative exergy analysis validates thermal matching as a critical principle: a 2D reactor with gradient heating shows a 1% improvement in exergy efficiency and a 5% improvement in energy storage efficiency over uniform heating. The transition from a 2D to a 3D heating surface geometry itself yields a further 2% exergy gain and a 7% improvement in energy storage efficiency by resolving the issue of insufficient gas residence time in high-temperature zones. Ultimately, the 3D reactor demonstrates superior geometric compatibility, achieving a total exergy efficiency of 49.21%. Under identical conditions, it outperforms the 2D benchmark with a remarkable 9.21% increase in exergy efficiency and a 6.16% improvement in energy storage efficiency. The work establishes that geometric reconfiguration of the reactor for system-level synergy, rather than isolated component optimization, is a dominant factor for high-performance solar fuel production. It provides a new design paradigm, resolving the thermal mismatch between PDC and reaction channels to minimize thermodynamic waste.