A Review of Thermal and Thermochemical Technologies for Concentrated Solar Processes, Products, and Applications

Abstract This review considers recent advancements across four critical domains related to thermal engineering and concentrated solar systems and products. First, the review examines Thermochemical Energy Storage (TCES) for Concentrating Solar (CS) plants, highlighting its potential for high-density, long-duration energy storage and integration strategies. Second, it evaluates heat transfer enhancement strategies in high-temperature solar reactors, focusing on cavity geometry, volumetric absorption, and hybrid integration to mitigate extreme thermal gradients. Third, it discusses solar-driven methane pyrolysis as an low-emissions pathway for hydrogen and solid carbon production, analyzing both direct and indirect reactor configurations. Finally, the paper reviews thermal and radiation effects in ammonia-hydrogen combustion, addressing the role of hydrogen blending on flame characteristics and nitrogen oxide (NO$_x$) emissions. Together, these sections provide a broad perspective on the design, optimization, and integration of next-generation solar-thermal and related thermochemical technologies.