Optimizing the energy flux in solar cavity absorber by adjusting the absorptivity distribution based on genetic algorithm

Abstract Concentrating solar power (CSP) systems play a critical role in advancing renewable energy transitions, yet the inherent non-uniformity of energy flux distribution on the inner walls of solar absorbers poses a significant technical challenge. This work proposes a novel method to enhance energy flux uniformity within cavity absorbers without modifying structural configurations or optical targeting strategies. A hybrid optimization framework combining ray-tracing with genetic algorithms was employed to optimize absorptivity distribution and its impact on energy flux distribution and energy efficiency was investigated. Simulation results demonstrate that through absorptivity optimization, the non-uniform factor of energy flux can be lowered from 1.668 to 0.808, with a concurrent suppression of peak energy flux by 75.5%. However, this optimization strategy compromises the absorber's optical efficiency (6.7% decline), for which the solar-to-thermal efficiency can also be lowered (2.9% decline). Introducing a reflective light cone inside the absorber can adjust the rays’ path and increase the energy absorption on the side walls. A solar-to thermal efficiency of 42.1%, which is comparable to that of the absorber with a uniform absorptivity of 0.9 (42.3%), can be realized, while maintaining a high level of uniformity. This work reveals the trade-off between the energy flux uniformity and energy efficiency under the strategy of absorption modification, and provides guidance for designing an indirectly irradiated solar absorber that combines both energy efficiency and uniform energy flux density.