Design optimization and numerical performance assessment of a novel beam-down solar-driven biomass gasification system for hydrogen-rich syngas production

Solar-driven biomass gasification technology has attracted attention due to its clean and efficient characteristics. In this study, we propose a beam-down solar-driven biomass gasification system and develop an optical-thermochemical coupling model to simulate the process. The optical and gasification performance of the system is thoroughly analyzed. The optical analysis shows that an optical efficiency of 76.04 % and a uniform heat flux distribution are achieved in the beam-down solar concentrating system, which consists of 33 heliostats, tower reflector (11 m in height and 3.2 m in diameter), and compound parabolic concentrator with an acceptance half-angle of 23°. The analysis of operating parameters reveals that the gasification performance of the system is optimal when the direct normal irradiation is 650 W/m2, the biomass feed rate is 0.2 kg/min, air is used as the gasifying agent, and the equivalence ratio is 0.04, the gasification efficiency reaches 96.30 %, the system energy efficiency is 48.92 %, and the H2/CO volume ratio is 1.04. Maximum syngas (2.04 Nm3/kg) and hydrogen (0.74 Nm3/kg) yields obtain at equivalence ratios of 0.2 and 0.02. The economic viability indicates that the levelized cost of hydrogen is $ 2.6/kg. This study demonstrates the significant potential of the beam-down solar tower system for biomass gasification.