Dynamic and techno-economic assessment of solar-assisted biomass gasification for continuous hydrogen production

Abstract

Solar-driven biomass gasification offers a promising route to produce green hydrogen while storing solar energy in chemical form. To mitigate solar intermittency, a solar/autothermal hybrid gasification strategy based on solar-input-dependent adjustment of gasifying-agent ratios is proposed. Using rice straw as the biomass feedstock, a thermodynamic analysis was first conducted to determine the optimal steam-to-feedstock (S/F) and oxygen-to-feedstock (O/F) molar ratios under varying solar input by maximizing the energy upgrade factor. With increasing solar input, O/F decreases monotonically, whereas S/F initially increases and subsequently decreases. Under the optimized operating conditions, the energy upgrade factor increases from 0.75 under autothermal operation to a maximum of 1.23 under solar-assisted operation. Based on the optimized operating strategy, a solar/autothermal hybrid biomass gasification system for high-purity hydrogen production was modeled and evaluated through a full-year hourly dynamic assessment. At a constant biomass feed rate of 4.515 kg s −1 , the proposed system produces 9221 t H 2 yr −1 , representing a 39 % increase compared with the reference autothermal system. An economic assessment indicates that the system is economically feasible (NPV > 0), with a levelized cost of hydrogen of 3.26 $ kg −1 , significantly lower than that of PV-powered water electrolysis in the same region. With further cost reductions in solar concentrating technologies, the economic advantage of the proposed hybrid system is expected to be further enhanced.