System-level simulation of a solar-driven liquid fuel production plant via gasification-Fischer-Tropsch route

Conversion of algae into liquid fuels via solar-driven supercritical water gasification (SCWG) with steam methane reforming (SMR) and Fischer–Tropsch (FT) synthesis offers a promising approach for production of clean fuels. While much research has been dedicated to the analysis of biomass gasification, methane reforming and FT synthesis separately, little emphasis has been placed on a fully integrated system based on these components especially when a variable heat source – i.e. concentrating solar thermal (CST) – is involved. As such, this paper investigates the annual dynamic performance and techno-economic feasibility of this technology at a system level. A detailed steady-state model of the SCWG-SMR and FT plants is developed in ASPEN Plus software. Based on performance curves of key component quantities at design and off-design points, an energy-based, system-level model of the whole solar fuel plant is developed in OpenModelica. The solar field is sized such that it can deliver 50 MWth to the receiver at design. The results of the parametric study suggest that the optimal solar multiple and syngas storage size are 3.5 and 16 hours, respectively, leading to a levelised cost of fuel (LCOF) of 3.2 AUD/L (∼2.3 USD/L) and a capacity factor of ∼71%. The total capital and annual operational costs of the system are found to be ∼162 M-AUD and ∼24 M-AUD per year, respectively. Although the estimated LCOF in this study seems to be relatively high compared to fossil fuel-based petroleum products, this technology is expected to be economically competitive in the near future through e.g. upscaling the plant size and further reduction in the algae production cost.