From Variable Renewables to Fuel - Systemic Flexibility Requirements for Integrated RWGS and Fischer-Tropsch Plants

Kurzfassung

Defining systemic boundary conditions for catalytic syngas conversion to SAF The transition to power-based sustainable aviation fuels (SAF) necessitates the coupling of fluctuating renewable energy sources with (electro-) chemical process chains. While upstream power generation varies significantly, downstream catalytic synthesis gas generation and synthesis processes, such as Reverse Water-Gas Shift (RWGS) and Fischer-Tropsch (FT), have traditionally been designed for steady-state baseload operation. This study addresses the techno-economic gap between intermittent power supply and the requirements of synthesis gas conversion. We present a system analysis of a Power-to-Liquid (PtL) process chain combining wind and photovoltaic (PV) power generation with electrolysis and a synthesis unit comprising Reverse Water-Gas Shift (RWGS) and Fischer-Tropsch reactors. The central aim is to identify the cost-optimal system configuration, thereby deriving specific operational requirements for syngas production and downstream processing, by analysing the economic viability of dynamic load-following capabilities against the capital expenditure required for increased intermediate storage. The methodology applies a hybrid modeling approach. The upstream section - comprising renewable generation, battery storage, electrolysis, H2 and CO2 storage - is simulated using fully dynamic, location-specific weather data. Crucially, within this module, we simultaneously optimize the sizing of components to minimize the cost of kerosene, which is produced in the downstream section. This is defined as the process steps following H2 and CO2 buffering (RWGS-FT), is modeled using a quasi-dynamic approach with distinct stationary operating modes (nominal, part load, shutdown). By coupling these domains via intermediate grids and gas storages, we derive the specific boundary conditions for catalytic synthesis production. The analysis aims to quantify the actual degree of flexibility required from the synthesis unit to positively impact the overall cost of SAF, thereby evaluating whether highly dynamic catalytic operation is economically justified compared to upstream buffering.