Simulation and Techno-Economic Evaluation of a Dynamic Power-to-Liquid Process

Kurzfassung

Due to the limited reserves of economically-recoverable fossil fuels and concerns about carbon dioxide emissions from their combustion, many countries have initiated a push to adopt more renewable energy sources in their grid. The fluctuating nature of renewable energy highlights the need for development of varied energy storage alternatives. Among the alternatives, chemical energy storage, in the form of liquid fuels, has gained attention among researchers and industry in the last decade. Various pathways for producing liquid fuels for different applications are subjects of active research. Most of the past and current research has mostly focused on techno-economic feasibility studies, assuming a steadystate operation. However, the fluctuating nature of renewable electricity necessitates a feasibility study of a process in dynamic operation. In this thesis, a case is made for dynamic operation of a Powerto-Liquid process, and an attempt is undertaken to examine commercial viability of intermittent operation compared to steady-state operation. For the dynamic simulation, the electricity profile is retrieved for a wind park of 10 MW rated capacity at Magdeburg, Germany. The maximum electricity output of the wind energy profile, 9.14 MW, is used as an input for steady-state simulation. The evaluation of steadystate Power-to-Liquid process resulted in net production costs of 3.92 €/l for a plant capacity of 206.9 kgproduct/hr. The C5+ selectivity for the Fischer-Tropsch synthesis was observed to be 79%, while that of CH4 was observed to be 12.84%. The dynamic simulation, based on wind electricity input, produced a total product yield of 198.39 tons over the year, compared to 1709 tons of steady-state simulation. Thus, the dynamic Power-to-Liquid process was observed to produce 11.6% product to that of steadystate operation. This reduction in capacity is reflected in the increased net production costs for fuel produced by dynamic operation, as the net production costs reached 17.65 €/l. This was contradictory to the hypothesis, that using the cheap renewable electricity directly could present an opportunity for cost reduction of Power-to-Liquid processes, compared to using the steadybut-expensive electricity from the grid.