Energy System Design for the Production of Synthetic Carbon-neutral Fuels from Air-captured CO2

Abstract

In this work, we investigate the design and operation of an energy system for the production of a carbon-rich CO2-neutral fuel, i.e. where hydrogen reacts with CO2 from air to give synthetic methane. As the systems consists of multiple energy conversion and storage technologies, we make use of the energy hub approach coupled with MILP optimization to identify optimal plant designs and operation. We investigate the effect of flexible vs. steady operation of the fuel synthesis and direct air capture, as well as the effects of different geographical locations. We find that if the system is optimized for cost, electricity is mainly supplied by the grid, and therefore the electricity prices and grid emission factors determine the economic and environmental performance. Moreover, the location plays a minor role in the cost of the minimum emissions point, as the direct air capture cost largely control the total plant costs. Along this line, the optimal design was found to rely on steady operation of the synthesis and direct air capture ensemble, as this allows for the lowest associated capital expenditure. © 2020 Elsevier B.V.