Power-to-methanol: The role of process flexibility in the integration of variable renewable energy into chemical production

Abstract

Chemical process electrification and renewable energy integration facilitate one another along the pathway towards a greener industry. However, integrating intermittent and variable renewable power into large-scale chemical processes, which conventionally are preferred to operate at a steady-state with a constant load, could lead to prohibitive costs if intermittency is addressed solely by energy storage. Here, we consider the concept of a flexible chemical process which can operate with a variable load throughout the year while meeting a specified annual production target. Using methanol production via carbon dioxide hydrogenation as a case study and by means of process conceptual design and optimisation, we investigate how the over-sizing of flexible process units and the introduction of intermediate storage in the chemical process offer the possibility to improve the overall performance of systems. The impact of the characteristics of renewable power is also explored by performing the analysis using meteorological data from two locations dominated respectively by wind and solar energy. This study shows clear potential benefits of process flexibility when the renewable energy supply is highly variable and is to achieve a high level of penetration. For a 100% renewable production, the introduction of flexibility reduces the levelised cost of methanol by approximately 21 and 34% for the two case study locations, respectively. The cost attribution reveals further insights into the origin of the economic advantages through examining the comparative costs of chemical production, energy generation, intermediate product storage and renewable energy storage. The learning from this work suggests that incorporating process flexibility through a holistically optimised design of energy storage and chemical production has the potential to offer an economically viable route to large-scale green chemical production through renewables-enabled electrification.