Three stages in the co-transformation of the energy and mobility sectors

Renewable electricity sources such as wind and solar power have shown a remarkable development in terms of efficiency, costs and availability, but system integration still remains a challenge. Realizing a fully renewable electricity supply will require large scale storage technologies and flexible users to overcome long periods of low power generation. At the same time, other sectors such as mobility and industry must be electrified to replace fossil fuels. Power-to-methane is a promising technology as it enables large-scale energy storage and sector coupling using existing infrastructures. In this work, we analyze the co-transformation of the German electricity, mobility and industry sectors, taking into account the recent decision to phase out coal by 2038. We evaluate the necessary capacities of renewables and sizes for storage options, as well as system costs and associated emissions using a techno-economic optimization model with a high technological and temporal resolution in the open-source framework OSeMOSYS. We find three rather different stages of the transformation driven by the decreasing emissions cap and the coal phase-out. Solar power is expanded vastly up to 2030, whilst coal is replaced mainly by fossil natural gas by 2040. Emissions caps become very challenging after 2040 to the extent that all flexibility options are greatly expanded: storage, curtailment and flexible power-to-methane.