The Roles of Chemical Energy Carriers in Future Renewable Energy Systems

Abstract

With climate change mitigation as one of the key goals of the energy transition, the use of fossil fuels and their connected greenhouse gas emissions has to decline sharply in the future. Renewable generation technologies alone however will be insufficient to fill the gap left by fossil fuels. Other than fossil fuels, renewable energy sources are constrained by their weather dependency and land requirements, making complementing storage and firming technologies necessary to ensure a reliable energy supply. To be successful, the energy transition has to address these key challenges of renewables, regional availability and weather dependency. Chemical energy carriers are a puzzle piece to the energy transition, expected to address these two challenges. They can be synthetically produced from renewable energy and sustainably sourced feedstocks. With properties similar to currently used chemical energy carriers of fossil origin, they offer attractive characteristics for use in energy storage, transport and as industry feedstock. However, because of their distinct chemical and physical properties, they are expected to be suited differently well to fulfil the various roles in future energy systems. In this thesis, the potential of candidate chemical energy carriers to fulfil the various roles are investigated. Using bottom-up energy system modelling, their performance and suitability for energy and feedstock imports, long-distance electricity transport as alternatives to demand-side flexibility, and long-term strategic energy storage are evaluated based on techno-economic criteria. The findings are complemented by the introduction of a software package for modelling input data on renewables for energy system models and the foundations for a global energy system model of high temporal and spatial resolution. With its results, this thesis lays the basis for future, more comprehensive analyses of the global roles of chemical energy carriers and their interactions with regional energy systems.