Role and trends of flexibility options in 100% renewable energy system analyses towards the Power-to-X Economy

Abstract

Flexibility options are essential components in highly renewable energy systems due to the inherent variability of renewable energy sources, such as solar photovoltaics and wind power. The adoption of renewable energy aligns with the United Nations Sustainable Development Goal 7, ensuring access to affordable, reliable, sustainable, and modern energy for all. This study investigates the impact of flexibility alternatives within the framework of 100% renewable energy systems through a systematic literature review to identify energy system analyses of at least 95% renewable energy supply for at least one sector in at least one scenario. 1067 articles from 1975 to 2023 were analysed to understand the functionality of flexibility options in highly renewable energy systems. The identified flexibility options include power-to-X, energy storage, demand response, power grids, and curtailment. The results indicate that within the field of 100% renewable energy systems, electricity-based solutions have emerged as the default. Various electricity-based fuels are used, with e-hydrogen and e-methane being the most widely discussed in 46% and 19% of articles, followed by Fischer-Tropsch and e-methanol with 3% of studies, respectively. Battery storage is covered by 60% of articles, followed by e-fuels options, and pumped hydro energy storage. Demand response was identified as the least included method. 46% of the articles highlight the role of transmission grids and 25% include curtailment. Early 100% renewable energy system analyses focused on flexibility in the power sector, whereas the shift of studies to a Power-to-X Economy has broadened research to flexibility options across the entire energy-industry system.