Sustainable systems must maintain their function even in the event of disruptions in order to be considered truly sustainable. The theory of resilience concerns the behavior of systems during and aftershocks. Initially, modern understanding of resilience focused on ecological systems; however, the theory was extended to include the ecological aspects and the also social aspects of a system. As a result of climate change, increased efforts have been made to ensure energy systems are more sustainable. The issue of resilience has therefore significantly gained importance of late to energy systems. In the future, modern energy systems will be increasingly exposed to disruptions, whether due to climate change, terrorism, or variable power supply from renewable energy sources. Protecting energy systems from all these threats is only possible at great cost, but it is much more sensible to design resilient systems that can quickly resume their system function after a disturbance. This review looks at research into the resilience and its application to energy systems and identifies similarities and differences. Starting with Holling’s contribution to resilience, the development of the theory is examined and the different definitions are compared. The differences between engineering and ecological resilience are also discussed. Additionally, the review examines, on the one hand, criticism of the theory of resilience and, on the other hand, remaining questions in relation to the application of resilience, such as the system’s state after the disruption. The paper subsequently examines the application of the theory of resilience to different energy systems. The review concludes with an outlook on the possibility of operationalizing resilience for energy systems.

Background: To reduce the effects of climate change, the current fossil-based energy system must transition to a low-carbon system based largely on renewables. In both academic literature and non-academic discourse concerning the energy transition, resilience is frequently mentioned as an additional objective or requirement. Despite its frequent use, resilience is a very malleable term with different meanings in different contexts. Main text: This paper seeks to identify how resilience is understood in the field of the energy system and whether there are similar aspects in the different ways the term is understood. To this end, we review more than 130 papers for definitions of energy system resilience. In addition, we use different aspects to categorize and examine these. The results paint a diverse picture in terms of the definition and understanding of resilience in the energy system. However, a few definition archetypes can be identified. The first uses a straightforward approach, in which the energy system has one clearly defined equilibrium state. Here, resilience is defined in relation to the response of the energy system to a disturbance and its ability to quickly return to its equilibrium. The second type of resilience allows for different equilibriums, to which a resilient energy system can move after a disruption. Another type of resilience focuses more on the process and the actions of the system in response to disruption. Here, resilience is defined as the ability of the system to adapt and change. In the papers reviewed, we find that the operational definition of resilience often encompasses aspects of different archetypes. This diversity shows that resilience is a versatile concept with different elements. Conclusions: With this paper, we aim to provide insight into how the understanding of resilience for the energy system differs depending on which aspect of the energy system is studied, and which elements might be necessary for different understandings of resilience. We conclude by providing information and recommendations on the potential usage of the term energy system resilience based on our lessons learned.

Energy policy makers need information about the greenhouse gas reduction potential that could be realized by changes to the operation of the currently existing European power plant fleet to enable short-term actions. Possible measures could reduce the climate impact of the European electricity system and, additionally, be realized quickly as new investments are avoided. In this paper, the Calliope based energy system model Stella of the European electricity system is presented and used for the first time, with the goal to quantify cost and CO ${}_2$ emissions optimal operation strategies of the existing European power plant fleet. By applying the model to six scenarios the results show that the greenhouse gas emissions of the European power plant fleet could be reduced by more than 50% with little additional costs compared to today’s power generation mix. It is shown that historic power plant operation follows only economic considerations while not fully covering its climate impact. The results demonstrate to policy makers the scale of reduction potential that could be achieved by short-term actions.