This editorial presents the motivations that were the focus of the papers that make up this Special Issue on energetic complementarity. The articles deal with the application of the concept of energetic complementarity in time under certain conditions and with the proposition of new means to evaluate complementarity in time between more than two renewable energy resources. An article further proposes a method for establishing energetic complementarity in space, a concept that is important and

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... cessary for management and planning of energy resources but does not yet have tools that allow it to be quantified and handled appropriately. In addition, two letters to the editor discuss issues that still need to be matured for a better understanding and application of the concept of energetic complementarity, both in time and space. Keywords Component: Energetic Complementarity The concept of complementarity is not new and has always been present in the work of engineers and managers who have dealt with the design and operation of energy systems over time. The growth of energy systems around the world, as a result of growing demand for energy supplies and rising expectations for better quality supplies, has resulted in the need to make better use of available energy resources. In this context, energetic complementarity deserves a formal and coherent treatment. Complementary energy resources can be exploited with hybrid systems with components with lower installed power or with lower capacities for energy storage and yet present equivalent or even better performance when compared to systems based on not so complementary recourses. It is obvious that the coinci-