A 'feasibility space' as a goal to be achieved in the development of new technologies for converting renewable energies.

This method article proposes the establishment of a feasibility space as an objective to be achieved during the development of new technologies to convert energy from renewable resources. The feasibility space can also be a reference when designing an energy system based on renewable resources. The feasibility space is a set of parameter values for the design stage that define the economic and technical feasibility of an energy system or a new technology, which must be satisfied when the energy system comes into operation or when the new technology for converting power goes into operation. The study of possible feasibility spaces allows characterizing energy systems or new technologies as attractive investments, or on the other hand, as unfeasible ventures.-The method proposes to establish a goal to achieve during the development of technologies for energy conversion.-The method provides a benchmark for both the stages of design and development of generation systems and new technologies.-The feasibility space constitutes a planning tool for power systems based on renewable resources of any size.

Spatial representation of temporal complementarity between three variable energy sources using correlation coefficients and compromise programming.

Renewable energy sources have shown remarkable growth in recent times in terms of their contribution to sustainable societies. However, integrating them into the national power grids is usually hindered because of their weather-dependent nature and variability. The combination of different sources to profit from their beneficial complementarity has often been proposed as a partial solution to overcome these issues. Thus, efficient planning for optimizing the exploitation of these energy resources requires different types of decision support tools. A mathematical index for assessing energetic complementarity between multiple energy sources constitutes an important tool for this purpose, allowing a comparison of complementarity between existing facilities at different planning stages and also allowing a dynamic assessment of complementarity between variable energy sources throughout the operation, assisting in the dispatch of power supplies. This article presents a method for quantifying and spatially representing the total temporal energetic complementarity between three different variable renewable sources, through an index created from correlation coefficients and compromise programming. The method is employed to study the complementarity of wind speed, solar radiation and surface runoff on a monthly scale using continental Colombia as a case study during the year of 2015.•This paper describes a method for quantifying and spatially representing energetic complementarity between three renewable energy sources.•The method quantifies energetic complementarity by combining known metrics: correlations and compromise programming.•The proposed index for energetic complementarity assessment is sensitive to the time scale adopted.

Simplified evaluation of energetic complementarity based on monthly average data.

Energetic complementarity is a subject that has been holding more and more attention from researchers in recent years, being a concept that can be applied both in energy planning stages and in phases of operation of energy systems based on renewable energy resources. The complementarity between two renewable sources of energy has three components: time-complementarity, energy-complementarity and amplitude-complementarity, and can be determined between raw energy availabilities or between energy generated by power plants. Complementarity can be evaluated between two renewable resources in the same place or between two renewable resources in different places and these two types can be denominated respectively as temporal and spatial complementarity. This method allows simplified evaluation of the energy complementarity between two renewable resources by comparing basic parameters obtained from series of monthly average values that characterize these resources. Finally, an application example clarifies the application of the method. •The method allows a quick and visual but expeditious evaluation of energetic complementarity.•This method provides a reference value for the application of more complex methods for evaluation of complementarity.•Monthly average data allows the comparison of renewable resources with different characteristics of intermittency and variability.

Qualitative evaluation of spatial complementarity between renewable energy resources with complementarity roses.

Energetic complementarity is a subject that has been concentrating more and more attention of the researchers around the world in the last years, a concept that can be applied both in energy planning and in operation of energy systems based on renewable energy resources. Spatial complementarity is the energetic complementarity evaluated between two renewable resources in different locations and, as well as the complementarity evaluated between resources in the same location, has three components: time-complementarity, energy-complementarity and amplitude-complementarity. At the same site, however, complementarity assessment can involve multiple resources simultaneously, and the study of these circumstances requires appropriate tools to handle such information.This method paper describes a method to build complementarity roses expressing the spatial complementarity between two or more renewable energy resources throughout a region, appropriate for the expression of this complementarity through maps.

Simulating hybrid energy systems based on complementary renewable resources.

The complementarity between energy resources can influence the performance of hybrid generation and storage systems, and can also decisively influence their design. Renewable resources may have intermittent characteristics that make the study of the influence of complementarity on the performance of hybrid systems quite difficult. The establishment of a performance limit of hybrid systems based on renewable resources and the study of the effects of complementarity considering this limit can provide interesting results. This performance limit can be established with an idealization of the mathematical functions describing the energy availability of the explored renewable resources. This article presents a method for analyzing the performance of hybrid systems based on complementary resources. The method allows to evaluate the influence of different levels of complementarity between the exploited resources on the cost of energy and capacity shortage. Utilizing idealized energy availability, the result sets a performance limit. •A method to evaluate the impact of complementarity on the performance and reliability of hybrid systems.•The energy availabilities of the renewable sources are idealized and allow the characterization of a limit of performance.•Different levels of complementarity can be related with design parameters of hybrid energy and storage systems.

Energy at the Junction of the Rivers Negro and Solimões, Contributors of the Amazon River, in the Brazilian Amazon.

The Negro and Solimoes rivers join in front of the Brazilian city of Manaus to form the Amazon River. This "meeting of the waters" is a natural phenomenon of great aesthetic beauty that has been the focus of attention of researchers all over the world in various scientific fields. The waters of the Negro are darker and warmer, while the waters of the Solimoes are lighter and cooler. These waters have very different characteristics and remain without mixing, flowing side by side for several miles. Some reports indicate a temperature gradient between the waters of the order of 6°C, which can be used in conjunction with very high flow rates delivered by the two rivers, with a heat engine operating on a thermodynamic cycle to provide electricity. This review paper identifies this energy resource and presents a preliminary assessment of the potential for power generation. A realistic assessment of the potential points to an available power of about 1 GW. It is clear that further studies are needed to accurately assess the available thermal gradient and its variation over time, to move forward in the design of the power converter, and to establish an appropriate location for a power plant.