Wave energy converters have been attracting attention of researchers and industries all over the world. Many approaches have been presented for the modeling of these devices, but the reader might have difficulties on linking them. In this article is presented a friendly guideline for the modeling of direct-drive point absorber wave energy converters. A popular and relatively complex design is used as a guiding example, namely, a point absorber converter with a heaving buoy as wave absorption device connected to a power take-off system based on a linear generator. Both frequency and time-domain hydrodynamic modeling approaches are considered, and the absorption device hydrodynamic parameters are obtained from a dedicated diffraction-radiation analysis tool. The motion dynamics involving ocean waves and the converter elements are based on ocean and mechanical engineering theory. The linear generator electromagnetic model is based on an equivalent rotating machine which facilitates the generator analysis and the control of the energy produced. This guideline is intended to be used and adapted by new developers to test and validate their own wave energy converters.

In this paper an analytical modeling of the BEM method (Blade Element Moment Theory) with complementary correction methods for the performance analysis of the horizontal axis propeller wind turbines is described. This modeling was built from comparative analyzes of several correction methods proposed in the literature, of which those that presented better results were chosen, considering both medium and large turbines. To validate the results obtained from this modeling, experimental data from four turbines (NASA MOD-X series) in the order of 100kW to 7.3MW were used. A critical and comparative analysis was carried out to discuss the coherence of the results when predicting the performance of these turbines, with the objective of enabling the use of this modeling in a generalized way for horizontal axis propeller wind turbines with wide power range.

The microgrids have been applied satisfactorily for the supply of energy to isolated places. In isolated microgrids, energy storage systems and dispatchable energy sources are fundamental for continuous operation, and for power balance. The dispatchable sources are useful as backup, for maintenance operations, and for battery bank equalization charges. Practical experiences in isolated microgrids that uses synchronous generator (driven by a prime mover) have a potential operation problem when working with rectifiers to charge the battery bank whenever the available renewable resources are not sufficient. This is due the generator reactance that causes voltage distortions at the generator terminals, power quality problems for the microgrid and, eventually, inhibition of rectifier operation whenever there is a thyristor switching. This paper proposes the design of a bidirectional DC-AC converter control loops for application in isolated microgrids, improving the power quality, efficiency and operation. In addition, the use of a bidirectional converter reduces energy conversion losses and reduces the costs of implementing the microgrid by replacing two pieces of equipment (AC-DC and DC-AC converters) for just a single one. The contributions of the paper are the design methodology of the control loops of a bidirectional converter, whose development and application in real environment allows it to perform as grid-forming converter in isolated microgrids.

In this article, the Boqueirão Channel located in São Marcos Bay, Brazil, is characterized in terms of tidal stream energy. From local measurements of both, bathymetry and tidal currents, the estuary is modeled using the Delft3D platform. The results show that the area has significant potential for tidal streams and provides good technical-economic viability due to its proximity to the coast and to a large consumption center.

In this article, results and indicators of the operation evolution of the solar-wind hybrid microgrid installed on the island of Lençóis, Maranhão, Brazil, after ten years of operation are reported. This microgrid is considered a national reference project due to the longevity and robustness in serving the marine islands. This analysis evaluates aspects such as load evolution, challenges identified and overcome, experience with the storage system, and improvements introduced. Indicators of efficiency and socio-economic impacts are also presented and discussed.