Abstract:Ocean energy holds out great potential for supplying remote maritime areas with their energy requirements, where the grid size is often small and unconnected to a continental grid. Thanks to their high maturity and competitive price, solar and wind energies are currently the most used to provide electrical energy. However, their intermittency and variability limit the power supply reliability. To solve this drawback, storage systems and Diesel generators are often used. Otherwise, among all marine renewable energies, tidal and wave energies are reaching an interesting technical level of maturity. The better predictability of these sources makes them more reliable than other alternatives. Thus, combining different renewable energy sources would reduce the intermittency and variability of the total production and so diminish the storage and genset requirements. To foster marine energy integration and new multisource system development, an up-to-date review of projects already carried out in this field is proposed. This article first presents the main characteristics of the different sources which can provide electrical energy in remote maritime areas: solar, wind, tidal, and wave energies. Then, a review of multi-source systems based on marine energies is presented, concerning not only industrial projects but also concepts and research work. Finally, the main advantages and limits are discussed.
Microgrids operating on renewable energy resources have potential for powering rural areas located far from existing grid infrastructures. These small power systems typically host a hybrid energy system of diverse architecture and size. An effective integration of renewable energies resources requires careful design. Sizing methodologies often lack the consideration for reliability and this aspect is limited to power adequacy. There exists an inherent trade-off between renewable integration, cost, and reliability. To bridge this gap, a sizing methodology has been developed to perform multi-objective optimization, considering the three design objectives mentioned above. This method is based on the non-dominated sorting genetic algorithm (NSGA-II) that returns the set of optimal solutions under all objectives. This method aims to identify the trade-offs between renewable integration, reliability, and cost allowing to choose the adequate architecture and sizing accordingly. As a case study, we consider an autonomous microgrid, currently being installed in a rural area in Mali. The results show that increasing system reliability can be done at the least cost if carried out in the initial design stage.
Power quality is an important issue for wave energy developers, as the wave energy converters output power profile presents a lot of fluctuations due to the oscillatory nature of the waves. In order to emulate an operating direct drive wave energy converter, study power quality improvement and test different control strategies, a wave-to-wire model has been developed. Although control study for wave energy converters is often limited to the hydrodynamic control, this paper addresses the dynamic modeling of all the conversion stages, from the waves to the electric network. First, the wave energy converter used for this study is presented and a model for the electric parts is proposed (including a back-to back converter). Then, control strategies are discussed, in order to regulate the generator electromagnetic torque, the DC-Iink voltage and the grid voltages and reactive power. Simulation results considering these control strategies are presented in the last part.
While marine renewable energies have seen some interest over the last years, the electricity supply of maritime remote areas still presents many constraints, such as high costs due to the storage requirements. The constraints related to the reliance show that the energy management system needs some flexibility, which can be done by managing the demand. The strategies based on load shed and load postponement are often considered. In this paper, anticipation based strategies are proposed in the aim to use the excess power for shiftable loads supply and to foster marine energies integration for the electricity supply of remote areas. A multi-source system including solar, wind, tidal and wave energies is considered, in which batteries are used to ensure the demand to be satisfied as much as possible. The developed strategies concern the electric room heaters and water heaters power demand. Significant effects on demand satisfaction, battery lifetime, system sizing and costs are observed in the carried out simulations, showing the positive effects brought by the proposed anticipation based strategies. Moreover, some situations of loss of power supply are avoided thanks to the proposed demand side management strategies.
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