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This paper deals with the sizing and rough optimization of a renewables-based farm devoted to energy production in a stand-alone marine context. The studied hybrid farm consists in combining wind turbines, tidal turbines, diesel generators, and pumped hydroelectric storage. The main sizing and optimization constraint is to achieve a compromise between the hybrid system overall cost, for a period of 15 years, and the CO2 emission minimization. The proposed sizing and optimization study is first based on the different available renewable sources, wind and tidal currents, characterization. This preliminary study is essential. Indeed, it will provide the renewables sources basic information in terms of wind and tidal speed potential for the hybrid farm components choice. After presenting the hybrid farm different components, the simulation constraint is defined (energy conservation at the grid) in order to form a power exchange network at the grid level but in a stand-alone context. The optimization results are analyzed to explore wind turbines, tidal turbines, and the proposed pumped hydroelectric storage sizes on the targeted objectives.

This paper deals with an energy characterization method of tidal sites. This method is illustrated by the study of a typical tidal site close to the Ouessant (Ushant) Island of the Bretagne region in France. The main objective of this study is to find the optimal location of a tidal turbine including the effect of using or not a yaw drive system. After presenting the different data used in this work, the marine current velocity is first evaluated at different specific locations and times of the studied zone. Afterwords, the tidal energy is evaluated for different systems (tidal turbine with a yaw and bidirectional tidal turbine with fixed axis) and presented in terms of energy distribution maps.

Estimating the energy potential of tidal stream site is a key feature for tidal energy system deployment. This paper aims to compare two methods of prediction of tidal current velocities. The first one is based on the use of a fully three-dimensional (3D) numerical approach. However, while being accurate, the numerical model is highly time-consuming. The second method is based on a linear approximation of the tidal current, which only requires preliminary knowledge of local current velocities time series during two typical tidal cycles. This second method allows a very quick evaluation of the tidal stream resource during a long time period. The proposed comparison is done in three different locations of a high potential tidal energy site in west of France. It is carried out in terms of current velocity and energy harnessing for several turbines technology options (with and without yaw). The achieved results show that the linear approximation gives satisfactory evaluation of the tidal stream potential and can be a very interesting tool for preliminary site evaluation and first technology options selection. However, the fully 3D numerical model can obviously be very useful in more advanced steps of a project.

The increasing awareness of the need to reduce pollution and global warming, and the increasing price of conventional energy resources, encouraged many countries to adapt new energy policies by including renewable energy resources, such as solar energy, wind energy, tidal energy. These new energy sources are usually connected to the gird via inverters, which presents fast dynamics due to their small output impedance. Such fast dynamics systems can contribute to voltage and frequency variations. These variations could be problematic in the particular case of stand-alone sites in absence of a main grid that could help regulating the voltage and the frequency. In this paper, a multi-source system for a stand-alone site will be studied under different control strategies. In particular, a power control, a voltage and frequency control, and an inverter virtual synchronous generator control strategies are adopted and evaluated. Afterwards, two specific multi-source control strategies, namely the traditional droop control and a virtual synchronous generator control, are simulated and evaluated based on a comparative study.