In order to explore the electrical performance of a piezoelectric paint based ocean energy harvester attached to a fish aggregating device under the real sea area, this study do the research about the influence of wave direction. The experiments of flexible piezoelectric energy device (FPED) facing different wave directions were conducted. A numerical model based on the Immersed Boundary Method (IBM) is proposed, and the coupling of the device and the wave under different wave directions is simulated. The reliability of numerical model was verified by the comparison between the numerical results with the experiment ones. The relationship between motion, output voltage and the wave direction is obtained.
Renewable energy sources are the fastest growing source of electricity generation and nearly reach 29.2% of global net electricity generation in the year 2040 (Conti et al., 2016). Among them, ocean energy is one of the most important and promising renewable energy sources on earth, which avoids the deterioration of power generation performance due to sea salt particles and does not depend on cut-in wind speed at sea when using solar energy and wind energy. However, the proportion of the installed capacity of the ocean energy in the total energy is still very small. The reasons of this phenomenon are that the exploitation of ocean energy sources technologies is still under development and demonstration stages since ocean energy has broadband and different energy scales in time and space and it is challenging to integrate ocean energy devices into large-sized ocean energy farms. Furthermore, a number of challenges, such as the effectiveness, reliability, competitiveness, costs and environmental sustainability, stand between the sector's current status and the aim of commercial utilization (de Andres et al., 2017).
According to the International Energy Agency (IEA), five kinds of technologies for ocean power generation can be used: (1) tidal rise and fall (barrages); (2) tidal/ocean currents; (3) waves; (4) temperature gradients; and (5) salinity gradients (Birol et al., 2017). Among these, tidal and wave energy were given more attention than others and had obvious distinction between them. The output of tidal devices is predictable long into the future due to the mathematical basis of tides while power generation with wave energy devices are unpredictable. This finally results in more preferability of tidal energy devices since its energy generation for grid usage is the predictability of output and avoid the necessity for conventional backup (Walker et al., 2011). Considering the effect, the future research of the wave energy devices should be not only focused on the amount of power generation but also the fluctuation and forecast of the output electric energy.
