Shahram Derakhshan - School of Mechanical Engineering, Iran University of Science & Technology, Tehran, Iran
Mahdi Moghimi - School of Mechanical Engineering, Iran University of Science & Technology, Tehran, Iran
Hadi Motawej - School of Mechanical Engineering, Iran University of Science & Technology, Tehran, Iran

Fossil Fuels are always considered as environmental pollutants. On the other hand, the political and economic situations highly affect the price of these fuels. Offshore wind and wave, as renewable energy sources, represent the better alternatives for electricity generation. Therefore, it is necessary that wind speeds effectively be estimated due to the absence of field measurements of the wind speed above the surface of the sea in many regions. In this paper, the annual-average wind speed above the sea is calculated mathematically. Wind data obtained from onshore monitoring stations were analyzed to obtain wind power density above the sea. In addition, this study provides information on the variation of the wave energy using Beaufort scale and wind speeds. This allows an approximate estimation of energies corresponding to various wave heights in that region. Besides, a mathematical model was developed to assess wave and wind hybrid energy system. Thus, using a mathematical model, wind-wave hybrid system components were: wind turbine, wave converter and foundation. The wave energy converter (WEC) selected for the hybrid device is Wavestar prototype which was combined with a wind turbine. As for case study, the wind speed as well as the resulting wind and wave power potential in the area of Eastern Mediterranean Sea and the North Sea were determined and the assessment were done for the designed hybrid system. It can be concluded that the annual energy production from hybrid wind-wave device in the North Sea is 64.3% more than its value in the Mediterranean Sea.

Offshore Wind Energy, Wind Power Density, Mean Wind Speed, Wave Energy, Hybrid Energy System