Macro and micro scale modeling of wave energy potential

Energy is an indispensable factor for increasing the quality of life and welfare of humanity. After finding the fire by the primitive people, they have taken a great step in their social and industrial development. By the end of the 18th century, Europeans found coal mines and used those natural resources to lay the foundations of the Industrial Revolution. In the course of this development, the industry using new fossil resources has developed and urbanization has increased greatly. With rapid development of industry, fossil energy resources which had formed over millions of years in the lower layers of the earth, are depleted rapidly. In addition, according to the researches of scientists, the production of energy from fossil fuels, causes environmental pollutions and deterioration of natural balance. In recent years, many studies have been conducted on alternative energy sources which meet the energy needs of people instead of fossil energy and have less environmental impacts. As a result of these researches, the concept of renewable energy sources has introduced. By the development of technology, it is possible to convert the energies of nature into electrical energy. Although the energy obtained from renewable energy sources with today's technological opportunities is more costly than the energy obtained from fossil sources but it should be considered that fossil source energy causes bigger environmental problems. The most important feature of renewable energy sources is their inexhaustibility and their lower damage to the environment. Solar, Wind, Wave, Tidal, Biomass, Hydroelectric and Geothermal energy can be considered as renewable energy sources. Nowadays, electrical energy has a direct impact on the life of the society and becomes one of the most important factors of human life quality. Usable electrical energy is one of the most important inventions of human and plays the main role in the development of social, economic and culture of humans. Nowadays, it is a fact that many objects that increase the welfare level of the society are working with electrical energy and the quality of life of people is based on electrical energy. Moreover, the role of rich and reliable energy sources should be kept in mind in the international relations of countries and should consider in establishment of the political power balance. For example, petroleum, as a fossil energy sources, has turned the countries of its origin into political and economic focal points. In this case, decreasing the dependency on foreign sources of energy for a developing country such as Turkey has great importance. For this reason, it has become a necessity to conduct a wide range of research into renewable energies. Nevertheless, in Turkey, there is no sufficient scientific research related to the subject of this thesis. The potential of energy generated from sea waves across the world is estimated to be above 2 TW. However, only 0.5 TW of this potential can be used with today's technology. Therefore, research and development activities in this area need to be accelerated in order to make the highest possible use of wave energy. The continuation of researches on this subject will make it possible to use the wave energy economically and the usage of it will become more widespread. This Ph.D. thesis, investigated the Sea Wave Energy potential for Turkey and presented reliable results. Obviously, Turkey has a great wave energy potential. It can be said that some energy needs can be met from the wave energy especially in the coastal areas which forms a large part of the country. For this purpose, the wave energy potential of Black Sea and Marmara Sea is calculated with MIKE 21SW which is the spectral wave module of MIKE by DHI. For the models that installed with a software, in order to be at a reliable level, the model input data, the structure of the mesh and the data which will compare with the model outputs must have a sufficient accuracy and number. "Marine Geoscience Data System" bathymetric values and ECMWF (the European Centre for Medium-Range Weather Forecasts) wind data have been used in the numerical modeling setup with software that mentioned above. The numerical model with fixed parameter values has been run on the various numbers of meshes. The result of the numerical model has been compared with various numerical meshes, to optimize mesh element count. These numerical meshes have a different number of elements. In addition, to verification and calibration the result of the numerical model TPAO and Ambarli buoys measurements wave data were used for the Sea of Marmara and Gelendzhik, Hopa, Sinop and Filyos buoys, Gloria and MHI drilling platform and AVISO 1, 2, 3 satellite measurements wave data for the Black Sea. The relationship between measurement values and model results was evaluated by statistical parameters such as r, R2, RMSE, MAE, MedSim, MedObs, BIAS and SI. The use of long-term data sets of ECMWF (1979-2016) significantly increased the reliability of the results obtained in this study. However, studies have been carried out on the microscale numerical model setup for use in regional wave energy potential researches. The study area covers the Black Sea and Marmara Sea for the macro scale model. In the micro-scale model, the coastline of Akçakoca district of Düzce province on the Black Sea was investigated. In the Marmara Sea, the number of optimized mesh elements for the macro scale numerical model is 4892. The numerical model was calibrated by preparing 20 scenarios with wave parameters that measured by TPAO buoy. In the calibration phase, a strong relationship between measured parameters and the numerical model results (r = 0.88) has been obtained. A 20-year (1994-2014) ECMWF wind data set was used for long-term wave energy estimation in the calibrated numerical model. The numerical model results are presented as monthly, seasonal and average of 20 years. According to the average monthly significant wave height values, the highest significant wave height occurred in August (0.40 m) and the lowest in May and June (0.20 m). As seasonality analysis, the highest significant wave heights were observed in winter and summer seasons and the highest significant wave height was obtained as 0.36 m. The spring season has the lowest significant wave height value. In general, the maximum of average significant wave height of 20 years was obtained as 0.30 m and in the central parts of Marmara Sea. According to the monthly average wave energy values in the Marmara Sea, the maximum values are obtained in November (1.1 kW / m). The minimum monthly wave energies occur in May and June (0.3 kW / m). In terms of seasonality, the highest wave energy was obtained in winter (maximum seasonal values of 0.75 kW / m) and the spring season has the lowest wave energy value. In general, the highest value in the average wave energy of 20 years was found to be 0.47 kW / m in the central parts of the Marmara Sea. The regions with the lowest wave energy in the regional wave energy study were identified as the gulfs of Izmit, Gemlik and Erdek. In setup of the large-scale modeling of the Black Sea, the optimized numerical mesh with 5928 element number and 37-year ECMWF wind data set were used. The prepared numerical model was calibrated by comparing numerical model results with the measured wave parameter data sets in various regions of the Black Sea. For various calibration points, the correlation coefficient between the measured wave parameters and numerical model results are between r = 0.9 and r = 0.77. As a result of this research, the months with the maximum average significant wave height are January (2.10 m) and February (2.07 m). In this study, the results of the numerical model on a monthly basis analysis, are compatible with the results of the studies by Rusu (2009), Aydoğan et al., (2013) and Akpınar and Kömürcü (2013). These results also show the highest seasonal wave height, obtained in the winter season (2.0 m). According to the average values of 37 years numerical model results, in the Western half of the Black Sea, larger significant wave heights are occurred in compared to the eastern half. The average annual significant wave height of this study is 1.4 m and it is greater than the 0.80 m average annual significant wave height that obtained by Akpınar and Kömürcü (2013). When the wave energy distribution maps are examined in the Black Sea, the greatest wave energy potential occurs in January (34.7 kW / m) and February (33.3 kW / m) and in winter. Accordingly, the energy potential of the winter season (31.7 kW / m) was approximately 6 times greater than the summer season (5.33 kW / m). Regionally analysis shows that, the western half of the Black Sea has more wave energy potential than the eastern half. Also, the larger wave energy potential appear in coastal areas close to the coast of Istanbul in Turkey (7 kW / m) was observed. Also, the greatest wave energy potential appears in coastal areas close to the Istanbul in Turkey (7 kW/m). The highest monthly average wave energy potential was obtained in December (12.01 kW / m), January (10.82 kW / m) and February (10.67 kW / m) in terms of the average wave energy in the whole of Black Sea domain. In addition, May (2.71 kW / m), June (1.77 kW / m) and July (2.77 kW / m) months have the minimum monthly average in term of average regional wave energy potential. The 37-year whole domain's average wave energy in the Black Sea is 6.35 kW / m. According to the results obtained from time series of wave power at various 10 points in the Black Sea domain, the energy power in the Black Sea has occurred in the range of 0- 10 kW/m in 70% of the year. Especially the wave energy obtained in the range of 2-5 kW / m was at least 36% of the year. In the last part of the thesis, the advantages and benefits of micro scale numerical model have discussed. The boundary conditions in setting of the micro scale model have taken from the results calculated by the macro scale numerical model. Additionally measured bathymetry maps have used for this model. A frequent mesh has been prepared to precisely represent the region in the numerical model. Macro and micro scale numerical model results were compared in micro scale model study area. Although these two models offer very close results in deep-sea sections, micro-scale numerical model results have been reduced at a distance of approximately 1.5 km from the coastline. Based on the results of this study it can be recommended that, micro scale numerical model have presented more realistic results in the coastal areas by using measured bathymetry set and finer computation mesh. It can be seen from the comparison of results of micro and macro scale models that the energy potential obtained by micro scale model is lower than the results of macro scale model towards the shoreline. Finally the most important outcomes of this study can be listed as below: • Optimizing the number of mesh elements used in numerical models in order to achieve fewer run times • The extraction of long-term wave energy potential for Black Sea and Marmara Sea. • Presenting a method to setup numerical modeling for local wave energy computations.