Large-scale wind turbines mostly use Continuously Variable Transmission (CVT) as the transmission system, which is highly efficient. However, it comes with high complexity and cost too. In contrast, the small-scale wind turbines that are available in the market offer a one-speed gearing system only where no gear ratios are varied, resulting in low efficiency of harvesting energy and leading to gears failure. In this research, an unsupervised machine-learning algorithm is proposed to address the energy efficiency of the automatic transmission system in vertical axis wind turbines (VAWT), to increase its efficiency in harvesting energy. The aim is to find the best adjustment for VAWT while the automatic transmission system is taken into account. For this purpose, the system is simulated and tested under various gear ratios conditions while a centrifugal clutch is applied to automatic gear shifting. The outcomes indicated that the automatic transmission system could successfully adjust the spinning in line with the wind speed. As a result, the obtained level of harvested voltage and power by VAWT with the automatic transmission system are improved significantly. Consequently, it is concluded that automatic VAWTs, equipped with the machine-learning capability can readjust themselves with the wind speed more efficiently.

Synthesis of 2H and 3C-polytype silicon carbide nanowhiskers mixture of silicon dioxide and carbon was performed by carbothermal reduction process. The reaction temperature for synthesis of 2H-SiC was varied from 1350 C to 1650 C and for the 3C-SiC this range was varied from 1450 C to 1650 C. Scanning Electron Microscopy (SEM) analyses showed that nanowhiskers structures of both 2H-SiC and 3C-SiC polytypes has a size up to 100 nm in diameters and several microns in length. However, the orientation and pattern of grains were different in both structures. While for 3C-SiC polytype, the shape has been classified as SiC majorly grew along [101] plane by X-ray Diffraction pattern and finalized by Raman shift peaks at 799 and 959 cm-1, the shape of 2H-polytipe silicon carbide was categorized as SiC majorly grown along [111] plane confirmed by Raman shift peak at 799 and 963 cm-1. The mechanism of vaporgas interaction was also suggested and discussed for both SiC nanowhiskers polytypes.