Mohammad samadi - Department of Marine industries, Science and Research Branch, Islamic Azad University, Tehran,
Madjid Ghodsi Hassanabad - Assistant Professor, Department of Marine industries, Science and Research Branch, Islamic Azad University, Tehran, Iran
babak mozaffari - Associate Professor, Department of Power electric, Science and Research Branch, Islamic Azad University, Tehran, Iran.

This study is a new design of a vertical axis turbine that generates renewable energy from low-speed currents tidal. Tidal Energy is one of the most important available resources among the renewable and environmentally friendly energy resources in oceans and seas. Tidal turbines are used to produce renewable energy. Some types of tidal turbines widely used and studied are vertical axis tidal turbines (VATT) such as Savonius, Darrieus, Gorlov, Lucid, etc., in which the flow direction is not essential for them. And some types of tidal turbines are Horizontal axis tidal turbines (HATT) which the flow direction is important and often have good performance than vertical axis turbines. These turbines are well suited for absorption of high-speed current, but most ocean areas have tidal flow at low speed. The main purpose of this research is a numerical study of tidal turbines with a horizontal and vertical axis rotor and designing and modeling VATT to increase the power efficiency in low-speed currents. In numerical modeling, the HATT at high speeds has high efficiency, and CP to TSR is more than ۰.۴, but with the design of the vertical Savonius turbine, with the focus of the flow on the concave blade and the removal of force from the convex blade, almost equality in speed Less than ۲m/s. In the modern design of the Savonius turbine, the ratio of CP to TSR has been increased three times and reaches more than ۰.۳ in compare the simple Savonius classic turbine. Therefore, due to advantages such as easier installation and lower maintenance costs of Savonius turbines, and with the new design, the use of these turbines in renewable energy will be appropriate.

Renewable Energy, Horizontal axis tidal turbine, Vertical axis tidal turbine, New tidal turbine, CFD modeling