Numerical Performance Assessment of a Flapping-Type Vertical Axis Wind Turbine with Chebyshev-Dyad Linkage

In order to harness wind energy with high coefficients, horizontal axis wind turbines (HAWT), like propeller-type wind turbines, have an advantage in terms of practical utilization because of their scale merit. However, large size and high tip-speed ratio are inherently related to material strength problems and low frequency noise emissions to the environment. In contrast to HAWT, we will discuss a flapping-type turbine driven at low speed. The flapping turbine works using lift force like the HAWT, but employs a new wind turbine concept in the present report. The concept involves the unique flapping motion of a wind blade mounted on a Chebyshev-dyad linkage by which the wing transforms wind energy into mechanical rotation. Both static and dynamic numerical estimates are developed to optimize all fundamental parameters of this linkage in order to obtain the desired torque. In this paper, the results of primitive optimization for determining the fundamental characteristics of motion and the trajectory of the wind turbine blade are demonstrated in order to obtain smooth rotation of the generator-driving shaft. It is also shown that the present turbine can be driven at low speed with a suitable energy conversion rate. Moreover, the practicality of operating slow flapping-type wind turbines is demonstrated, focusing on usage near residential areas or, e.g., on rooftops owing to lower noise. The feasibility of “figure eight” trajectory diversity is discussed along with geometrical parameters. Assuming one-blade motion with a variable trajectory for optimization, the smooth motion and required torque at slow rotation speeds are studied.

Performance Assessment of a Calm Flapping Wind Turbine with Small Attack Angle

The objective of this research is mainly focused on environment-friendly and moderately slow flapping wind turbine which can easily operate in or near urban areas or rooftops owing to scale merit with low-frequency turbine noise, installation cost, avian mortality rate and safety consideration etc. The authors are focusing on lift based (LB) slow flapping wind turbine operated within a small attack angle amplitude whereas the previous research treated a lift and drag based (LDB) flapping turbine. Here, a unique trajectory for the wing motion was yet designed by using the Chebyshev dyad linkage mechanism as well as the previous report. The wind energy transferred to the mechanical rotation, adopting a single symmetric wing NACA0012. To obtain a smooth flapping motion for the blade, we optimize all fundamental parameters with our simulation model for optimum performance of the turbine. Both static and dynamic analysis has been conducted to confirm the feasibility of the present design. In addition, wind turbine performance was studied for a suitable range of free stream wind velocities. This report confirms that the developed flapping wind turbine can drive at slow speed with suitable energy extraction rate at different wind velocities. Moreover, we made a simple comparative study of the outcomes obtained from our previous lift and drag based flapping wind turbine with present one, i.e., lift based flapping turbine.