In the last decade there are many studies and researches dedicated to improving the performance of Vertical Axis Wind Turbines (VAWT), especially those with low power, due to advantages over Horizontal Axis Wind Turbines (HAWT), one of them being the possibility of installation in isolated areas, in rural areas or even in urban areas (on buildings).

In this paper two models of VAWT are investigated: one using a blade system with a biplane configuration on each arm and, another one is a two blade H-type VAWT with variable pitch. The first model has been designed to operate at a maximum power in the range of the TSR between 2 - 2.5. Under certain conditions, the biplane configuration yields an increased lift and, depending on the relative position of the blades that form the biplane, yields a high C_L/C_D ratio, compared to the equivalent monoplane configuration.

A computational methodology has been developed using the moving grid option offered by the ANSYS Fluent code, to evaluate amount of energy extracted from the wind. A transient simulation is done using a SST (Shear Stress Transport) turbulence model. Main parameters like moment coefficient C_m, and power coefficient C_P are numerical investigated and compared with the experimental data to justify these two model design.

The preliminary results show that the biplane solution is superior to the classic solution, i.e., of H – Darrieus type. For the VAWT model with variable pitch a higher power coefficient at low Tip Speed Ratio (TSR) is obtained. Performances of the both turbines model tend to be equal at a TSR values greater than 2.5 – 3.

These configurations can be promising solutions for low power VAWTs (1-5 kW).

Key words  Small VAWT, Fixed-pitch blade, Bi-plane blade, Variable-pitch blade, CFD