Design and Analysis of a 2kW Wind Turbine with a Flange Type Velocity Booster for Low Wind Speeds

Abstract

Demand for the energy is raising with the population growth and technological advancement. There is a global trend to invest in renewable sources of energy to fulfil that demand due to increasing environmental effects which fossil fuels cause on earth. Other than this, renewable energy sources are ideal for places where there is no reliable electrical access.

Similar situation occurred in Sri Lankan dairy industry, where small scale dairy farmers need a reliable source of power for their milk cooling systems, wind-PV hybrid system was proposed to fulfil their energy needs.

This study is focused on designing a wind turbine for above project. Region where this wind turbine is to be installed is subjected to low wind conditions. Thus, wind speed augment device is also needed, and designed.

First NREL pulse VI turbine was modelled and analyzed in Star CCM+ which is a finite volume based commercial CFD code. Then the available experimental data was used to compare numerical results. Comparison indicates satisfactory similarity. Thus, numerical code can be considered as valid and later used for wind turbine analysis of this project.

Then, a 2 kW horizontal axis wind turbine was designed using NACA 634421 and FX 76 MP 140 air foils according to Blade Element Momentum theory. Then the performance characteristics of the turbine was evaluated using star CCM+. Power output of the turbine at designed wind velocity 7.5 m/s and TSR 7.5 was 2273.4 W. Power coefficient is 0.48 at this point which indicates the success of design.

Next, four flanged type velocity booster models were designed with size constrains considering manufacturing and handling easiness. Flow behavior through these booster models were numerically analyzed. Scaled down models of 2 of these boosters were tested in a wind tunnel and numerical data were validated against those experimental results.

Finally previous turbine was again analyzed numerically for its performances with each of four booster models. All four models indicated significant improvement in performances of the turbine. Turbines with booster model 1 and booster model 3 indicated similar behavior and improve the power output by a factor of 2 compared to the stand-alone turbine, while turbine with booster model 2 indicated slightly lower performance with power output increase by a factor of 1.98. Booster model 4 indicated even lower performances, but still increased the power output by a factor of 1.7. Both booster model 1 and 3 are recommended to use for smaller turbines considering their higher performance. Booster model 4 is also suitable, despite its comparatively lower performance due to its compact design. Considering the power requirement and size of this turbine, booster model 4 was selected due to its size and performance. Required power output was achieved using scaled down turbine and booster by 25% of its original design size. This was an additional advantage which leads to lower structural loads and lower material usage.