Numerical Analysis of Buoyant Balloon for Airborne Wind Turbines

Abstract

In India, nearly 45 TWh of wind power has been harnessed over a decade using low to medium altitude winds. Winds at higher altitudes remain stable and have higher velocity; it can be harnessed by the use of turbines placed in buoyant filled balloons at higher altitudes. Studies suggest the usage of the convergent-divergent shape of the balloon can increase the velocity of air at the minimum area where the turbine can be placed. The buoyant balloon is designed in the shape of an airfoil. To reduce the effect of drag, different NACA 4-digit airfoils are taken for analysis in XFLR5 by varying thickness from 10 to 30% of the chord length, the maximum camber of 1–3% of chord, and maximum camber position in tenths of chord was varied from 1 to 9% with an increment of 1%. The results indicate that NACA 1730 shows the least coefficient of drag about 8.345E–03 at 0° angle of attack. The preliminary calculation has shown the volume of 19.16 m3 of hydrogen gas is required to make the entire Airborne Wind Turbine (AWT) float in the air. The length of the airfoil to accommodate the volume is found to be 2.82 m. Numerical analysis of the balloon model is done using ANSYS FLUENT.