Design parameters of a lighter than air wind energy system and its applicability in Egypt

• The Ellipse-based shell with 40 % thickness can offer a reduction in the shell's dimensions and surface area compared to the airfoil-based shell, in addition to increasing the wind velocity by 1.32, which gives the best results for a 5 kW LTA system design. • Average wind velocity at the shell throat of the ellipse shape with 40 % thickness is 32 % higher than the free stream wind speed compared to 35 % for Eppler 863 and 40 % for NACA 9430. • The annual energy yield of the ellipse-based shell is 278 % of that of the bare turbine at the new minya location in egypt. • Considering the difficulties associated with realising the cambered airfoil shape by shell inflation and the large chord/throat diameter ratio required, the ellipse shape is recommended for LTA system applications. The Lighter-than-Air wind system (LTA) is an innovative approach to wind energy harvesting using buoyant structures to capture stronger and more consistent wind currents at elevated heights. This research focuses on optimizing shell shape for these systems by comparing different designs based on payload capacity. This study evaluates two airfoil shell forms, symmetric and cambered airfoils, against a 40 % thickness ellipse-based shell. The analysis employs a 5-kW wind turbine model as a case study, incorporating payload assessments and computational fluid dynamics (CFD) simulations to evaluate each design flow acceleration rate. The ERA5 reanalysis utilized wind speed data to assess the energy yields at various altitudes in rural areas in Egypt. The results indicate that the maximum air velocity at the throat of the elliptical shell was 132 % higher than the free stream velocity. Compared to a turbine without a shell at 50 m height, the ellipse-based shell at 150 m altitude increased the annual energy generation by over 67 %. The NACA 9030 airfoil showed a 10 % increase over the ellipse-based shell and a 6 % improvement over the Eppler 863 shell. The critical wind speed for the drag-to-buoyancy behavior transition of the full-scale elliptical model increased to 35 m/s, surpassing the NACA 9430 shell, which occurs at 23 m/s. Additionally, the elliptical shell allows for a 15 % reduction in chord length compared to the NACA 9030 shell. These findings demonstrate the potential of LTA wind systems, particularly those using ellipse-based shells, to improve wind energy harvesting efficiency and reduce material costs.