Session: 41-05 Small, vertical and new concept turbines

Submission Number: 176652

Design and Analysis of 5 kW Small-Scale Horizontal Axis Wind Turbine Blade for Lighter than Air Wind Energy System in Egypt
 

Securing dependable electricity access constitutes a significant challenge in rural and remote areas, where the expansion of conventional electric grids often proves both economically and logistically impractical. In such contexts, small-scale wind turbines (SSWTs) emerge as a viable and environmentally sustainable alternative. Technological advancements have facilitated the development of "Lighter than Air" (LTA) airborne wind systems, which significantly extend the operational capabilities of SSWTs. These state-of-the-art systems elevate a small wind turbine to greater altitudes, utilising buoyant platforms—such as aerostats or blimps—to access stronger and more consistent wind currents found well above the surface. This elevation presents both a promising opportunity and a complex design challenge: to engineer a turbine capable of efficiently harnessing energy from both standard and uniquely accelerated wind patterns inherent to the LTA framework.

This study presents the design, analysis, and validation of a 5-kilowatt (kW) horizontal axis wind turbine (HAWT) blade, specifically designed for use within a lighter-than-air (LTA) airborne system. Our approach focuses on creating a durable and highly efficient blade that can perform well under diverse wind conditions, from typical ambient scenarios to accelerated flows in the LTA shell diffuser environment. The primary phase concentrated on aerofoil selection, a critical step. We carefully reviewed multiple low Reynolds-number (Re) aerofoils celebrated for their excellent aerodynamic properties, emphasising a high lift-to-drag ratio (C_l/C_d). We chose five aerofoil candidates—SG6043, SG6050, SG6051, a composite of SG6043-SG6050, and a combination of SG6043-SG6051—for comprehensive aerodynamic evaluation across different conceptual blade models. The careful selection of these aerofoils, adept at low Re values found in small-scale rotors, was vital for optimising energy capture.

The fundamental aspect of the rotor design process involved the application of the Blade Element Momentum (BEM) theory. This robust computational framework enabled a systematic resolution of various rotor design scenarios. These scenarios included a constant wind speed profile, serving as a baseline for comparison with traditional Horizontal Axis Wind Turbines (HAWTs), in addition to a novel design methodology. This innovative approach is fundamentally based on the actual wind profile along the blade length, determined by the complex flow dynamics within an ellipse-shaped Lighter Than Air (LTA) shell. This internal wind profile was previously derived and quantified through detailed Computational Fluid Dynamics (CFD) simulations, as documented in an earlier publication by the authors. Furthermore, the BEM findings were juxtaposed with results from a linearized blade analysis, providing an analogous scenario and an alternative design methodology for comparison. The primary focus of the analysis was the velocity distribution within the LTA shell, particularly at the shell throat, the constricted area where the wind turbine rotor is strategically deployed.

Following a comprehensive evaluation, the rotor combination SG6043-SG6050 was identified as the optimal choice. This particular airfoil combination was selected due to its superior structural integrity and strength at the blade root, which is critical for enduring the operational stresses prevalent in the augmented flow environment while concurrently sustaining an acceptable output power relative to the maximum power output of the SG6043 aerofoil-based turbine blade. The findings unequivocally demonstrated the aerodynamic advantage conferred by the LTA-optimised design. For the baseline constant speed wind profile, the rotor's power coefficient (C_P) was 0.44. Notably, when the design was based on the LTA wind profile, the C_P reached a value of 0.56, indicating an enhancement of nearly 27% in the maximum power coefficient for the newly designed rotor. Subsequently, the characteristic curves of the wind turbine were rigorously examined and developed using established operational procedures. These curves reflect the significant enhancement achieved by the newly investigated rotor design technique tailored for LTA wind turbines. The analysis suggests that the blade's cut-off wind speed is 20 metres per second (m/s), while the optimal Tip Speed Ratio (TSR) is 6.57. This research substantiates the viability and superior efficiency of designing SSWTs specifically to exploit the unique flow augmentation characteristics intrinsic to LTA airborne wind energy systems.

Presenting Author: Ahmed Elbaz The British University in Egypt

Presenting Author Biography: Dr Elbaz graduated in 1984 from the Energy and Automotive department at Ain Shams University. He joined the same department as a demonstrator and finished his MSc in mechanical engineering from the same department in 1987. He then joined the University of Manchester Institute of Science and Technology (UMIST) as a PhD student. He worked with one of the key scientists in turbulent flow modelling, Brian Launder, from 1987 to 1992. Having obtained his PhD, he joined Ain Shams University in 1992 as a lecturer. He stayed at Ain Shams University till 2013, when he joined the British University in Egypt as an associate professor and was promoted to full-time professor in 2015. He is working in the field of thermofluidic engineering. He has more than 40 articles and supervised more than 40 MSc and PhD students. Recently, his interest is focused on research work in the wind energy conversion systems.

Authors:

Engy Elshazly The British University in Egypt
Zhihui Ye London South Bank University
Isaa Shaer London South Bank University
Ahmed Elbaz The British University in Egypt