Design and Construction of H-Type Wind Turbine for Biu Community in Borno State Nigeria

 Corresponding author: C Nathan Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Design and Construction of H-Type Wind Turbine for Biu Community in Borno State Nigeria C Nathan *, AA Barnabas and PW Izuchukwu Department of Mechanical Engineering, Nigerian Army University Biu, Borno State, Nigeria. Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 Publication history: Received on 23 March 2025; revised on 06 May 2025; accepted on 09 May 2025 Article DOI: https://doi.org/10.30574/gjeta.2025.23.2.0144 Abstract The global demand for sustainable energy sources has intensified the exploration of wind energy, especially for rural and off-grid communities. This study focuses on the development of a small-scale H-Type vertical-axis wind turbine (VAWT) as a viable solution for decentralized power generation in Biu, Nigeria. The H-Type turbine was selected for its simple design, low maintenance requirements, and ability to operate efficiently in varying wind directions. Materials used for the turbine included aluminum alloy blades, a steel tower, a permanent magnet generator, and reinforced concrete foundations. The construction involved fabricating and assembling key components—rotor blades, hub, shaft, tower, and generator—followed by installation and structural testing. Performance evaluation was conducted using standard formulas for power output, tip speed ratio, and efficiency, across varying wind speeds from 3 to 7 m/s. Results indicated that the turbine operated efficiently within the target wind speed range, achieving a maximum power output of 91.5 W at 7 m/s, with the nominal design output at 46.3 W. Efficiency peaked at 150% at moderate wind speeds (4.5 m/s), showing robust performance for small-scale applications. Structural analysis confirmed that stresses on components remained well within safe operational limits, ensuring turbine durability. The study concludes that H-Type VAWTs present a promising, low-cost solution for rural electrification, with further optimization recommended to enhance performance across broader environmental conditions. Keywords: Wind Turbine; Renewable Energy; H-Type Design; Rotor Blade; Tip Speed Ratio 1. Introduction Renewable energy is vital for addressing global energy challenges, reducing reliance on fossil fuels, and supporting sustainable development. Among renewable sources, wind energy plays a significant role due to its efficiency, availability, and environmental benefits. Vertical Axis Wind Turbines (VAWTs), particularly the H-Type configuration, have emerged as a promising solution for urban and off-grid applications due to their adaptability, low maintenance requirements, and ability to capture wind from any direction [18,20]. Access to energy in Nigeria is still very alarming, especially in rural communities where conditions like those in Biu rely on inefficient sources for their energy needs, hence constraining development. The appropriate wind energy systems for such local conditions include decentralized H-Type VAWTs for reliable and sustainable energy generation [2,6]. Biu, located in Borno State, Nigeria, is situated at approximately 10°36'40" North latitude and 12°11'42" East longitude [19]. The town lies on the Biu Plateau at an average elevation of 626 meters above sea level [21]. However, some sources reported the elevation to be around 762 meters [15]. Biu's wind patterns are influenced by its topography and climate. The Harmattan season, spanning from November to February, is characterized by dry, cool winds from the northeast, providing moderate to high wind speeds suitable for wind energy generation [1]. From a meteorological perspective, it was discovered that in a year, the wind speed over Biu falls within an average range of 3 m/s to 8 m/s; sometimes gusts Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 87 rise above 10 m/s [17]. During this period, wind speeds are more stable and consistent, which enhances the operational efficiency of wind turbines. Figure 1 shows the map of Borno and Biu. Figure 1 Map Showing Borno and Biu Wind energy conversion transforms kinetic energy into mechanical and electrical energy. Vertical-axis wind turbines (VAWTs), like the H-Type, operate in turbulent and multidirectional wind conditions without yaw mechanisms, making them ideal for areas like Biu [13]. These turbines rely on aerodynamic forces, with performance influenced by parameters like blade geometry, tip-speed ratio (TSR), and power coefficient (Cp) [10]. H-Type turbines use straightbladed designs, optimized for lift-to-drag ratios, enhancing energy capture at low wind speeds [14]. Their straightbladed shape reduces manufacturing costs and streamlines construction. By producing a pressure differential between their surfaces, the airfoil-inspired blades provide lift. An efficient blade design increases energy conversion efficiency by ensuring lift surpasses drag [16]. Advances in airfoil profiles, such as NACA 2412, improve efficiency and self-starting capabilities [8]. Theoretical models, including Betz’s Law, set a maximum efficiency of 59.3%, which modern designs aim to approach through innovations in blade design and materials [5,11]. Wind turbines may be classified into two major groups: horizontal-axis wind turbines and vertical-axis wind turbines. HAWTs are the ones normally used in large-scale wind farms with blades mounted on a horizontal axis, needing a yaw mechanism for alignment with the wind direction. They are very efficient for steady, high-speed winds but are less suitable for variable or turbulent conditions, making them less ideal for decentralized applications [12]. VAWTs, of which the H-Type turbine is one, have their rotor axis perpendicular to the ground and hence do not need yaw mechanisms. With its straight blades in the shape of "H", manufacturing and maintenance of the H-Type are relatively simpler than the curved-blade designs like the Darrieus and Savonius turbines [5,16]. Table 1 shows the comparative analysis of HAWTs and VAWTs. Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 88 Table 1 Comparative Analysis of HAWTs vs. VAWTs Parameter HAWTs VAWTs (H-Type) Wind Directionality Requires yaw mechanism Operates in any wind direction Complexity High-due to yaw and pitch systems Low-no yaw mechanism needed Efficiency Higher in steady, high-speed winds Effective in turbulent or low-speed winds Maintenance Higher-much more complex systems Lower-simpler design and thus less maintenance Applications Large-scale wind farms Rural, off-grid and decentralized systems Environmental Impact Taller structures can be intrusive Lower visual and ecological footprint This study focuses on accessible and sustainable solutions to demonstrate the efficiency of an H-Type Wind Turbine for different wind conditions. It points toward its potential in rural electrification, urban use, and environmentally conscious energy production while giving insight into turbine design and performance optimization. The development of vertical-axis wind turbines took shape in the 1970s, wherein the Darrieus model patented by Georges Darrieus in 1926 emerged as one of the important designs. These turbines are characterized by their curved blades with a vertical axis of rotation and are thus independent of the direction of the wind; however, they were prone to mechanical stresses and low efficiencies at lower wind speeds [9]. Advanced material use, such as carbon fiber composites, has been employed to reduce blade weight without any reduction in the structural integrity of the blades, increasing rotational dynamics and turbine lifespan. For the structural components, aluminum alloy and galvanized steel are commonly used owing to their good strength and anti-corrosion properties [13,14]. The characteristic features of H-Type turbines include: • Straight-blade designs that can operate in multidirectional winds [7]. • Flexibility in the blade-for required power adjustment [3] • Minimal environmental impacts; low noise levels, easy to be accepted and integrated into landscapes [4]. 2. Materials and Methods The material choice is the main part of the operation, durability, and efficiency of the H-Type Wind Turbine. The list of various components, descriptions and their specifications are given in table 2 Table 2 Components, Description, and Specifications for a Small-Scale H-Type Wind Turbine Component Description Specifications Rotor Blades Converts wind energy into rotational motion using aerodynamic profiles. Length: 1.2–1.5 m; Material Thickness: 2–4 mm; Blade Angle: 12°–20°; Weight: 2–3 kg each Tower Supports the turbine at an elevated height for optimal wind capture. Height: 4–8 m; Diameter: 100–150 mm; Wall Thickness: 3–5 mm; Weight Capacity: ≥200 kg Hub/Radial Arm Connects the rotor blades to the main shaft, ensuring balanced rotation. Diameter: 150–200 mm; Weight: 5–10 kg; Bolt Holes: 3–5, depending on blade count Shaft Transfers mechanical energy from the hub to the generator. Length: 600–1000 mm; Diameter: 25–40 mm; Material Yield Strength: ≥250 MPa Generator Converts mechanical energy into electrical energy. Power Rating: 500–1000 W; Voltage Output: 12–24 V; Efficiency: ≥85%; Weight: 7–10 kg Base and Foundation Anchors the tower securely to the ground for stability. Base Area: 0.5–1 m²; Depth: 0.6–1 m; Concrete Grade: ≥25 MPa; Rebar Diameter: 12–16 mm Bearings Allows smooth and efficient rotation of the shaft and hub. Inner Diameter: 25–40 mm; Load Capacity: ≥1.5 kN; Material Hardness: 60–64 HRC Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 89 Control System Housing Protects the charge controller, inverter, and monitoring systems from the elements. Dimensions: 200 × 300 × 150 mm; Material Thickness: 3–5 mm; Ingress Protection (IP): ≥65 Cables and Connectors Transmits power from the generator to the storage or output system. Cable Diameter: 4–8 mm; Voltage Rating: 600– 1000 V; Insulation Thickness: 1–2 mm Fasteners and Bolts Secures turbine components to ensure structural integrity. Bolt Diameter: 10–20 mm; Length: 50–120 mm; Coating Thickness: ≥85 μm (galvanization) Battery Lead acid 12v 18AH/20HR Charge Controller LCD screens display charging status, battery levels, and fault alerts 20A The construction process involves the assembly of turbine components and installation on-site. Steps include: • Foundation Preparation: Laying a robust base to secure the turbine tower. • Tower Erection: Installing the tower and ensuring its alignment. • Blade and Rotor Assembly: Mounting blades to the rotor hub and ensuring balanced rotation. Figure 2 Design Model of the Blade • Generator Installation: Connecting the drivetrain to the generator. Figure 3 Turbine Setup Design Mode • Guiding Wall Integration (Optional): Installing and configuring guiding walls around the rotor to optimize airflow. • System Testing: Ensuring all components function correctly under simulated wind conditions. Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 90 2.1. Design Calculations Several key calculations are necessary to determine the turbine's performance parameters and component specifications. These include power output estimation, rotor dimensions, blade design, and structural strength. 2.1.1. Power Output The theoretical power available from wind can be calculated using the following formula: 𝑃 = 1 2 𝜌AV3Cp …………………….(1) Where: P: Power output (Watts) ρ: Air density (1.225kg/m3 at sea level) A: Swept area of the rotor (m2) V: Wind speed (m/s) Cp : Power coefficient (maximum value is 0.59, as per Betz's limit; practical values range from 0.3 to 0.4 for small-scale turbines). Formula for Swept Area The swept area of the rotor is the total area covered by the rotating blades of a wind turbine as they move through the air. It directly impacts the amount of wind energy the turbine can capture. For a Horizontal Axis Wind Turbine (HAWT) with a circular rotor: Swept Area (A) = 𝜋R2 ………………………(2) Where: R is the rotor radius (half the blade length). For a Vertical Axis Wind Turbine (VAWT) like the H-type: Swept Area (A) = 𝐻 × 𝐷 ………………..(3) Where: H: Height of the turbine blades. D: Diameter of the turbine. 2.1.2. Rotor Design The rotor's swept area is crucial for determining energy capture. It is calculated as: A= πR2 (For a Horizontal Axis Wind Turbine (HAWT) with a circular rotor) A = 𝐻 × 𝐷 (For a Vertical Axis Wind Turbine (VAWT) like the H-type) Where: R: Rotor radius (R= D/2) H: Height of the turbine blades. D: Diameter of the turbine. Blade Tip Speed Ratio (λ) The tip speed ratio is a dimensionless parameter given by: λ = 𝑤𝑅 𝑉 ……………….(4) Where: Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 91 ω: Angular velocity of the rotor (rad/s) R: Rotor radius (m) V: Wind speed (m/s) For H-Type turbines, λ typically ranges from 2 to 5 2.1.3. Blade Design The lift and drag forces on the blades are determined by the airfoil shape and angle of attack (𝛼): FL= 1 2 ρV2CLA ………………(5) FD= 1 2 ρV2CDA …………….(6) Where: FL: Lift force (N) FD: Drag force (N) CL: Lift and drag coefficients (dependent on the airfoil and α) For optimal performance, the ratio CL CD should be maximized. 2.2. Structural Load Calculations The turbine must withstand forces such as wind load and centrifugal forces: 2.2.1. Wind Load on Tower Fw= 1 2 ρAtV2Cd ………………… (7) Where: Fw: Wind force (N) At: Projected area of the tower (m2) Cd: Drag coefficient (typically 1.2 for cylindrical structures). Centrifugal Force on Blades Fc = mω2R …………….(8) Where: Fc: Centrifugal force (N) m: Mass of a blade (kg) ω: Angular velocity (rad/s) R: Rotor radius (m) These calculations help ensure the structural integrity of the turbine. 2.2.2. Structural Strength of Tower The stress (σ) on the tower is calculated using: σ = 𝑀 𝑍……………………………. (9) Where M: Bending moment caused by wind load at the base (M = Fw × h), with h = 6.4 m. Z: Section modulus of the cylindrical tower (Z = π𝑑3 32 , with d = 0.1m). 2.3. Efficiency Calculation The efficiency (η) of the wind turbine is given by: Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 92 η = Poutput Pinput × 100 ………………..(10) Where, Poutput Actual power generated by the turbine Pinput: Theoretical power available from wind 3. Results and Discussions Figure 4 illustrates the power curve, showing how the turbine generates energy under varying wind conditions. The curve demonstrates how efficiently the turbine converts available wind energy into mechanical power. Observations from testing confirm that the turbine performs optimally in the mid-range (4.5 m/s) wind speeds typical of small-scale installations. Figure 4 Graph illustrating the relationship between power out and wind speed Figure 5 compares the theoretical power and the actual power output at different wind speeds. Both theoretical and actual power outputs increase with wind speed, showing a consistent upward trend. However, the actual power output is consistently higher than the theoretical power, as seen in the blue and yellow curves. Figure 5 Graph of theoretical Power Output and Actual Power Output as functions of wind speed Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 93 Figure 6 shows the efficiency percentage at varying wind speeds. Efficiency fluctuates slightly across the range of wind speeds. The efficiency starts high (above 130%) for lower wind speeds (3.0–3.5 m/s), peaks at 4.5 m/s (150%), and then gradually decreases as wind speed increases. Figure 6 Graph of Efficiency (%) versus Wind Speed (m/s) Figure 7 provides a clear visual representation of the trends, highlighting the discrepancies between theoretical and actual performance and showing efficiency variations with wind speed. This helps identify areas for model refinement and system optimization. Theoretical power increases with wind speed, following the expected cubic relationship. Actual power output also increases with wind speed but is consistently higher than the theoretical power at all wind speeds. Efficiency is highest at lower wind speeds (over 130%) and peaks at medium wind speeds (150% at 4.5 m/s). As wind speed increases, efficiency gradually decreases, dropping to about 123% at 7.0 m/s. This decline suggests the presence of aerodynamic or mechanical losses at higher speeds. Figure 7 Graph showing the relationship between wind speed, theoretical power, actual power output, and efficiency Figure 8 shows the Stress distribution chart illustrates the operational stresses experienced by various components of the H-Type wind turbine. The stresses in all components are well below their material yield strengths, ensuring safe and reliable operation under design conditions. The blue bars show the actual stress experienced by each component while the orange bars indicate the allowable stress for each component. Global Journal of Engineering and Technology Advances, 2025, 23(02), 086-096 94 Figure 8 Stress Distribution Across Turbine Components Figure 9 shows the safety factor comparison across components. It evaluates the margin of safety for each component by comparing its operational stress to its material yield strength. All safety factors exceed the critical threshold of 1, confirming that the turbine is over-engineered for durability, even under peak wind conditions. Figure 9 Safety Factor Comparison Across Components Figure 10 and figure 11, analyzes the turbine's aerodynamic efficiency by plotting the Tip Speed Ratio (λ) against wind speed. The graph shows the relationship between wind speed (m/s) with two parameters: Tip Speed Ratio (TSR) and Power Output (W) for the H-Type wind turbine: As wind speed increases, the power output of the wind turbine grows almost linearly, which is expected due to the cubic relationship of wind power and wind speed in theoretical wind turbine performance. At lower wind speeds (e.g., 3.0 m/s), the power output is minimal (8.4 W). At higher wind speeds (e.g., 7.0 m/s), the power output significantly increases to 91.5 W. The TSR increases slightly with wind speed, stabilizing in the range of 2.5 to 3.9. This shows the turbine is operating efficiently at various wind speeds by maintaining a relatively stable TSR. A consistent TSR indicates that the rotor blades are well-designed to capture energy at different wind velocities, ensuring optimal aerodynamic performance. This analysis confirms that the turbine performs effectively across a wide range of wind speeds, delivering increasing power output while maintaining a favorable TSR. This indicates its suitability for the conditions in Biu, Nigeria, where wind speeds may vary but remain within a moderate range.