Small-scale Wind Turbine Research Articles

Experimental and numerical analysis of NREL S823 airfoil with auxiliary airfoil integration

ABSTRACT This study explores the potential for using an auxiliary airfoil to improve the aerodynamic characteristics of an NREL (National Renewable Energy Laboratory) S823 airfoil designed explicitly for small-scale wind turbines. The experimental investigation is carried out on a standard S823 airfoil (S823(S)) and an S823 with the inclusion of an auxiliary airfoil (S823(A)), at different angles of attacks (0º-20º) and different low wind speeds (4–10 m/s). The result shows that the S823(A) model consistently outperforms the S823(S) model in terms of lift-related metrics. It exhibited a 10% increase in CL values. Specifically, the S823(A) model achieved a maximum CL value of 1.284 at 10 m/s, which is an 8% improvement over the S823(S) model’s maximum of 1.191 at the same wind speed. Besides, the S823(A) model demonstrated superior performance in the sliding ratio, with values consistently higher by approximately 11%, 9%, 10%, and 14% at wind speeds of 4 m/s, 6 m/s, 8 m/s, and 10 m/s, respectively. Moreover, numerical simulations were carried out for both the models at similar conditions, which reveal that using an auxiliary airfoil reduces flow separation on the pressure side, along with well controlling the Turbulence Kinetic Energy (TKE) dissipation of the S823(A) model. Moreover, the airfoil flow visualization reveals that the auxiliary airfoil promotes smoother airflow separation, especially near the trailing edge of the airfoil. This reduces turbulence and improves the overall stability and controllability of the airfoil across different AoAs. Overall, the S823(A) model offers superior aerodynamic performance, improved lift-to-drag ratio, and better control characteristics across a range of angles of attack compared to the S823(S) model that improves the overall aerodynamic performance of the main airfoil.

Optimization of a hybrid renewable energy system for off-grid residential communities using numerical simulation, response surface methodology, and life cycle assessment

This paper presents an optimized hybrid renewable energy system tailored for off-grid residential communities, integrating wind, solar, and hydrogen technologies to meet electricity, cooling, heating, and water needs. The proposed optimization methodology combines numerical simulation, response surface methodology (RSM), and life cycle assessment (LCA), ensuring robust performance across diverse conditions. Key components include fuel cells, reverse osmosis systems, heat pumps, photovoltaic/thermal solar collectors, wind turbines, and hydrogen generation systems. The optimization process targets critical variables such as PVT panel area, the number of wind turbines, and fuel cell power. The optimal configuration was found to include 24 small-scale wind turbines, 159.46 m2 of PVT collectors, and 79.73 kW of fuel cell power. This configuration generated surplus electricity with net electricity usage (NEU) values of −123084.27 kWh/year in New York, −224245.29 kWh/year in Forks, and −215949.30 kWh/year in Santa Barbara. Additionally, the optimized systems achieved a significant reduction in life cycle cost (LCC), with Forks showing the lowest LCC at 304428.97 USD. The environmental impact was also minimized using the novel optimization approach, with the optimized systems achieving negative 100-year global warming potential (GWP100) values, indicating a net reduction in greenhouse gas emissions.

MPPT Optimal Torque Control Strategy for a PMSG-based Wind Turbine Emulator

A wind turbine emulator is a valuable tool, which enables real-time physical simulation of a wind turbine behavior using a dedicated experimental test setup, providing a controlled environment for research and development purposes. One significant advantage of using this tool is its ability to test control algorithms designed to maximize power extraction from the wind turbine. This paper continues previous work on developing a small-scale variable-speed wind turbine emulator based on a Permanent Magnet Synchronous Generator for stand-alone applications (Benhacine et al., 2024). This paper presents enhancements made to the emulator. These improvements facilitate the assessment of a maximum power point tracking control strategy designed to optimize power extraction from the wind turbine.

Numerical investigation of turbulent flow over a small-scale vertical axis wind turbine

The present paper aims to analyse the aerodynamics of turbulent fluid flow over a vertical axis wind turbine (VAWT). A 2D study is carried out for a two-bladed SAVONIUS wind turbine, where the rotor diameter is D=20cm. The governing equations (Unsteady Reynolds Averaged Navier Stokes URANS) are solved numerically using a CFD (computational fluid dynamics) open-source code based on the finite volume method; the SST turbulence model is applied for the system closure. An arbitrary mesh interface (AMI) technique is applied at the sliding interface boundary, which is a circular surface separating between the rotating zone and the fixed zone where the mesh remains stationary. The numerical results allow predicting the vorticity and pressure distributions over a rotating wind turbine for different tip speed ratios in order to characterize the generated wake. The velocity deficit is calculated for different positions behind the rotor to characterize the disturbance rate of the flow.

Determining Payback Period and Comparing Two Small-Scale Vertical Axis Wind Turbines Installed at the Top of Residential Buildings

In recent years, residential buildings have seen a notable increase in energy consumption. To address this, it is crucial for researchers to invest in renewable energy technologies, aiming to develop highly sustainable and nearly-zero energy buildings. Many countries are started to commit to this goal, seeking to phase out fossil fuels due to their harmful environmental effects. Wind energy stands out as a promising renewable resource, especially in areas with strong wind patterns. This study focuses on a case in Karaburun, Izmir province, Türkiye, where annual wind speeds range from 6 to 8 m/s and evaluates the performance of two types of small-scale Vertical Axis Wind Turbines (VAWTs) in reducing energy consumption in a three-story residential building, along with associated costs. Utilizing advanced simulation tools like ANSYS Fluent and DesignBuilder Software, the study examines Ice-Wind VAWTs and Savonius VAWTs. The findings reveal that installing 15 Ice-Wind VAWTs on the building's roof can reduce energy consumption by approximately 22.5%, with each turbine costing about $2000 and a payback period of around 14.57 years. Conversely, using 15 Savonius VAWTs can reduce energy consumption by 36%, with each turbine costing about $2300 and a payback period of around 8.93 years. These results indicate that the Savonius turbine offers a faster return on investment compared to the Ice-Wind turbine under the specified conditions. Overall, this study highlights the significant benefits and cost implications of integrating renewable energy solutions like VAWTs into residential buildings.

Aerodynamic analysis of a small-scale Savonius wind turbine incorporated with wind lenses: A CFD approach for wake pattern and power prediction

Aerodynamic analysis of a small-scale Savonius wind turbine incorporated with wind lenses: A CFD approach for wake pattern and power prediction

Study on novel control method for small wind – solar hybrid power system using photovoltaic cooperating system in parallel connection mode

Currently, a small-scale wind turbine can be connected to the Power Conditioning System (PCS) of the solar power system by simulating the technical characteristics of the solar panels to enhance the efficiency of the PCS on cloudy or rainy weather days. However, the working efficiency of the entire system has not been optimized because the use of traditional control techniques. P-I control has several problems of high starting overshoot, and slow response to sudden disturbances. Besides, P&O MPPT control has fluctuations in output power and slow response time at peak solar cell power due to weather effects. Therefore, this research proposes a novel control system including Artificial Neural Networks (ANN) MPPT control and digital slide mode control (DMSC) for the power conversion circuit to connect small-scale wind turbine power with the PCS of the solar power system in the parallel mode. The novel control solution in this study can minimize the disadvantages of PI control and P&O MPPT control. The study results showed that DSMC controller has better performance than the PI controller when controlling the PVCS in parallel mode with more 17.5 % power, no static error, 20 % less chattering of the power value of PVCS in the steady state, and 20 % less static error of power. Besides, the ANN MPPT controller also works better when changing solar radiation and has a harvested power of about 0.6 % higher than the power generated by the P&O MPPT controller.

Reconstructing Energy-Efficient Buildings after a Major Earthquake in Hatay, Türkiye

Türkiye’s earthquake zone, primarily located along the North Anatolian Fault, is one of the world’s most seismically active regions, frequently experiencing devastating earthquakes, such as the one in Hatay in 2023. Therefore, reconstructing energy-efficient buildings after major earthquakes enhances disaster resilience and promotes energy efficiency through retrofitting, renovation, or demolition and reconstruction. To this end, this study proposes implementing energy-efficient design solutions in dwelling units to minimize energy consumption in new buildings in Hatay, Southern Turkiye, an area affected by the 2023 earthquake. This research focused on a five-story residential building in the district of Kurtlusarımazı, incorporating small-scale Vertical-Axis Wind Turbines (VAWTs) with thin-film photovoltaic (PV) panels, along with the application of a green wall surrounding the building. ANSYS Fluent v.R2 Software was used for a numerical investigation of the small-scale IceWind turbine, and DesignBuilder Software v.6.1.0.006 was employed to simulate the baseline model and three energy-efficient design strategies. The results demonstrated that small-scale VAWTs, PV panels, and the application of a green wall reduced overall energy use by 8.5%, 18%, and 4.1%, respectively. When all strategies were combined, total energy consumption was reduced by up to 28.5%. The results of this study could guide designers in constructing innovative energy-efficient buildings following extensive demolition such as during the 2023 earthquake in Hatay, Türkiye.

Effect of rotation on achieving constant voltage in three-phase self-excited induction generator for small scale wind turbines application

Three-phase Self-Excited Induction Generators (SEIGs) are commonly employed for electricity generation in remote or isolated areas. SEIGs are preferred in such regions due to their ability to create a magnetic field by adding a capacitor to one of their terminals. Nevertheless, a significant challenge in utilizing SEIGs is maintaining a consistent output voltage in the presence of load fluctuations. This study aims to investigate the impact of generator rotation on the SEIG's output voltage and determine the optimal rotation speed required for achieving a stable output voltage. Ensuring stable voltage regulation is crucial to guarantee the proper functioning of all loads connected to the SEIG. Furthermore, operating the SEIG in parallel with other generators is advantageous. The methodology employed in this study involves varying the load supplied by the SEIG at different capacitor values. Unwanted voltage variations occur due to load fluctuations within a generating system or SEIG. Adjustments to the generator's rotation speed are made to uphold a uniform voltage level. The variables considered in this study include the generator's rotation speed, capacitor size, and load fluctuations. Simulation results demonstrate that the SEIG's output voltage is affected by the generator's rotation speed, and maintaining a consistent voltage necessitates appropriate adjustments to capacitor values and generator speed. This research enhances understanding of SEIG characteristics and offers guidance on effective settings for maintaining a stable output voltage at various generator rotation speeds. Future research can focus on practically implementing these findings to enhance the performance of SEIGs in real-world applications

Commercial Small-Scale Horizontal and Vertical Wind Turbines: A Comprehensive Review of Geometry, Materials, Costs and Performance

The effective exploitation of renewable energy sources is one of the most effective solutions to counter the energy, environmental and economic problems associated with the use of fossil fuels. Small-scale wind turbines (converting wind energy into electric energy with a power output lower than 50 kW) have received tremendous attention over the past few decades thanks to their reduced environmental impact, high efficiency, low maintenance cost, high reliability, wide wind operation range, self-starting capability at low wind speed, limited installation space, reduced dependence on grid-connected power and long transmission lines, low capital costs, as well as the possibility to be installed in some urban settings. However, there are significant challenges and drawbacks associated with this technology from many different perspectives, including the significant discrepancy between theoretical performance data provided by the manufacturers and real field operation, that need to be investigated in greater depth in order to enable a more widespread deployment of small-scale wind turbines. In this review, a complete and updated list of more than 200 commercially available small-scale horizontal and vertical wind turbine models is provided and analysed, detailing the corresponding characteristics in terms of the number and material of blades, start-up wind speed, cut-in wind speed, cut-out wind speed, survival wind speed, maximum power, noise level, rotor diameter, turbine length, tower height, and specific capital cost. In addition, several scientific papers focusing on the experimental assessment of field performance of commercially available small-scale horizontal and vertical wind turbines have been reviewed and the corresponding measured data have been compared with the rated performance derived from the manufacturers’ datasheets in order to underline the discrepancies. This review represents an opportunity for the scientific community to have a clear and up-to-date picture of small-scale horizontal as well as vertical wind turbines on the market today, with a precise summary of their geometric, performance, and economic characteristics, which can enable a more accurate and informed choice of the wind turbine to be used depending on the application. It also describes the differences between theoretical and in-situ performance, emphasizing the need for further experimental research and highlighting the direction in which future studies should be directed for more efficient design and use of building-integrated small-scale wind turbines.

The Effect of Nacelle Shape and Blade Geometry on the Performance of Small Scale Wind Turbine

The Effect of Nacelle Shape and Blade Geometry on the Performance of Small Scale Wind Turbine

Fluid-structure interaction and life prediction of small-scale damaged horizontal axis wind turbine blades

Throughout their operational lifespan and exposure to various environmental conditions, wind turbines experience diverse loading scenarios that could lead to blade cracking, affecting their structural integrity. This research focuses on analyzing the blade lifespan of two small-scale wind turbines, namely Air Silent X and Pikasola. The investigation introduces deliberate irregularities like holes, erosion, and cracks to examine their effects on blade durability. Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are used to assess aerodynamic loads, deflection, and stress levels on the blades under different wind speeds. Leveraging the fracture analysis tool within ANSYS, the study predicts blade lifespan in terms of cycles. The findings revealed that anomalies located near high-stress regions tend to reduce the lifespan of blades compared to those positioned in lower-stress areas.

Icing Wind Tunnel and Erosion Field Tests of Superhydrophobic Surfaces Caused by Femtosecond Laser Processing

Ice accumulation on lift-generating surfaces, such as rotor blades or wings, degrades aerodynamic performance and increases various risks. Active measures to counteract surface icing are energy-consuming and should be replaced by passive anti-icing surfaces. Two major categories of surface treatments—coating and structuring—already show promising results in the laboratory, but none fulfill the current industry requirements for performance and durability. In this paper, we show how femtosecond laser structuring of stainless steel (1.4301) combined with a hydrocarbon surface treatment or a vacuum treatment leads to superhydrophobic properties. The anti-ice performance was investigated in an icing wind tunnel under glaze ice conditions. Therefore, flexible steel foils were laser-structured, wettability treated and attached to NACA 0012 air foil sections. In the icing wind tunnel, hydrocarbon treated surfaces showed a 50 s ice build-up delay on the leading edge as well as a smoother ice surface compared to the reference. To demonstrate the erosion resistance of these surfaces, long-term field tests on a small-scale wind turbine were performed under alpine operating conditions. The results showed only minor erosion wear of micro- and nano-structures after a period of six winter months.

Evaluation of a Savonius wind turbine in the vicinity of a circular cross-sectional building

Today's urban areas are filled with tall buildings that require significant energy. To enable the implementation of small-scale wind turbines for dispersed electricity generation in cities, it is crucial to evaluate their performance in close proximity to buildings. This study aims to assess the performance of conventional Savonius rotors near a circular cross-sectional building for the first time. The performance of a Savonius wind rotor is being studied at different installation angles (30°, 45°, 60°, and 90°) with a constant non-dimensional gap space (S/D) of 2.0 between the rotor center and building envelope under a constant free-wind speed of 6 m/s. Two possible wind rotor rotation scenarios, inward and outward, are thoroughly tested and studied. Computations are carried out for tip speed ratios (TSR) of 0.4, 0.8, and 1.2. The obtained results are successfully validated for both the Savonius rotor in the free-wind flow (without a building) and a circular cross-sectional building (without a wind rotor) as well. The results show that installing a Savonius rotor at angles of 60° and 90° provides the maximum power coefficient based on the TSR. In contrast, placing the rotor at 30° reduces its performance even more than the reference case. For optimal rotor angles, inward rotation is preferred over outward rotation regardless of the TSR. Finally, there are improvements of 208.72 %–439.95 % compared to the reference case for 60° and 90° under inward rotation.

Comparative study of passive magnetic bearing using four ring magnets: a critical review

Researchers on reducing energy losses caused by friction in small-scale wind turbines. This is crucial because a significant amount of energy is wasted due to friction in the main roller bearing. In order to overcome this, the concept of levitation has gained popularity. Levitation is achieved by employing the repelling forces between two opposing poles of a permanent magnet (PM), significantly reducing friction between the turbine stator and rotor. As a result, the overall energy production of the turbine increases. The use of passive permanent magnet bearings has several disadvantages, such as limited load-bearing capacity and rigidity. To address these limitations, we conducted numerical studies on four different configurations in order to enhance load-bearing capacity and stiffness. The results showed that the radial configuration outperformed the axial-type configuration in terms of stiffness and load-bearing capabilities in all four arrangements. Furthermore, it was revealed that radial passive magnetic bearings with adequate air gaps are not only more efficient but also less expensive than employing iron cores at the rear and between ring magnets for small-scale wind turbines.

Dragonfly-Inspired Blades for high Aerodynamic Performance small Horizontal Axis Wind Turbine

Inspired from the fascinating realm of Dragonfly features, this study intricately investigates the aerodynamic performance of a distinctive 1 m diameter small-scale Horizontal Axis Wind Turbine characterized by a unique bio-inspired tandem-blades configuration. Based on experimental wind tunnel tests and computational fluid dynamics simulations, the turbine performance is explored at different Tip Speed Ratios (TSRs). Remarkably, the bio-inspired turbine exhibits exceptional traits, achieving a notable peak power coefficient of approximately 0.35 at a low TSR of 3. A detailed investigation includes thorough analyses of pressure contours, relative velocity distributions, and individual blade contributions, revealing unique dynamics within the tandem configuration. The fore blade notably prevails in extracting wind energy, showcasing superior performance. While the hind blade influence in enhancing the fore blade efficiency emerges, underscoring the role of blade interactions in this bio-inspired designs. This study contributes significantly to the comprehension of the new design dragonfly-inspired wind turbine aerodynamics.

Enhancing Power Output of Ducted Wind Turbines through Flow Control

This study focuses on the performance enhancement of a ducted small-scale National Renewable Energy Laboratory (NREL) Phase VI wind turbine, utilizing a Wind Lens diffuser. The investigation is conducted at the critical cut-in wind speed of 5 m/s. The research evaluates the integration of passive flow control devices, including Vortex Generators, Microtab, and Slot, strategically positioned across the Wind Lens to augment the mass flow through the rotor. The results indicate significant amplifications in the turbine output of up to 127%, attributable to airflow manipulation across the diffuser, resulting in increased torque and power output. The study highlights the effectiveness of employed flow control devices in managing turbulence and/or flow separation, thereby enhancing aerodynamics, particularly under low wind conditions. A comprehensive analysis of various parameters such as pressure and flow fields, turbulence, and other relevant metrics is conducted to ascertain their collective influence on rotor aerodynamics. The results demonstrate the potential of these passive flow control devices in advancing small-scale wind turbine technology, especially in regions with low wind potential. Moreover, the design simplicity and cost-effectiveness of these passive flow control devices suggest wider applicability in the renewable energy sector, contributing to the reduction of carbon-intensive energy reliance.

Aerodynamic performance and starting torque enhancement of small-scale Darrieus type straight-bladed vertical axis wind turbines with J-shaped airfoil

Wind energy is one of the most eminent renewable sources for the generation of power. The increasing enthusiasm toward the advancement of small-scale Darrieus type straight-bladed vertical axis wind turbines (SB-VAWTs) can offer a potential remedy for addressing power shortage and the unpredictability of climate conditions. These particular wind turbines provide distinct advantages over their counterparts due to their linear blade design and uncomplicated structure. However, enhancements are required in their aerodynamic efficiency and self-initiation capabilities. These challenges stem from using traditional straight blade configurations and symmetrical airfoils. By substituting these conventional elements with J-shaped straight blades and along with cambered airfoils, these issues can be effectively overcome. The current study aims to investigate the effect of J-shaped straight blades with a series of cambered airfoils to improve the aerodynamic performance and starting torque of small-scale Darrieus type SB-VAWTs. Therefore, experimental and numerical studies are conducted to analyze the J-shaped airfoil impact with various opening ratios systematically. The J-shaped blade profile is designed by eliminating some portion toward the trailing edge of a conventional airfoil. This analysis demonstrated that the J-shaped blade incorporating a cambered NACA 4418 airfoil outperforms its alternative cambered airfoil designs. The performance of SB-VAWT improves by about 25% by the J-shape of the cambered NACA 4418 airfoil with a 70% opening ratio. Moreover, the use of J-shaped airfoils enhances the self-starting torque of SB-VAWT compared to conventional airfoils.

Assessment of small-scale wind turbines for domestic use in different situations

Assessment of small-scale wind turbines for domestic use in different situations

Innovative Compact Twin Whirly Bird-based Wind Turbine: A Sustainable Solution for EV Charging Infrastructure

The global adoption of whirly bird vent roofs across various industries underscores their utility in harnessing wind energy for cooling purposes within warehouses and similar environments. The innovation proposed in the current study builds upon this established technology by integrating semi-perpetual motion principles into a compact twin whirly bird-inspired wind turbine design. This novel approach aims to enhance power generation efficiency, thereby offering a sustainable solution for energy production. The compact twin whirly bird turbine concept represents a significant advancement, particularly in the context of powering electric vehicle (EV) chargers. As the demand for EVs continues to surge, concerns persist regarding the availability of charging infrastructure. By integrating the proposed innovative wind turbine technology into the EV charging ecosystem, we address this critical issue while simultaneously promoting the adoption of renewable energy sources. The key to our proposal is the deployment of small-scale wind turbines in diverse public locations, thereby democratizing access to clean energy generation. Unlike conventional large-scale wind turbines, our whirly bird-inspired turbines boast versatility in installation, akin to streetlamps, facilitating widespread deployment across urban landscapes. While these turbines may yield comparatively modest power outputs relative to megawatt-scale counterparts, their strategic placement ensures a decentralized network capable of powering EV charging stations. In summary, our research presents a compelling solution that bridges the gap between EV charging infrastructure availability and the utilization of renewable energy sources. By leveraging the inherent advantages of whirly bird-inspired wind turbines, we offer a practical pathway towards sustainable energy provision in public spaces, thereby facilitating the widespread adoption of electric vehicles.