Small-sized Wind Turbine Research Articles

Dynamic analysis of a small-sized wind turbine in the Midwest of Brazil

Dynamic analysis of a small-sized wind turbine in the Midwest of Brazil

Current Trends and Innovations in Enhancing the Aerodynamic Performance of Small-Scale, Horizontal Axis Wind Turbines: A Review

Abstract Wind energy has proven to be one of the most promising resources to meet the challenges of rising clean energy demand and mitigate environmental pollution. The global new installation of wind turbines in 2022 was 77.6 GW, bringing the total installed capacity to 906 GW, documenting an astounding 9% growth in just one year (Lee and Zhao, 2023, Global Wind Report, GWEC. Global Wind Energy Council). Sizeable research continues to focus on improving wind energy conversion, safety, and capacity. However, funding allocations and research have not matched this sustained market growth observed over the last few decades. This is particularly the case for small-size wind turbines. We define small-scale wind turbines as those with an output power of 40 kW or less that can nonetheless be interconnected to provide larger power output. Thus, the paper focuses on small-scale horizontal-axis wind turbines (HAWT) with emphasis on current technology trends including data gathering, aerodynamic performance analysis of airfoils and rotors, as well as computational approaches. The paper also highlights the challenges associated with small-scale HAWTs thereby conjecturing about future research directions on the subject. The literature review suggests that small-scale HAWT wind turbines are suitable for harnessing energy in communities with limited resources where grid-supplied power is out of reach. The power coefficient of these turbines ranges from 0.2 to 0.45 which shows that it could greatly benefit from research, built on targeting these modest performance scales by using efficient airfoils, mixed airfoils, optimizing the blade geometry, shrouding the wind turbine rotor, using maximum power tracking control, etc. This review paper is an attempt to prioritize and layout strategies toward evaluating and enhancing the aerodynamic performance of small-scale HAWTs.

Assessments regarding the performances of wind turbines from the roofs of buildings

In the current energy context, wind energy remains the main renewable energy source. Greater attention should be paid to small-sized wind turbines, mounted on the roofs of buildings, for their many advantages: easy to construct, do not require additional space, easy maintenance, eliminate losses from the system and transport costs, can provide alone or in addition to energy solar, the entire energy need of buildings, etc. The present paper analyzes three models of wind turbines that can be placed on the roofs of buildings: crossflow wind turbine Banki, ridge blade turbine and aeroMINE model. The analysis refers to their constructive solutions, the working principle, the optimal design for a good power coefficient and the energy that can be obtained with these small turbines for urban applications and not only.

Orta ve Küçük Ölçekli Rüzgar Türbinlerinin Yaşam Döngüsü Boyutunda Sürdürülebilirliği: Literatür Taraması

With the growing interest in renewable energy systems, studies on the sustainability of small-scale wind turbines have been published in recent years. A literature review was conducted in this study to compile scientific studies conducted to evaluate the environmental effects of medium and small-sized wind energy systems using the life cycle assessment. Life cycle assessment is a method of evaluating the environmental sustainability of a product, process, or system that is becoming more important in the context of decisions and policies in the energy sector. The environmental effects of medium and small-sized wind turbines on the life cycle size have been investigated in this study, which looked at studies conducted since 2004. The vast majority of these studies conducted environmental sustainability assessments based solely on a few environmental impact indicators such as global warming potential. There are only a few studies that consider a wider range of environmental effects. The collection and analysis of studies examining the life cycle environmental sustainability of medium and small-scale wind turbines are important for determining the future vision of small-scale energy production systems.

Vibration damping of a vertical axis wind turbine in operating conditions

Distributed power generation technologies have been, over the years, gaining more and more attention from the industry as well as from the academia, due to the global interest in the exploitation of renewable energy sources even in urban areas. From this perspective, small size wind turbines, often with vertical axis layout and a nominal power between 1-3 kW, are being installed in urban areas on rooftops of residential, commercial, industrial buildings and even on metallic carpentry towers. As wind turbines tend to produce noise and vibrations, especially in presence of vortexes, wakes and unsteadiness, efficient devices for mitigating the vibrations transmitted to the supporting structure have to be added in order to limit the generation of stresses. Actually, the social acceptance of the installation of small wind turbines in built environment is tightly connected to the acoustic comfort for the inhabitants. The present study has been developed thanks to a joint collaboration between the Department of Engineering of the University of Perugia (Italy) and FH Technikum Wien (Austria) within the participation to the IEA Wind-Task 41: “Distributed Wind”. The work aims at mechanically characterizing the vibration damping provided by a mechanical device installed on the top of the turbine tower support. The decoupler, specifically designed for this purpose, has been tested in different conditions (in field and laboratory) and with different approaches, in order to have an overall evaluation of its performance. At first, vibrations are measured in open field in a real test case scenario with two installation arrangements: on the rooftop of a small building and on a tubular tower. Subsequently, the decoupler has been removed from its original location and tested in laboratory with external excitation from shaker.

A Study on Relationship among Blade Camber Direction and Pitch Angle and Performance of a Small Straight-Blade Darrieus Wind Turbine by Using Scale Test Model and Gurney Flap

Straight-blade Darrieus vertical axis wind turbines are used as medium and small size wind turbine because of higher power output in vertical axis wind turbine (VAWT). In our previous study, the relationship between the performance and Reynolds number based on airfoil chord length had been investigated by using small-scale test models of lift-type VAWT, and the results showed that the performance of tested wind turbine models with small diameter was clearly lower than that of the large-scale field test machine, and its performance also varies significantly with the blade pitch angle. In this study, we focused on the performance of a small-scale straight-blade Darrieus VAWT, the relationship among the blade airfoil camber direction and the pitch angle, and the performance of the small-scale VAWT was examined experimentally by using a small-scale VAWT test model with Gurney flap which was a small flat plate. Gurney flaps with its height h, as a ratio to the blade chord length c, h/c = 0.036 to 0.055, were attached to the blades of the VAWT test model, in addition, the attaching direction of the Gurney flap on the blade was examined for both inward and outward of the rotor, and the pitch angle was also examined for a range of −5 to 10 degrees. These results are discussed comparing with the result of the VAWT without Gurney flap and considering the numerical results for the single blade with/without the Gurney flap. The results showed that the performance of the tested VAWT was reversed between the inward and outward Gurney flaps around a pitch angle of 10 degrees. That is, the inward Gurney flap was superior at a pitch angle of less than 10 degrees, while the outward Gurney flap was effective at a pitch angle of more than 10 degrees. Furthermore, for the tested small-scale VAWT model, the optimum pitch angle was about 5 degrees, and the inward and shorter Gurney flap showed higher power performance of the VAWT under this pitch angle condition.

Fabrication of small size wind turbine and studying its characterization

Wind energy is one of the renewable energies. the horizontal axis wind turbine (HAWT) fabricated in Iraq Tikrit, the system operating at low speeds. The characteristics of the two and three blade turbine are comparing. the results for best performance, We found that when used three-blade increasing the output power of the system, so when using two blades, the power (314.1 W) and the number of cycles (62.1) at wind speed (6.6 m/s), and also when using three blades, the power (354.40 W) and the number of cycles (67.9) at the same Wind speed.

Dynamic modelling and thermoeconomic analysis of micro wind turbines and building integrated photovoltaic panels

During the past few years a significant effort has been performed in order to promote the use of renewable energy sources. However, one of the main barriers for a mature commercialization is due to the unpredictability of the renewable power production, mainly in case of wind and solar energy. Unfortunately, electric storage devices are often poorly profitable. Therefore, some more stable renewable energy systems must be designed. In this framework, this paper presents a novel hybrid renewable system consisting of Building Integrated PhotoVoltaic panels and small-scale Wind Turbines and double-stage heat pumps. This combination is very promising since it reduces the typical fluctuations of solar or wind systems, achieving a more stable profile of the overall power production. A detailed dynamic simulation model is developed in TRNSYS environment, including validated models for all the components and a suitable thermoeconomic analysis. A case study is implemented for a hotel building, where the space heating and cooling energy is supplied by an electrically driven reversible air-to-water Heat Pump, supplied by the electricity produced by Building Integrated PhotoVoltaic panels and Wind Turbines. the thermal energy recovered from the HP desuperheater is coupled with the thermal energy produced by a two-stage cascade cycle Heat Pump to produce domestic hot water. Results are presented in terms of hourly, monthly and yearly system performance data as well as by discussing the results of a detailed sensitivity analysis performed to detect the optimum configuration and weather zone of this hybrid renewable system. An analysis of the building envelope features is also performed, according to the nearly zero energy buildings target. Results showed that the combination of photovoltaic and wind technologies allows one to significantly enhance the stability of the renewable power production. Results also show that the use of heat pumps leads to a reduction of the primary energy demand for building space heating/cooling and domestic hot water by 30%. A payback period of about 5.2 years is obtained and the optimum configuration suggests adopting one 20 kW Wind Turbine for the selected case study. • Building integrated photovoltaic panels coupled with small size wind turbines. • Dynamic simulation model developed with TRNSYS software. • Sensitivity analysis on the building envelope features and weather zones. • Simple payback period of about 4.4 years for two 20 kW wind turbines.

Low Reynolds number effects on aerodynamic loads of a small scale wind turbine

Small-scale or scaled-down wind turbines for model experiments mostly operate in low-Reynolds-number flow. The nonlinear variations of aerodynamic coefficients with respect to the angle of attack caused by viscous effects and laminar boundary layer separation affect the wind turbine performance under these conditions. Although the vortex lattice method (VLM) is an efficient way to predict rotor performance, it tends to suffer from numerical error because nonlinear aerodynamic characteristics cannot be considered. In this study, the nonlinear vortex lattice method (NVLM) is adopted to compute the aerodynamic loads of two small-scale wind turbines. This method involves a sectional airfoil look-up table and vortex strength correction and can be applied to a wide range of operating conditions. The simulations of TU Delft and NTNU wind turbines are conducted to validate the prediction capability of numerical models by comparing predictions with the measurements. It was found that the overall results from the NVLM simulation are more accurate than the VLM results, which implies that the nonlinear aerodynamic characteristics associated with low-Reynolds-number flow should be considered to accurately assess the aerodynamic performance of small-sized wind-turbines, particularly at the low tip speed ratio at which the rotor blade may experience flow separation and dynamic stall.

Computational modelling and simulation of the feasibility of a novel dual purpose solar chimney for power generation and passive ventilation in buildings

This paper presents numerical study and analysis of a novel application of a proposed solar chimney system to help solve the problem of ventilation (thermal comfort) and energy management (inadequate power supply) of buildings in the tropics. The main objective of the study is to determine the feasibility of the proposed system vis-à-vis the airflow rate within the room for adequate ventilation and within the solar chimney for required velocity to power a small size wind turbine. The commercial Computational Fluid Dynamics package FLUENT (ANSYS WORKBENCH 14.5) was used for the simulation. The computational domain consist of a 2-D 4 × 4 m2 room and solar chimney with varying heights between 5 and 9 m and gap between 0.5 and 1 m. The solar radiation condition with solar heat flux (SHF) of between 200 and 1,000 W/m2 and ambient wind conditions of no wind and wind speed of 1.0 to 8.0 m/s were simulated. The validation of simulated results with experimental data from previous studies showed conformity with a deviation not more than 2.5%. Results showed that the room mass flow rate increased from 1.0 kg/s with no wind effect to about 30.1 kg/s with induced wind of 1.0 to 8.0 m/s. The air mass flow rate increased from about 0.57 to 0.91 kg/s at chimney height of 5 and 9 m respectively for no wind condition and SHF of 400 W/m2. The power outputs obtained from the SC with SHF of 400 W/m2 for chimney height of 5 and 9 m were 32.8 and 85.2 W/m2 respectively. The results presented helps layout and establish the fundamentals and system response to temperature and airflow of a solar chimney system used for the combined purpose of passive ventilation and power generation in a building.

Dynamic simulation, energy and economic comparison between BIPV and BIPVT collectors coupled with micro-wind turbines

The work presents a dynamic simulation and an energy and economic analysis of two different Building Integrated Solar Technologies, namely: Building Integrated PhotoVoltaic (BIPV) collectors and Building Integrated hybrid PhotoVoltaic-Thermal (BIPVT) collectors. Both systems are coupled with small size Wind Turbines (WTs), to reduce the fluctuations of power production typical of solar systems. A case study is presented, referred to a hotel building, where a reversible air-to-water Heat Pump (HP) is used for space heating and cooling, driven by the electric energy provided by PV collectors and WTs. In order to optimize the HP performance in cooling mode, thermal energy is recovered from the HP desuperheater and used to produce domestic hot water (DHW). A two-stage cascade cycle HP for DHW purposes was also investigated, as a further alternative. The systems were simulated by means of a dynamic simulation model, developed in TRNSYS. The results show that the BIPV-based system is more profitable than the BIPVT one, achieving a simple payback period of about 4.5 years; for both systems, the optimum size of the WT system, for a given area of PV collectors, was also investigated.

A ring-vortex actuator disk method for wind turbines including hub effects

Due to its robustness and simplicity, the simple actuator disk is still the most used and popular method for performance analysis of horizontal axis wind turbines. However, the hub blockage effect is generally disregarded in this approach, thus worsening the accuracy of its results. This is particularly true for small-sized wind turbines whose ratio between the hub and rotor radii can be as large as 25–30%. In order to obtain some insights onto the impact of the hub blockage-effect on the performance prediction, this paper presents a free-wake ring-vortex actuator disk method accounting for an axisymmetric hub of general shape. The fundamental concept of a uniformly loaded disk without wake rotation is adopted. In the proposed method, the flows induced by the disk and the hub are both modelled by ring sheet-vortices which are discretised through a classical panel method. An iterative solution procedure is developed to evaluate the density strength distribution of the sheets and the wake shape. To this aim, the homogeneous Dirichlet boundary condition is used for the velocity just beneath the hub sheet, while the free force condition is imposed all along the wake boundary. The latter is also required to be aligned with the overall flow field. The method is verified comparing its results with those of a Computational-Fluid-Dynamics-based approach, and of the classical axial momentum theory showing a very good agreement in both cases. Finally, some insights on the hub blockage effect are presented showing that, for a small-sized wind turbine, this effect significantly affect the flow distribution all along the blade span. In the analysed cases, the increment in the axial velocity at the disk, due to the hub blockage, goes from 20% in the hub proximity to 2% at the tip. The above values suggest that the hub blockage effect should never be disregarded in the analysis of small-sized wind turbines.

Non-linear and intelligent maximum power point tracking strategies for small size wind turbines: Performance analysis and comparison

Abstract Small scale WTs (wind turbines) are known a great interest energy feeding, especially for isolated area, and water pumping application. It is very crucial to operate a WT around its maximal efficiency in order to extract a maximum energy from the wind. To achieve this goal, various MPPT (maximum power point tracking) strategies are proposed in literature. The conventional MPPT strategies, which are considered as model based methods, are unable to accomplish this objective since their designs are always based on the plant model as well as the climatic parameters. In this context, this paper presents principle and design of two modeless methods: non-linear and intelligent strategies based on HCS method. The intelligent MPPT is implemented by using FLC (fuzzy logic control) due to its ability to cope with various problems associated with conventional methods. The principle of the presented methods is based on perturbing the rotor speed and observing its results on output power. The performances of the methods are deeply analyzed and compared in terms of mechanical power extracted, electrical energy as well as load factor. Simulation under Matlab/Simulink environment of a small-scale wind turbine (6 kW) based on SCIG (Squirrel Cage Induction Generator) under various turbulent wind speed profiles, allows proving that the intelligent MPPT presents best performances compared to the conventional HCS method.

Meta-heuristic multidisciplinary design optimization of wind turbine blades obtained from circular pipes

Aim of this paper is to present a methodology useful to optimize the geometry of the blades of a small-size wind turbine which are obtained from a circular pipe: an optimal chord distribution and airfoil sweep can be obtained with a proper cutting path. A strong reduction in manufacturing costs and time can be achieved for blades which are a critical element in wind turbine systems, especially in case of renewable plants in developing countries. An algorithm has been developed to obtain the shape of the blades and wind turbine performances are computed by the Blade-Element Method, due to its low computational simplicity; the XFoil tool has been used to compute the aerodynamic of the blades. Heuristic algorithms have been applied to obtain a feasible design solution assuring the best efficiency of the wind turbine. Also structural considerations are kept into account to provide a feasible configuration able to withstand the forces acting on the rotating blades. Results obtained suggest that an optimal design of such a kind of blades can be obtained thanks to this methodology. The mathematical framework developed for the optimization is efficient and the heuristics algorithms allow the convergence to feasible configurations. The computing time is compatible with a practical application of the method also in industries.

The effects of blade pitch angle on the performance of small-scale wind turbine in urban environments

Due to the growing importance of wind power as a clean and renewable energy source, the use of small-scale wind turbines in urban environments has increased lately. The blade pitch control is an effective method to improve the aerodynamic response of a wind turbine, usually applied to large-scale wind turbines. This study presents the effects of varied blade pitch on the aerodynamic performance of a small-size wind turbine. The blades were sketched out according to the Blade Element Moment (BEM) theory, applying the aerodynamic profile NREL-S809 and designed for a tip speed ratio of eight. To analyze the influence of the blade pitch angle on the energy conversion, a comparative study was carried out varying the pitch angle to five different values. Using the analysis of variance (ANOVA), it was possible to demonstrate that blade pitch control could be an effective method also for small-sized wind turbines. A performance chart from the results of blade pitch experiments shows that the power coefficient varies significantly when the angle changes. As conclusion, it is highlighted that an enhanced behavior could be attained by the use of a pitch angle controller resulting in a better recovery of the energy available in the wind.

Small wind turbines: A numerical study for aerodynamic performance assessment under gust conditions

Abstract In the present work, a numerical study aimed to analyse the effect of an extreme loading event on a Horizontal Axis Wind Turbine (HAWT) is performed. A 3D unsteady CFD model of the NREL Phase VI small-sized wind turbine is validated against experimental data, with the incompressible solver of ANSYS Fluent and an unstructured moving mesh strategy. Then the Extreme Operating Gust (EOG) model from IEC 61400-2 is considered as the inlet condition. The results of the aerodynamic response and of the structural ultimate check, based on the IEC guidelines, are presented for both the operating and the parked turbine, in order to underline the benefit of the safety position in terms of lower stress transferred to the critical root section.

Shape Optimization of Low Speed Wind Turbine Blades using Flexible Multibody Approach

It is proposed that the small-size wind turbines can demonstrate the innovative solution for the wind energy conversion for low speed regions. An innovative design, control, and monitoring processes require accurate and validated dynamic model of such turbines. In this investigation, the flexible multibody dynamics approach is used to extend the traditional method of dynamic modeling of small-size wind turbines. A systematic approach is developed based on Floating Frame of Reference formulation (FFR) that includes the dynamics of the flexible blades as well as the aerodynamic loads. A trade-offs procedure to optimize the airfoil geometric shape is introduced of small-size wind turbines for performance and energy conversion. The conclusion figure out the correct size as well as the most optimal airfoil shapes for small-size wind turbines suitable for low wind speed conditions.

Design and performance evaluation of hinge type pitch control system in small-size wind turbine

The present study is about pitch control system of a small wind turbine using hinge mechanism. Small wind turbines generally apply stall control method or breaking equipment over the rated wind speed by reason of price or efficiency. However we perform pitch control applying the hinge mechanism which is simpler than that of medium and large size wind turbines. The hinge mechanism is a kind of linkage. It is composed of a rotation motion part, a linear motion part and a connection part. Pitch angle is controlled by the rotation parts which are connection to blades. In order to determine relationship between the hinge links and pitch angle, kinematic analysis is performed. Also, we derive design specifications of the actuator which drives the hinge mechanism by the Jacobian analysis. Simulation using MATLAB analyses forces and velocities of the hinge type pitch control system. Finally, as applying it to a 20 kW small wind turbine, the performances are evaluated by wind tunnel test.

Dynamic modelling and experimental validation of small-size wind turbine using flexible multibody approach

The wind energy is observed as an essential and powerful energy resource for the socio-economic development. It is proposed that the small-size wind turbines can demonstrate the innovative solution for the wind energy conversion for low speed regions. An innovative design, control, and monitoring processes require accurate and validated dynamic model of such turbines. In this investigation, the flexible multibody dynamics approach is used to extend the traditional method of dynamic modeling of small-size wind turbines. A systematic approach is developed based on floating frame of reference formulation (FFR) that includes the dynamics of the flexible blades as well as the aerodynamic loads. Beam element is used to model the blade structure with variable twist angle. In order to counteract the effect of the geometric stiffening, which comes due to high speed rotations, the coupling terms in the expression of axial strain energy are taken into account. In the other hand, the circulation theory is used to calculate the pressure coefficient difference along the blade, and the generalized aerodynamic forces are established. An experimental test-rig equipped with wind generator is used for the FFR model validation. The equipment gives a maximum discharge flow of 10 (m/s) in a 500 (mm) diameter duct. The dynamic effect of the twist angle of 30 (cm) diameter of rotor blades is studied based on the measured rotor speed of the wind turbine. The comparison of experimental results and numerical solution shows a very good agreement and consequently the wind turbine model obtained is suitable for stress analysis, structural and control design. It is concluded that the FFR formulation is best suited for large rotation and small deformation problems, which coincide with the operational conditions of small-size wind energy systems.

Economics of wind energy utilisation for water pumping and CO2 mitigation potential in Niger Delta, Nigeria

ABSTRACTThe wind characteristics of six locations in Niger Delta, Nigeria, and the economics of the application of wind energy for water pumping and possible avoidable CO2 emissions through wind utilisation were examined. The wind data were measured at 10 m height and analysed using the two-parameter Weibull model. Small size wind turbines were accessed with Goulds 45J03 water pump series. The average power density, average energy density and annual energy across locations ranged between W/m2, kWh/m2 and kWh/m2/year, respectively. Bergey Excel-10 kW turbine had the lowest cost of energy and water pumping cost of $/kWh and $/m3, respectively. The annual capacity of water yield varies from 21,847 to 120,206 m3/year on a total dynamic head of 50 m. Furthermore, the annual diesel saved across the locations ranged from 1605 to 8696 l/year (17.47 to 94.67 GJ/year), while the annual averaged CO2 saved was between 4.32 and 22.93 tons/year.