Conventional Wind Turbine Research Articles

Influence of Tip Speed Ratio on the efficiency of Savonius wind turbine with deformable blades

Improving machines efficiency and searching for their new applications are the main topics in the development of the renewable energy industry. In the case of Savonius type wind turbines, the works aim at the improvement of aerodynamic performance. The CFD simulations of a turbine equipped with deformable blades showed a significant positive impact of this enhancement on the machine aerodynamic efficiency. Previously, the investigation was carried out for a TSR (Tip Speed Ratio) equal to 0.8, typically recognized as the point of maximal efficiency for conventional Savonius wind turbines with rigid blades. However, the continuously altering shape of blades during their rotation can influence the optimal TSR. Therefore, the efficiency of the deformable blade turbine was investigated in a wide range of TSR. In this paper, the previously developed quasi-2D model with a two-way Fluid-Structure Interaction method was employed to obtain turbine efficiency characteristics as a function of TSR. The maximum power coefficient Cp was achieved at TSR = 0.9. Obtained characteristic was compared with data for a conventional rigid blades turbine, gathered with a comparable sliding mesh model.

Integrated dynamic analysis of a spar floating wind turbine with a hydraulic drivetrain

Conventional drivetrains with gearbox failures are associated with major downtime in offshore wind turbines. This impacts the maintenance cost and cost of energy. A hydraulic transmission eliminates the need for gearbox and potentially improves the turbine reliability. This paper explores the application of a novel high-pressure transmission machinery to a utility-scale spar floating wind turbine. We present a dynamic model of a hydraulic system consisting of a hydraulic pump, pipelines, a hydraulic motor, and an induction generator. The motor is placed inside the spar platform and operates at a fixed displacement. The hydraulic system is coupled with the aero-hydro-elastic code HAWC2 through an external dynamic link library. The dynamic responses of a 5 MW spar floating wind turbine and a land-based reference wind turbine with this hydraulic system were investigated under various wind and wave conditions. A comparison is made between the characteristics of the two wind turbines under operational conditions and both turbines show decent behaviors, and the statistics of power generation is at the same level compared to that of conventional wind turbines. Through simulation studies, we verify the feasibility and the engineering practice of the proposed hydraulic drive solution to floating wind turbines.

Assessment of the Black Sea High-Altitude Wind Energy

Airborne wind energy systems (AWESs) represent a novel idea that aims to gather energy from stronger winds aloft while operating at altitudes above conventional wind turbines (WTs). For this study, we examined the wind resources at a height of 100 m available for traditional wind turbines with aerial wind energy technologies, in addition to the wind potential at higher altitudes up to 500 m. The considered period was 20 years from January 2002 to December 2020, and the data were extracted from the ERA5 reanalysis database. We studied the possibility of placing 500 kW and 5 MW airborne systems in the Black Sea and the Azov Sea and compared them with a conventional turbine. As expected, the western part of the Black Sea presented the best results, both for the 500 kW airborne system with an annual energy production (AEP) of 2.39 GWh and a capacity factor of 55%, and for the 5 MW airborne system, which has an annual electricity production of 15.81 GWh and a capacity factor of 36%. Better results were recorded for the Sea of Azov for both the 500 kW and the 5 MW airborne systems, with an AEP of 2.5 and 15.81 GWh and a capacity factor of 58% and 36%, respectively.

Climate emergency-focused economic model

This paper deals with the existing carbon dioxide mitigation efforts toward the Paris agreement and shows that current economic rules and the first law of thermodynamics, all of which are linear, are necessary but not sufficient tools to solve the nonlinear problems of global warming. In this respect, the quasi-linear, Pareto principle-based green economy has been modified by the second law of thermodynamics, which deals with the useful work potential of energy systems and resources for added value in society, aka exergy. It is argued that the aged Pareto principle, which may only associate with the first law of thermodynamics, recognizes less than half of the total root causes of emissions. For example, fossil fuels are currently treated as a simple economic commodity in the stock market, subject to market rules rather than environmental parameters, whereas exergy destructions are the primary root causes of emissions. A new model was developed for evaluating and rating green energy systems, which calculates the exergy destruction-based emissions and optimizes systems for minimum emissions. Five cases are presented to quantify the face value of the Pareto principle against renewable energy resources and systems. These cases are, namely, solar energy, wind energy, geothermal energy with organic Rankine cycle, heat pumps, and Fresnel lenses for photovoltaic panels. Sample results show that the Pareto principle may not rate these systems because its equivalent unit exergy value (0.21 kWh/kWh), also described as virtual Pareto temperature (363.9 K), is less than the unit exergy of renewable energy systems under their normal domain of operations. One of these results regarding wind energy is that the 80/20 Pareto principle has equivalent unit exergy of 0.21 kW hexergy/kW henergy, corresponding to a wind velocity of three meters per second, which is less than the practical cut-in speed of a conventional wind turbine. Therefore, the Pareto principle may not be a measuring stick for wind energy and other resources. It has also been shown why the global average of rational exergy management efficiency of 0.21 is not improving because the Pareto principle limits it.

On the feasibility of a flexible foil with passive heave to extract energy from low wind speeds

We explore numerically and theoretically the capability of flexible foils elastically mounted to translational springs and dampers at the leading edge to extract energy from low-speed winds through its passive heave motion. Given the spring and foil stiffnesses, for each damper constant the theory (which is valid for high Reynolds numbers and small foil deflection amplitudes, i.e., in absence of separation) provides analytically a minimum wind velocity for flutter instability, above which energy can be harvested, that depends on the thickness-to-chord-length ratio of the foil. Simple analytical expressions for the flutter frequency are also provided. Minimum wind speeds and corresponding flutter frequencies are characterized for a carbon fiber foil as the spring stiffness and damper constant are varied, finding that energy can be extracted from wind speeds lower than in conventional wind turbines. These theoretical predictions are assessed from full numerical simulations at Reynolds numbers corresponding to these wind velocities and for chord lengths of the order of the meter (i.e. about 106) using appropriate turbulence models, which allow to compute the power extracted from the wind that the flutter stability analysis cannot provide.

Development of A Small-Scale Vortex-Induced Wind Turbine

Over the last several years, there has been a significant and encouraging interest in the generation of power from wind. However, a massive wind turbine can only operate in a high wind speed condition. The vortex bladeless wind turbine is a completely new idea in wind turbines with a different mode of operation. It is designed to operate in low wind conditions, making it an ideal choice for areas with such conditions, such as Malaysia. This study aims to develop and evaluate a functional prototype of a vortex bladeless wind turbine that can be used to harvest wind energy in a low wind speed condition. A vortexbladeless wind turbine is fabricated based on existing research on the principle of the vortex shedding phenomenon. It is built in a cylindrical shape with an approximately 2 m height measuring from the base to the top of the mast and 0.2 m in diameter. The structure of a bladeless wind turbine is a flexible cylindrical mast over the setup that captures potential forms of energy from moving airstreams and uses a vortex induced vibration (VIV) mechanism to produce vibration in the structure. The testing wasdone by using a wind tunnel’s exhaust that produced 1 m/s to 10 m/s of air flow, which simulates a low-to-medium wind speed condition. The vibration is turned into electrical energy, using a power generating system like an electromagnetic induction mechanism. The analysis of the results is based on numerous data points gathered during the testing, including the frequency of oscillation, vortex shedding, natural frequency, and resonance parameter. Through the investigation, the results show that the phenomena of induced vibration were working at even critically low speeds, which starts at 3.3 m/s, where standard and conventional wind turbines may fail to produce the desired outcomes as they are outside of their operating windspeed. The frequency of vortex shedding increases with windspeed, from 0.94 Hz at 1 m/s to 9.39 Hz at 10 m/s. On this basis, it is confirmed that the prototype of the vortex bladeless wind turbine is working properly in harvesting wind energy, though several improvements need to be made.

An overview of aerodynamic performance analysis of vertical axis wind turbines

In this paper, an attempt has been made to highlight major developments of vertical axis wind turbines (VAWTs) in the last few decades. The effects of various design parameters such as airfoil, number of blades, solidity, aspect ratio, blade helicity, and overlap ratio have been critically analyzed. Wind energy is the most promising renewable, cost-effective, efficient, and accessible source for both domestic and commercial applications. Horizontal axis wind turbines are highly developed and are being used for medium-to-large scale power projects. VAWT are considered viable options for urban and semi-urban areas. These turbines have several characteristics, such as omnidirectional, power generation in weak and unstable winds, esthetically sound, safety, and low noise. Darrieus turbines with a fixed blade-type have starting problems at low wind speeds. Savonius turbines have good starting capability; however, their power coefficients are lower than other types of VAWT. To overcome the shortcomings of conventional wind turbines, an innovative engineering solution was sought in the design of hybrid VAWT. The analysis revealed that hybrid wind turbines have addressed the deficiencies to an extent; however, the overall performance is still less than that of conventional wind turbines. Several recommendations have been made based on state-of-the-art information from the perspective of future studies and acceptability. It was concluded that vast opportunities for wind turbine applications are available in urban areas; however, further academic research is required on critical aspects such as self-starting at low wind speeds, efficiency, structural reliability, design improvement for aerodynamic performance, and wind resource assessment.

Design of Solar Panel as Wind Turbine Blades

Abstract: The purpose of this system is to generate the green energy by using wind and solar technology. In conventional wind turbines friction losses due to bearings are more which affect the performance of the turbine. To reduce this friction loss we implement the concept of magnetic levitation in our project. We fabricate Hybrid wind Turbine which produces electricity on the principle of faradays law produced can be Stored of electromagnetic induction as well as solar technology. The electricity can be stored continuously for whole day. Keywords: Hybridized Power Generation, PV cells, Renewable energy systems.

Solar coupled Vortex Bladeless Wind Turbine system with BESS in rural electrification

In the future, the generation of electricity will be based on renewable energy source (RES). Due to natural calamities, the power generation from the wind and solar system is unstable. To maintain the system’s stability, the hybrid RES is preferred due to its efficient operation. Solar PV and conventional wind plants are costly, and they occupy more space. To overcome these problems, the wind energy conversion system (WECS) was used in the conventional system. Vortex Bladeless Wind Turbine (VBWT) is used in the place of WECS. In this work, VBWT is designed and incorporated with PV to provide uninterrupted power. Unlike conventional wind turbine, VBWT operates without blades. The cost of the system is 1/3rd of the conventional wind system. Also, the PV module is used with Maximum Power Point Tracking (MPPT) in each array on the system using PSO to operate efficiently. In this work, rural area electrification is considered and it is operated by combining the VBWT and the PV system.

Electricity Generation by Vertical Axis Turbine

Abstract: Wind energy is the kinetic energy associated with movement of large masses of air. These motions result from uneven heating of atmosphere by sun creating temperature, density, pressure differences. It is an indirect form of solar energy The device used to convert kinetic energy of wind into electrical power is called a wind turbine. Vertical Axis wind power generators, represent a very promising future for wind power generation. In present study an attempt is made to utilize at low velocity wind below 4m/s for useful power generation using magnetic levitation for vertical axis wind turbine (VAWT) termed as Maglev turbine. A single large Maglev turbine can give output more than conventional horizontal axis wind turbine (HAWT). The rotor that is designed to harness enough air to rotate the shaft at low and high wind speeds while keeping the center of mass closer to the base of yielding stability due to Maglev effect. The efficiency of turbine is increased by replacing the conventional bearings by magnets in repulsion; the magnetic levitation helps the turbine to spin at much faster rate as it eliminates the stresses on the shaft of turbine. The major components are placed at the ground level which ensures the safety of turbine.

Surface impacts of large offshore wind farms

Future offshore wind farms around the world will be built with wind turbines of size and capacity never seen before (with diameter and hub height exceeding 150 and 100 m, respectively, and rated power exceeding 10 MW). Their potential impacts at the surface have not yet been studied. Here we conduct high-resolution numerical simulations using a mesoscale model with a wind farm parameterization and compare scenarios with and without offshore wind farms equipped with these ‘extreme-scale’ wind turbines. Wind speed, turbulence, friction velocity, and sensible heat fluxes are slightly reduced at the surface, like with conventional wind turbines. But, while the warming found below the rotor in stable atmospheric conditions extends to the surface with conventional wind turbines, with extreme-scale ones it does not reach the surface, where instead minimal cooling is found. Overall, the surface meteorological impacts of large offshore wind farms equipped with extreme-scale turbines are statistically significant but negligible in magnitude.

Experimental and Numerical Investigation to Assess the Performance of Helical Bach Vertical Axis Wind Turbine at Low Wind Velocity Conditions

Abstract Many turbine models have been evolved to ameliorate the functioning of the small wind energy system. The newly developed helical Bach-type vertical axis wind turbine (VAWT) is used in this analysis with an idea to improve the overall performance. The shape of the conventional Bach-type vertical axis wind turbine is a modified form of a Savonius model which has both circular and straight portions to the blade profile. The simple Bach model has a maximum coefficient of performance corresponding to the blade arc angle of 45 deg and 225 deg. However, it consists of negative torque at the rotational angles of about 120–180 deg and 300–360 deg. Moreover, in the newly developed helical Bach, rotors can reduce the variation in torque in the rotational cycle; thereby, uniform torque is achieved in all angular position with improved performance. In this paper, experiments were conducted in the natural wind at Wind Turbine Research Station, Kayathar, Tamil Nadu, India. In addition to experimental work, the three-dimensional steady-state numerical investigations have been performed in the helical Bach vertical axis wind turbine. It is found that the numerical results are well matched with the experimental data. Based on the above computational study, it is found that helical Bach models have an increase in overall performance compared to the conventional Bach models and helical Savonius model.

Multi-Objective Optimization of Lobed Enclosure for Wind Turbine Applications Using Gray Relation Analysis

Abstract Lobed mixer wind turbines have the lobed mixer added around the turbine, enhancing the wind power compared to conventional wind turbines. This article aims to design a bare lobed mixer that satisfies the multi-objectives of maximizing average throat (where the turbine blades are fixed) velocity uavg and minimizing drag coefficient Cd. The objectives are set considering that a bare enclosure with a higher uavg will produce higher power output when the turbine is included. Numerical simulations were performed to understand the flow characteristics of the non-lobed and lobed enclosure using ansys fluent. The lobed mixer angle was varied using a one factor at a time (OFAT) approach, and the angle with the highest uavg/Cd was found. Then, by fixing the lobed mixer angle, multi-objective gray relation analysis (GRA) was used to optimize the lobed mixer’s three geometrical parameters, such as the number of lobes, lobe width, and lobe height simultaneously. The GRA results show that lobe height is the most significant parameter affecting throat velocity and drag coefficient, and the optimum combination which fulfills both objectives were found. The most significant lobe height was further analyzed to improve uavg using the OFAT approach. Then in the optimized enclosure, the plug/center body was included at the axis, and the performance of two different plug geometries was compared. NACA 0024 was found to be better plug cross section. Thus, the proposed design of lobed enclosure helps to enhance the average velocity as 1.76 times the freestream velocity and reduce the drag coefficient by 5.43% than the case without lobes. Hence lobed mixer is a better option to use as an enclosure, especially to reduce the drag forces.

Robust adaptive direct speed control of PMSG-based airborne wind energy system using FCS-MPC method

Electricity generation using airborne wind energy system (AWES) tends to be more efficient than that of conventional wind turbines due to their ability at extracting higher speeds from wind at higher altitudes by the tethered kite generator system (TKGS). The speed regulation of a permanent synchronous machine (PMSM) attached to a kite to maximize harvested power from wind is the topic of the present research. To track the optimal speed produced by TKGS, a finite-control-set model predictive control (FCS-MPC) with a new cost function is directly employed to generate appropriate gate signals for a 3-level neutral point clamped (3-L NPC) inverter that drives a PMSM. A novel adaptive algorithm is also provided for adjusting the weight coefficients of the cost function to improve the system’s performance across a wider range of change in the operating conditions. Moreover, a terminal sliding mode disturbance observer (TSMDO) is designed to estimate the load torque. A terminal sliding mode speed controller (TSMSC) is also used to produce the current reference for the optimizing algorithm in FCS-MPC. The proposed control scheme eliminates the need for a cascade structure while significantly reduces current deformation and torque oscillations. Additionally, the controller operates as fast as a traditional direct speed controller without the use of a cascade structure and is more robust against parameter uncertainties. To illustrate the success of the suggested controller, the results of simulations are presented in MATLAB/SIMULINK® software. The performance of the proposed technique is evaluated in three situations which simulates a grid-connected PMSM fed by a back to back 3-L NPC. In the first scenario, it is demonstrated that the suggested technique performs well when the system’s operational conditions vary. The performance of the adaptive tuning mechanism of the cost function weight factors is investigated in the second scenario, which takes into account model parameter uncertainty. The impacts of the disturbance observer (DO) on the system performance are explored in the final scenario, and it is discovered that the disturbance observer may increase the speed response and DC link voltage tracking performance. All of the simulation results show that the new technique outperformed the traditional FSC-MPC.

Design and Fabrication of Windmill by Using Maglev Technology

Renewable energy is electricity produces from sources, such as wind, solar, geothermal and various forms of biomass. The popularity of renewable energy has experienced with a significant upsurge in recent times due to the exhaustion of conventional power generation methods and increasing realization of its adverse effects on the environment. Bases on research, it is estimated that renewable sources might contribute about 20% – 50% to energy consumption in the latter part of the 21st century. Worldwide there is now over two hundred thousand wind turbines operating with a total name plate capacity of 432,000 MW as of end 2015.Unlike the traditional horizontal axis wind turbine, this design is levitated via Maglev (magnetic levitation) vertically on a rotor shaft. It serves as an efficient replacement for ball bearings used on the conventional wind turbine and is usually implemented with permanent magnets. This levitation will be used between the rotating shaft of the turbine blades and the base of the whole wind turbine system. It does not need to vast spaces required by more conventional wind turbines.

Structural Design of Wind Turbine Blades with an Additively Manufactured Graded Lattice Core using Topology Optimisation

Conventional wind turbine blade manufacture relies on large, expensive moulds. Instead, using additive manufacturing to print the internal structure of blades, upon which it would be possible to lay composite plies, could significantly reduce manufacturing costs and, as one could “3D print” topologically optimal designs, improve structural efficiency. In general, topology optimisation integrates well with additive manufacturing. There are, however, two main challenges associated with the adoption of topology optimisation in wind blade design, i.e. accounting for: (i) the aeroelastic response of blades; and (ii) the variety of different materials that would be employed, in the composite laminates as well as the printed structure. To address these challenges, the present paper proposes a new multi-step design and optimisation framework relying on the combination of three software. First, a conventional aero-servo-elastic model is used to evaluate blade loads and displacements. Next, a topology optimisation software is used to optimise the blade laminates and core structure. Third, a lattice generator is used to convert the topological optimised “grey” design into an equivalent cellular design that can be printed using additive manufacturing. The full methodology of this design framework and an initial proof-of-concept topology optimisation solution are presented in this paper.

Design Guidelines for Deployable Wind Turbines for Defense and Disaster Response Missions

Access to on-site electrical energy is critical to ensuring a successful military or humanitarian response to conflicts and disasters. These missions typically rely on access to liquid fuel that could be vulnerable to disruption or attack during transport. Generating power on location with wind technology—whether at a contingency base or disaster response coordination point—can reduce this risk and enhance mission reach by diversifying energy sources. Common characteristics of these missions are short planning and execution time horizons and a global scope of potential locations. Compared to conventional wind turbine applications, defense and disaster response applications place a premium on rapid shipping and installation, short-duration operation (days to months), and quick teardown upon mission completion. These design drivers depart from features found in conventional distributed wind turbines, thus necessitating unique design guidance. The supporting information for this guidance comes from available relevant references, technical analyses, and input from industry and military stakeholders. This paper serves as a summary of the full report, Design Guidelines for Deployable Wind Turbines for Military Operational Energy Applications (Sandia report SAND2021-14581 R [1]), which presents the best currently available design guidance for deployable wind turbines to facilitate the effective development and acquisition of technology solutions to support mission success.

Design and Review of Spiral Wind Turbine

The present study emphases on “Generation of power using spiral wind turbine”. The function of wind turbine is to convert wind energy into mechanical energy and then generator converts mechanical energy into electrical energy. The study specifically about the size and dimensional parameter that need to be considered while designing spiral wind turbine and also about making the turbine more energy efficient than conventional wind turbine, and to overcome all possible drawbacks of conventional turbine.

Aerodynamic Performance and Wake Flow of Crosswind Kite Power Systems

This paper presents some results from a computational fluid dynamics (CFD) model of a multi-megawatt crosswind kite spinning on a circular path in a straight downwind configuration. The unsteady Reynolds averaged Navier-Stokes equations closed by the k−ω SST turbulence model are solved in the three-dimensional space using ANSYS Fluent. The flow behaviour is examined at the rotation plane, and the overall (or global) induction factor is obtained by getting the weighted average of induction factors on multiple annuli over the swept area. The wake flow behaviour is also discussed in some details using velocity and pressure contour plots. In addition to the CFD model, an analytical model for calculating the average flow velocity and radii of the annular wake downstream of the kite is developed. The model is formulated based on the widely-used Jensen’s model which was developed for conventional wind turbines, and thus has a simple form. Expressions for the dimensionless wake flow velocity and wake radii are obtained by assuming self-similarity of flow velocity and linear wake expansion. Comparisons are made between numerical results from the analytical model and those from the CFD simulation. The level of agreement was found to be reasonably good. Such computational and analytical models are indispensable for kite farm layout design and optimization, where aerodynamic interactions between kites should be considered.

Optimisation of H-Darrieus VAWT Solidity for Energy Extraction in Cooling Tower Exhaust Systems

The technologies surrounding renewable energy have been receiving surmountable attention to producing clean energy and reducing the dependency on depleting fossil fuel sources. In this context, research investigations on vertical axis wind turbines (VAWT) in free stream flow condition has been extensively conducted to improve the energy extraction efficiency from the wind. VAWTs are particularly advantageous in locations not suitable for conventional horizontal axis wind turbines (HAWT). However, the applications of VAWTs are still limited due to their lower performances compared to their counterparts. Furthermore, the wind energy extraction problem is more prominent in urban areas with unpredictable and inadequate wind speed conditions. The present study focuses on an alternative way to harness wind energy from unnatural sources such as cooling tower exhaust systems with the reliable and consistent exhaust air. A three-dimensional numerical study has been conducted to investigate the performance of a 3-bladed H-Darrieus wind turbine (HDWT) using S-1046 airfoils of four different solidities under accelerated wind conditions of a cooling tower. The HDWT model is positioned at the cooling tower outlet, where it rotates using sliding mesh to measure the power output. Shear stress transport (SST) k- turbulence model solver was used to solve the implicit unsteady Reynolds-Averaged Navier-Stokes equations. It is observed that the higher solidity HDWT reached peak power coefficient at a lower tip speed ratio (TSR). In contrast, lower solidity HDWT achieved peak power coefficient at higher TSR. The higher solidity 0.375 and 0.450 produced a maximum power coefficient of 0.233 at TSR of 2.0.