Turbine Power Output Research Articles

Preliminary Design of an Axial-Flow Turbine for Small-Scale Supercritical Organic Rankine Cycle

A small-scale organic Rankine cycle (ORC) with kW-class power output has a wide application prospect in industrial low-grade energy utilization. Increasing the expansion pressure ratio of small-scale ORC is an effective approach to improve the energy efficiency. However, there is a lack of suitable expander for small-scale ORC that can operate with a high efficiency under the condition of large expansion pressure ratio and small mass flow rate. Aiming at the design of high-efficiency axial-flow turbine in small ORC system, this paper investigates the performance of a kW-class axial-flow turbine and proposes a method for efficiency improvement. First, the preliminary design of an axial-flow turbine is conducted to optimize the geometric parameters and aerodynamic parameters. Then, the effects of tip clearance and trailing edge thickness on turbine performance are analyzed under design and off-design conditions. The results show that the efficiency of the two-stage or three-stage turbine is evidently better than that of the single-stage one. The output power and efficiency of the three-stage turbine are close to that of the two-stage turbine while the speed is lower. Meanwhile, the trailing edge loss and leakage loss can be significantly reduced via reducing the trailing edge thickness and tip clearance, and thus the turbine efficiency can be improved significantly. The estimated efficiency arrives at 0.82, which is 33% higher than that of the conventional turbine. Considering the limitation of turbine speed, three-stage axial-flow turbine is a feasible choice to improve turbine efficiency in a small-scale ORC.

Study on characteristics of turbine wake and the effect of array arrangement

A prerequisite in undertaking large-scale developments and utilisation of tidal current energy is to comprehend the hydrodynamic characteristics of the wake field of tidal current turbines. The wake of an upstream turbine can strongly affect the power output of downstream turbines and their arrangement. The structure of turbine wakes was investigated. One experiment was conducted on a two-bladed horizontal turbine in a laboratory flume. Actuator disc momentum theory, combined with Reynolds-averaged Navier–Stokes equations, was used to parameterise the tidal turbine. The numerical model was validated using experimental data. The degree of wake mixing improved when the axial distance was eight times the turbine diameter (8D) or larger. The influence of the arrangement and spacing of turbines was investigated at two tidal farms, one with three aligned turbines and one with seven staggered turbines. The incoming flow velocity of the downstream turbine was reduced by 31% when turbines were linearly aligned. The extent of influence of the third column was larger than that of the second column, indicating an expanding wake. Different lateral spaces of staggered turbines were analysed. Different distances between rows strongly influenced both the incoming velocity of downstream turbines and the expansion of the whole wake. The incoming flow of the third column reduced by 31, 17 and 16% with increasing lateral space. The flow velocity increased as water passed over the turbine tip. For staggered turbines, a centreline spacing of up to 1.5D for adjacent rows is recommended.

Experimental and Numerical Evaluation of Performance of a Variable Pitch Vertical-Axis Wind Turbine

Abstract The research work depicts the study of the comparison of a 1 kW fixed pitch vertical-axis wind turbine (VAWT) and a variable pitch VAWT via analytical, numerical, and experimental results. Being an emerging technology, wind turbine is becoming a source of attraction for the researchers. The VAWT in comparison to the horizontal-axis wind turbine (HAWT) has shown numerous benefits. The fundamental purpose of this study is to maximize the output power and output torque of the wind turbine. For achieving an improved output, a novel and unique mechanism, termed as pitching mechanism, is employed that follows the variable pitch concept. The mathematical modeling was performed for the straight blade variable pitch VAWT and for the fixed rotor. The four-bar mechanism was developed to execute the variable pitch mechanism and implemented in the form of the computer-aided design, model. A scaled down three-dimensional (3D) model of the rotor was manufactured using the 3D printing technique. The aerodynamic forces such as lift and drag were measured upon the rotor as per the testing on the rotor in the wind tunnel. Computational fluid dynamics (CFD) simulations were run for the fixed pitch and the variable pitch rotor. The transient analysis was performed for the azimuthal angle ranging from 0 to 360 deg and for a pitch angle varying from +25 to −25 deg in ansys software. The comparative study was undertaken, keeping in view the analytical, simulation, and experimental results. A worthy agreement was observed among analytical, software, and experimental results, and a promising increase in power and torque was observed due to the introduction of the variable pitch mechanism. The power produced by the variable pitch design showed a significant increase in the power production compared to the fixed pitch design. The numerical and experimental values of cp for the variable pitch design were quite comparable.

Blades Optimization for Maximum Power Output of Vertical Axis Wind Turbine

Wind power is a significant and urging sustainable power source asset to petroleum derivatives. Wind machines, for example, H-Darrieus vertical pivot wind turbines (VAWTs) have increased much notoriety in research network throughout the most recent couple of decades because of their applications at destinations having moderately low wind speed. Be that as it may, it is noticed that such wind turbines have low effectiveness. The point of this examination is to plan rotor cutting edges which could create most extreme power yield and execution. Different plan factors, for instance, harmony length, pitch edge, rotor distance across, cutting edge length and pitch point are explored to upgrade the presentation of VAWT. Rotor cutting edges are manufactured using the NACA-0030 structure and tried in wind burrow office and contrast its outcomes and DSM 523 profile. Numerical simulations are performed to get best geometry and stream conduct for achieving greatest power. It is seen that for higher tip-speed-proportion (TSR), shorter harmony length and bigger distance across the rotor (i.e., lower robustness) yields higher effectiveness in NACA 0030. Nevertheless, for lower TSR, the more drawn out agreement length and slighter distance across rotor (i.e., higher strength) gives better implementation. The pitch point is - 2° for TSR = 3 and - 3° for TSR = 2.5. The most extreme power yield of the wind turbine is acquired for the sharp edge profile NACA 0030. Besides, instantaneous control coefficient, power coefficient (CP) is the greatest reason for azimuthal edge of 245° and least esteem for 180°.

CFD Prediction of Performance of Wind Turbines Integrated in the Existing Civil Infrastructure

Power generation from wind energy is almost entirely performed in rural locations or at sea, and very little attention has been given to the use of wind turbines in urban locations. Since the re-emergence of wind turbines, the majority of their applications are in large commercial wind farms in rural areas or out at sea, and there is an increasing focus on the use of wind turbines within an urban environment possibly using existing structures, such as bridges and viaducts. There are very few existing buildings which have been designed from the ground-up to include wind turbines in the structure. In order to estimate the wind resources and the performance of a turbine at a particular site, a CFD model is designed and CFD calculations are performed. In order to simplify the modelling of a wind turbine actuator, disc theory is applied. Actuator disc theory is used, as it allows the aerodynamic behaviour of a wind turbine to be analyzed by just considering the energy extraction process without a specific wind turbine design. The power output of wind turbines installed beneath an already existing civil infrastructure is determined and analyzed.

Numerical Study of the Dynamic Stall Effect on a Pair of Cross-Flow Hydrokinetic Turbines and Associated Torque Enhancement Due to Flow Blockage

An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could either produce higher torque or create more energy loss. For both of the scenarios where a blade interacted with the channel wall or another blade, the key behind torque enhancement was forcing the flow through its suction side and manipulating the LEV.

Wave energy harvesting impulse turbine having ring type blade: Experiments with unsteady flow

Oscillating water column (OWC) wave energy converters employ air turbines coupled with an electrical generator to convert the wave energy into electrical energy. In the present study, a ring-type axial flow impulse turbine of diameter 196 mm was manufactured to carry out the experiments in an unsteady flow test rig. The tests were done for the stroke lengths (SL) of 0.2m, 0.3m, and 0.4m, and the periods (TP) varied from 6 to 12 s. A rheostat was connected to the generator, and the turbine pressure drop and power output variations were recorded for different generator loading conditions. The flow rates for the exhalation phase were measured and time-series analysis of the pressure drop and rotor speed was done. A suitable resistive load was found out for obtaining the highest power output. A relationship between average power and average pressure drop was established. Furthermore, a relationship was established between the turbine pressure coefficient and the turbine power coefficient. Lastly, a study on damping characteristics of the turbine was also done to study the effect of damping on the turbine's overall performance.

Validation and comparison of turbulence models for predicting wakes of vertical axis wind turbines

Vertical axis wind turbine (VAWT) array design requires adequate modelling of the turbine wakes to model the flow throughout the array and, therefore, the power output of turbines in the array. This paper investigates how accurately different turbulence models using 2D computational fluid dynamics (CFD) simulations can estimate near and far wakes of VAWTs to determine an approach towards accurate modelling for array design. Three experiments from the literature are chosen as baselines for validation, with these experiments representing the near to far wake of the turbine. Five URANS turbulence models were chosen due to their common and potential usage for VAWT CFD: models k–ω SST, k–ω SST LRN, k–ω SSTI, transition SST, and k–kl–ω. In addition, the lifting line-free vortex wake (LLFWV) model was tested as an alternative to CFD for the far turbine wake where it was appropriate for use. The results for turbulent kinetic energy and vorticity were compared for the first experiment, whilst streamwise and cross-stream velocity were used for the other two experiments. It was found that none of the turbulence models tested or LLFVW produced adequate estimations within the methodology tested, however, transition SST produced the closest estimations. Further adjustments to the methodology are required to improve accuracy due to their large impact on results including use of 3D CFD, adjustment of surface roughness, and inlet flow characteristics.

Correlations of power output fluctuations in an offshore wind farm using high-resolution SCADA data

Abstract. Space–time correlations of power output fluctuations of wind turbine pairs provide information on the flow conditions within a wind farm and the interactions of wind turbines. Such information can play an essential role in controlling wind turbines and short-term load or power forecasting. However, the challenges of analysing correlations of power output fluctuations in a wind farm are the highly varying flow conditions. Here, we present an approach to investigate space–time correlations of power output fluctuations of streamwise-aligned wind turbine pairs based on high-resolution supervisory control and data acquisition (SCADA) data. The proposed approach overcomes the challenge of spatially variable and temporally variable flow conditions within the wind farm. We analyse the influences of the different statistics of the power output of wind turbines on the correlations of power output fluctuations based on 8 months of measurements from an offshore wind farm with 80 wind turbines. First, we assess the effect of the wind direction on the correlations of power output fluctuations of wind turbine pairs. We show that the correlations are highest for the streamwise-aligned wind turbine pairs and decrease when the mean wind direction changes its angle to be more perpendicular to the pair. Further, we show that the correlations for streamwise-aligned wind turbine pairs depend on the location of the wind turbines within the wind farm and on their inflow conditions (free stream or wake). Our primary result is that the standard deviations of the power output fluctuations and the normalised power difference of the wind turbines in a pair can characterise the correlations of power output fluctuations of streamwise-aligned wind turbine pairs. Further, we show that clustering can be used to identify different correlation curves. For this, we employ the data-driven k-means clustering algorithm to cluster the standard deviations of the power output fluctuations of the wind turbines and the normalised power difference of the wind turbines in a pair. Thereby, wind turbine pairs with similar power output fluctuation correlations are clustered independently from their location. With this, we account for the highly variable flow conditions inside a wind farm, which unpredictably influence the correlations.

Wind turbine power prediction considering wake effects with dual laser beam LiDAR measured yaw misalignment

Accurate power prediction of a wind turbine under wake is important for wake suppression control, which is of great significance to reduce the energy loss of a wind farm. The power output of a wind turbine affected by wake is determined by yaw misalignment angle, equivalent inflow wind speed and the size of wake area imposed. However, with current techniques, it is difficult to measure the yaw misalignment angle of a wind turbine under wake that hinders the calculation of its equivalent inflow wind speed. By exploring the interference mechanism of the wake effects to the measurement of yaw misalignment angle with dual laser beam wind LiDAR an approach to calculate realistic yaw misalignment angle of a wind turbine under wake is proposed. Based on this and combined with the wake superposition model, the equivalent inflow wind speed of the wind turbine under wake can be determined. This enables a model to predict the power output of a wind turbine under wake effects. The model is verified by comparisons between prediction results and the data collected in Supervisory Control And Data Acquisition system from a wind farm with five inline wind turbines. It shows that with the wake compensation, the predicted equivalent wind speeds have achieved higher than 90% of accuracy and the output power predictions have maximum 7% accuracy improvements. The proposed calculation method of yaw misalignment angle with wind LiDAR and the power output prediction model of wind turbines under wake provide important basis for wind farm wake control.

An effective framework for wake predictions of tidal-current turbines

Deployment of tidal array farms is the next stage of tidal energy development which concentrates on the capture of the enormous energy. Characterization into the wake of tidal turbine aids in determining the tidal farm layout and energy yields. This paper develops a framework that employs the Computational Fluid Dynamics (CFD) simulation and machine learning to analyze turbine wake with high accuracy and good efficiency. Multilayer perceptron neural network (MLP-NN) was introduced to establish the interrelation between the incoming flow conditions and the wake profiles. The Reynolds-averaged Navier-Stokes equations (RANS) are associated with a k − ε turbulence model to offer a number of datasets of wake profile for training, testing, and validation of the MLP-NN models. It was found that the MLP–NN–based model has achieved a considerably high level of accuracy by comparing it with empirical and numerical models. The reliability of the MLP-NN based model coupled with the wake combination RSS model to predict the resultant wake profile and power output of multiple turbines are also assessed. The techniques significantly enhance the efficiency and accuracy of wake predictions.

Local topography‐induced pressure gradient effects on the wake and power output of a model wind turbine

Wind-tunnel experiments were performed to study the effect of favorable and adverse constant pressure gradients (PG) from local changes in the topography right downwind of a model wind turbine. Particle image velocimetry was used to characterize the near and intermediate wake regions. We explored five scenarios, two favorable, two adverse PG, and a case with negligible PG. Results show that the PGs induce a wake deflection and modulate the wake. They imposed a relatively small impact on the turbulence kinetic energy and kinematic shear stress but a comparatively dominant effect on the bulk flow on the flow recovery. Based on this, a simple formulation is used to describe the impact of PG on the wake. We modeled the base flow through a linearized perturbation method; the wake is obtained by solving a simplified, integrated streamwise momentum equation. This approach reasonably estimated the flow profile and PG-induced power output variations.

High ambient temperature effects on the performance of a gas turbine-based cogeneration system with supplementary fire in a tropical climate

High ambient temperature negatively affects gas turbine performance, especially in a tropical climate. Cogeneration improves fuel utilization by taking advantage of the energy discharged as waste heat in the exhaust gases. This case study assesses the effects of high ambient temperature on the performance of a natural gas-based cogeneration plant in Barranquilla, Colombia, a location with a hot and humid tropical climate throughout the year with an annual average temperature of 27.4 °C. The cogeneration plant encompasses gas and vapor turbine generation, supplementary fire, waste heat recovery, and process heat exchange. Validated ASPENHYSYS® simulation allows comparing gas-turbine-alone indicators with those at ISO conditions, i.e., 15 °C and 101.3 kPa. Ambient temperature reduces gas turbine power output by up to 22% and decreases thermal efficiency by around 0.06% for every °C rise above ISO conditions. Cogeneration with and without supplementary fire increases power output by 17% and 5% compared to gas-turbine-alone operation. The energy utilization factor increases by 27–37% without supplementary fire and above 37% with supplementary fire. Results give insight into the challenges of cogeneration plants in a tropical climate. Further studies should include the effects of high humidity on power plant performance and the potential benefits of cooling inlet air.

Rancang Bangun Turbin Angin Untuk Pembangkit Listrik Tenaga Angin (Sebagai Alternatif Pembangkit Listrik Daerah Pesisir Pantai)

The basic working principle of a wind turbine is to convert mechanical energy from the wind into rotary energy on the blades, the turbine rotation is used to turn a generator to produce electricity. The wind turbine under study is a propeller wind turbine whose axis is placed horizontally. The purpose of this study was to determine the output power produced by the wind turbine. Methods The research was conducted using experimental methods. The results showed that the designed wind turbine was able to produce electrical power at wind speeds of less than 40 m/s, overall based on the research that the maximum power value occurred at 17:00 with a wind speed of 28 m/s the power generated was 0.054 Watt, while the lowest turbine output power occurred at 15:00 with a wind speed of 18 m/s turbine output power of 0.025 Watt.

Rancangan Bangun Turbin Mikrohidro Tipe Archimedes Screw Dengan Kapasitas Daya 560 Watt

The performance of a micro-hydro turbine was influenced by several factors, namely the design and the enviromental. This study aims to obtain the appropriate design parameters for the manufacture of screw turbines. This research was focused on blade dimensions and turbine screw pitch distance. The calculations were performed using several screw turbine fixing formulations. The design results show that the optimum blade diameter and turbine pitch range are 0.213 m and 0.312 m at 0.2 m3 / s of turbine inlet water flow and 563.3 Watt turbine shaft output power. The turbine screw test results of the design were carried out in the river flow of Puri Kedaton Housing, Pematang Gajah Village, Rt 13, Jambi Province. The test results show that the highest turbine power occurs at 30 kg shaft loading with a turbine output power of 445 Watts and an efficiency of 78.9%.

Exact output regulation for wind turbine active power control

The recent proliferation of converter-based generators for the grid connection of renewable energy sources has introduced a number of security challenges, including frequency stability. Frequency regulation is achieved through active power generation, requiring power generators to regulate their power output in real time to match a time-varying power command curve specified by the transmission system operator. Control methodologies to enable the turbine power output regulation have been investigated in the wind energy literature for more than a decade.In this paper, we investigate a classical control methodology known as exact output regulation that has been widely used for the twin problems of output regulation and disturbance rejection. We demonstrate how the method may be adapted to achieve output power regulation for a wind turbine. The method assumes that wind preview information from LIDAR measurements is available for the design of the torque and pitch control input signals. To evaluate the potential of the method to improve wind turbine capability for the provision of frequency regulation services, we compare its performance with that of two baseline controllers, one pitch-based and one torque-based, for the tracking of a specified time-varying power command signal. Our simulations show that the proposed methodology can substantially improve the output power regulation, reduce fatigue loads and also reduce actuator usage, relative to the baseline controllers.

Horizontal axis wind turbines passive flow control methods: a review

In improving wind turbine torque and power output, the aerodynamic characteristics of wind turbines blades play an important role. Unleashing easy but efficient flow enhancement techniques over aerofoil sections used in horizontal axis wind turbines (HAWT) has become essential in the increasing demand for this source of renewable energy. These techniques or methods are primarily categorized into two kinds: active and passive. Active methods of flow control need energy expensewhereas passive flow control methods are needless of auxiliarypower. This paper investigates various passive flow control strategies that have great potential to boost the aerodynamics of blades of HAWT. The mechanisms and working principles, along with the findings from various experimental studies and CFD results for passive flow control systems are included in this article. Also, some of these studies are supported by demonstrating the lift and coefficient of drag (CD) variation with the angle of attack (AoA). The review suggests simple, cost-effective ways of improving lift and controlling the aerofoil stalling behaviors to obtain higher power efficiency for HAWT.

A model for booster station matching of gas turbine and gas compressor power under different ambient conditions

Transporting natural gas across different locations require compressor stations to provide the pressure needed to keep the gas moving. This paper presents a model for matching the gas turbine and gas compressor power required under different environmental conditions to support the continuous gas transmission across other locations. The trans-Saharan gas pipeline (TSGP) project proposed to transport gas from Nigeria to Algeria has been used as a case study in this paper. The TSGP project is a Nigerian Government initiative to rejig its gas development and transportation infrastructure to meet its internal and external market demand. The numerical method used in this paper integrates the effect of the ambient temperature in the power matching of the gas turbine and gas compressors. There are 18 compressor stations across the TSGP network, and compressor station 2 is used as the reference point. The daily temperature fluctuation is segmented into hours of the day, emphasising considerable ambient temperature variation at 3:00 h, 9:00 h, 15:00 h. One benefit of the model against others in the open literature is accounting for changes in the ambient temperature along the pipeline network and gas compression stations. Accounting for changes in ambient temperature provides accuracy to near real-life operational experience for gas distribution via pipelines. The model also accounts for variations in turbine entry temperature (TET) to compensate for changes in the ambient conditions to meet the power requirements of the gas turbine and the gas compressor. The results show that for every 1% increase in ambient temperature, a 3.5% increase in power is required to drive the gas compressor and a 1% decrease in gas turbine output power. The effect of the 1% increase in ambient would require a 3.5% increase in TET to meet both the gas turbine and gas compressor requirement.

The Active Frequency Control Strategy of the Wind Power Based on Model Predictive Control

In this paper, an active frequency control strategy of wind turbines based on model predictive control is proposed by using the power margin of wind turbines operating in load shedding mode. The frequency response model of the microgrid system with the load shedding of the wind turbines is used to predict the output power and system frequency deviation of the wind turbine. According to the prediction information, the output power control signal of the model predictive controller in the wind turbine can be optimized. On this basis, a wind turbine active participation frequency control strategy based on model predictive control is designed by rolling prediction and optimization. The wind turbine power control signal after the strategy is used to adjust the output power of the wind turbine and balance the change of the active power of the system to reduce the frequency deviation.

Numerical investigation of the power and self-start performance of a folding-blade horizontal axis wind turbine with a downwind configuration

ABSTRACT This study proposes an oblique folding mechanism design inspired by the wings of Borneo camphor seeds to enable the blades of wind turbines to pitch and cone. The blade pitching increases the power output, while the blade coning reduces the blade root stress and increases the yaw stability of the wind turbine. Numerical predictions of the power and self-start performance of a downwind folding-blade horizontal axis wind turbine were conducted. For comparison, a benchmark wind turbine with a constant chord blade section with an SD8000 airfoil and zero blade twist was also modeled. The maximum power coefficient (CP ) of the folding-blade wind turbine is 0.404 which is 28.22% higher than that of the benchmark wind turbine, when the fold axis angle is 50° and the pitch angle is 3.834°. The maximum starting torque of the folding-blade wind turbine is 0.720 Nm at a pitch angle of 64.59°, which is 1153.97% higher than that of the benchmark wind turbine. This finding confirms that a folding blade can increase the power output, start-up capability and passive yaw capability of a wind turbine. In conclusion, the proposed folding design can be adopted as an alternative for pitching and coning wind turbine blades.