Turbine Size Research Articles

Introducing the C1 Wedge Connection

AbstractIncreasing loads on the connections of tubular towers that support wind turbines are making the traditional bolted L‐flange more challenging to design, while the large mass of components and tools make installation challenging from a safety perspective. The C1 Wedge Connection is a symmetrical connection between tubular sections. The connection consists of a cylindrical lower flange and a fork‐shaped upper flange that slides over the lower flange. Both flanges have radial elongated holes distributed along the perimeter allowing the C1 fasteners to pull the two flanges together. The fastener assembly of the C1 Wedge Connection uses a small, horizontally placed bolt to pull two wedges together. The wedges transform and magnify the horizontal bolt force into a larger preload between the flanges by pulling them together. The orientation of the bolt in the fastener prevents significant load fluctuations under external loading. As a result, unlike a bolted L‐flange, the C1 Wedge Connection is less susceptible to preload loss, thereby eliminating the need for regular maintenance and inspection. The scalability of the C1 Wedge Connection makes it suitable for larger loads. These larger loads are expected with increasing size of wind turbines and when connections are used in more demanding locations such as hurricane and seismic conditions or where connections are subjected to high dynamic loads caused by extreme wave conditions or on floating foundations.

A multi-rotor medium-voltage wind turbine system and its control strategy

With the continuous increase in wind turbine power ratings, the growing turbine size makes the turbine manufacture, transport and installation more challenging. At MWs power level, the conventional two-level converters with a 690V voltage have to handle very high current, which causes substantial losses and high cost of power cables, switchgears, etc. To solve this issue, a multi-rotor medium-voltage modular wind turbine configuration is proposed in this paper. Each cell is composed of a turbine rotor, a permanent magnet synchronous generator (PMSG) and a converter. Each PMSG is driven directly by each rotor. The input and output power stages of each converter consist of a three-phase active rectifier and an H-bridge inverter. H-bridge inverters are connected in series to achieve medium-voltage grid connection. This wind turbine configuration has advantages such as more wind power capture, higher reliability, lower transport and installation cost, easy extension to higher power and grid voltage ratings and fault-tolerant operation capability. A control strategy of the wind turbine with maximum wind power capture is proposed. An imbalance compensation control scheme is also proposed to keep three phase output current balanced. Simulation results and experimental tests have validated the proposed wind turbine topology and control strategy.

A model for estimating life cycle environmental impacts of offshore wind electricity considering specific characteristics of wind farms

Offshore wind electricity is becoming an important source of renewable energy due to its global warming potential (GWP). However, the GWP can vary significantly, depending on many factors, including the capacity of the installation, distance from the shore, supporting structure and maintenance requirements. Currently, there is a lack of life cycle assessment (LCA) studies that take these specific conditions into account. As a consequence, developers and policy makers rely on average GWP values which could lead to inaccurate estimates of the GWP and other impacts. To address this gap, this paper presents a new model for estimating the life cycle impacts of offshore wind electricity taking into account specific technical characteristics of individual installations and whole wind farms. Aimed at non-experts, the model provided freely with this paper is developed in Excel and follows the ISO 14040/44 LCA methodology. Supported by the built-in background LCA databases, it requires users to specify only a few key characteristics of an existing or proposed installation, thus facilitating quick and yet robust estimations of impacts. Eleven impacts can be considered, including GWP, depletion of resources, human toxicity and eco-toxicities. The application of the model is illustrated by quantifying the LCA impacts of 20 offshore wind farms (OWF) operating in the UK. The results show that the impacts vary considerably with the specific characteristics of OWF, including the age, type and size of wind turbines, their capacity and distance from the shore. For example, the GWP ranges by a factor of three (6.4–19.5 g CO 2 eq./kWh) and the other impacts by a factor of 2.2–3.2. The developed model can be used by designers, developers and policy makers to customise the inputs for a specific OWF and estimate the impacts quickly and cost-efficiently, without the need for prior expertise in LCA and extensive data collection.

External conditions to be considered in the design of larger wind turbines

As the size of offshore wind turbines increases, the maximum height of the blade tips will soon reach 300m.

MEDICAL VS SURGICAL TREATMENT FOR SYMPTOMATIC ENLARGED INFERIOR TURBINATE: A COMPARATIVE STUDY

Objective: To determine the nasal patency after reducing the size of hypertrophied inferior turbinate with medication and surgery.
 Study Design: Prospective comparative study.
 Place and Duration of Study: Department of Ear, Nose, Throat, Head and Neck Surgery, Medical Teaching Institute, Lady Reading Hospital, Peshawar Pakistan, from Jan to Dec 2019.
 Methodology: This study was conducted at the After-sample size calculation using an online sample size calculator (OpenEpi) and after obtaining informed consent patients were divided into two groups. Patients in group A were put on medicine only and in group B surgery was conducted to reduce the size of hypertrophied inferior turbinate. Data were analyzed using SPSS version 25 and p<0.05 was considered significant.
 Results: This study comprised of total 86 patients, in the age range 15-55 years with mean ± SD age 33.47 ± 9.57 years. Males were 47 (54.7%) and females were 39 (45.3%) with male to female ratio of 1.2:1. In group A, males were 22 (25.25%), females were 21 (24.41%), while in group B males were 25 (29.1%) and females were 18 (20.3%). There was no statistically significant difference in nasal patency between the two groups before treatment (p=0.59) and after 10 days of treatment (p=0.69). However, at the end of one month, there was a statistically significant difference in nasal patency between the medically treated and surgically treated groups of patients (p=0.023).Conclusion: Surgical treatment is significantly effective than medical treatment alone.

Centrifugal Compressor and Bell mouth Air Intake Preliminary Design for Micro Turbojet Engine

This paper presents a design of centrifugal compressor and air intake for micro turbojet engine of 200 N thrust. Because of the small size of the micro turbine engines the air intake is designed in the form of bellmouth air intake in order to capture the needed amount of mass flow rate (0.45 kg/s). The function of the air intake is to deliver the air to the entry of the centrifugal compressor. The air intake has been drawn with start-up motor to take in the consideration the effect. The centrifugal compressor was designed to deliver 3.8 pressure ratio with efficiency about 77%. The compressor impeller was built with 7 main blades and 7 splitters in order to reduce the effect of slip at the exit of the impeller due to pressure difference between pressure and suction side of the main blade. Diffuser of 13 vanes also was designed to increase the static pressure, direct the flow to the combustion chamber and decrease the flow velocity before to enhance the combustion process. The structural integrity for impeller was validated using ANSYS software for aluminum alloy 7075-T6; 7075651. In addition, the aerodynamic analysis was investigated using NUMECA software. The most important findings of the extensive analysis were; the impact of air intake on compressor performance is very crucial. It add an increment in efficiency and pressure ratio, it should be taken in consideration in early design stage of the compressor. The highest performance characteristics of compressor were achieved by accurate design optimization of impeller-diffuser interaction.

Proposal of a Novel Mooring System Using Three-Bifurcated Mooring Lines for Spar-Type Off-Shore Wind Turbines

Floating wind turbine vibration controlling becomes more and more important with the increase in wind turbine size. Thus, a novel three-bifurcated mooring system is proposed for Spar-type floating wind turbines. Compared with the original mooring system using three mooring lines, three-bifurcated sub-mooring-lines are added into the novel mooring system. Specifically, each three-bifurcated sub-mooring-line is first connected to a Spar-type platform using three fairleads, then it is connected to the anchor using the main mooring line. Six fairleads are involved in the proposed mooring system, theoretically resulting in larger overturning and torsional stiffness. For further improvement, a clump mass is attached onto the main mooring lines of the proposed mooring system. The wind turbine surge, pitch, and yaw movements under regular and irregular waves are calculated to quantitatively examine the mooring system performances. A recommended configuration for the proposed mooring system is presented: the three-bifurcated sub-mooring-line and main mooring line lengths should be (0.0166, 0.0111, 0.0166) and 0.9723 times the total mooring line length in the traditional mooring system. The proposed mooring system can at most reduce the wind turbine surge movement 37.15% and 54.5% when under regular and irregular waves, respectively, and can at most reduce the yaw movement 30.1% and 40% when under regular and irregular waves, respectively.

Nonparametric importance sampling for wind turbine reliability analysis with stochastic computer models

Using aeroelastic stochastic simulations, this study presents an importance sampling method for assessing wind turbine reliability. As the size of modern wind turbines gets larger, structural reliability analysis becomes more important to prevent any catastrophic failures. At the design stage, operational data do not exist or are scarce. Therefore, aeroelastic simulation is often employed for reliability analysis. Importance sampling is one of the powerful variance reduction techniques to mitigate computational burden in stochastic simulations. In the literature, wind turbine reliability assessment with importance sampling has been studied with a single variable, wind speed. However, other atmospheric stability conditions also impose substantial stress on the turbine structure. Moreover, each environmental factor’s effect on the turbine’s load response depends on other factors. This study investigates how multiple environmental factors collectively affect the turbine reliability. Specifically, we devise a new nonparametric importance sampling method that can quantify the contributions of each environmental factor and its interactions with other factors, while avoiding computational problems and data sparsity issue arising in rare event simulation. Our wind turbine case study and numerical examples demonstrate the advantage of the proposed approach.

The Efficiency Comparison of Hydro Turbines for Micro Power Plant from Free Vortex

In this research paper, the relationship between a crossflow turbine and propeller turbine size changes and the pond size in a free vortex power generation system was investigated. This relationship can be written in the form of a new mathematical equation using the principles of the response surface methodology (RSM) method. This study aimed to compare the efficiency of a crossflow turbine and propeller turbine to enhance a micro power plant from free vortex. The pond size in a micro power plant from free vortex was 1 m in diameter and 0.5 m in height with a 0.2 m outlet drain at the bottom. All turbines were tested at different water flowrates of 0.2, 0.3, 0.4, 0.5, and 0.6 m3/s to identify the rpm, water head, voltage, and electric current to access the waterpower, power output, and overall efficiency. At a 0.02 m3/s water flowrate, the crossflow turbine had greater overall efficiency than the propeller turbine, reaching 9.09% efficiency. From the comparison of the results of the two turbines used in the 0.5 m high cylinder-shaped generator pond, the turbine type, turbine size (height and diameter), number of blades, and water flowrate are key factors that affect the overall efficiency. The crossflow turbine can achieve greater efficiency than the propeller turbine in this generator system.

Optimal Sizing of Standalone PV-Wind Hybrid Energy System in Rural Area North Egypt

This paper studies the sizing of stand-alone renewable energy system applied in rural areas in the north of Egypt. The available renewable energy sources in these areas are investigated to be integrated to supply the different types of electrical loads. The quality and quantity of these sources over various weather and climate changes are studied to construct a robust energy system. The load demand in such areas is determined according to all activities require electrical energy. This study considers the different economic levels and technologies which affect the load demand value. The technique and economical indices required to obtain the optimal are investigated and applied in the various estimated cases. The genetic algorithm (GA) technique is applied to determine the size and number of photovoltaic panels and wind turbines. The obtained solution takes into account the loss of power supply probability and the minimization of system cost. This study presents an essential phase in the sustainable development of such rural areas.

Dynamic Study of Load Detachment in Supercritical Carbon Dioxide Brayton Cycle

The supercritical carbon dioxide Brayton cycle has become the choice of a wide range of users because of its higher efficiency and smaller turbine size, and is often used in space vehicles, sodium cooled fast reactors, Marine power equipment and other energy storage and power generation applications. However, in the process of use, the detachment of the load is a common problem, if not well handled often cause the system to crash. In this paper, based on the software Simulink in MATLAB, the moment of inertia of turbine and generator is regarded as fixed value, the key parameter differential equations of Brayton cycle are derived, and the dynamic recompression and intercooling Brayton cycle models are established. The response parameters of the system after load disconnection and different time tie-back are studied. The responses of key parameters of the system after load detachment were obtained. It was found that the recompression model had higher stability under load detachment and tie-back conditions than the intercooling model, and the length of parameter variation after load detachment was linear. The earlier the tie-back was, the faster the system could restore stability.

Comparison of cost indicators of Ukrainian wind farms with cost indicators of wind energy global producers

Efficiency improvement in wind conversion field is the most critical scientific-and-technical problem, which is chiefly settled by increasing the power of wind turbines. A new technique was pioneered for determining the efficiency of wind turbines operation in the wind conditions of the Northern Black Sea region of Ukraine. It is found out that the main parameters that have an impact on the cost of electricity are as follows: the cost of a wind turbine itself and annual electric energy production. The cost indicators of wind turbines of the Ukrainian wind farms were defined in the wind conditions of the Northern Black Sea region in 2018, according to which it was ascertained that the cost of electric energy generated in Ukraine was by 17 % cheaper as compared to the world cost value. In illustration of application of the first ever developed technique, we have made the assessment of effective operation of the Ukrainian wind farms in the years of 2019 – 2020. The results obtained bear compelling evidence as to the correlations between the cost of produced electric energy and the size of wind turbines. In view of the above, application of wind turbines of super-large sizes in the conditions of the Northern Black Sea area of Ukraine (as well as in other regions of the world) is hardly expedient due to increase in the cost of electric power generated by them.

Design of a 3.4‐MW wind turbine with integrated plasma actuator‐based load control

AbstractHistorically, cost reduction in wind energy has been accomplished by increasing hub heights and rotor diameters to capture more energy per turbine. The growth in rotor and turbine costs with increasing turbine sizes is also driven by the additional structure that must be added to withstand unsteady aerodynamic loads caused by turbulence, gusts, wind shear, misaligned yaw, upwind wakes, and the tower shadow. In this paper, we present a holistic design solution to integrate active load control using a controllable Gurney flap based on plasma actuators. We illustrate the design solution for a land‐based 3.4‐MW wind turbine rotor. Comparisons to a baseline reference 3.4‐MW wind turbine show significant load reduction (15–18% DEL reduction for flap‐wise blade root moments), rotor mass reduction (5–8%), and LCOE reduction (1.16–3.11%). To achieve these results, a comprehensive sequential‐iterative design procedure is introduced to integrate the controllable Gurney flap into the turbine design and to drive the design solution toward the best LCOE reduction solution. Results are presented for mapping fatigue load reductions into cost reductions. In addition, an evaluation of active load control extended from Region‐III to also include Region‐II showed a further 34% reduction in DEL.

Structural design optimization of a wind turbine blade using the genetic algorithm

With the increasing size of wind turbines in terms of their dimensions and capacity, structural design optimization for their blades is becoming all the more important. This study suggests an improved optimization framework. Blade optimization is performed in two stages: the ply lay-up pattern of the spar cap in the initial blade configuration based on the existing configuration, followed by the cross-sectional design optimization at several spanwise locations. The genetic algorithm is adopted and, in terms of the structural integrity evaluation, the final configuration results are found to be safe; in addition, the number of plies in the spar cap rapidly decreases through the two-stage design optimization procedure. As a result, the blade is lighter, and the lighter blade also reduces the applied load on the wind turbine. This will have an excellent effect that leads to a reduction in the weight of the entire turbine system.

Out-of-plane vibration mitigation of wind turbine blade using highly efficient nonlinear energy sink

Nowadays, the use of wind as one of the main sources of low carbon and renewable energy is expanding rapidly all around the world. Recently, with the development of wind farms and the consequent increase in the size of wind turbines, their maintenance has become more difficult. Therefore, researchers have deeply focused on the analysis and the control of their vibration. In this study, a wind turbine blade with a type of nonlinear absorber, called highly efficient nonlinear energy sink is analyzed, and the interaction between the heavy and long blade and the nonlinear energy sink (NES), under the influence of gravity in the vertical plane and wind force varying periodically due to height dependence is examined. For this purpose, the equations of motion for the blade connected to the NES are extracted using the energy method and solved numerically. Finally, the sensitivity of the parameters affecting the performance of the NES is analyzed and the performance of the system under rotation of the standalone blade and also the rotation of the blade in the presence of the optimal NES is studied.

Performance analysis of vertical axis water turbines under single-phase water and two-phase open channel flow conditions

We conduct performance analyses of a family of vertical axis water turbines (VAWTs) under single-phase water and two-phase open channel flow conditions using unsteady Reynolds-averaged Navier-Stokes (URANS) numerical simulations. The performance, including self-starting capability and energy harvesting efficiency, of a recently developed hybrid Darrieus-Modified-Savonius (HDMS) design is examined under single-phase water flow conditions. With a two-way coupled fluid-structure interaction (FSI) approach, we demonstrate that the water turbine has excellent self-starting capability. After that, the effects of the Reynolds number, tip speed ratio (TSR), and geometric design of the turbine, including turbine size, solidity, and number of blades, are systematically studied. Since the main function of the modified Savonius rotor is to assist self-start, and this part has a negligible effect on energy harvesting performance when the turbine is under stable operation, only the Darrieus rotor is studied under two-phase open channel flow conditions to save computational cost. A key finding is that larger blockage ratios result in better energy harvesting performance of the water turbines. When the blockage ratio is 60% and the TSR of the turbine is 5.0, the power coefficient of the water turbine can reach up to 73%, which exceeds Betz's limit.

Design a cooling pillow to support a high-speed supercritical CO2 turbine shaft

• High speed supercritical CO 2 turbine rotor shaft cooling zone. • Modeling a cooling pillow to cool the shaft and to provide dynamic support. • Design charts and figures for the cooling zone. • Rotor dynamic analysis through the Campbell diagram. • Trade-off analysis in designing the cooling zone. Supercritical CO 2 cycles offer a new thermal power generation paradigm but their commercial deployment has been slow due to significant turbine design challenges. Rotor bearings and seal design are identified as the critical challenges due to the high temperatures, high pressures, and high rotational speeds, a combination of extreme values not encountered in any other past turbine applications. This paper presents a new supercritical CO 2 turbine configuration that addresses these challenges by introducing a rotor shaft cooling zone to control the temperatures encountered by the seals and the bearings. This makes it possible to use proven conventional seal and bearing technology. The salient feature is referred to as a ‘cooling pillow’ that cools the rotor shaft to a tolerable seal temperature by circulating supercritical CO 2 fluid through the annulus and at the same time provides dynamic support to the rotating shaft against vibration. Turbulent heat transfer and frictional heat generation correlations for the annuli have been employed to evaluate the cooling performance and the simplified Reynolds equation for hydrodynamic fluid film lubrication has been employed to evaluate the dynamic performance. Design charts and figures are presented using non-dimensional parameters to help with the design of supercritical CO 2 turbines at different temperatures and sizes. The COMSOL rotor-bearing system simulator consisting of bearing and disks with the main shaft has been employed to produce Campbell plots and carry out a parametric study of rotor vibration frequencies varying with the cooling zone design. The cooling capacity is found to be significantly higher than the cooling load required. Moreover, the convection heat transfer coefficient and dimensionless temperature distribution are independent of radial clearance and this offers trade-offs in terms of controlling rotor vibrations. Through the pursuit of such trade-offs, it is demonstrated that dynamic performance can be improved by up to 55% and 60% for the 0.5 MW and 10 MW turbine sizes, respectively.

Feasibility study of an integrated COGES-DF engine power plant in LNG propulsion for a cruise-ferry

The feasibility study of an integrated COmbined Gas Electric and Steam-reciprocating engine propulsion plant for a Liquified Natural Gas (LNG) fueled cruise-ferry is assessed in this paper. Specifically, the purpose of this work is to respond to GNV shipowners’ need to equip ships with a propulsion system highly efficient in a wide ship speed range. The issue was addressed through the repowering study of the GNV La Suprema ship. Several power plant configurations based on different dual-fuel (DF) engine and gas turbine combinations have been tested in a cogeneration efficiency maximization study performed over a wide ship speed range. Afterwards, the best power plant was identified. Analysis showed that COmbined Gas Electric and Steam (COGES) plants have a great potential for marine propulsion application due to their benefits in cogeneration efficiency, emissions and required volumes. Furthermore, integrating a COmbined Gas Electric and Steam plant with small size dual-fuel engines revealed high cogeneration efficiency over wide ship operating conditions. The propulsion plant comprising a COmbined Gas Electric and Steam plant based on GE25.1 gas turbine and small size dual-fuel engines was proved to guarantee high cogeneration efficiency (47–52%) over a wide ship speed range (16–26 knots). In particular, a 51% cogeneration efficiency is provided for the current operating condition of GNV La Suprema. Moreover, the energy efficiency design index (EEDI) for the different investigated plants has been also evaluated, to verify their compliance with IMO limits. The selected propulsion plant provides an EEDI margin of 1.42–2.89 gCO2/(t*nm) with respect to the 2025 requirements. Finally, economic analysis was performed for four different ship routes and capital/operational costs have been computed. Overall, the proposed COmbined Gas Electric and Steam-reciprocating engine power plant revealed to be economically feasible over all of the operating conditions accounted for.

Sensitivity Study of the Influence of Blade Sectional Stiffness Parameters on the Aeroelastic Response of Wind Turbines

With the development of wind turbines as a result of large-scale and offshore trends, the wind turbine size is becoming increasingly larger. The passive control technique is used to alleviate the increasing loads on the blade for the sake of improving the durability of the wind turbine. The ply design of shells considering the coupling effect of bending and torsion is one of the passive control techniques. The bending torsion coupling stiffness is one of the parameters of the blade section stiffness matrix. In order to fully understand the influence of each blade stiffness parameter on the aeroelastic responses of wind turbines and to consider the influence of structural characteristics on the aeroelastic responses in blade design, the influences and sensitivity of each stiffness parameter in the 6 × 6 stiffness matrix of the blade sections on the aeroelastic responses of the wind turbines are systematically studied under steady wind condition. The aerodynamic forces in the aeroelastic model are calculated by an AeroDyn module based on blade element momentum theory, and the structural dynamic responses of the blade are calculated using generalized Timoshenko beam theory and geometric exact beam theory. The NREL baseline 5 MW wind turbine and blade properties are used in this study, where the diagonal stiffness parameters and non-diagonal stiffness parameters of the matrixes of each blade section are scaled according to certain principles. The results show that the axial stiffness, the flap-wise stiffness, and the torsional stiffness in the diagonal are sensitive to the root loads and tip displacement of the blade. The flap-wise bending torsion coupling stiffness, the flap-wise shear-torsion coupling stiffness, and the edge-wise shear-torsion coupling stiffness in the non-diagonal are also sensitive to the aeroelastic responses. For completeness, the effects of other stiffness parameters on the aeroelastic responses are also analyzed and discussed.

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

Infrasound, i.e., low-frequency noise in the frequency range of 10–200 Hz, produced by rotating wind turbine blades has become a matter of concern because it is harmful to human health. Today, with the rapid increase of wind turbine size, this kind of noise is more worrying than ever. Although much effort has been made to design quiet wind turbine blades, today there is still a lack of effective techniques to reduce infrasound emissions from existing blades. To fill this gap in technology, a biomimetic technique that can be readily applied to reduce infrasound emissions of existing wind turbine blades is studied in this paper using both numerical simulation and experimental testing approaches. The numerical study of the technique is based on the analysis of the sound field distribution near the blade, which is derived by performing both aerodynamic and acoustic simulations of the blade. The experimental study of the technique is based on laboratory tests of two scale models of the blade. Both numerical and experimental studies have shown that the shedding vortices behind the blade can be successfully suppressed by semi-cylindrical rings wrapped on the blade. Consequently, both infrasound and the overall sound pressure level of the noise produced by the blade are significantly reduced. Although the rings fail to show good performance in reducing high-frequency noise, it is not a problem for human health because high-frequency noise is weak and moreover it attenuates rapidly as distance increases. The research also showed that the proposed technique can, not only reduce the infrasound produced by the blade, but can also improve the power coefficient of wind turbines.