MW Turbine Research Articles

A discrete control algorithm synthesis for the live-steam-line heating system

An original mathematic model of a main live-steam-line heating system for the 6 MW turbine is reviewed. The present model is composed from a system of ODE with divergences and constant coefficients, along with an object structure is shown, numerical values of parameters are determined. The transfer function method is used for the model analysis, which is necessary for the main problem resolving. It consists of a discrete control algorithm construction to provide an appropriate heat transition process of an aperiodic type with quality performance required. The con- trol algorithm is based on the functional minimization condition, which is used here as the minimum energy speed up the process. The gradient method and etalon-model method are also used to get an optimal system stage. Due to methods applied, a main variable parameter influence on a system performance is analyzed, optimal adjustment value is retrieved, which allows you to provide the required quality for the heating system performance in all operating modes.

Viability of hydrogen production from a dedicated offshore wind farm-underground storage in the Irish Sea in 2030

This paper presents a concept of hydrogen production (H2P) from a dedicated offshore wind farm (OWF) and stored underground. A new model is introduced to assess the viability of a fixed-bottom OWF in a potential offshore wind pipeline in the Irish Sea, where all costs are projected in 2030. It explains the need to develop market opportunities for the vast offshore wind potential in Ireland, to ascertain both decarbonisation and energy security in multiple sectors, where dedicated HP-OWFs are potential drivers. It reviews hydrogen storage methods and shows artificial underground salt caverns suitable to store hydrogen at large scales and long- terms. The OWF consists of 16×6.33MW turbines and proton exchange membrane electrolysers. The net present values and discounted payback periods (DPBs) are calculated at offloading periods of 2, 7, 15, 30 and 60 days, and in good agreement, where the DPBs are 7.8, 8.6, 10.0, 12.1 and 20.3 years, respectively. Both economic indicators show that the H2P-OWF is profitable with the hydrogen price at €5/kg but marginal at €3/kg. Offloading at shorter periods of 2-15 days is more profitable. A seven-day offloading period requiring 120 ton storage capacity and compatible to the future tankers is recommended.

Comparison of dynamic response and levelized cost of energy on three platform concepts of floating offshore wind turbine systems

Spar, semisubmersible and barge platforms are modelled based on the full-scale demonstration projects in Japan for a generic 5 MW turbine. Three platforms are evaluated with the structural and stability parameters. The characteristic of floater motions and mooring forces are clarified by performing the dynamic analysis. The dynamic responses are validated with the water tank tests. The levelized cost of energy is assessed by using the engineering cost model.

Influence of Extension Length of Rotor End Windings on the Three-Dimensional Electromagnetic Field and Temperature Rise in the Large Turbine Generator End Zone With Magnetic Screen

Leakage magnetic field from the rotor end windings affects obviously the electromagnetic losses and temperature of end components in the turbine generator end zone with magnetic screen. As the capacity of turbine generator increases, this effect of rotor end windings has become more prominent. To investigate influence of the extension length of rotor end windings on the electromagnetic and thermal fields in the turbine generator end zone with magnetic screen, three-dimensional transient electromagnetic field model of 1250 MW turbine generator end zone is given. Leakage magnetic field and losses of end components are compared and studied in the end zone under the different extension lengths of rotor end windings. Based on the calculation results of electromagnetic losses (heat sources) and flow network (boundary conditions), three-dimensional fluid-thermal coupling field is calculated in the turbine generator end zone with magnetic screen. Distribution of complex fluid velocity in the end zone is obtained. Influence of the different extension lengths of rotor end windings on the stator-end copper coil, screen plate, finger plate, press plate, magnetic screen, and stator end core is researched in the turbine generator end zone. The accuracy of calculation results is validated by experimental values.

Incoming flow measurements of a utility-scale wind turbine using super-large-scale particle image velocimetry

We present incoming flow characterization of a 2.5 ​MW turbine at high spatio-temporal resolution, using super-large-scale particle image velocimetry (SLPIV). The datasets have a field of view of 85 ​m (vertical) × 40 ​m (streamwise) centered at 0.2 rotor diameter upstream. The mean field shows the presence of the induction zone and a distinct region with enhanced vertical velocity. In comparison to vortex theory, SLPIV streamwise velocity presents a steeper velocity drop close to the rotor plane and a more confined induction zone. Time series of nacelle sonic anemometer and SLPIV measured streamwise velocity outside the induction zone show generally matched trends with time-varying discrepancies due to the induction and nacelle effects. The discrepancy, characterized by the sonic-SLPIV velocity ratio, is normally distributed and is less than unity 85% of the time. Data shows both yaw error and incident angle have direct impacts on this ratio, while the intensity of short-term velocity fluctuation has limited effect. Increased yaw error leads to an increase in both the mean and the spread of the ratio. The ratio decreases when the incident angle changes from pointing downward to zero. Further change from zero to pointing upward causes it to plateau with its fluctuations augmented.

The Dynamics of a Rotor System of a 1100 MW Turbine Unit

The calculations data of the critical rotational speeds of the shaft line on yielding supports with the support yield in the vertical and horizontal directions of the modernized turbine unit K-1000-60/1500-2 (after modernization, the turbine unit type is designated as K-1100-60/1500-2M) have been presented. 1000 MW turbine units comprising a high-pressure cylinder and three low-pressure cylinders have been in operation at nuclear power plants since 1984. The design models of shafting are based on technical and improved theories of variable cross-section rods on elastic-damper supports, taking into account the coupling of vibrations in two planes, inertia of rotation, gyroscopic moments and aerodynamic forces on the disks. Additionally, the stress condition of the most dangerous sections of welded rotors has been investigated in case of a sudden short circuit in the generator. The conditions of the shafting for the cases of two- and three-phase short circuits were considered. The calculations of the critical rotational speeds of the shaft line and of the strength of the rotors in case of a short circuit were performed using software packages developed in the IPMash of the NAS of Ukraine, Joint-Stock Corporation “Turboatom”. The calculation data show that no dangerous resonance vibrations of the shaft line of the upgraded К-1100-60/1500-2М turbine unit are detected and the strength of the shaft line in case of a sudden short circuit in the generator is in conformity with the requirements of regulatory and technical documents.

Study on a novel district heating system combining clean coal-fired cogeneration with gas peak shaving

The existing coal-fired heating mode in north China has a higher energy consumption and causes heavy haze in winter. Combining with natural gas, deeply exploring the energy saving potential in coal-fired Cogeneration can provide an effective way for solving the problems. This paper proposes the methods to utilize exergy loss in the existing district heating system: 1) On the heat network, high temperature hot water or gas is used for driving the absorption heat exchangers (AHEs), by which the temperature of return water backing to CHP plant can be greatly reduced. 2) While in the CHP plant, a cascaded heating process with absorption heat pump (AHP) is constructed for efficient recovery of the condenser waste heat, by which the heating capacity of CHP plant can be significantly improved. Based on this, this paper proposes a new type of district heating system, in which clean coal-fired cogeneration is the dominant and novel gas peak-shaving is the supplements. Corresponding analysis model is established, taking a CHP plant with 2 × 330 MW turbine units as an example. Comparing with previous district heating system with gas peak-shaving boiler, the new system has apparent advantages: Firstly, the comprehensive exergy efficiency is increased from 47% to 66%, the coal consumption is reduced from 14.48 kg/GJ to 9.74 kg/GJ, while the natural gas consumption is reduced from 17.65 Nm3/GJ to 8.56 Nm3/GJ. Secondly, the emission of SO2 is decreased by 50.6%, of smoke is decreased by 32.9%, and of NOx is decreased by 35.6%. Finally, the energy cost is decreased from 55.1 CNY/GJ to 28.2 CNY/GJ, and the payback rate of incremental investment is 22%.

Design and in-field testing of the world’s first ReBCO rotor for a 3.6 MW wind generator

The main aim of the EU H2020 project EcoSwing was to demonstrate a technical readiness level of 6–7 for high-temperature superconducting (HTS) technology operating in a wind generator. To reach this goal, a full-scale synchronous HTS generator was successfully designed, built and field-tested in a 3.6 MW turbine. The generator has a rotor with 40 superconducting coils of 1.4 m long. The required >20 km of coated conductor was produced within the project’s time schedule. All coils were tested prior to assembly, with >90% of them behaving as expected. The technical readiness level of HTS coils was thus increased to level 7. Simultaneously, the maturing of cryogenic cooling technology over the last decade was illustrated by the several Gifford-McMahon cold-heads that were installed on-board the rotor and connected with the stationary compressors through a rotating coupling. The cryogenic system outperformed design expectations, enabling stable coil temperatures far below the design temperature of 30 K after only 14 d of cool-down. After ground-based testing at the IWES facility in Bremerhaven, Germany, the generator was installed on an existing turbine in Thyborøn, Denmark. Here, the generator reached the target power range and produced power for over 650 h of grid operation.

Acoustic Emissions from Wind Turbine Blades

Research on broadband aerodynamic noise from wind turbine blades is becoming important in several countries. In this work, computer simulation of acoustic emissions from wind turbine blades are predicted using quasi empirical model for a three-bladed horizontal axis 3 MW turbine with blade length ~47 m. Sound power levels are investigated for source and receiver height of 80 m and 2 m above ground and located at a distance equal to total turbine height. The results are validated using existing experimental data for Siemens SWT-2.3 MW turbine having blade length of 47 m, as well as with 2.5 MW turbine. Aerofoil self-noise mechanisms are discussed in present work and results are demonstrated for wind speed of 8 m/s. Overall sound power levels for 3 MW turbine showed good agreements with the existing experiment data obtained for SWT-2.3 MW turbine. Noise map of single source sound power level, dBA of an isolated blade segment located at 75 %R for single blade is illustrated for wind speed of 8 m/s. The results demonstrated that most of the noise production occurred from outboard section of blade and for blade azimuth positions between 80° and 170°.

Upscaling and levelized cost of energy for offshore wind turbines supported by semi-submersible floating platforms

This study aimed to clarify upscaling and levelized cost of energy for offshore wind turbines supported by semi-submersible floating platform. Firstly, the upscaling rules of turbines, floaters and mooring lines are investigated, and the upscaling procedure is proposed based on the construction constraints and the static balance. Then, floater models are upscaled for 5, 10 MW turbines based on the semi-submersible floater for 2 MW turbine designed in Fukushima FORWARD project. By performing dynamic analyses, it is found that, the kinematic law for floaters is satisfied in the heave direction and relaxed in the surge and pitch direction. The dynamic similarity for mooring lines is satisfied by changing the mooring line quality. Finally, the levelized cost of energy is assessed by using engineering models and experience of demonstration projects. The initial cost is reduced 45 % and 57 % respectively for 5 MW and 10 MW comparing to 2 MW turbine.

Effect of Wake Meandering on Aeroelastic Response of a Wind Turbine Placed in a Park

A wind turbine operating inside a wind farm is subjected to increased turbulence intensity and reduced wind speeds resulting in increased fatigue loadings and reduced power production. Furthermore, meandering of the wakes results in increased dynamic loading of the wind turbine. In the present study, a standalone dynamic wake meandering (DWM) model has been developed and implemented in commercial code SIMA. The standalone DIWA model does not require a direct coupling with aeroelastic code, hence it is computationally fast. Although the standalone tool is a good alternative for power and thrust prediction, it does not have the capability to predict the turbine aeroelastic loads. The new DWM program is referred as “Disturbed Inflow Wind Analyzer” (DIWA). Benchmarking studies of DIWA with the literature data are presented and discussed. Overall the DIWA compares well with the literature data and the discrepancies between DIWA and the literature data are discussed. The present studies show that the wake deficit profiles are very sensitive to the eddy viscosity parameters. Finally, the turbulence boxes generated using DIWA have been used for understanding the aeroelastic behaviour of NREL 5MW turbine and one of the wind turbines from the Lillgrund wind park. The estimated power production using both aeroelastic coupled with DIWA turbulence boxes and standalone DIWA (without aeroelastic) are in good agreement with the literature data. The trends of fatigue loads are predicted well, with a few exceptions.

Numerical investigation of influence of different underexcited operations on temperature distribution in the large turbine generator end domain with copper screen

Overheating of the complex end parts has become one of the main problems affecting safe and stable turbine generator operation under the underexcited operation. In order to study the temperature distribution in the large turbine generator end domain with copper screen under the different underexcited operations, a 330 MW turbine generator is studied. Three-dimensional fluid-thermal coupling model for the end domain of turbine generator is established. Three-dimensional transient magnetic field of the large turbine generator end domain with copper screen is calculated with 0.85 pf underexcited operation and 0.9 pf underexcited operation. Loss values of the end metal parts from the three-dimensional transient magnetic field are applied to end domain as heat source with 0.85 pf underexcited operation and 0.9 pf underexcited operation. Outlet-pressure values and fan inlet velocity from flow network calculations are applied to the end domain as boundary conditions in the fluid and thermal coupling analysis. The three-dimensional fluid and thermal fields in the turbine generator end domain are calculated with 0.85 pf underexcited operation and 0.9 pf underexcited operation. Distribution of the radial fluid velocity component around the stator winding is determined. Temperature distribution of the end metal parts in the large turbine generator end domain with copper screen is studied with 0.85 pf underexcited operation and 0.9 pf underexcited operation. Temperature calculation results of the copper screen are compared with measured values. Calculation results are in good agreement with measured values.

Characterization of seismic signals induced by the operation of wind turbines in North Rhine-Westphalia (NRW), Germany

In recent years, the impact of wind turbines (WTs) on seismological stations has been noticed, since WT-induced ground motions perturbed the seismic background noise level at seismological monitoring sites. The resulting deterioration of the recording quality at seismic stations leads to a conflict between seismological network and WT operators. As a first step towards the solution of the conflict - or at least a peaceful coexistence - it is of paramount importance to understand the characteristics of seismic signals generated by WTs. For this study, a 6.5-week measurement campaign was conducted at a wind park (WP) consisting of five 2 MW turbines in North Rhine-Westphalia (Germany) with eleven mobile seismic stations installed at distances of 1–10 km from the WP. At each measurement point, power spectral density (PSD) spectra are calculated and correlated with different operating states of the WTs. Changes in the operating states of the WT are reflected in the noise level at the seismic stations with different distances to the WP. An analysis of the radiated frequencies from the WT foundation into the subsurface is carried out by performing shutdown and switch-on tests at the WP. In this way, seismic signals generated by WTs are identified and used to illustrate how frequency-dependent peaks in WT-induced seismic noise are attenuated with distance. The attenuation of the peaks can be described by a power-law decay proportional to r−b, with r as the distance between station and WT and b as the decay parameter with values between 2.4 and 5.5. The relationship between the noise level at a seismic station and the number of WTs in operation, that behave as interacting sources for the background noise level, could be determined as $\sim \sqrt {N}$ , with N being the number of switched-on WTs.

Global estimations of wind energy potential considering seasonal air density changes

The literature typically considers constant annual average air density when computing the wind energy potential of a given location. In this work, the recent reanalysis ERA5 is used to obtain global seasonal estimates of wind energy production that include seasonally varying air density. Thus, errors due to the use of a constant air density are quantified. First, seasonal air density changes are studied at the global scale. Then, wind power density errors due to seasonal air density changes are computed. Finally, winter and summer energy production errors due to neglecting the changes in air density are computed by implementing the power curve of the National Renewable Energy Laboratorys 5 MW turbine. Results show relevant deviations for three variables (air density, wind power density, and energy production), mainly in the middle-high latitudes (Hudson Bay, Siberia, Patagonia, Australia, etc.). Locations with variations from −6% to 6% are identified from summers to winters in the Northern Hemisphere. Additionally, simulations with the aeroelastic code FAST for the studied turbine show that instantaneous power production can be affected by greater than 20% below the rated wind speed if a day with realistically high or low air density values is compared for the same turbulent wind speed.

Onshore wind farm siting prioritization based on investment profitability for Greece

A feasibility study is presented on mid-size onshore wind farms in Greece, taking into consideration two metrics for the evaluation of the profitability of the pertinent investment, namely the net present value, and the internal rate of return. An operationally complete wind park of ten 3.2 MW turbines is considered, incorporating all required power conversion/transmission, and transportation infrastructure that an owner would have to construct. Actual wind speed data are employed from 285 weather stations installed throughout the country and covering a period of 1 to 12 years. The costs of installation, operation, and financing are explicitly accounted for over a standard lifecycle of twenty years. Given the regulated wholesale price for renewable electrical power, the proximity of many sites to ports, and the relatively uniform cost of investing, it is the wind potential that remains the governing factor affecting the financial viability of the wind park. Accordingly, the most profitable areas are the Aegean islands, the south-central mainland coastline, east Peloponnese, and south Attica. Most other regions of mainland Greece are found to be either marginally profitable or to generate a net loss given the current wholesale prices, wind turbine technology and investment costs.

Load case reduction for offshore wind turbine support structure fatigue assessment by importance sampling with two‐stage filtering

AbstractA complete fatigue assessment for operational conditions for offshore wind turbines involves simulating thousands of environmental states. For applications such as optimization, where this assessment needs to be repeated many times, that presents a significant computational problem. Here, we propose a novel way of reducing the number of simulated environmental states (load cases) while maintaining an acceptable accuracy. From one full fatigue analysis of a base design, the OC3 monopile (with the NREL 5MW turbine), the distribution of fatigue damage per load case can be used to estimate the lifetime fatigue damage of a range of modified designs. Using importance sampling and a specially adapted two‐stage filtering procedure, we obtain pseudo‐optimal sets of load cases from which the fatigue damage is estimated. This is applied to seven different designs that have been modified to emulate iterations of an optimization loop. For several of these designs, sampling less than 1% of all load cases can give damage estimates with median errors of less than 2%. Even for the most severe cases, using 3% of the environmental states yields a maximum error of 10%. While further refinement is possible, the method is considered viable for applications within design optimization and preliminary design.

Prediction and multi‐objective optimization of tidal current turbines considering cavitation based on GA‐ANN methods

AbstractAs a new type of energy, tidal current energy is increasingly gaining attention worldwide. However, the tidal current energy development field faces a key technical problem of how to improve the generation efficiency and service life of tidal current generators. In this study, an innovative optimized design method of the horizontal axis tidal turbine was applied to the rotor blade design. To be specific, blade cavitation was considered as a factor for optimization and then was improved using a modern optimization method that combined artificial neural networks and genetic algorithms, solving for a numerical solution. In the optimization program, the annual energy output and the superficial area of the rotor blade served as the optimization goals, and the chord length and the twist angle served as the optimization variables. The cavitation constraint was different from the traditional method in that the judgment criterion of occurrence of cavitation was no longer the minimum pressure coefficient but the maximum stress coefficient. The combination of the artificial neural network and the genetic algorithm not only realized high optimization accuracy but also greatly saved computation time. To verify the validity of the optimization method, a 1 MW turbine was designed, and the optimal solution was chosen from the formed Pareto optimal solution set for modeling, and the new model was compared with the model quoted in the reference. The simulation result shows that the turbine designed using the optimization method not only reduces the surface area of the rotor blade and improves the annual energy output, but also remarkably improves the blades' cavitation resistance. The optimization analysis and comparison using different cavitation judgment criteria shows that the cavitation resistance of blades obtained using the maximum stress coefficient as the judgment criterion is more advantageous.

A new method for spatial allocation of turbines in a wind farm based on lightning protection efficiency

AbstractExisting studies of the spatial allocation of wind farms are typically based on turbine power generation efficiency and rarely consider the damage caused by lightning strikes. However, lightning damage seriously affects the economic performance of wind farms because of the high cost of repairing or replacing damaged blades. This paper proposes a method for the spatial optimization of multiple turbines based on lightning protection dependability. Firstly, the lightning protection efficiency of turbine blade protection systems is analyzed by combining the physical mechanisms of lightning leader progression with a conventional electro‐geometric model to develop an electro‐geometric model of turbine blades (EGMTB). Then, the optimized spatial allocation of multiple turbines in a wind farm is investigated using the EGMTB. The results are illustrated from an example wind farm with 1.5 MW turbines, which shows that the optimal spacing between two turbines perpendicular to the prevailing wind direction L⊥ is 4R‐6R, where R is the length of a turbine blade. This spacing is shown to effectively shield turbine blades from lightning damage over a wide range of lightning currents (>26‐60 kA). Note that, the suggested L⊥ will be smaller considering the influence of lightning polarity as it takes more difficulty developing upward leader (UL) in the condition of positive lightning striking. Experiments verify the effectiveness and correctness of this method.

The super-turbine wind power conversion paradox: using machine learning to reduce errors caused by Jensen's inequality

Abstract. Wind power is a variable generation resource and therefore requires accurate forecasts to enable integration into the electric grid. Generally, the wind speed is forecast for a wind plant and the forecasted wind speed is converted to power to provide an estimate of the expected generating capacity of the plant. The average wind speed forecast for the plant is a function of the underlying meteorological phenomena being predicted; however, the wind speed for each turbine at the farm is also a function of the local terrain and the array orientation. Conversion algorithms that assume an average wind speed for the plant, i.e., the super-turbine power conversion, assume that the effects of the local terrain and array orientation are insignificant in producing variability in the wind speeds across the turbines at the farm. Here, we quantify the differences in converting wind speed to power at the turbine level compared with a super-turbine power conversion for a hypothetical wind farm of 100 2 MW turbines as well as from empirical data. The simulations with simulated turbines show a maximum difference of approximately 3 % at 11 m s−1 with a 1 m s−1 standard deviation of wind speeds and 8 % at 11 m s−1 with a 2 m s−1 standard deviation of wind speeds as a consequence of Jensen's inequality. The empirical analysis shows similar results with mean differences between converted wind speed to power and measured power of approximately 68 kW per 2 MW turbine. However, using a random forest machine learning method to convert to power reduces the error in the wind speed to power conversion when given the predictors that quantify the differences due to Jensen's inequality. These significant differences can lead to wind power forecasters overestimating the wind generation when utilizing a super-turbine power conversion for high wind speeds, and indicate that power conversion is more accurately done at the turbine level if no other compensatory mechanism is used to account for Jensen's inequality.

Effect of Boundary Layer and Rotor Speed on Broadband Noise from Wind Turbines

Trailing edge surface of aerofoil is an important source of broadband aerodynamic noise production. In this paper, three aerofoil self-noise mechanisms from turbulent boundary layer near trailing edge surface are studied. Numerical computations were performed for a three bladed 2 MW horizontal axis upwind turbine of blade length 37 m and source height of 80 m, for wind speeds of 8-15 m/s. A weighted 1/3rd octave band sound power levels (SPL) are evaluated for receiver located at distance of total turbine height and at 2 m above ground. The results obtained for sound power level using baseline models showed maximum values occurring between 300 Hz and 1 kHz region of spectrum. The trends for BPM model showed a reduction of ~2 dBA near 1 kHz region of spectrum at 10 m/s, but Grosveld’s and Lowson model were identical and agreed over the entire spectrum. The effect of rotational speed on sound power levels using three baseline models are illustrated at a wind speed of 8 m/s for 2 MW turbine. Results showed that for a change of ±10% rotor speed from the rated value, there is an increase of 2 to 6 dBA over the entire sound spectrum due to differences in blade tip speed.