Sensitivity Analysis of Turbine Fatigue and Ultimate Loads to Wind and Wake Characteristics in a Small Wind Farm

Wind turbines are designed using a set of simulations to determine the fatigue and ultimate loads, typically focused solely on unwaked wind turbine operation. These structural loads can be significantly influenced by the wind inflow conditions. When placed in the wake of upstream turbines, turbines experience altered inflow conditions, which can additionally influence the fatigue and ultimate loads. Although significant research and effort has been put into measuring and defining such parameters, limited work has been done to quantify the sensitivity of structural loads to the inevitable uncertainty in these inflow conditions, especially in a wind farm setting with waked conditions. It is therefore important to understand the impact such uncertainties have on the resulting loads of both non-waked and waked turbines. The goal of this work is to assess which wind-inflow- and wake-related parameters have the greatest influence on fatigue and ultimate loads during normal operation for turbines in a three-turbine wind farm. Twenty-eight wind inflow and wake parameters were screened using an elementary effects sensitivity analysis approach to identify the parameters that lead to the largest variation in the fatigue and ultimate loads of each turbine. This study was performed using the National Renewable Energy Laboratory 5 MW baseline wind turbine with synthetically generated inflow based on the International Electrotechnical Commission (IEC) Kaimal turbulence spectrum with IEC exponential coherence model. The focus was on sensitivity to individual parameters, though interactions between parameters were considered, and how sensitivity differs between waked and non-waked turbines. The results of this work show that for both waked and non-waked turbines, ambient turbulence in the primary wind direction and shear were the most sensitive parameters for turbine fatigue and ultimate loads. Secondary parameters of importance for all turbines were identified as yaw misalignment, u-direction integral length, and the exponent and u components of the IEC coherence model. The tertiary parameters of importance differ between waked and non-waked turbines. Tertiary effects account for up to 9.0 % of the significant events for waked turbine ultimate loads and include veer; non-streamwise components of the IEC coherence model; Reynolds stresses; wind direction; air density; and several wake calibration parameters. For fatigue loads, tertiary effects account for up to 5.4 % of the significant events and include vertical turbulence standard deviation; lateral and vertical wind integral lengths; lateral and vertical wind components of the IEC coherence model; Reynolds stresses; wind direction; and all wake calibration parameters. This information shows the increased importance of non-streamwise wind components and wake parameters in fatigue and ultimate load sensitivity of downstream turbines.

Optimization of the stereo system calibration parameters for photogrammetric measurements in the conditions of field experiments

Optical methods for deformation diagnostics and surface shape measurement are often used in scientific research and industry. Most of these methods are based on the triangulation of a set of two-dimensional points from different images corresponding to the three-dimensional points of an object in space. Triangulation is based on the stereo system calibration parameters, which are determined before the experiment. Measurements during conditions with increased vibration loads can lead to a change in the relative position of the cameras of the stereo system (decalibration). This leads to a change in the actual calibration parameters and an increase in the measurement error. This work aims to solve the problem of increasing the measurement accuracy of the photogrammetric method in the case of high vibration loads. For this, it is proposed to use an optimization algorithm for calibration parameters to minimize the reprojection error of three-dimensional points calculated using triangulation. The paper presents the results of a computer simulation of decalibration of a video camera stereo system, an algorithm for optimizing the external parameters of a stereo system, and an assessment of its performance.

Multi-station calibration strategy for evaluation and sensitivity analysis of the snowmelt runoff model using MODIS satellite images

In this study, the snowmelt runoff model (SRM) was employed to estimate the effect of snow on the surface flow of Aji-Chay basin, northwest Iran. Two calibration techniques were adopted to enhance the calibration. The multi-station calibration (MSC) and single-station calibration (SSC) strategies applied to investigate their effects on the modeling accuracy. The runoff coefficients (cs and cr) were selected as calibration parameters because of their uncertainty in such an extended basin. To determine the most substantial input of the model which is the snow-covered area (SCA) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor imagery, MOD10A2 images were collected with spatial and temporal resolutions of 500 meters and 8 days, respectively. The results show an average of 15% improvement in the model performance in the MSC strategy from the data period of 2008–2012. Also, an appropriate agreement with physical characteristics of the study area could be seen for the calibration parameters. The contribution of snowmelt in the river flow reaches its peak in April and May, then with increasing temperature, the contribution decreased gradually. Furthermore, analysis of parameters indicates that the SRM is sensitive to recession coefficient and runoff coefficients.

Assessment of recommended and acceptable image quality indicators’ values, based on materials, obtained with various aerial surveying systems for mapping purposes

The results of fine quality indicators assessment for images, obtained with various aerial surveying systems for mapping purposes are presented. The values of parameters that characterize technical conditions, technical parameters of airborne imaging and technologic settings for imagery postprocessing, natural conditions of aerial surveying are determined. The author presents a comparative analysis of fine quality indicators assessment both for photos, the quality of which was found to be satisfactory as production technical control results and those rejected due to some relevant indicators (haze, blurring, etc) and accepted unsuitable for creating cartographic products based on them. It is shown, that some quality indicators, such as spatial resolution, sharpness and the degree (standard deviation) of random noise, are advisable to be determined at performing factory calibration of aerial cameras and included in certificate as well as other calibration parameters as metrological characteristics of the obtained imagery. Acceptable values of fine quality indicators, obtained during joint analysis of previous theoretical researches results and experimental verification, based on images, obtained by various aerial surveying systems for mapping purposes were generalized and recommended during the research.

Localization Of A Mobile Fastening Robot

<div>The goal of this research is to develop a localization system for a mobile fastening robot using a camera and ultrasonic sensors. Localization is performed by using triangulation methods on three target fastener heads. Camera calibration parameters are determined and used to obtain a corrected image on which a Circular Hough Transform algorithm is used to determine the location of the three target fastener heads relative to the camera. The distance to the fastener heads is determined using readings from two ultrasonic sensors. A Kalman Filter is developed and used to reduce the noise of the ultrasonic sensor readings. In addition to filtering, calibration techniques are used to correct the readings of the final localization system. Testing of the complete system is done using a coordinate measuring machine. </div>

Localization Of A Mobile Fastening Robot

<div>The goal of this research is to develop a localization system for a mobile fastening robot using a camera and ultrasonic sensors. Localization is performed by using triangulation methods on three target fastener heads. Camera calibration parameters are determined and used to obtain a corrected image on which a Circular Hough Transform algorithm is used to determine the location of the three target fastener heads relative to the camera. The distance to the fastener heads is determined using readings from two ultrasonic sensors. A Kalman Filter is developed and used to reduce the noise of the ultrasonic sensor readings. In addition to filtering, calibration techniques are used to correct the readings of the final localization system. Testing of the complete system is done using a coordinate measuring machine. </div>

LOCALIZATION OF A MOBILE FASTENING ROBOT

<div>The goal of this research is to develop a localization system for a mobile fastening robot using a camera and ultrasonic sensors. Localization is performed by using triangulation methods on three target fastener heads. Camera calibration parameters are determined and used to obtain a corrected image on which a Circular Hough Transform algorithm is used to determine the location of the three target fastener heads relative to the camera. The distance to the fastener heads is determined using readings from two ultrasonic sensors. A Kalman Filter is developed and used to reduce the noise of the ultrasonic sensor readings. In addition to filtering, calibration techniques are used to correct the readings of the final localization system. Testing of the complete system is done using a coordinate measuring machine. </div>

The Simrad EK60 echosounder dataset from the Malaspina circumnavigation

We provide the raw acoustic data collected from the R/V Hesperides during the global Malaspina 2010 Spanish Circumnavigation Expedition (14th December 2010, Cádiz-14th July 2011, Cartagena) using a Simrad EK60 scientific echosounder operating at 38 and 120 kHz. The cruise was divided into seven legs: leg 1 (14th December 2010, Cádiz-13th January 2011, Rio de Janeiro), leg 2 (17th January 2011, Rio de Janeiro-6th February 2011, Cape Town), leg 3 (11th February 2011, Cape Town-13th March 2011, Perth), leg 4 (17th March 2011, Perth-30th March 2011, Sydney), leg 5 (16th April 2011, Auckland-8th May 2011, Honolulu), leg 6 (13th May 2011, Honolulu-10th June 2011, Cartagena de Indias) and leg 7 (19th June 2011, Cartagena de Indias-14th July 2011, Cartagena). The echosounder was calibrated at the start of the expedition and calibration parameters were updated in the data acquisition software (ER60) i.e., the logged raw data are calibrated. We also provide a data summary of the acoustic data in the form of post-processed products.