Atmospheric Drivers of Wind Turbine Blade Leading Edge Erosion: Review and Recommendations for Future Research

Leading edge erosion (LEE) of wind turbine blades causes decreased aerodynamic performance leading to lower power production and revenue and increased operations and maintenance costs. LEE is caused primarily by materials stresses when hydrometeors (rain and hail) impact on rotating blades. The kinetic energy transferred by these impacts is a function of the precipitation intensity, droplet size distributions (DSD), hydrometeor phase and the wind turbine rotational speed which in turn depends on the wind speed at hub-height. Hence, there is a need to better understand the hydrometeor properties and the joint probability distributions of precipitation and wind speeds at prospective and operating wind farms in order to quantify the potential for LEE and the financial efficacy of LEE mitigation measures. However, there are relatively few observational datasets of hydrometeor DSD available for such locations. Here, we analyze six observational datasets from spatially dispersed locations and compare them with existing literature and assumed DSD used in laboratory experiments of material fatigue. We show that the so-called Best DSD being recommended for use in whirling arm experiments does not represent the observational data. Neither does the Marshall Palmer approximation. We also use these data to derive and compare joint probability distributions of drivers of LEE; precipitation intensity (and phase) and wind speed. We further review and summarize observational metrologies for hydrometeor DSD, provide information regarding measurement uncertainty in the parameters of critical importance to kinetic energy transfer and closure of data sets from different instruments. A series of recommendations are made about research needed to evolve towards the required fidelity for a priori estimates of LEE potential.publishedVersio

Design mining interacting wind turbines

© 2016 by the Massachusetts Institute of Technology. An initial study has recently been presented of surrogate-assisted evolutionary algorithms used to design vertical-axis wind turbines wherein candidate prototypes are evaluated under fan-generated wind conditions after being physically instantiated by a 3D printer. Unlike other approaches, such as computational fluid dynamics simulations, no mathematical formulations were used and no model assumptions weremade. This paper extends that work by exploring alternative surrogate modelling and evolutionary techniques. The accuracy of various modelling algorithms used to estimate the fitness of evaluated individuals from the initial experiments is compared. The effect of temporally windowing surrogate model training samples is explored. A surrogateassisted approach based on an enhanced local search is introduced; and alternative coevolution collaboration schemes are examined

WIND ENERGY MAPPING USING SYNTHETIC APERTURE RADAR

ABSTRACT Wind energy off-shore is gaining much interest due to the high wind power potentials. The need is to map wind climatology and regional wind patterns in coastal regions. In the WEMSAR (Wind Energy Mapping using Synthetic Aperture Radar) project three European sites will be covered near Norway, Denmark and Italy. Data to be used are from the ERS-2 C-band scatterometer with a 50 km resolution, from ERS-2 Ku-band and Topex Poseidon Ku-Band altimeter with a 7 km resolution and from SAR. The SAR data will be block averaged into 400 m resolution from ERS-2 C_VV, Radarsat C_HH and Envisat ASAR C_VV and C_HH beginning year 2000. For SAR data, the algorithm CMOD IFRE2 (Institute Francaise de Recherche pour L'Exploitation de la Mer) is used based on 3433 collocated pairs of buoys of NOAA and ECMWF (European Centre for Medium Range Weather Forecasts) with the accuracy of ∀2 m/s for a single retrieval. In the validation part of the WEMSAR project for wind energy retrieval, the ESA SAR (SAR.PRI (precision image format)) will be used because of the need for absolute calibration. Validation data are from long-term off-shore and coastal meteorological masts at the sites. Some masts are dedicated to wind power measurements including the roughness of sea and wave height. Optimal validation is crucial as wind energy varies with the third power of the wind speed. Also, the 10 or 19.5 m wind speeds will have to be calculated into 50-100 m height, i.e. the hub height of modern 600-1500 kW wind turbines. This calculation includes stability correction of the wind profiles. Wind analysis at mesoscale (1 km grid) with the non-hydrostatic KAMM (Karlsruhe Atmospheric Mesoscale Model) and WAsP (the Risoe Wind Atlas Analysis and Application Program) for micro-siting will be used. The aim is to link from meteorological mast data to spatial mapping of the wind energy potential based on satellite SAR data in coastal areas

Summer Algal Blooms in a Coastal Ecosystem: the Role of Atmospheric Deposition Versus Entrainment Fluxes

The nitrogen inputs from atmospheric deposition and bottom water entrainment to the surface layer were modelled in the summer period (May–September) over a 11-year period (1989–1999) and compared to investigate the significance of these fluxes for generating blooms in the Kattegat. In the summer periods the average atmospheric deposition was 2.81 mg N m-2 d-1 compared to average entrainment fluxes of 5.42 mg N m-2 d-1, 1.21 mg N m-2 d- and 1.15 mg N m-2 d-1 for the northern, central and southern part of the Kattegat, respectively. Atmospheric nitrogen deposition alone could not sustain biomass increases associated with observed blooms and entrainment fluxes dominated the high nitrogen inputs to the surface layer. The potential for a bloom through growth was typically obtained after several days of high nitrogen inputs from entrainment in the frontal area of the northern Kattegat and to some extent from atmospheric deposition. The modelled nitrogen input in this area could account directly for 30% of the observed blooms in the Northern sub-basin, and through advective transport 24% and 19% of the observed blooms in the central and southern Kattegat. The direct nitrogen inputs through atmospheric deposition and entrainment to the central and southern sub-basins were small and could not be linked to any bloom observation. 2004 Elsevier Ltd. All rights reserved.JRC.H.5-Rural, water and ecosystem resource