Resource Documents: Technology (158 items)
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Author: Mishnaevsky, Leon
Abstract – A review of the root causes and mechanisms of damage and failure to wind turbine blades is presented in this paper. In particular, the mechanisms of leading edge erosion, adhesive joint degradation, trailing edge failure, buckling and blade collapse phenomena are considered. Methods of investigation of different damage mechanisms are reviewed, including full scale testing, post-mortem analysis, incident reports, computational simulations and sub-component testing. The most endangered regions of blades include the protruding parts (tip, leading edges), tapered and transitional areas and bond lines/adhesives. Computational models of different blade damage mechanisms are discussed. The role of manufacturing defects (voids, debonding, waviness, other deviations) for the failure mechanisms of wind turbine blades is highlighted. It is concluded that the strength and durability of wind turbine blades is controlled to a large degree by the strength of adhesive joints, interfaces and thin layers (interlaminar layers, adhesives) in the blade. Possible solutions to mitigate various blade damage mechanisms are discussed.
Leon Mishnaevsky, Jr.
Department of Wind Energy, Risø Campus, Technical University of Denmark, Roskilde, Denmark
Materials 2022, 15(9), 2959; doi:10.3390/ma15092959
Download original document: “Root Causes and Mechanisms of Failure of Wind Turbine Blades: Overview”
Beton und Stahl für den Windrad-Bau in der Wilstermarsch [Concrete and steel for wind turbine foundations]
Author: Schleswig-Holstein Magazin
06.12.2021 | Schleswig-Holstein Magazin
Author: Smil, Vaclav
Wind turbines are the most visible symbols of the quest for renewable electricity generation. And yet, although they exploit the wind, which is as free and as green as energy can be, the machines themselves are pure embodiments of fossil fuels.
Large trucks bring steel and other raw materials to the site, earth-moving equipment beats a path to otherwise inaccessible high ground, large cranes erect the structures, and all these machines burn diesel fuel. So do the freight trains and cargo ships that convey the materials needed for the production of cement, steel, and plastics. For a 5-megawatt turbine, the steel alone averages [pdf] 150 metric tons for the reinforced concrete foundations, 250 metric tons for the rotor hubs and nacelles (which house the gearbox and generator), and 500 metric tons for the towers.
If wind-generated electricity were to supply 25 percent of global demand by 2030 (forecast [pdf] to reach about 30 petawatt-hours), then even with a high average capacity factor of 35 percent, the aggregate installed wind power of about 2.5 terawatts would require roughly 450 million metric tons of steel. And that’s without counting the metal for towers, wires, and transformers for the new high-voltage transmission links that would be needed to connect it all to the grid.
A lot of energy goes into making steel. Sintered or pelletized iron ore is smelted in blast furnaces, charged with coke made from coal, and receives infusions of powdered coal and natural gas. Pig iron is decarbonized in basic oxygen furnaces. Then steel goes through continuous casting processes (which turn molten steel directly into the rough shape of the final product). Steel used in turbine construction embodies typically about 35 gigajoules per metric ton.
To make the steel required for wind turbines that might operate by 2030, you’d need fossil fuels equivalent to more than 600 million metric tons of coal.
A 5-MW turbine has three roughly 60-meter-long airfoils, each weighing about 15 metric tons. They have light balsa or foam cores and outer laminations made mostly from glass-fiber-reinforced epoxy or polyester resins. The glass is made by melting silicon dioxide and other mineral oxides in furnaces fired by natural gas. The resins begin with ethylene derived from light hydrocarbons, most commonly the products of naphtha cracking, liquefied petroleum gas, or the ethane in natural gas.
The final fiber-reinforced composite embodies on the order of 170 GJ/t. Therefore, to get 2.5 TW of installed wind power by 2030, we would need an aggregate rotor mass of about 23 million metric tons, incorporating the equivalent of about 90 million metric tons of crude oil. And when all is in place, the entire structure must be waterproofed with resins whose synthesis starts with ethylene. Another required oil product is lubricant, for the turbine gearboxes, which has to be changed periodically during the machine’s two-decade lifetime.
Undoubtedly, a well-sited and well-built wind turbine would generate as much energy as it embodies in less than a year. However, all of it will be in the form of intermittent electricity—while its production, installation, and maintenance remain critically dependent on specific fossil energies. Moreover, for most of these energies—coke for iron-ore smelting, coal and petroleum coke to fuel cement kilns, naphtha and natural gas as feedstock and fuel for the synthesis of plastics and the making of fiberglass, diesel fuel for ships, trucks, and construction machinery, lubricants for gearboxes—we have no nonfossil substitutes that would be readily available on the requisite large commercial scales.
For a long time to come—until all energies used to produce wind turbines and photovoltaic cells come from renewable energy sources—modern civilization will remain fundamentally dependent on fossil fuels.
Water droplet erosion of wind turbine blades: mechanics, testing, modeling and future perspectives
Mohamed Elhadi Ibrahim and Mamoun Medraj
Department of Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada
[Abstract] The problem of erosion due to water droplet impact has been a major concern for several industries for a very long time and it keeps reinventing itself wherever a component rotates or moves at high speed in a hydrometer environment. Recently, and as larger wind turbine blades are used,erosion of the leading edge due to rain droplets impact has become a serious issue. Leading-edge erosion causes a significant loss in aerodynamics efficiency of turbine blades leading to a considerable reduction in annual energy production. This paper reviews the topic of water droplet impact erosion as it emerges in wind turbine blades. …
A probabilistic long-term framework for site-specific erosion analysis of wind turbine blades: a case study of 31 Dutch sites
Amrit Shankar Verma, Zhiyu Jiang, Zhengru Ren, Marco Caboni, Hans Verhoef, Harald van der Mijle-Meijer, Saullo G.P. Castro, and Julie J.E. Teuwen
Faculty of Aerospace Engineering, University of Technology, Delft, The Netherlands; Department of Ships and Ocean Structures, SINTEF Ocean, Trondheim, Norway; Department of Engineering Sciences, University of Agder, Grimstad, Norway; Department of Marine Technology, Norwegian University of Science and Technology, Trondheim, Norway; TNO Energy Transition, Petten, The Netherlands
[Abstract] Rain-induced leading-edge erosion (LEE) of wind turbine blades (WTBs) is associated with high repair and maintenance costs. The effects of LEE can be triggered in less than 1 to 2 years for some wind turbine sites, whereas it may take several years for others. In addition, the growth of erosion may also differ for different blades and turbines operating at the same site. Hence, LEE is a site- and turbine-specific problem. In this paper, we propose a probabilistic long-term framework for assessing site- specific lifetime of a WTB coating system. Case studies are presented for 1.5 and 10 MW wind turbines, where geographic bubble charts for the leading-edge lifetime and number of repairs expected over the blade’s service life are established for 31 sites in the Netherlands. The proposed framework efficiently captures the effects of spatial and orographic features of the sites and wind turbine specifications on LEE calculations. For instance, the erosion is highest at the coastal sites and for sites located at higher altitudes. In addition, erosion is faster for turbines associated with higher tip speeds, and the effects are critical for such sites where the exceedance probability for rated wind conditions are high. …
RADAR-derived precipitation climatology for wind turbine blade leading edge erosion
Frederick Letson, Rebecca J. Barthelmie, and Sara C. Pryor
Department of Earth and Atmospheric Sciences and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York
[Abstract] Wind turbine blade leading edge erosion (LEE) is a potentially significant source of revenue loss for windfarm operators. Thus, it is important to advance understanding of the underlying causes, to generate geospatial estimates of erosion potential to provide guidance in pre-deployment planning and ultimately to advance methods to mitigate this effect and extend blade lifetimes. This study focuses on the second issue and presents a novel approach to characterizing the erosion potential across the contiguous USA based solely on publicly available data products from the National Weather Service dual-polarization RADAR. The approach is described in detail and illustrated using six locations distributed across parts of the USA that have substantial wind turbine deployments. Results from these locations demonstrate the high spatial variability in precipitation-induced erosion potential, illustrate the importance of low probability high impact events to cumulative annual total kinetic energy transfer and emphasize the importance of hail as a damage vector.
Rain erosion maps for wind turbines based on geographical locations: a case study in Ireland and Britain
Kieran Pugh and Margaret Stack
Department of Mechanical Engineering, University of Strathclyde, Glasgow, Scotland
[Abstract] Erosion rates of wind turbine blades are not constant, and they depend on many external factors including meteorological differences relating to global weather patterns. In order to track the degradation of the turbine blades, it is important to analyse the distribution and change in weather conditions across the country. This case study addresses rainfall in Western Europe using the UK and Ireland data to create a relationship between the erosion rate of wind turbine blades and rainfall for both countries. …
[Introduction] … One common advance is to install much larger blades, however, this is coupled with substantially greater tip velocities of the blades. These increased velocities create a higher risk of degradation of the leading edge due to impacts from rain erosion. With tip speeds from turbines reaching 300mph, the repeated impact of raindrops is sufficiently energetic to erode the material. The erosion rates of wind turbines have a direct relationship to the environment they are erected. More rainfall will result in more erosion of turbine blades. Typically wind turbine farms are constructed in barren locations due to land availability, wind speeds and away from local beauty spots; however, this results in turbines being subjected to harsh conditions and in some locations heavy rainfall. …
Mapping hail meteorological observations for prediction of erosion in wind turbines
Hamish Macdonald, David Infield, David H. Nash, and Margaret M. Stack
Wind Energy Systems CDT and Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow, Scotland
[Abstract] Wind turbines can be subject to a wide range of environmental conditions during a life span that could conceivably extend beyond 20 years. Hailstone impact is thought to be a key factor in the leading edge erosion and damage of the composite materials of wind turbine blades. Using UK meteorological data, this paper demonstrates that the rotational speed is a crucial factor in determining the magnitude of the kinetic energy associated with singular impact and is likely to be significant for incidents of hail. …
Forurensing fra vindturbinvinger
[Leading edge erosion and pollution from wind turbine blades]
Asbjørn Solberg, Bård-Einar Rimereit, and Jan Erik Weinbach
The Turbine Group, Stavanger, Sogndal, and Trondheim, April 22, 2021 [in Norwegian]. Download.
[Foreword] We have put together a report on an undercommunicated topic: microplastic emissions and possible toxic compounds in them. … Already in 2013, rotor blades for wind turbines accounted for 27% of Europe’s consumption of fiberglass-reinforced epoxy. Depending on the production method for the rotor blades, the epoxy contains as much as ~33% bisphenol A. … Bisphenol A is on the «Norwegian priority list of dangerous substances». (Vi har satt samme en rapport om et underkommunisert tema; utslipp av mikroplast og mulige giftige forbindelser i disse. Allerede i 2013 utgjorde rotorblad til vindkraftverk 27 % av Europas forbruk av glassfiberarmert epoksy. Avhengig av produksjonsmetode for rotorbladene så inneholder epoksyen så mye som ca. 33 % Bisfenol A. Bisfenol A står på «Den norske prioritetslista over farlige stoff».)