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For wind turbines under offshore conditions, ice accretion occurs on the blade surface in winter because of the cold and humid environment, which leads to the performance degradation of the wind turbine. The characteristics of icing on the wind turbine blade surface under the in-cloud condition with salinity are explored. A blade segment with an airfoil of NACA0018 is selected. The tests of icing on the blade surface in different conditions of salinities, temperatures, and wind speeds are conducted in a return-flow icing wind tunnel. Two parameters are defined to evaluate icing characteristics. The distribution and amount of ice are analyzed quantitatively. Results show that salinity can restrain the amount of ice accretion. Oppositely, low temperatures and high wind speeds can increase the amount of ice. A self-developed device was manufactured to measure the adhesion strength of ice. The effects of salinity, temperature, and wind speed on adhesion strength are studied. Research indicates that adhesion strength decreases sharply first and then slowly with an increase in salinity. Even though low temperature and high wind speed both increase the adhesion strength, the growth rate decreases. The research provides a reference for anti- and de-icing technologies of offshore wind turbines. [ABSTRACT FROM AUTHOR]

Ice accretion poses substantial safety hazards for the manned and unmanned aviation industries. Its study is essential for icing events risk assessment and for the development of efficient ice protection systems. The existing ice accretion measurement techniques—casting, molding, and laser-scanning—are time-consuming, sometimes cumbersome to use, and highly expensive, while hand tracing is inexpensive, but has lower accuracy and time-consuming post-processing. This work presents two low-cost, fast, and easy-to-use measurement techniques for 2D ice accretion profiles. Both employ algorithms of automatic ice shape detection, one based on unmediated image-processing, another based on the processing of manual ice tracings. The techniques are applied to ice accretion experiments conducted in an icing wind tunnel at low Reynolds numbers, and their results are validated against ice thickness caliper measurements. A comparison of the results shows that both techniques accurately measure the leading-edge ice thickness and the 2D shape of the ice accretion profiles. One technique is faster, with higher measurement accuracy, but produces interrupted-line 2D ice profiles and requires good lighting conditions, while the other generates continuous-line 2D profiles and has no application restriction, but it is slower, with lower accuracy. A discussion is conducted, aiming to help one determine the best applications for each ice accretion measurement technique presented. [ABSTRACT FROM AUTHOR]

Ice accretion on rotary-wing unmanned aerial vehicles (RWUAVs) needs to be studied separately from the fixed-wing UAVs because of the additional flow complexities induced by the propeller rotation. The aerodynamics of rotatory wings are extremely challenging compared to the fixed-wing configuration. Atmospheric icing can be considered a hazard that can plague the operation of UAVs, especially in the Arctic region, as it can impose severe aerodynamic penalties on the performance of propellers. Rotary-wing structures are more prone to ice accretion and ice shedding because of the centrifugal force due to rotational motion, whereby the shedding of the ice can lead to mass imbalance and vibration. The nature of ice accretion on rotatory wings and associated performance degradation need to be understood in detail to aid in the optimum design of rotary-wing UAVs, as well as to develop adequate ice mitigation techniques. Limited research studies are available about icing on rotary wings, and no mature ice mitigation technique exists. Currently, there is an increasing interest in research on these topics. This paper provides a comprehensive review of studies related to icing on RWUAVs, and potential knowledge gaps are also identified. [ABSTRACT FROM AUTHOR]

When wind turbines work in a cold and humid environment, especially offshore condition, ice accretion on the blade surfaces has a negative effect on the aerodynamic performance. In order to remove the ice from the wind turbine blade, the adhesive characteristics of atmospheric icing on the blade surface should be mastered under various conditions. The objective of this study is to evaluate the effects of offshore atmospheric conditions, including wind speeds, ambient temperatures and, especially, the salt contents on ice adhesion strength for wind turbine blades. The experiments were conducted on a NACA0018 blade airfoil under conditions including an ambient temperature of −3 °C~−15 °C, wind speed of 6 m/s~15 m/s and salt content of 1~20 mg/m3. The results showed that salt content was the most important factor affecting the ice adhesion strength, followed by ambient temperature and wind speed. The interactive effect of wind speed and salt content, ambient temperature and salt content were extremely significant. The research can provide a reference for the anti-icing for offshore wind turbines. [ABSTRACT FROM AUTHOR]

With the continuous expansion of Unmanned Aerial Vehicle (UAV) applications, the threat of icing on UAV flights has garnered increased attention. Understanding the icing principles and developing anti-icing technologies for unmanned aircraft is a crucial step in mitigating the icing threat. However, existing research indicates that changes in Reynolds numbers have a significant impact on the physics of ice accretion. Icing studies on aircraft operating at high Reynolds numbers cannot be directly applied to unmanned aircraft, and mature anti-icing/deicing techniques for manned aircraft cannot be directly utilized for UAVs. This paper firstly provides a comprehensive overview of research on icing for fixed-wing UAVs, including various methods to study unmanned aircraft icing and the identified characteristics of icing on unmanned aircraft. Secondly, this paper focuses on discussing UAV anti-icing/deicing techniques, including those currently applied and under development, and examines the advantages and disadvantages of these techniques. Finally, the paper presents some recommendations regarding UAV icing research and the development of anti-icing/deicing techniques.

Ice accretion poses substantial safety hazards for the manned and unmanned aviation industries. Its study is essential for icing events risk assessment and for the development of efficient ice protection systems. The existing ice accretion measurement techniques—casting, molding, and laser-scanning—are time-consuming, sometimes cumbersome to use, and highly expensive, while hand tracing is inexpensive, but has lower accuracy and time-consuming post-processing. This work presents two low-cost, fast, and easy-to-use measurement techniques for 2D ice accretion profiles. Both employ algorithms of automatic ice shape detection, one based on unmediated image-processing, another based on the processing of manual ice tracings. The techniques are applied to ice accretion experiments conducted in an icing wind tunnel at low Reynolds numbers, and their results are validated against ice thickness caliper measurements. A comparison of the results shows that both techniques accurately measure the leading-edge ice thickness and the 2D shape of the ice accretion profiles. One technique is faster, with higher measurement accuracy, but produces interrupted-line 2D ice profiles and requires good lighting conditions, while the other generates continuous-line 2D profiles and has no application restriction, but it is slower, with lower accuracy. A discussion is conducted, aiming to help one determine the best applications for each ice accretion measurement technique presented.

Ice accretion on rotary-wing unmanned aerial vehicles (RWUAVs) needs to be studied separately from the fixed-wing UAVs because of the additional flow complexities induced by the propeller rotation. The aerodynamics of rotatory wings are extremely challenging compared to the fixed-wing configuration. Atmospheric icing can be considered a hazard that can plague the operation of UAVs, especially in the Arctic region, as it can impose severe aerodynamic penalties on the performance of propellers. Rotary-wing structures are more prone to ice accretion and ice shedding because of the centrifugal force due to rotational motion, whereby the shedding of the ice can lead to mass imbalance and vibration. The nature of ice accretion on rotatory wings and associated performance degradation need to be understood in detail to aid in the optimum design of rotary-wing UAVs, as well as to develop adequate ice mitigation techniques. Limited research studies are available about icing on rotary wings, and no mature ice mitigation technique exists. Currently, there is an increasing interest in research on these topics. This paper provides a comprehensive review of studies related to icing on RWUAVs, and potential knowledge gaps are also identified.

Atmospheric icing, the accumulation of ice on surfaces, is a severe concern for the aviation industry. Deicing and icing prediction tools are necessary for pilots to ensure flight safety, and while there is established technology for large aircraft icing, more research is needed for smaller uncrewed aerial vehicles (UAVs). Here, we present measurements from 59 flights of a multirotor UAV into wintertime low stratus clouds of temperatures between − 3 and − 10 °C. The UAV is equipped with rotor heating to allow flights up to 10 min in icing conditions. Icing severity was quantified by using the rate of increase in battery current during icing, and was then compared with simultaneous, co-located measurements of liquid water content (LWC). LWC measurements were (a) calculated from cloud droplets measured with an in situ holographic imager on a tethered balloon system and (b) retrieved from remote sensing observations (microwave radiometer, ceilometer, cloud radar). We show that, for these environmental conditions, icing was strongly positively correlated to LWC over an LWC range of 0.02 to 0.5 g m−3, independent of temperature and mean droplet size, though droplets > 50 μm in diameter may contribute to increased icing severity. We also show that the LWC retrieved from remote sensing agrees well with the in situ measurements, indicating that remote sensing measurements can effectively be used to assess icing conditions. These are the first known measurements of multirotor UAV icing with co-located LWC measurements in natural clouds. • Icing severity quantified for a multirotor drone using the change in battery current. • Data presented from 59 flights of the drone into supercooled stratus clouds. • Icing severity was found to correlate strongly with supercooled liquid water content. [ABSTRACT FROM AUTHOR]

Atmospheric icing has been recognized as hindrance in proper utilization of good wind resources in cold regions. There is a growing need to better understand the ice accretion physics along wind turbine blades to improve its performance and for optimal design of anti/de-icing system. This article describes a study of ice accretion along wind turbine blade profiles using thermal infrared imaging. Surface temperature distribution along four different blade profile surfaces is studied at different operating conditions. Analysis shows that surface temperature distribution along blade profile surface during ice accretion process is a dynamic process and change in atmospheric conditions and blade geometric characteristics significantly affects the surface temperature and resultant ice accretion. The effect of blade geometry on ice accretion is more prominent in case of wet ice conditions due to low freezing fraction and water run back along blade profile surface. [ABSTRACT FROM AUTHOR]

Abstract Surfaces exposed to atmospheric cold temperature and humid environments are prone to ice accretion. Airplanes, electrical power transmission cables, and wind turbines are typical examples for which icing has to be considered. The measurement of the resulting ice shapes is a challenging process. While macroscopic characteristics of the ice geometry can be observed using photography and optical scanning techniques, microscopic measurements are difficult to conduct because grooved surface partially occludes the geometry of chasms. To overcome this optical inaccessibility, we propose a method to carry out detailed high‐resolution measurements of the accretion surface with micro‐computed tomography. This approach provides a unique visualization of the empty spaces in the feather region. The information obtained by this technique can improve the understanding of ice accretion physics and its computational modeling.

Atmospheric icing can cause severe damage and danger for many different sectors of society, and accurate forecasts of icing can help mitigate this. The aim of the study is to demonstrate how new ceilometer-based icing observations can be used in icing model verification. The study focuses on icing in the lowest 2 km of the atmosphere. The lowest 400 m of the atmosphere is essential for wind energy production and electricity power lines, while the higher elevations are essential from the aviation point of view. For aviation, the most risky situations are take-offs and landings. The ceilometer observations provide a new way to investigate atmospheric icing. Ceilometers provide vertical profiles of clouds which can be further processed in order to identify in-cloud icing conditions. The new type of ceilometer-based icing observations enables more detailed verification of icing forecasts both in the vertical and in terms of geographical location. Overall, the model shows good skill in predicting clear-sky situations. The verification results show that the icing model performs better for inland areas than for coastal areas, which is attributed to the tendency of the model to forecast clouds, and in-cloud icing, at higher altitudes than observed. [ABSTRACT FROM AUTHOR]

Surfaces exposed to atmospheric cold temperature and humid environments are prone to ice accretion. Airplanes, electrical power transmission cables, and wind turbines are typical examples for which icing has to be considered. The measurement of the resulting ice shapes is a challenging process. While macroscopic characteristics of the ice geometry can be observed using photography and optical scanning techniques, microscopic measurements are difficult to conduct because grooved surface partially occludes the geometry of chasms. To overcome this optical inaccessibility, we propose a method to carry out detailed high‐resolution measurements of the accretion surface with micro‐computed tomography. This approach provides a unique visualization of the empty spaces in the feather region. The information obtained by this technique can improve the understanding of ice accretion physics and its computational modeling. [ABSTRACT FROM AUTHOR]

Ice accretion on commercial aircraft operating at high Reynolds numbers has been extensively studied in the literature, but a direct transformation of these results to an Unmanned Aerial Vehicle (UAV) operating at low Reynolds numbers is not straightforward. Changes in Reynolds number have a significant impact on the ice accretion physics. Previously, only a few researchers worked in this area, but it is now gaining more attention due to the increasing applications of UAVs in the modern world. As a result, an attempt is made to review existing scientific knowledge and identify the knowledge gaps in this field of research. Ice accretion can deteriorate the aerodynamic performance, structural integrity, and aircraft stability, necessitating optimal ice mitigation techniques. This paper provides a comprehensive review of ice accretion on fixed-wing UAVs. It includes various methodologies for studying and comprehending the physics of ice accretion on UAVs. The impact of various environmental and geometric factors on ice accretion physics is reviewed, and knowledge gaps are identified. The pros and cons of various ice detection and mitigation techniques developed for UAVs are also discussed.

The reliability and efficiency of power grids directly contribute to the economic well-being and quality of life of citizens in any country. This reliability depends, among other things, on the power lines that are exposed to different kinds of factors such as lightning, pollution, ice storm, wind, etc. In particular, ice and snow are serious threats in various areas of the world. Under certain conditions, outdoor equipment and hardware may experience various problems: cracking, fatigue, wear, flashover, etc. In actual fact, a variety of countermeasures has been proposed over the past decades and a certain number have been applied by utilities in various countries. This contribution presents the status and current trends of different techniques against atmospheric icing of power lines. A snapshot look at some significant development on this topic over the last four decades is addressed. Engineering problems in utilizing these techniques, their applications, and perspectives are also foreseen. The latest up-to-date review papers on the applications and challenges in terms of PhD thesis, journal articles, conference proceedings, technical reports, and web materials are reported.

Wet snow is a primary cause of atmospheric icing, which can lead to severe damage to power towers and lines, resulting in electrical breakdowns and blackouts. This study investigates the influence of climate change on heavy wet snowfall events in Japan by using climate projections obtained from the database for policy decision-making for future climate change (d4PDF). The projected future climate in the regional model simulations shows nonuniform spatial distribution of wet snowfall. The increases in the risk of extreme wet snowfall are found over northern part of Japan Alps (mountainous regions in central Japan) and Hokkaido (northern part of Japan). Self-organizing maps (SOMs) are applied using the surface atmospheric circulation to explore the weather patterns (WPs) associated with changes in heavy wet snowfall. The SOMs show that some WPs have a significant effect on the magnitude, frequency, and location of heavy wet snowfall in Japan. Additionally, the impact of climate forcing on WPs associated with heavy wet snowfall is evaluated to understand the spatially heterogeneous changes in wet snowfall. The SOM analysis results suggest that the future changes in spatially heterogeneous extreme wet snowfall can be attributed to differences in WP responses to climate change. These differences can be attributed to the future variations in the region of the atmospheric layer at temperatures near 0 °C (rain–snow transition layer) among WPs, which can alter the spatial distribution and frequency of heavy wet snowfall. The findings can help inform structural design requirements to withstand regional climate change. [ABSTRACT FROM AUTHOR]

Prediction of ice shapes on a wind turbine blade makes it possible to estimate the power production losses due to icing. Ice accretion on wind turbine blades is responsible for a significant increase in aerodynamic drag and decrease in aerodynamic lift and may even cause premature flow separation. All these events create power losses and the amount of power loss depends on the severity of icing and the turbine blade profile. The role of critical parameters such as wind speed, temperature, liquid water content on the ice shape, and size is analyzed using an ice accretion prediction methodology coupled with a blade element momentum tool. The predicted ice shapes on various airfoil profiles are validated against the available experimental and numerical data in the literature. The error in predicted rime and glime ice volumes and the maximum ice thicknesses varies between 3% and 25% in comparison with the experimental data depending on the ice type. The current study presents an efficient and accurate numerical methodology to perform an investigation for ice‐induced power losses under various icing conditions on horizontal axis wind turbines. The novelty of the present work resides in a unified and coupled approach that deals with the ice accretion prediction and performance analysis of iced wind turbines. Sectional ice profiles are first predicted along the blade span, where the concurrence of both rime and glaze ice formations may be observed. The power loss is then evaluated under the varying ice profiles along the blade. It is shown that the tool developed may effectively be used in the prediction of power production losses of wind turbines at representative atmospheric icing conditions. [ABSTRACT FROM AUTHOR]

Atmospheric ice accretion is considered a severe safety issue for technical systems such as communication infrastructure, power lines, blades of wind turbines, and so on in cold climate regions. Among different sensing systems to detect and provide reliable information about the state of ice, capacitive sensing has been reported as a suitable technique. In capacitive sensing, measured capacitances are influenced due to ice accretion. Signal processing for ice sensors requires to estimate parameters for the state of ice from the data. In this paper, we present a model-based estimation approach for capacitive ice sensors. We analyze different electrode topologies for ice sensing and provide a statistical analysis of the sensor behavior. We hereby consider the random nature of natural ice accretion. From simulations, we show how a statistical model for the measurement process can be derived and demonstrate the construction of estimation algorithms within the Bayesian framework. We will demonstrate the capability of our approach for automated ice detection by means of long-term field data showing the ability to estimate ice layers with a precision better than 1 mm. [ABSTRACT FROM AUTHOR]

Atmospheric in-flight icing on unmanned aerial vehicles (UAVs) is a significant hazard. UAVs that are not equipped with ice protection systems are usually limited to operations within visual line of sight or to weather conditions without icing risk. As many military and commercial UAV missions require flights beyond visual line of sight and into adverse weather conditions, energy-efficient ice protection systems are required. In this experimental study, two electro-thermal ice protection systems for fixed-wing UAVs were tested. One system was operated in anti-icing and de-icing mode, and the other system was designed as a parting strip de-icing system. Experiments were conducted in an icing wind tunnel facility for varying icing conditions at low Reynolds numbers. A parametric study over the ice shedding time was used to identify the most energy-efficient operation mode. The results showed that longer intercycle durations led to higher efficiencies and that de-icing with a parting strip was superior compared to anti-icing and de-icing without a parting strip. These findings are relevant for the development of energy-efficient systems in the future.

Abstract This paper focuses on the meteorological icing phase of typical icing events to determine the factors that affect the ice accretion rate on a wind turbine blade. The linear mass density of ice on the nacelle of a 2 MW horizontal-axis wind turbine is estimated with a camera and is compared to the linear mass density of ice on a blade evaluated by a commercial blade ice detector (e.g. a fos4X ice detector). An automated image analysis software measures the dimension of the ice on a cylindrical tube located on the nacelle and calculates the linear mass density of the ice. The fos4X ice detector estimates the total ice load on the blade by measuring variations in the vibration frequencies of the blade. The total load is then divided by the blade length to obtain the linear density. On-site results were compared to simulations for validation. The ISO 12494 method for theoretical ice accretion on a cylindrical tube was adapted to simulate ice accretion on a rotating wind turbine blade. The main results show that wind speed and turbine rotor RPM directly influence the blade ice accretion rate. A correlation is made between blade and nacelle icing, with on-site results matching the simulation. In summary, for an operating turbine, as wind speed decreases, the rate of ice accretion on the blade increases relative to the ice accretion rate on the nacelle. [ABSTRACT FROM AUTHOR]

This article aims to predict ice loads on a wind turbine blade section at 80% of blade span, using FENSAP ICE. Using low and high liquid water content conditions of stratiform and cumuliform clouds, different icing events are simulated. Ice accretion predictions with single-shot and multi-shot approaches are presented. Blade surface roughness is also investigated, as well as the relationships between ice mass, liquid water content, median volume diameter, and temperature. [ABSTRACT FROM AUTHOR]

This article describes a multiphase computational fluid dynamics-based numerical study of the aeroacoustics response of symmetric and asymmetric wind turbine blade profiles in both normal and icing conditions. Three different turbulence models (Reynoldsaveraged Navier-Stokes, detached eddy simulation, and large eddy simulation) have been used to make a comparison of numerical results with the experimental data, where a good agreement is found between numerical and experimental results. Detached eddy simulation turbulence model is found suitable for this study. Later, an extended computational fluid dynamics-based aeroacoustics parametric study is carried out for both normal (clean) and iced airfoils, where the results indicate a significant change in sound levels for iced profiles as compared to clean. [ABSTRACT FROM AUTHOR]

This paper presents a new method to detect atmospheric icing conditions using different arrangements of thermally heated and instrumented cylindrical probes. The proposed method offers a new low-cost alternative to detect icing conditions. A mathematical model describing the heat transfer behaviour of each probe has been developed and validated experimentally in a temperature-controlled wind tunnel. In situ measurements under icing conditions have shown great potential for the detection of the onset, the duration and the intensity of an icing event. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study to predict ice loads on a wind turbine blade section at 80% of blade span. Air flow, droplet impingement and ice accretion simulations are conducted in FENSAP ICE. The effect of low and high liquid water content (LWC) conditions on blade thickness is presented. All NREL airfoil families used for HAWTs are examined to study blade design's effect on ice accretion. Ice shapes are numerically predicted at different atmospheric temperatures and LWC conditions. The degradation in aerodynamic characteristics due to ice formation is predicted. The numerical predictions suggest a 10%–65% reduction in lift coefficient due to ice accretion, which is highly dependent on the accreted ice shape. [ABSTRACT FROM AUTHOR]

Icing on blade surface of wind turbine greatly affects the performance of wind turbine which becomes a very serious problem for the wind turbine installed in cold and wet regions both for larger-scale wind turbine and small-scale ones. The Straight-bladed Vertical Axis Wind Turbine (SB-VAWT) is a kind of lift-type VAWT which is widely used for small-scale wind power generation. Icing on blade of SB-VAWT will also affect both the starting performance and out power performance. To verify the icing characteristics of blade rotating at low tip speed ratio of the SB-VAWT during its starting stage, wind tunnel icing experiments have been carried out on a rotor with blade airfoil of NACA0018 in a wind tunnel icing experimental system by using natural low temperature in winter proposed in this study. The icing distributions were recorded by a high speed camera at different tip speed ratios from 0 to 1. The weight of icing on blade was also measured. Furthermore, the icing area ratio and icing rate were calculated and analyzed. The main results show that the ice accretion on a rotating blade of SB-VAWT at low tip speed ratio is quite different from the blade in static condition. The icing distributed on the whole surface of blade and the icing area increases along blade airfoil outline with the increasing of icing time and rotational speed. The whole weight of icing on all blades of wind turbine increased with the increasing of blade number. [ABSTRACT FROM AUTHOR]

The capacitive method is considered to be a suitable icing-detection technology, but the lack of fundamental parameters restricts the development of icing-detection sensors. In this paper, an artificial icing laboratory, a capacitive sensor, and some simulation conductors have been designed for obtaining the artificial icing samples. Subsequently, the same characteristic values of artificial icing have been measured by an LCR device, under a selected frequency. This research found that the value of the icing dielectric constant closely correlated with its density, internal sublayer, and the test temperature. Finally, a fitting formula has been presented for calculating the relative dielectric constant, which may provide some important reference value for the design of icing-detection sensors.

A new installation at the Anti-Icing Materials International Laboratory was developed to study the effects of icing on the degradation of a hovering drone rotor aerodynamic performance and to test different potential ice protection solutions. Following a study on icing parameters effects on aerodynamic performance, this paper studies a methodology developed to assess the performances of coatings as a potential ice protection system under severe icing conditions and rotor speeds up to 4950 RPM. Four different coatings, commercial or under development, were applied to the rotor blades and their effect on the resulting ice accumulation and aerodynamic degradation were measured and compared to those previously obtained on similar, uncoated blades. Results show that passive icephobic coatings in general are a promising solution to limit the negative effect of icing conditions for drone applications, without any additional energy consumption from the system. Moreover, the repeatability assessment of tests under similar conditions and for the same coating showed agreement within ±5% between repetitions, showing no signs of ice protection efficiency degradation for any of the tested coatings. • The work of this article marks the continuity of a series of studies done with a new spinning rotor drone test setup in hover flight mode performed at the 9-m high cold chamber of the Anti-Icing Materials International Laboratory (AMIL). Four different surface protection coatings are applied on their own set of blades for testing in the cold room. The resulting ice accumulation and performance degradation of the spinning rotor are then monitored, recorded and compared to the results obtained of bare uncoated blades. The effects and performances of the coatings tested are then assessed. • This report presents a new test methodology and setup to assess the performances of protective surfaces as a passive ice protection system for small and medium drone rotors, which differs than for the rotorcraft application actually found in the literature. It also presented unique results on the possibility of using those surfaces for drones, which cannot be simply deduced from rotorcraft studies found in the literature. This demonstrates the importance of this work and of this new methodology and test setup for the industry since the literature greatly lacks reported data of similar icing tests using ice protection coatings on a UAV. • This first test campaign has proven the ability of icephobic surface coatings to efficiently perform as ice protection systems. Moreover, coatings have a positive potential of being combined with an active ice protection system (such as electrothermal) as a way to reduce the power consumption of those systems. Further research will be done with additional products and also combined with active ice protection systems to help lower their power consumption. [ABSTRACT FROM AUTHOR]

Atmospheric icing is a major weather hazard, known to cause problems for many sectors of society, in particular for power transmission lines. Considering that such structures are designed with a typical expected lifetime of 70 years, climate change impacts on extreme ice loads should be considered. Atmospheric ice accumulation can be modelled with meteorological input from numerical weather prediction models and extreme loads can thereby be estimated. Here we apply dynamical downscaling of the two global climate models, CESM2 and MPI-ESM1‐2-HR, and three future scenarios, using a regional model, WRF, to obtain high resolution data for future atmospheric ice load projections. Results based on both climate models indicate that future 10-year return values of wet snow loads are generally decreasing in the lowlands and increasing at higher elevation for all three scenarios, linked to a general increase in temperature and extreme precipitation. Results for future 10-year rime ice loads differ between the two downscaled models due to differences in regional warming levels and model biases. More research, involving downscaling of more climate models or the use of other methodologies, is needed to obtain more robust projections and uncertainty estimates before design engineers can make any considerations about future ice loads. However, large uncertainties in climate model projections of regional climate challenge the constraint. • North Atlantic warming hole causes large spread in regional climate projections. • The warming hole is extreme in CESM2, while more average in MPI-ESM1–2-HR. • Rime ice results are uncertain, partly due to the differing model warming levels. • Future extreme wet snow loads are generally increasing in higher terrain. [ABSTRACT FROM AUTHOR]

In this case study several periods of measured active icing events have been compared with calculated active icing. Icing events from three winter seasons in Sweden have been selected as a base for studying how well a commonly used method to calculate icing can capture icing events, as well as to try out a new approach. Another purpose is to enlighten parties interested in atmospheric icing of the challenges of calculating icing. For those with little knowledge of Numerical Weather Prediction (NWP) models it can be hard to understand why there are differences between two models, or even the same model using different physical parameterisation schemes. In this study data from two NWP models have been used to calculate icing, as well as being compared with a new approach using meteorological measurements to calculate icing. Using meteorological measurements to calculate icing is an interesting alternative as it is computationally less expensive than using a NWP model to generate the necessary data. All tested methods could at times capture the dynamics of the measured icing, though there are on occasion large differences between the different calculated icing and also between calculations and measurements. This highlights the importance of having an understanding of NWP models when studying atmospheric icing; there can be a large spread between different models, and also when using the same model with different schemes. The results show that calculated icing is comparable to measured icing and that the methodologies investigated are viable options for calculating atmospheric icing. [ABSTRACT FROM AUTHOR]

An ice-detachment failure model is proposed for iced overhead electrical conductors to predict the transient response of line systems subjected to shock loads. The model considers the bending strains in the ice deposit, the adhesive force at the ice–cable interface and the cohesive force within the ice. It is implemented into finite element analysis by setting a critical vertical acceleration corresponding to inertia forces overcoming the adhesive/cohesive forces on the ice chunk. The model is validated by results from reduced and real scale de-icing tests of glaze ice but the approach can apply to different types of atmospheric icing. [ABSTRACT FROM AUTHOR]

Ice accretion on cable-stayed bridge surfaces increases loading, affects the structures' aerodynamic behavior, and heightens the risk of ice pieces detaching and falling onto bridge traffic. Here we propose a comprehensive laboratory-based procedure for evaluating materials to reduce ice accretion and prevent ice shedding on cable-stayed bridge. We then assess our laboratory-based procedure by testing four high-density polyethylene sheath configurations for cable-stayed bridges. These sheaths differ in their surface finishes, chemistry, and surface roughness. We present a three-step controlled-environment procedure involving (i) the physical characterization of the surface; (ii) an evaluation of surface behavior under laboratory icing tests; and (iii) an assessment of ice accretion at −10 °C under freezing rain conditions, followed by shedding and melting phases. This testing procedure provides a simple means of evaluating geometric changes and surface modifications, including icephobicity, under repeatable and comparable conditions. Our approach could serve in the design and optimization of materials prior to their deployment under actual operational conditions. • A laboratory-based procedure for evaluating stay cable sheaths subjected to icing conditions. • A three-step characterization has been performe to evaluated the sheath including the behaviour of the accumulated ice. • Simulated ice accretion a forced melting phase can test various ice-shedding control strategies under a range of icing. [ABSTRACT FROM AUTHOR]

Wind energy is a promising way in the middle of growing demand for clean energy in high north, where atmospheric icing is a hazard for safe operations of wind turbines. In this research work, the vibrational effects due to atmospheric ice accretion on a multi megawatt large wind turbine are numerically investigated using a finite element based approach. Three different icing scenarios were addressed and accreted on-blade ice mass was calculated analytically based upon ISO 95214 standards. Special attentions are given to the first natural frequency of the wind turbine blade and its interaction when the exciting frequency approaches the natural frequency of the wind turbine tower. Results show variations of natural frequencies due to different accreted icing loads scenarios, which may have different implications to the integrity of the structure. [ABSTRACT FROM AUTHOR]