71 research outputs found
Study of Atmospheric Ice Accretion on Wind Turbine Blades
No full textThis Ph.D. work concerns itself with the atmospheric ice accretion on wind turbine blades. The wind energy has been at the forefront of the renewable energy generation for the last several decades, with the amount and capacity of installed wind turbines steadily increasing. The cold climate (CC) regions around the world like Finland, Germany, Slovak Republic, Norway, Czech Republic, UK, Sweden, Bulgaria, Hungary, Russia, Canada and USA have great potential of wind resources. Estimated wind energy capacity in CC is about 60 GW. [1] However, due to this steady increase in the installed power capacity, more and more turbines have to be placed in regions with harsh geographical conditions, such as arctic regions, in which the temperatures below the normal operating conditions can result in the atmospheric icing to accumulate on the wind turbines particularly along blades. The icing on wind turbines blades leads to negative effects, such as, decreased lift and increased drag, increased mechanical wear and fatigue, possibility of ice throw, which negatively impacts the personnel and life in the area, aeroacoustics noise, generated from iced wind turbines, etc. The icing on wind turbines occurs when super-cooled water droplets collide with the wind turbine structure in the passing clouds (in-cloud icing) and/or freezing rain or drizzle freezes on the exposed wind turbine structure (precipitation icing). Within the scope of this Ph.D. work, the focus is made on the in-cloud icing on the wind turbines.
While there are existing standards and guidelines for the design and operation of wind turbines in normal, temperate climates, for example, the International Electrotechnical Commission standards for offshore turbines, including IEC 61400-1, IEC 61400-3, and the standards for the processes of type certification, which are commonly used to certify turbines in Europe (IEC 2001, 2005, 2010a, 2010b). However, no such definite framework exists for the design, operation and maintenance of wind turbines in cold, ice-prone regions. Thus, the better understanding of the atmospheric ice accretions on wind turbines and their negative effects, such as losses in power production due to the icing is a critical objective for the successful operation of the wind power in CC, ice-prone regions.
For the purposes of better understanding of the icing physics, involved in the icing on the wind turbines, the analytical, numerical and the experimental tools are used in this project. The analytical modelling is done by using the ISO 12494 standard: “Atmospheric Icing on Structures” with some modifications done to it, in order to permit analytical modelling of ice accretion on wind turbines, using basic circular cylinders from ISO 12494 as a reference collector. The numerical modelling scheme employs the usage of modern Computational Fluid Dynamics (CFD) tools such an ANSYS FENSAP-ICE and ANSYSFluent which are used to study the ice accretion process on airfoils and blades. These CFD tools allow for the study of icing physics in greater detail than the analytical model allows, for example by simulating the resultant ice shapes and their impact on the aerodynamic performance of the iced airfoils, when compared to the clean ones. The experimental methodology of this work encompasses usage of the icing tunnel experimental data, for the validation purposes of the numerical modelling, and the field measurements data from the Supervisory Control and Data Acquisition (SCADA) system, taken from a wind park operating in the CC region. The main reason for this is to perform a wind resource assessment study in the CC, ice prone region, in addition to the use of supplementary statistical and numerical modelling tools, such as T19IceLossMethod and WindSim.
The results of atmospheric ice accretion on the wind turbine blades show that the aerodynamic performance changes mainly due to difference in droplet freezing fraction as due to low freezing fraction for the glaze ice conditions, higher amount of the water runback and the aerodynamic heat flux along leading edge is observed which results in the complex horn type ice shapes. The phenomenon of the flow interaction in the third dimension results in the velocity magnitudes being reduced in the 3D simulations, when compared to the 2D simulations. This, in turn, affects the ice accretion process, as the higher velocity magnitudes in the 2D cases result in the higher droplet inertia, collision efficiencies and the maximum impingement angles, which results in more ice mass accreted along the leading edge with the thicker and larger ice shapes present in the 2D simulations.
The results of wind resource assessment of ice prone region show that power production for wind parks can be lower in CC regions when compared to identical wind parks/turbines situated in warmer temperate climates. However, the icing-related issues and the associated power losses need to be solved. It shows that duration and timing of the icing event is different for different wind turbines in a wind park, which clearly indicates that the icing events depend upon the meteorological conditions, airflow behaviour and also the location of the wind turbine. Even in the same wind park, it is not given that ice will accrete on all wind turbines under the same instrumental and on-site conditions. The wind park layout and changes in flow behaviour affects the occurrence of ice accretion, despite the favourable conditions for icing events being present.
Two main topics have been considered in this Ph.D. work: the atmospheric ice accretion on wind turbine blade and the performance losses associated with it; and the wind resource assessment in the ice prone region. Both of these topics are of major importance for the wind industry in CC, ice prone regions, due to the challenges present in the form of potential icing conditions and events and the resultant energy production losses. The results obtained in this Ph.D. thesis can be summarized, in short, as follows: power losses due to icing on wind turbines occur not because of a single reason, but through a combination of effects that need to be taken into account carefully during the wind park design process. These effects include the blade profile surface roughness and heat fluxes, which change significantly during the ice accretion process, and, in turn, affect the airflow and droplet behaviour. The change in the accreted ice shape affects both the airflow behaviour and the aerodynamics performance. With the increase in the atmospheric temperature, the type of accreted ice also changes from dry rime to wet glaze ice, which leads to a change in the ice density and also the accreted ice shapes on the wind turbine blades. Generally, wet ice growth is more damaging for wind turbine operations in icing conditions as compared to dry rime ice growth, due to higher degradation of aerodynamic characteristics under the glaze icing conditions.
The results obtained in this work also provide the need and motivation for improving the understanding about icing effects on the wind turbine blades and the improvement of the existing (or creating new) anti-/de-icing technologies
Feasibility Study of Hydrogen Production from Wind Energy in Narvik
No full textThe use of renewable energy sources is gaining momentum globally as possible replacements for fossil fuels which have proven to be serial contributors to global warming. Hydrogen is one such environmentally friendly fuel with zero carbon emission proven to be reliable for use in the transport sector. Since hydrogen is an energy carrier, its mode of production has for a long time relied on high carbon emission fuels that negate its authority as emission-free fuel.
Therefore, this study investigates a green hydrogen production method based on water electrolysis using electrical energy from wind power. The project entails a detailed wind resource assessment around Narvik region through historical meteorological data analysis, and CFD simulations using Windographer and WindSim software programs to ascertain the viability of the wind power potential of the area. Thereafter, the project establishes suitable location(s) for appropriate wind turbine siting to generate optimal net AEP for use in the electrolysers. Subsequently, a detailed analytical calculation is conducted on the possible amount of hydrogen that can be produced when a water electrolyser system is installed at the Djupvik site based on the net AEP values obtained. Finally, there is determination of the probable cost estimates for such a venture
Wind resource assessment in cold climate regions
No full textCold regions have good potential for wind energy development, but icing on wind turbines is recognize as a hindrance limiting the wind energy production in ice prone cold regions. This master thesis work is linked with Wind-CoE project of Arctic Technology Research Team and is aimed on better understanding of wind resource assessment in cold regions. Three years (2013-15) field SCADA data from Nygårdsfjellet wind park located in an ice prone region near Narvik is used for this study. This work encompass both analytical and numerical analysis to better estimate the annual energy production (AEP) and study of wind flow physics over complex terrain. Computational fluid dynamics based numerical techniques has been used. A good agreement is found between analytical and numerical results
Ice Accretion on Fixed-Wing Unmanned Aerial Vehicle—A Review Study
No full textIce 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
Numerical Study of Atmospheric Ice Accretion on Various Geometric Cross-sections
No full text This paper describes the numerical study of atmospheric ice accretion on four different geometric cross sections, circular, parabola, triangle and cube. Most structures are the combination of these four basic geometric cross sections. Understanding of the atmospheric ice accretion physics on these will provide a base for further analyses of ice accretion and its effects on complex structures. CFD based numerical analyses are carried out in this research work to understand the rate and shape of atmospheric ice growth on these cross sections. For constant wind speed and atmospheric temperature, the ice growth is simulated as function of time, where more ice accretion is found on cube as compared to three other cross sections. Parametric study to understand the effect of iced surface roughness showed a significant difference in ice growth, when compared with the case, where no surface roughness was assumed on the cross sections. </jats:p
On the Fidelity of RANS-Based Turbulence Models in Modeling the Laminar Separation Bubble and Ice-Induced Separation Bubble at Low Reynolds Numbers on Unmanned Aerial Vehicle Airfoil
No full textThe operational regime of Unmanned Aerial Vehicles (UAVs) is distinguished by the dominance of laminar flow and the flow field is characterized by the appearance of Laminar Separation Bubbles (LSBs). Ice accretion on the leading side of the airfoil leads to the formation of an Ice-induced Separation Bubble (ISB). These separation bubbles have a considerable influence on the pressure, heat flux, and shear stress distribution on the surface of airfoils and can affect the prediction of aerodynamic coefficients. Therefore, it is necessary to capture these separation bubbles in the numerical simulations. Previous studies have shown that these bubbles can be modeled successfully using the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) but are computationally costly. Also, for numerical modeling of ice accretion, the flow field needs to be recomputed at specific intervals, thus making LES and DNS unsuitable for ice accretion simulations. Thus, it is necessary to come up with a Reynolds-Averaged Navier–Stokes (RANS) equation-based model that can predict the LSBs and ISBs as accurately as possible. Numerical studies were performed to assess the fidelity of various RANS turbulence models in predicting LSBs and ISBs. The findings are compared with the experimental and LES data available in the literature. The structure of these bubbles is only studied from a pressure coefficient perspective, so an attempt is made in these studies to explain it using the skin friction coefficient distribution. The results indicate the importance of the use of transition-based models when dealing with low-Reynolds-number applications that involve LSB. ISB can be predicted by conventional RANS models but are subjected to high levels of uncertainty. Possible recommendations were made with respect to turbulence models when dealing with flows involving LSBs and ISBs, especially for ice accretion simulations
Ice Accretion on Rotary-Wing Unmanned Aerial Vehicles—A Review Study
No full textIce 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
Cable Propelled Gondola System Operation in Icing Conditions
No full textThe scope of this study comprehends problems associated with modern urban vehicles
known as cable propelled gondolas system operations in icing conditions. The aspects
under consideration are problems related to the operations, safety, and maintenance of
cable car systems in harsh climate conditions. The geographical location of the gondola
cars makes them vulnerable to severe weather conditions especially in cold climates of
the northern hemisphere, where icing on its components is an operational, maintenance,
and safety concern. The harsh climate conditions can cause unadorned malfunctions
posing a threat to the integrity the of system as well as a high risk to human safety. The
study basis on the identification of these problems in operational, maintenance and safety
domain including implications the industry faces in the form of severe accidents costing
precious lives and lost capital. Furthermore, it incorporates the ice detection, anti/de-icing
approaches as well as the safety strategies in use nowadays. The massive increase in
operations and dynamic climate conditions gondola cars require serious attention. This
study unsheathes serious underlying problems that severely affect the gondola operations,
makes them prone to major maintenance shutdowns and poses high risk to structural and
human safety. The identified problems in this study and severity of risks draw attention
to need for practicable solutions incorporating de-icing and ice removal techniques for
safe operation of gondolas in cold climates saving time, effort, inconvenience, and
prodigious lost capital
Numerical analyses of proton electrolyte membrane fuel cell's performance having a perforated type gas flow distributor
No full textNumerical Study of Atmospheric Icing on Non Rotating Circular Cylinders in Tandem Arrangement
No full textNumerical study of atmospheric ice accretion on two non-rotating circular cylinders in tandem arrangement was carried out at different operating and geometric conditions. To validate the numerical model, initially the results of ice accretion on single circular cylinder were compared with the experimental data obtained from CIGELE atmospheric icing research wind tunnel (CAIRWT) [1, 2]. A good agreement was found between experimental and numerical results. Numerical analyses of ice accretion on two circular cylinders in tandem arrangement showed that accreted ice loads decreases with the increase in distance between the cylinders and also affects the rate and shape of ice accretion. Parametric study at different droplet sizes and temperatures showed a significant change in ice accretion. This research work provides a useful base for better understanding and further investigation of atmospheric ice accretion on circular overhead power network cables in tandem arrangement, installed in the cold regions
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