Field observations has shown that wind turbinesare especially exposed to lightning strikes. The probability forlightning strikes to offshore wind turbines has been analysed ina previous article. In this project the probability for upwardself-initiated lightning strikes to onshore wind turbines anda lightning protection tower was analysed. This was done bycollecting elevation data and recreating the site topographyin COMSOL Mutliphysics 5.5, and also by collecting weatherdata which were analysed in MATLAB. The probability for thecritical electrostatic field was then calculated and analysed. Theresult shows that the risk of lightning strike is correlated to thetopography and cloud height. / Fältobservationer har visat att vindkraftverk är särskilt utsatta för blixtar. En tidigare studie har analyserat sannolikheten för blixtar på vindkraftverk belägna ute till havs. I det här projektet analyserades sannolikheten för blixtar på vindkraftverk och en vädermast på land. Detta gjordes genom att samla väder och topografidata från de undersökta områdena, som sedan modellerades i COMSOL Multiphysics 5.5. Sannolikheten att ett kritiskt elektriskt fält uppstår beräknades med hjälp av MATLAB. Resultatet visar att risken för blixtar är korrelerat med topografin och molnhöjden. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

<p>Ice forming on wind turbine blades can cause loading imbalance and reduce power production of the turbine. Heating systems that prevent or remove ice on wind turbine blades are one of the more promising solutions to mitigate ice accretion. Methods to apply heat include direct application through electro-thermal resistance heaters mounted on the external surface of the blade or by indirect heating by forcing hot air through a channel along the leading edge of the blade. Heating systems for aircraft blades have become standardized and in some cases compulsory on aircraft to preserve human life; however, the technology is not directly transferable to the blades on wind turbines. The relative power of the anti-icing or de-icing system is critical to providing a cost benefit of having the system.</p> <p>This thesis investigates the heat transfer involved for electro-thermal and hot air heating strategies. An appropriate range of operating conditions and blade constructions are considered in order to characterize the effectiveness of both systems. A numerical model is developed to solve the one dimensional, differential heat transfer equations. The heater power required to prevent ice accumulation (anti-icing) on wind turbine blades is determined for electro-thermal heating. Anti-icing with hot air is shown to be unrealistic for a practical range of operating conditions.</p> <p>The low conductivity of the blade core creates a bottleneck for the de-icing system. It is shown that alternative core materials (Nomex/aluminum honeycomb) can reduce this effect. Electro-thermal and hot air de-icing each have their advantages and cannot be equally compared. In this thesis the suitability of each system has been analysed for a range of operating conditions and wind turbine constructions; the designer can then implement the most suitable strategy for their individual application.</p> / Master of Applied Science (MASc)

En ökad energianvändning, tillsammans med utbyggnaden av vindkraft, förväntas leda till ökade avfallsmängder från uttjänta vindturbinblad och krav på en hållbar hantering över hela värdekedjan. Komplexiteten i materialen som används i vindturbinbladen försvårar återvinningen, vilket leder till att majoriteten av bladen hamnar på deponi med både miljöföroreningar och resursförluster som resultat. Studien syftar till att undersöka möjligheterna och utmaningarna med återanvändning av vindturbinblad till olika tillämpningsområden genom att utvärdera befintlig forskning samt genomförda och potentiella projekt, med fokus på miljömässiga, tekniska och ekonomiska aspekter. Data samlades in genom både kvantitativa och kvalitativa metoder, vilket omfattar litteraturstudier och semistrukturerade intervjuer med relevanta aktörer inom vindkrafts- och återvinningsindustrin. Metoden innefattar även en SWOT-analys och en fallstudie som undersöker återanvändning av vindturbinblad i Umeå kommun, inklusive en undersökning av kommunens marknadsbehov samt vilka möjligheter och utmaningar potentiella aktörer ser kring återanvändningsprocessen. De sammanlagda resultaten från litteraturstudie, intervjuer och SWOT-analys visar på flera tekniska, ekonomiska och miljömässiga möjligheter med återanvändning av vindturbinblad, inklusive möjligheten att potentiellt minska både materialkostnader och växthusgasutsläpp jämfört med alternativen förbränning eller deponering. Flertalet utmaningar identifierades, inklusive utmaningar kring nedmontering, transport, testning av materialets styrka samt brist på information kring materialets innehåll. Även ekonomiska och logistiska hinder kring ansvar hos tillverkare och verksamhetsutövare samt bristen på samarbete för att skapa en effektiv värdekedja konstaterades. Resultatet lyfter betydelsen av samarbete mellan aktörer, tillverkare och avfallshanterare som avgörande för att skapa effektiva lösningar och möjliggöra återanvändning av vindturbinblad. Fallstudien av Umeå kommuns marknadsbehov visar att återanvändning av vindturbinblad skulle kunna täcka en betydande del av kommunens behov för lekplatser, gångbroar och stadsmöbler och samtidigt bidra till en besparing av koldioxidutsläpp. Trots ekonomiska, tekniska och logistiska utmaningar kring nedmontering, bearbetning och transport, ser potentiella aktörer skapande av hållbara affärsmodeller och teknisk kapacitet som positiva möjligheter. Studien bidrar till ökad förståelse och kunskap kring möjligheter och utmaningar med återanvändning av vindturbinblad, vilket är avgörande för att effektivisera processen för nuvarande och framtida aktörer inom branschen. Det är särskilt relevant utifrån de förväntade avfallsmängderna i framtiden och behovet av en effektiv värdekedja. / An increased use of energy, coupled with the expansion of wind power, is expected to lead to increased amounts of waste from end-of-life wind turbine blades and demands for sustainable management across the entire value chain. The complexity of the materials used in wind turbine blades makes recycling difficult, which leads to the majority of blades ending up in landfills with both environmental pollution and resource losses as a result. The study aims to investigate the opportunities and challenges of repurposing wind turbine blades for various application areas by evaluating existing research as well as completed and potential projects, with a focus on environmental, technical and economic aspects. Data was collected through both quantitative and qualitative methods, including literature studies and semi-structured interviews with relevant stakeholders in the wind power and recycling industry. The method also includes a SWOT analysis and a case study that investigates repurposing of wind turbine blades in the municipality of Umeå, including an investigation of the municipality's market needs as well as what opportunities and challenges potential stakeholders see in the repurposing process. The combined results from literature studies, interviews and SWOT analysis shows several technical, economic and environmental opportunities with repurposing of wind turbine blades, including the possibility of potentially reducing both material costs and greenhouse gas emissions compared to the alternatives of incineration or landfilling. Several challenges were identified, including challenges around disassembly, transport, testing the material's strength and lack of information about the material's content. Financial and logistical obstacles regarding the responsibility of manufacturers and operators as well as the lack of cooperation to create an efficient value chain were also found. The result highlights the importance of cooperation between stakeholders, manufacturers and waste handlers as crucial to creating effective solutions and enabling the reuse of wind turbine blades. The case study of Umeå municipality's market needs shows that reuse of wind turbine blades could cover a significant part of the municipality's needs for playgrounds, pedestrian bridges and urban furniture and at the same time contribute to saving carbon dioxide emissions. Despite financial, technical and logistical challenges surrounding dismantling, processing and transport, potential stakeholders see the creation of sustainable business models and technical capabilities as positive opportunities. The study contributes to increased understanding and knowledge about opportunities and challenges with the reuse of wind turbine blades, which is crucial for streamlining the process for current and future stakeholders in the industry. It is particularly relevant based on the expected amounts of waste in the future and the need for an efficient value chain.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In this study the recently proposed slip-synchronous permanent magnet generator (SS-PMG), is considered as an alternative to other wind generator topologies. The SS-PMG is connected directly to the grid without the need for a power electronic converter and it can also be connected directly to the turbine without a gearbox. Due to the SS-PMG requiring no gearbox or power electronic converter it is evident that this type of generator have a significant advantage regarding reduced maintenance and operation costs. The SS-PMG consist of two integrated permanent magnet generating units, a directly turbine connected slip permanent magnet generator (slip-PMG) and a directly grid connected permanent magnet synchronous generator (PMSG). In this, study many of the implementation aspects of the SS-PMG are addressed. It is found that the short-circuit torque and current profiles of both the slip-PMG and PMSG are significantly influenced by the end-winding inductance and PM end-effects. A new analytical method is proposed for the calculation of the end-winding inductance in this study and a new approach is devised to take the PM end-effects into account. A very important aspect considered in this thesis, is the stability of the SS-PMG connected directly to the grid regarding turbine, generator and grid voltage disturbances, which influences the design of the PMSG and slip-PMG units. Furthermore, it is important that the final SS-PMG design comply to the relevant grid code specifications. For both the PMSG and slip-PMG an extensive design optimisation is done, with several novel wind generator concepts introduced. In this study the dynamic behaviour, grid connection aspects and operational principles of the SSPMG are verified by means of practical tests in the laboratory and for the SS-PMG interfaced with an existing 15 kW wind turbine system in the field. / AFRIKAANSE OPSOMMING: In hierdie studie word die onlangs voorgestelde, glip-sinchroon permanent magneet generator (GSPMG), oorweeg as ’n alternatief vir ander wind generator topologieë. Die GS-PMG word direk aan die netwerk gekonnekteer sonder die nodigheid van ’n drywingselektroniese omsetter en dit kan ook direk aan die turbine gekoppel word sonder ’n ratkas. Omdat die GS-PMG geen ratkas of drywingselektroniese omsetter benodig nie, is dit duidelik dat hierdie tipe generator ’n geweldige voordeel het rakende verminderde onderhoud en operasionele kostes. Die GS-PMG bestaan uit twee geïntegreerde permanent magneet generator eenhede, ’n direkte turbine gekoppelde glip permanent magneet generator (glip-PMG) en ’n direkte netwerk gekonnekteerde permanent magneet sinchroon generator (PMSG). In hierdie studie word baie van die implementerings aspekte van die SS-PMG aangeraak. Daar word gevind dat die kortsluit draaimoment en stroom profiele van beide die glip- PMG en PMSG geweldig deur die end-wikkeling induktansie en PM randeffekte beïnvloed word. Dus, word ’n nuwe analitiese metode voorgestel vir die uitwerk van die end-wikkeling induktansie in hierdie studie en ’n nuwe benadering word voorgestel om die PM randeffekte in ag te neem. ’n Baie belangrike aspek om te oorweeg in hierdie tesis, is die stabiliteit van die GS-PMG direk aan die netwerk gekoppel rakende turbine, generator en netwerkspanning steurnisse, wat die ontwerp van die PMSG en glip-PMG eenhede beïnvloed. Dit is ook belangrik dat die finale SS-PMG ontwerp voldoen aan die relevante netwerkkode spesifikasies. Vir beide die PMSG en glip-PMG word ’n deeglike ontwerpsoptimering gedoen, met talle nuwe wind generator konsepte voorgestel. In hierdie studie word die dinamiese gedrag, netwerk konneksie aspekte en operasionele kenmerke van die GSPMG geverifieer met behulp van praktiese toetse in die laboratorium en vir die SS-PMG geïntegreer met ’n bestaande 15 kW wind turbine stelsel in die veld.

This thesis presents the results of wind tunnel experiments performed for various model wind turbine arrays. The aim is to understand how siting affects power output. To optimize wind farm efficiency the experiments vary the parameters of the model wind turbines and the layout of the wind turbine array. The parameters include the alignment, height, spacing, and the rotational direction of the model wind turbines. These experiments employ mechanical torque sensors to simultaneously measure the torque and rotor angular velocity, which yields a direct measurement of the fluid mechanical power extracted by the turbine at multiple locations. For a 4 × 3 array, the power is calculated at the center turbine in each of the rows. Variations in wind farm efficiency ranging from 55% to 90% are observed between the 13 different layouts tested. Modifications to the layout of the wind turbine array clearly affects the power output of the wind turbines downstream. The results of such experiments highlight the importance of studying the relationship between wind farm layout and power output.

Transient simulations were performed with MATLAB Simulink on a mutual wind park topology, where three vertical axis wind turbines equipped with permanent magnet synchronous generators were connected to a mutual DC-bus through passive diode rectification. The aim with the work was to show the effects of two different kinds of loads on the system in respect to generator torque, rotor speed, produced power by the generators and the power on the DC-bus. The loads were a variable voltage source and a resistance with the value 2.0 Ω. It was shown that the transient behavior of the system in respect to both kinds of loads exhibited a high level of stability when the wind speed was altered. It was also shown that the system when equipped with a voltage source load began to oscillate with the natural frequency of a two mass rotating spring system if a sudden increase of the voltage made the DC-bus voltage larger than the peak of the internal induced voltage of the generators. Small variations of the DC voltage however exhibited a stable behavior.

Le Vietnam est un pays en voie d’industrialisation rapide ce qui engendre une croissance élevée des besoins énergétiques. La consommation énergétique du Vietnam est en augmentation mais pas de façon égale dans tout le pays. En effet, 66.9% de la population du Vietnam vit en zone rurale en 2014. Une grande partie de la population vit encore pauvrement dans des sites isolés avec des accès très restreint aux énergies. Le Vietnam Master Power Plan VII (2011) indique que 759.986 habitations n’ont pas accès à l’électricité.Cependant, le Vietnam est un pays qui possède un grand potentiel en énergie renouvelable (l’énergie solaire, l’énergie éolienne, l’énergie hydroélectrique, l’énergie Biomasse). Le Vietnam a élaboré une stratégie de développement des énergies renouvelables, afin de mobiliser toutes les ressources pour réduire la dépendance aux combustibles fossiles. Les sites isolés se situent principalement au Nord-Ouest du Vietnam, près de la frontière avec le Laos et la Chine, où il existe un grand potentiel d’énergie hydraulique et/ou solaire. Il faut quand même signaler que ces énergies sont souvent saisonnières et, par exemple, une microcentrale hydroélectrique ne peut pas satisfaire la demande en énergie électrique lors de la saison sèche. Donc, un système utilisant deux sources d’énergies renouvelables (panneaux photovoltaïques et microcentrale hydroélectrique) est l’une des solutions optimales pour alimenter en électricité un site isolé au Vietnam. L’objectif de cette thèse est la gestion optimale de l’électricité renouvelable d'un tel système.Afin de satisfaire à une utilisation maximale, le principe de suivi du point maximum (ou Maximum Power Point Tracking – MPPT) est mis en application. Pour la chaine de conversion photovoltaïque, un contrôleur flou à une entrée est proposé afin de suivre le point de puissance maximale du panneau solaire.Pour la chaine de conversion hydroélectrique, une turbine Pelton couplée à un générateur synchrone à rotor bobiné permet d’alimenter en électricité une charge triphasée. Une plateforme d'essais est réalisée dans le laboratoire CReSTIC, IUT de Troyes pour effectuer une validation expérimentale du système de régulation d’une Microcentrale hydroélectrique.Pour la réalisation d’un système de production d’électricité hybride, un superviseur flou est conçu pour obtenir un comportement optimal du système. Après, une étude sur les avantages et inconvénients de ce type de systèmes hybrides pour un site isolé a été effectuée (amélioration de la formation des adultes, augmentation du temps de travail pendant la nuit, réduction du coût du carburant).Ce travail contribue à la connaissance d'une gestion optimale des énergies renouvelables pour site isolé en révélant les avantages et les qualités de l’utilisation des ressources d’énergie renouvelables au gouvernement et à d’autres investisseurs locaux ou internationaux au Vietnam. / As a rapidly industrializing country, the economy of Vietnam's has become very energy intensive. Thought, 66.9% of Vietnam's population lives in rural area in 2014. Many people still live in remote farming areas that are stricken with poverty. The Vietnam Master Power Plan VII (2011) indicates that still 818,947 households are not connected to the national grid, and 759,986 households do not have any access to electricity.Vietnam has high potential on renewable energy resources (Wind, Solar, Hydro, Biomass, and Geothermal). Using hybrid renewable energy system is considered to be one of the most feasible options to bring electricity to local people to improve life quality. The off-grid communities in Vietnam are located mainly in the north-west of Vietnam, near the border with Laos and China, where exist a great potential on Hydro power and/or solar power. A micro hydro power plant cannot satisfy the load demand, especially in dry season. Therefore, additional energy sources such as PV arrays have been suggested to complement power efficiency. Thus, this working discusses the pre-feasibility for small hybrid power generation system consisting of a PV generating unit with storage and a micro hydro generation unit for off-grid areas in Vietnam.The objective of this thesis is to optimize the production of renewable electricity for this type of small hybrid power generation system. For the photovoltaic conversion system, a one input fuzzy logic controller for maximum power point tracking is designed. For the Micro-hydro power plants (MHPP), a Pelton turbine is coupled to a would rotor synchronous generator to supply electricity for a three phase load. To keep the MHPP frequency and voltage outputs constant (50 Hz, 230 V) in spite of changing user loads, the controller is necessary. The experimental results of MHPP frequency and voltages control show the ability of our controller. For the realization of small hybrid power generation, a fuzzy supervisor is adapted to obtain an optimal behavior of the system. Finally, a study on the advantages of this type of hybrid system is carried out (improvement of adult training, increased night working hours, and reduction fuel costs). This thesis contributes to the knowledge of Renewable Energy (RE) by revealing the suitable usability and prospects of RE resources to the government and other local or international investors in Vietnam.

An Ocean Current Turbine (OCT) numerical simulation for creating, testing and tuning flight and power takeoff controllers, as well as for farm layout optimization is presented. This simulation utilizes a novel approach for analytically describing oceanic turbulence. This approach has been integrated into a previously developed turbine simulation that uses unsteady Blade Element Momentum theory. Using this, the dynamical response and power production of a single OCT operating in ambient turbulence is quantified. An approach for integrating wake effects into this single device numerical simulation is presented for predicting OCT performance within a farm. To accomplish this, far wake characteristics behind a turbine are numerically described using analytic expressions derived from wind turbine wake models. These expressions are tuned to match OCT wake characteristics calculated from CFD analyses and experimental data. Turbine wake is characterized in terms of increased turbulence intensities and decreased mean wake velocities. These parameters are calculated based on the performance of the upstream OCT and integrated into the environmental models used by downstream OCT. Simulation results are presented that quantify the effects of wakes on downstream turbine performance over a wide range of relative downstream and cross stream locations for both moored and bottom mounted turbine systems. This is done to enable the development and testing of flight and power takeoff controllers designed for maximizing energy production and reduce turbine loadings. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

O presente trabalho apresenta uma metodologia de simulação numérica de perfis aerodinâmicos bidimensionais com foco na utilização para o projeto e otimização de pás e rotores de pequenas turbinas eólicas de eixo horizontal, bem como o emprego desses métodos em simulações nas quais efeitos de alta solidez do rotor e baixos números de Reynolds são avaliados. Essa metodologia inclui geração de malhas, seleção de métodos numéricos e validação, tendo as escolhas sido guiadas pelas práticas mais bem sucedidas na simulação de perfis aerodinâmicos, e foi aplicada na simulação dos aerofólios NACA 0012, S809 e SD7062. O código comercial ANSYS Fluent foi utilizado em todas as simulações. Na simulação de aerofólios isolados a altos números de Reynolds dos perfis NACA 0012 e S809, o modelo Transition SST (γ-Reθ) apresentou resultados mais próximos a dados experimentais do que aqueles apresentados pelo modelo k-ω SST para CL e CD, além de produzir resultados para CP que mostraram boa precisão quando comparados aos mesmos dados experimentais. Resultados de CL, CD, CF e CP são apresentados para 20 diferentes condições de operação às quais o perfil SD7062 foi submetido, com números de Reynolds variando entre 25.000 e 125.000. As distribuições dos dois últimos coeficientes sobre os dorsos do aerofólio evidenciam com clareza a presença e magnitude da bolha de separação laminar. Os coeficientes de sustentação e arrasto mostram o impacto negativo da presença da bolha nessa faixa de números de Reynolds. Além disso, nos casos simulados, o arrasto aumenta em função da diminuição do Re. Um design de pá produzido com o auxílio do código de otimização SWRDC, baseado em algoritmos genéticos, é apresentado. Três seções ao longo da envergadura dessa pá foram simuladas em uma bateria de 45 simulações, sob diversas condições de operação em função de solidez, ângulo de ataque e razão de velocidade de ponta de pá. Esses resultados mostram que a bolha de separação laminar se move na direção do bordo de ataque com o aumento da solidez, do ângulo de ataque e da TSR. Além disso, distribuições do CP mostram aumento de pressão em ambos os dorsos do perfil quando submetido aos efeitos da solidez, embora esses efeitos tenham sido responsáveis por um aumento na relação CL/CD nos casos estudados. / This thesis presents a methodology of two-dimensional airfoil simulation focusing on its application on the design and optimization of blades and rotors of small horizontal axis wind turbines, and its application in a set of numerical simulations involving high rotor solidity and low-Re effects. This methodology includes grid generation, selection of numerical methods and validation, reflecting the most successful practices in airfoil simulation, and was applied in the simulation of the NACA 0012, S809 and SD7062 airfoils. The ANSYS Fluent commercial code was used in all simulations. Results for the isolated NACA 0012 and S809 airfoils at high Reynolds numbers show that the Transition SST (γ-Reθ) turbulence model produces results closer to experimental data than those yielded by the SST k-ω model for CL and CD, having also produced CP plots that show good agreement to the same experimental data. Plots of CL, CD, CF and CP for the SD7062 airfoil are presented, for simulations at 20 different operating conditions. The CF and CP distributions evidence the negative impact of the laminar separation bubble in the range of Reynolds numbers evaluated. Results show that, for Re between 25,000 and 125,000, drag increases with decreasing Re. A blade design generated using the SWRDC optimization code, based on genetic algorithms, is presented. Three sections of the resulting blade shape were selected and were tested in a set of 45 simulations, under an array of operating conditions defined by solidity, angle of attack and TSR. Results show that the laminar separation bubble moves towards the leading edge with increasing solidity, angle of attack and TSR. Furthermore, CP plots show an increase in pressure on both surfaces when the airfoil is subject to solidity effects, although these effects show an increase in the lift-to-drag ratio at the conditions evaluated.

During the last three decades, the hub height of wind turbines has increased from 24 to 162 meters and with an increasing demand for break-through innovations in green energy production it seems likely that this trend will continue. The meteorological preconditions for extreme-scale wind turbines are investigated for Scandinavia using 33 years of reanalysis data from MERRA (Modern-Era Retrospective Analysis for Research and Applications). Second degree polynomials are fitted to the wind and temperature profiles and evaluated at 100, 200 and 300 m above ground level (AGL). The spatial and temporal variation of average wind speed and median wind power density is studied. Simple metrics such as the wind shear and risk of icing, measured as occasions with temperature below freezing, are used to give an idea of the loads on the wind turbines. Winter is the windiest season, and generally the wind speed is highest over sea and in the Scandinavian mountain range. Going from 100 to 300 m AGL the average wind speed increases with 1 m/s over sea and 2 m/s over land. During night the wind speed increases over land but decreases over sea compared to daytime values. On average the wind shear is about 3.6 times larger in the 50-100 m layer than in the 100-300 m layer. The calculated wind field at 100 m AGL has been compared with results from the MIUU-model, developed at the Department of Meteorology, Uppsala University. The general features are captured but there are important discrepancies between the coast and the mountains in the northern part of Sweden. MERRA data has been validated in different ways, for example by comparing with measured wind speed and temperature profiles. The temperature profiles are in good agreement while the wind profiles differ significantly. It is also shown that MERRA data is not internally consistent in the mountain range, causing a large uncertainty. In future studies, the risk of icing could be explored further. Also, the distribution of sound from extreme-scale wind turbines could be investigated. / Under de senaste tre decennierna har navhöjden för vindkraftverk ökat från 24 till 162 meter och med en ökande efterfrågan på banbrytande innovationer inom produktion av grön energi är det troligt att denna trend kommer att fortsätta. De meteorologiska förutsättningarna för extremskaliga vindkraftverk i Skandinavien undersöks baserat på 33 års återanalysdata från MERRA (Modern-Era Retrospective Analysis for Research and Applications). Andragradspolynom anpassas till vind- och temperaturprofilerna och evalueras på höjderna 100, 200 och 300 meter över markytan. Variationen i rummet och med tiden av medelvindhastigheten och medianen av vindenergiintensiteten studeras. Enkla mått som vindskjuvningen och risken för nedisning, mätt som antalet tillfällen då temperaturen understiger fryspunkten, används för att ge en uppfattning om risken för belastningarna på vindkraftverken. Vintern är den årstid då det blåser mest och i allmänhet är vindstyrkan högst över hav och i fjälltrakterna. Förflyttar man sig från 100 till 300 m över markytan ökar medelvindhastigheten med 1 m/s över hav och med 2 m/s över land. Under natten ökar vinden över land men minskar över hav i jämförelse med värdena under dagen. I medeltal är vindskjuvningen 3.6 gånger större i 50-100 m skiktet jämfört med 100-300 m skiktet. Det beräknade vindfältet på 100 m över markytan har jämförts med resultat från MIUU-modellen, utvecklad vid institutionen för meteorologi, Uppsala universitet. De allmänna dragen är samma men det finns viktiga avvikelser mellan kusten och fjälltrakterna i norra Sverige. MERRA-data har validerats på olika sätt, till exempel genom att jämföra med uppmätta vind- och temperaturprofiler. Temperaturprofilerna visar god överensstämmelse men det är signifikanta skillnader mellan vindprofilerna. Det visas också att MERRA-data inte är konsistent i fjälltrakten, vilket medför en stor osäkerhet. I framtida studier kan risken för nedisning studeras utförligare liksom ljudutbredningen från extremskaliga vindkraftverk.