Previous simulations have shown that wind farms have an impact on the near-surface atmospheric boundary layer (ABL) as turbulent wakes generated by the turbines enhance vertical mixing of momentum, heat and moisture. These changes alter downstream atmospheric properties. With the exception of a few observational data sets that focus on the impact to near-surface temperature within wind farms, little to no observational evidence exists with respect to vertical mixing. These few experimental studies also lack high spatial resolution due to their use of a limited number of meteorological sensors or remote sensing techniques. This study utilizes an instrumented small unmanned aerial system (sUAS) to gather high resolution in-situ field measurements from two state-of-the-art Midwest wind farms in order to differentially map downstream changes to relative humidity. These measurements are complemented by numerical experiments conducted using large eddy simulation (LES). Observations and numerical predictions are in good general agreement around a single wind turbine and show that downstream relative humidity is altered in the vertical, lateral, and downstream directions. A suite of LES is then performed to determine the effect of a turbine array on the relative humidity distribution in compounding wakes. In stable and neutral conditions, and in the presence of a positive relative humidity lapse rate, it is found that the humidity decreases below the turbine hub height and increases above the hub height. As the array is transitioned, the magnitude of change increases, differentially grows on the left-hand and right-hand side of the wake, and move slightly upward with downstream distance. In unstable conditions, the magnitude of near-surface decrease in relative humidity is a full order of magnitude smaller than that observed in a stable atmospheric regime.

The use of alternative fuels, particularly renewable energy sources, has been an important strategy to achieve greenhouse gas emission reductions. In Bolivia, many rural areas struggle with an unreliable power supply. The most common electricity solution in such isolated areas is to have off-grid systems, where hybrid systems have become a feasible solution. In this study, a hybrid system in the rural village El Espino is optimized using a linear programming tool called MicroGridsPy. Currently, the village is powered by a hybrid system consisting of solar photovoltaics, a diesel generator and lead-acid batteries as a storing system. To optimize the system in a sustainable way, considering economic, environmental and social aspects, two wind turbines of the nominal capacities 5 and 10 kW are studied and introduced to the hybrid system. To find synergies between the wind and solar energy, the irradiance and wind speed of the study area are simulated using a Weather Research and Forecasting (WRF) model. The power output from the wind turbines can then be obtained by modelling the power curves and then be added to the optimization model. The optimization is performed both with and without the wind turbines to evaluate the impact of them. In the optimization model, characteristics of the components, techno-economic parameters, including investment costs, and constraints such as renewable penetration, and cost of the curtailment are set. The obtained results include that the wind speed is higher during the winter season, and that the wind power output, regardless of turbine size, is proportional to the wind speed. Furthermore, the 10 kW wind turbine is proven to be the most suitable for the system of the two compared. The economical values of the system, such as NPC and LCOE are higher, the higher the renewable penetration, but lower for the system with wind turbines. This implicates that adding wind energy to the hybrid system could be beneficial from both an environmental and economical point of view. One conclusion that can be drawn is that wind turbines are a feasible technology for rural electrification, and that the optimization tool is sensitive to cost. Furthermore, it is found that the wind and solar energy are suitable complements to each other both season wise and daily. / Användningen av alternativa bränslen, särskilt förnybara energikällor, har varit en viktig strategi för att minska utsläppen av växthusgaser. I Bolivia kämpar många landsbygdsområden med en opålitlig strömförsörjning. Den vanligaste lösningen för elektricitet i sådana områden är off-grid system, där hybridsystem har blivit en lämplig lösning. I denna studie, optimeras ett hybridsystem beläget i byn El Espino, med ett linjärt programmeringsverktyg; MicroGridsPy. För närvarande drivs byn av ett hybridsystem bestående av solceller, en dieselgenerator och blybatterier för att lagra energin. För att optimera systemet på ett hållbart sätt, utifrån ett ekonomiskt, miljömässigt och socialt perspektiv, studeras två vindturbiner med de nominella kapaciteterna 5 och 10 kW, för att sedan introduceras till hybridsystemet. För att göra detta simuleras områdets solstrålning och vindhastighet med hjälp av en WRF-modell (Weather Research and Forecast). Effekten från vindturbinerna kan då erhållas genom att modellera effektkurvorna, och kan därefter läggas till i optimeringsmodellen. Optimeringen utförs både med och utan vindturbiner för att på så sätt utvärdera deras inverkan på systemet. I optimeringsmodellen fastställs egenskaper hos komponenterna, techno-ekonomiska parametrar, inklusive investeringskostnader och begränsningar såsom förnybar penetration och kostnad för energispill. De erhållna resultaten visade bland annat att vindhastigheten är högre under vintersäsongen, och att effekten är proportionell mot vindhastigheten, oavsett storlek på vindturbin. Vidare har vindturbinen med kapacitet 10 kW visat sig vara den mest lämpade för systemet av de två jämförda. Systemets ekonomiska värden, såsom NPC och LCOE, är högre, ju högre förnybar penetration, men lägre för systemet med vindturbiner. Detta implicerar att vindenergi kan vara till nytta för hybridsystemet, både ur miljösynpunkt och ur en ekonomisk synvinkel. En slutsats som kan dras är att vindturbiner är en passande teknik för landsbygdselektrifiering, och att optimeringsverktyget som användes är känslig mot kostnader. Vidare konstateras att vind- och solenergi kompletterar varandra både säsongsvis och på daglig basis.

The Thesis shows the perspectives of involving renewable energy resources into the energy balance of Russia, namely the use of wind energy for the purpose of energy supply for the objects of the Russian Gas transportation system. The methodology of the wind energy technical potential calculation is designed and the wind energy technical potential assessment for onshore and offshore zones of Russia is presented. The analysis of Russian Gas transportation system in terms of energy consumption is carried out when comparing the map of wind resources in Russia with the map of Russian Gas transportation system and the perspective of wind turbines installation is shown in order to offset energy consumption of the selected object of the Gas transportation system. The decision-making algorithm for wind turbines selection is developed for installation on the wind farm. Also indicators of investment attractiveness of the project of using wind turbines for compression stations energy supply were calculated.

Asymmetric bending is explored as a means of inducing bend-twist coupling in an isotropic, fixed-wing airfoil. An analytical model describing the bend-twist coupling behavior of a constant-section airfoil undergoing steady wind loading is derived from Euler-Bernoulli beam theory, and evaluated over a range of structural and material stiffness. Finite element analysis is carried out in the ANSYS Parametric Design Language environment for an asymmetric, two-dimensional beam. Three-dimensional finite element analysis is carried out for two candidate blade models created in Pro/Engineer based on the NACA 64618 airfoil. Deformation results for the two- and three-dimensional finite element models are compared with analytical solutions. Results of this investigation highlight the dependency between the cross-sectional properties of a spar support and its tendency to exhibit twist-coupling under transverse loading.

The current generation wind turbines are upscaled into multi megawatt range in terms of output power. However, the energy benefit from the turbine is offset by the increased mass and cost. Twenty MW wind turbines are now feasible with rotor diameters up to 200 m, according to a new report from the EU-funded UpWind project in 2011. The question is, how much bigger can wind turbines get realistically? One concept worth considering, and the one that is the subject of this thesis, is to have more than one rotor on a single support structure. Such turbines could have a greater power to weight ratio. Multi-rotor systems also offer the advantage of standardization, transportation and ease of installation and maintenance. In this thesis the NREL 5 MW single rotor baseline wind turbine is compared with a 5 MW multi-rotor wind turbine. The multiple rotors are downscaled using scaling curves keeping the 5 MW baseline machine as reference.

Wind power is a renewable energy source that is making great strides in the global energy sector. While wind power is a renewable energy source, it is not entirely free from carbon emissions. This is because the production of wind turbines is dependent on the use of energy, and as a result can emit large amounts of carbon dioxide. This is because the production of wind turbines is dependent on the use of energy and as a result can emit large amounts of carbon dioxide. The emissions come from two sources, the materials used in the wind turbine and the energy used in the manufacturing process. Because wind turbine production is global, the geographical location also affects the climate impact. The purpose of this study is therefore to evaluate the climate impact from material and energy use for the different turbine components. Furthermore, it aims to evaluate the total climate impact between on-and offshore wind power as well as evaluate the climate impact between production in Sweden, Germany and China. The climate impact is based on 13 Vestas LCA reports, together with a model developed in excel. The results show that the location of production plays a significant role in the total emissions, due to the large variation in the electricity mix between different countries. Generally, the steel components are the largest contributors to the total CO2 emissions. Consequently, offshore wind has a higher climate impact than its onshore counterpart because the offshore foundation is made of steel. The result is, however, limited due to the lack of standardisation and since specific information regarding wind power is hard to acquire. / Vindkraft är en förnyelsebar energikälla, som gör stora framsteg inom den globala energisektorn. Samtidigt som vindkraften är förnyelsebar, är den inte helt fri från koldioxidutsläpp. Detta beror på att produktionen av vindkraftverk kräver energi och kan därför släppa ut stora mängder koldioxid. Utsläppen kommer från två källor, de material som används i vindkraftverket och energin som behövs vid tillverkningen. Eftersom produktion av vindkraftverk sker på ett globalt plan, har även den geografiska platsen där tillverkningen sker en påverkan på klimatpåverkan. Syftet med denna studie är att undersöka klimatpåverkan från material och energianvändningen fördelat över vindkraftverks huvudkomponenter. Utöver detta, syftar den även till att undersöka den totala klimatpåverkan mellan land- och havsbaserad vindkraft samt hur klimatpåverkan skiljer sig åt mellan produktion i Sverige, Tyskland och Kina. Studien utgår från 13 Vestas LCA rapporter och använde en excelmodell för att utvärdera utsläppen av koldioxid. Resultatet visar att den geografiska platsen där produktionen sker har stor betydelse för de totala utsläppen, eftersom det är stor variation i energimix mellan olika länder. Överlag är det de stora stålkomponenterna som har störst bidrag till klimatpåverkan. Till följd av detta har havsbaserad vindkraft större klimatpåverkan än landbaserad, eftersom fundamentet primärt består av stål. Resultatet är dock begränsat, på grund av bristen av standardisering i rapportering och eftersom det är svårt att tillhandahålla specifika data gällande vindkraft.

[pt] Nos últimos anos tem-se observado o crescente fomento de pesquisas globais por sistemas de energias renováveis que proporcionem menor impacto ambiental, garantindo às necessidades do presente sem comprometer a capacidade das gerações futuras. Tal propósito tem impulsionado o avanço da pesquisa em diferentes áreas do campo da energia eólica global, objetivando-se entender o comportamento estrutural e mecânico de cada componente, a fim de garantir uma engenharia de maior segurança e qualidade, bem como reduzir o tempo de indisponibilidade dos aerogeradores. O presente estudo tem como objetivo avaliar o comportamento estrutural de um aerogerador onshore de eixo horizontal, com rotor de três pás, submetido a campos normais e extremos de velocidade do vento definidos de acordo com a IEC 61400- 1 - Wind Turbines Design Requirements. Devido ao acesso limitado às informações técnicas dos aerogeradores comercializados pelos fabricantes, será realizada a análise para o aerogerador de referência de 5 MW desenvolvido pelo Laboratório Nacional de Energias Renováveis (NREL) dos Estados Unidos, o qual disponibilizou as especificações técnicas do aerogerador para acesso público. O comportamento da estrutura será avaliado através da simulação do sistema acoplado rotor-torre-fundação no código FAST, que é um simulador aero-hidro-servo-elástico desenvolvido pelo NREL, o qual está abertamente disponível e bem documentado no meio científico. Os casos de vento normal e extremo, estabelecidos pela IEC 61400-1 e utilizados no FAST, são processados pelo programa TurbSim, também disponibilizado pelo NREL. A análise modal do aerogerador é realizada pelo software SAP2000 para obtenção das frequências naturais e avaliação da característica dos modos de vibração da estrutura. O modelo de elementos finitos considera a torre e as pás discretizadas em elementos de viga. / [en] In recent years there has been a global research for forms of renewable energy which could provide less environmental impact as well as guarantee energy for future generations. This scenario leads to the rise of studies in wind power field which scrutinizes the wind turbine aiming to understand the structural and mechanical behaviour of each component in order to assure safer and quality engineering as well as reducing the wind turbines downtime. The present study aims to understand the structural behavior of an onshore three-bladed horizontal-axis wind turbine subjected to the normal and extreme wind speed fields defined in accordance with IEC 61400- 1 - Wind Turbines Design Requirements. Due to limited access to technical information on wind turbines marketed by manufacturers, the analysis will be performed for the 5 MW Reference Wind Turbine developed by the National Renewable Energy Laboratory (NREL) of the United States, which made the technical specifications of the turbine available for public access. The behavior of the structure will be evaluated through the simulation of the rotor-tower-foundation coupled system in the FAST code, which is an aero-hydro-servo-elastic simulator developed by NREL, which is openly available and well documented in the scientific community. The cases of normal and extreme wind, established by IEC 61400-1, used in FAST, are processed by the TurbSim program also provided by NREL. The modal analysis of the wind turbine is performed using the software SAP2000 in order to obtain the natural frequencies and evaluate the characteristic of the structure s vibration modes. The finite element model considers the tower and the blades discretized into beam elements.

This master thesis handles the development of an automatic benchmarking program for wind turbines and the thesis works as the theoretical basis for this program. The program is created at the request of the power company OX2 who wanted this potential to be investigated. The mission given by the company is to: 1. to find a good key point indicator for the efficiency of a wind turbine, 2. to find an efficient way to assess this and 3. to write a program that does this automatically and continuously. The thesis determines with a study of previous research that the best method to utilize for these kinds of continuous analyses are artificial neural networks which can train themselves on historical data and then assess if the wind turbine is working better or worse than it should with regards to its history. This comparison between the neural network predicted operation and the actual operation works as the measurement of the efficiency, the key point indicator for how the turbine work compared to how it historically should operate. The program is based on this principle and is completely written in MATLAB. Further testing of the program found that the best variables to use are wind speed and the blade pitch angle as input variables for the neural network and active power as the target used as the variable to predict and assess the operation. The final program was able to be fully automated and integrated into the OX2 system thanks to the possibility to continuously import wind turbine data through APIs. In the final testing was the program able to identify 75% of the anomalies manually found in the half year and in the five turbines used for this thesis, the small anomalies not found manually but identified by the program excluded. / Den här masteruppsatsen hanterar utvecklandet av ett automatiskt driftanalyseringsprogram för vindkraftverk och fungerar som det teoretiska underlaget för detta program. Programmet utvecklades på uppdrag av kraftbolaget OX2 som ville undersöka potentialen för ett sådant analysprogram i deras verksamhet. Uppdraget givet var att: 1. ta fram en bra indikator när det gäller den faktiska effektiviteten av ett vindkraftverk, 2. att hitta ett effektivt sätt att använda detta måttet i en analys där målet är att hitta avvikelser, och 3. skriva ett program som automatiskt kan använda måttet och metoden över tiden. Rapporten kommer via litteraturstudie fram till att tidigare forskning visar på att neurala nätverk är den mest lovande metoden för att genomföra sådan här analys. Dessa nätverk kan träna sig själva på historiska data och sedan analysera om vindturbinen arbetar bättre eller sämre än historiskt. Den här jämförelsen mellan den historiskt grundade förutspådda kraften ut och den faktiska kraften ut fungerar som kvalitetsmåttet på hur bra turbinen fungerar. Programmet är baserat på den här principen och är helt skriven i MATLAB. Vidare tester av programmet visar att de bästa variablerna att använda för att förutspå kraften ut är vindhastigheten och bladens vinkel mot vinden. Slutprogrammet var kapabelt att fullt automatiskt och integrerat i OX2s system identifiera 75% av alla avvikelser som manuellt hittats i ett halvårs data på de fem turbinerna använda för rapporten, småfel hittade av programmet men inte manuellt exkluderat.

Climate change is an evermore urging existential treat to the human enterprise. Mean temperature and greenhouse gas emissions have in-creased exponentially since the industrial revolution. But solutions are also mushrooming with exponential pace. Renewable energy technologies, such as wind and solar power, are deployed like never before and their costs have decreased significantly. In order to allow for further transformation of the energy system these technologies must be refined and optimised. In wind energy one important field with high potential of refinement is aerodynamics. The aerodynamics of wind turbines constitutes one challenging research frontier in aerodynamics today.   In this study, a novel approach for calculating wind turbine flow is developed. The approach is based on the partially parabolic Navier-Stokes equations, which can be solved computationally with higher efficiency as compared to the fully elliptic version. The modelling of wind turbine thrust is done using actuator-disk theory and the torque is modelled by application of the Joukowsky rotor. A validation of the developed model and force implementation is conducted using four different validation cases.   In order to provide value for industrial wind energy projects, the model must be extended to account for turbulence (and terrain in case of onshore projects). Possible candidates for turbulence modelling are parabolic k-ε and explicit Reynolds stress turbulence models. The terrain could possibly be incorporated consistently with the used projection method by altering the finite difference grid layout.

In recent years, wind energy technology has become one of the top areas of interest for energy harvesting in the power electronics world. This interest has especially peaked recently due to the increasing demand for a reliable source of renewable energy. In a recent study, the American Wind Energy Association (AWEA) ranked the U.S as the leading competitor in wind energy harvesting followed by Germany and Spain. Although the United States is the leading competitor in this area, no one has been able successfully develop an efficient, low-cost AC/DC convertor for low power turbines to be used by the average American consumer. There has been very little research in low power AC/DC converters for low to medium power wind energy turbines for battery charging applications. Due to the low power coefficient of wind turbines, power converters are required to transfer the maximum available power at the highest efficiency. Power factor correction (PFC) and maximum power point tracking (MPPT) algorithms have been proposed for high power wind turbines. These turbines are out of the price range of what a common household can afford. They also occupy a large amount of space, which is not practical for use in one's home. A low cost AC/DC converter with efficient power transfer is needed in order to promote the use of cheaper low power wind turbines. Only MPPT is implemented in most of these low power wind turbine power converters. The concept of power factor correction with MPPT has not been completely adapted just yet. The research conducted involved analyzing the effect of power factor correction and maximum power point tracking algorithm in AC/DC converters for wind turbine applications. Although maximum power to the load is always desired, most converters only take electrical efficiency into consideration. However, not only the electrical efficiency must be considered, but the mechanical energy as well. If the converter is designed to look like a purely resistive load and not a switched load, a wind turbine is able to supply the maximum power with lower conduction loss at the input side due to high current spikes. Two power converters, VIENNA with buck converter and a Buck-boost converter, were designed and experimentally analyzed. A unique approach of controlling the MPPT algorithm through a conductance G for PFC is proposed and applied in the VIENNA topology. On the other hand, the Buck-boost only operates MPPT. With the same wind profile applied for both converters, an increase in power drawn from the input increased when PFC was used even when the power level was low. Both topologies present their own unique advantages. The main advantage for the VIENNA converter is that PFC allowed more power extraction from the turbine, increasing both electrical and mechanical efficiency. The buck-boost converter, on the other hand, presents a very low component count which decreases the overall cost and volume. Therefore, a small, cost-effective converter that maximizes the power transfer from a small power wind turbine to a DC load, can motivate consumers to utilize the power available from the wind.