This study assesses the viability of temporarily halting wind turbine operations as amitigation measure to protect bird populations during migration periods. Conducted in thenorthern Baltic, it examines the migration patterns, timings, and altitudes of various birdspecies, aiming to identify the most critical times for implementing turbine stoppages.Utilizing statistical analyses, including F-tests to evaluate migration intensity differencesamong species, the report proposes that strategic, short-duration shutdowns cansignificantly reduce avian collisions. The research emphasizes the importance of species-specific approaches and evaluates the cost-effectiveness of various bird collision reductiontechniques, such as blade painting and thermal detection for dynamic shutdowns. Thisapproach seeks to balance the ecological impact of wind turbines with the necessity forrenewable energy development, offering practical solutions that could enhance biodiversityconservation efforts without substantially compromising energy production efficiency.

This study assesses the viability of temporarily halting wind turbine operations as amitigation measure to protect bird populations during migration periods. Conducted in thenorthern Baltic, it examines the migration patterns, timings, and altitudes of various birdspecies, aiming to identify the most critical times for implementing turbine stoppages.Utilizing statistical analyses, including F-tests to evaluate migration intensity differencesamong species, the report proposes that strategic, short-duration shutdowns cansignificantly reduce avian collisions. The research emphasizes the importance of species-specific approaches and evaluates the cost-effectiveness of various bird collision reductiontechniques, such as blade painting and thermal detection for dynamic shutdowns. Thisapproach seeks to balance the ecological impact of wind turbines with the necessity forrenewable energy development, offering practical solutions that could enhance biodiversityconservation efforts without substantially compromising energy production efficiency.

Offshore wind farm (OWF) construction in the UK is progressing rapidly alongside increasing spatial pressures on marine ecosystems and social and economic activities. A need for increased protection of habitats, species and ecological processes that support environmental and economic benefits is being met by designation of marine protected areas (MPAs). Mitigation and spatial planning solutions are required to enable protection of vital ecological habitats, features and processes and support sustainable economic development. A potential solution is to co-locate OWFs and MPAs. This study uses a multi-disciplinary approach to examine if evidence on the environmental effects of existing OWFs and associated effects on fishing activity (as an existing resource use) benefits MPA goals. Through a systematic review and meta-analyses of existing data, knowledge of OWF effects on species abundance and economic effects on fishing were identified as key evidence gaps. The ecological evidence need was approached through a case study of ecological effects of North Hoyle OWF, North Wales, UK, using existing pre and post-construction monitoring data, as well as primary baited remote underwater video data, collected 5 years later (8 years post-construction). Results suggested habitat and species recovered to a stable state that showed some community differences to pre-construction conditions. The presence of OWF monopiles is likely to have increased existing heterogeneity of substratum and increased opportunities for scavenging species. Species benefitting and disadvantaged by habitat provided within the OWF reflected meta-analyses trends. Extended baseline monitoring to provide confident identification of natural levels of variation in sediment and fauna was lacking. Analysis of fishing activity and landings before and after OWF construction in three UK case study regions approached effects on resource users. Fishing activity in the three case study areas showed broad scale similarity to national trends. Small-scale activity patterns indicated greater reductions in mobile (towed) fishing gear effort near to operating OWFs than in static gear activity (using pots or static nets). Semi-structured interviews conducted with fishermen in each region revealed loss of ground and disruption as negative effects from OWFs, in addition to existing pressures. Benefits including habitat creation and species augmentation, as well as reduction of cumulative lost ground, were identified by fishermen from co-location of MPAs and OWFs. Ecological effects of OWFs suggested benefits from habitat creation, species augmentation and potential for protection of sandbank habitats between monopiles. Mitigation requirements were identified to maximise these potential benefits to an MPA network.

Wind farms are costly projects and prior to the construction, comprehensive wind resource assessment processes are carried out in order to predict the future energy yield with a reliable accuracy. These estimations are made to constitute a basis for the financial assessment of the project. However, predicting the future always accommodates some uncertainties and sometimes these assessments might overestimate the production. Many different factors might account for a discrepancy between the pre-construction wind resource assessment and the operational production data. This thesis investigates an underperforming wind farm in order to ascertain the reasons of a discrepancy case. To investigate the case, the relevant data and information along with the actual production data of three years are shared with the author. Prior to the construction, a wind resource assessment was carried out by an independent wind consultancy company and the work overestimated the annual energy production (AEP) by 19.1% based on the average production value of available three years. An extensive literature review is performed to identify the possible contributing causes of the discrepancy. The data provided is investigated and a new wind resource assessment is carried out. The underestimation of the wind farm losses are studied extensively as a potential reason of the underperformance. For the AEP estimations, WAsP in WindPro interface and WindSim are employed. The use of WindSim led to about 2-2.5% less AEP estimations compared to the results of WAsP. In order to evaluate the influence of long term correlations on the AEP estimations, the climatology datasets are created using the two different reanalysis datasets (MERRA and CFSR-E) as long term references. WindSim results based on the climatology data obtained using the MERRA and CFSR-E datasets as long term references overestimated the results by 10.9% and 8.2% respectively.

Oberschwingungen als ein Merkmal der Elektroenergiequalität gewinnen durch die starke Netzintegration leistungselektronisch geregelter Anlagen wie Windenergieanlagen und nichtlineare Lasten zunehmend an Bedeutung. Bestehende Normen entsprechen nicht den zukünftigen Erfordernissen des Elektroenergiesystems und bedürfen diesbezüglich einer Überarbeitung. In der Arbeit werden wesentliche Einflussfaktoren auf das Oberschwingungsverhalten von Windparks identifiziert, beschrieben und modelliert. Dabei wird der stochastische Charakter der Oberschwingungen mithilfe von probabilistischen Ansätzen erfasst. Des Weiteren wird ein neuer Ansatz zur Untersuchung der Wechselwirkung zwischen dem Windpark und dem vorgelagerten Netz entwickelt. Der Ansatz ermöglicht, die vom Windpark verursachte Änderung der Oberschwingungsspannung am Netzanschlusspunkt zu ermitteln. Diese Arbeit liefert einen Beitrag zur Verbesserung bestehender Normen für die Anbindung von Windparks. / Harmonics, as one of the power quality criteria, are increasingly gaining attention due to the progressive contribution of renewable energy resources and the application of the nonlinear load in the power system. Current standards do not conform to the future requirements of the power system, thus requiring a revision. In this work, main influence factors on the harmonic behavior of wind farms are identified, explained, and modelled. Thereby, the stochastic nature of harmonics is taken into account using probabilistic approaches. Moreover, a novel approach is developed to investigate the interaction between the wind farm and the upstream grid. With the aid of this approach, it is possible to determine the voltage change caused by the wind farm at the point of connection. This work contributes to improve the existing standards for the connection of wind farms.

This paper sets out to analyze the observed wake effect at Block Island Wind Farm. A comparison is made between several wake simulation methods and the observed data at Block Island using analytic and CFD (Computational Fluid Dynamics) modelling methods.  The observed wake results at Block Island show a similar trend evident in earlier papers- a large power deficit found between the first two Wind Turbine Generators (WTGs) in the row followed by a slight variation in power along the row for the remainder of the WTGs. A noticeable difference is seen between the last two WTGs in the row where an increase in power is found. This increase in power is thought to be due to the alignment of the wind farm. Nevertheless, when the observed data is compared with the modeled results, the observed data seem to underestimate the wake effect due to misalignment issue with the nacelle wind direction measurement. A sensitivity analysis is conducted on the Wake Decay Constant (WDC) and Turbulence Intensity (TI) values. The results show a maximum power variation of ≈30% between a WDC value of 0.07 and 0.04 and ≈18% for TI values between 8% and 14%. The findings show that a value in the higher range of the examined WDC (0.06 and 0.07) and TI (12% and 14%) values represent a better comparison to the observed data. Nevertheless, it is not recommended to alter these parameters to fit the observed data. Furthermore, due to high uncertainty in the data measurements, and hence observed results, a clear conclusion indicating which wake model best represents the wake effect at Block Island cannot be stated.

Made available in DSpace on 2014-12-17T15:38:43Z (GMT). No. of bitstreams: 1 RafaellaLI.pdf: 2919587 bytes, checksum: 351adeebcfb2468e37cefb99bcc196c1 (MD5) Previous issue date: 2008-06-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The purpose of this study was to investigate the social-environmental implications of the first large scale wind farm recently built in Brazil (2006), Parque E?lico de Rio do Fogo (PERF), to the nearby communities. The research was base on the adjustment of the DIS/BCN tool to analyze social impact and it was linked to the multi-method approach. Applying the autophotography strategy, cameras were given to five children from the district of Zumbi, the nearest location to PERF, and they were asked to individually photograph the six places they liked the most and the six places they liked the least in their community. Then, these children were interviewed individually and collectively about the photographs. Adult locals in Zumbi, residents of Zumbi/Rio do Fogo settlement, members of the State and Municipal government and representatives of the PERF were also interviewed with the aid of some of the pictures taken by the children and others that might trigger something to say, as a strategy called sample function. The five children presented positive image towards PERF; all of them chose to photograph it as one of places they liked. Adult population of Zumbi presented positive visual evaluation towards PERF. A small number of the interviewees were aware of the environmental and social benefits of wind energy production. Residents did not participate of the decision making process regarding PERF. They approved the project, especially because of the jobs provided during construction. Nowadays, PERF is something apart from their lives because it no longer provides jobs or any other interaction between the facility and the locals. Residents relate to the land, not with the facility. However, there is no evidence of rejection towards PERF, it is simply seen as something neutral to their lives. The low levels of education, traditional lack of social commitment and citizenship, and the experience accumulated by PERF?s planners and builders in other countries, may be contributing points to the fact that Zumbi residents did not oppose to PERF. It is clear that the country needs a legislation which seriously considers the psycho-social dimension involved in the implementation of wind farms / O prop?sito deste estudo foi investigar as implica??es s?cio-ambientais do recente (2006) primeiro parque e?lico de grande porte do Brasil, Parque E?lico de Rio do Fogo (PERF), sobre as comunidades vizinhas. O trabalho foi baseado em adapta??o da ferramenta DIS/BCN para an?lise de impactos sociais, vinculada a uma abordagem multim?todos. Conforme a estrat?gia da autofotografia, foram entregues c?meras fotogr?ficas para cinco crian?as do distrito de Zumbi, localidade mais pr?xima ao PERF e pedido a elas que, individualmente, fotografassem os seis lugares de que mais gostavam e os seis lugares de que menos gostavam em sua comunidade. Posteriormente, essas crian?as foram entrevistadas individual e coletivamente a respeito das fotografias. Tamb?m foram entrevistados residentes adultos de Zumbi, moradores do Assentamento Zumbi/Rio do Fogo, membros do governo estadual e municipal, e representantes do PERF, com aux?lio de algumas fotografias das crian?as e outras, que provocassem algo a dizer, em uma estrat?gia de investiga??o denominada fun??o de modelo. As cinco crian?as apresentaram imagem positiva do PERF; todas escolheram fotograf?-lo como um dos lugares de que gostavam. A popula??o adulta de Zumbi apresentou avalia??o visual positiva do PERF. Um n?mero reduzido de entrevistados conhecia os benef?cios ambientais e sociais da produ??o de energia e?lica. Os residentes n?o participaram do processo de decis?o a respeito do PERF; eles aprovaram a iniciativa especialmente por conta do fomento de empregos durante a constru??o. Atualmente, o PERF ? algo alheio ?s suas vidas por n?o haver mais ofertas de empregos, nem outra forma de intera??o moradores-empreendimento. Os residentes se relacionam com o terreno e n?o com o empreendimento. No entanto, n?o h? evid?ncias de rejei??o ao PERF, os moradores apenas o v?em como algo neutro ?s suas vidas O baixo n?vel educacional, a falta de vertebra??o social e a atua??o de uma empresa com larga experi?ncia na implanta??o de parques e?licos em outros pa?ses podem ser fatores que contribu?ram para a n?o oposi??o dos moradores de Zumbi ao PERF. Fica clara a falta que faz no pa?s uma legisla??o que considere seriamente a dimens?o psico-social envolvida na implanta??o de parques e?licos

Made available in DSpace on 2017-07-10T17:11:45Z (GMT). No. of bitstreams: 1 DISSERTACAO VANESSAVIQUETTI LOWENBERG.pdf: 2250957 bytes, checksum: 81895e5a2a510f6aea4627b4b6c0d230 (MD5) Previous issue date: 2013-04-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work considers the connection of wind power units to the distribution system, aiming at verifying the maximum power limits that can be connected complying with given connection requirements. The maximum power limits have been characterized in terms of maximum integration levels, to the equivalent capacity in the connection node, and in terms of maximum penetration levels, to the full load power feeder. The steady-state voltage in the distribution system nodes has to comply with a priori given maximum variation limits for all possible wind farm working conditions, supplying from 20 to 100% of its nominal power. The research has been developed in two different distribution feeders: a 5-nodes distribution feeder, connecting the wind farm at four different points and considering three different load levels; a 32-nodes distribution feeder, connecting the wind farm to ten different nodes of the system and also considering three different load levels. The maximum integration and penetration levels of wind power have been evaluated in terms of (i) the connection node characteristics (equivalent X/R ratio impedance and voltage); (ii) the feeder load; (iii) the connection node. The connection of either one or two wind farms has been considered for both feeders, assuming wind farms with equal characteristics. The analysis showed strong influence of the impedance X/R ratio on the maximum wind energy integration and penetration levels. The feeder load influences these levels in a non-linear manner and in some cases also an in inverse way, i.e. the load increasing can either increase or decrease the maximum integration level. The equivalent voltage influence on the maximum wind power integration and penetration was not evident in the performed tests. The feeder structure did influence the levels since, in many cases, the maximum integration and penetration levels of wind power have not been determined by the voltage in the connection node but by the voltage in other feeder s node. In general, the connection of two wind farms showed higher wind energy penetration levels compared to only one wind farm, being more or less expressive according to the connecting node characteristics. / Este trabalho se insere no contexto do estudo da conexão de unidades de geração eólica em sistemas de distribuição no sentido de verificar quais os limites máximos de potência que po- dem ser interligados atendendo a determinados requisitos de conexão. Os limites máximos de potência são caracterizados em termos dos níveis máximos de inserção de geração eólica, relativos à capacidade equivalente vista pelo nó de conexão, e da máxima penetração de geração eólica, relativos à carga instalada no alimentador. Exige-se que a tensão de regime permanente nos nós do alimentador de distribuição atenda a limites máximos pré-estabelecidos de variação para todas as condições operativas possíveis do parque eólico produzindo desde 20% até 100% de sua potência nominal. O estudo foi realizado através de simulação computacional sobre dois alimentadores de distribuição diferentes: um alimentador com 5 nós, conectando o parque eólico em quatro diferentes pontos deste sistema e considerando três níveis diferentes de carregamento; e um alimentador com 32 nós, conectando o parque eólico em dez diferentes pontos deste sistema e considerando também três níveis diferentes de carregamento. Os níveis máximos de inserção e penetração de geração eólica foram analisados em função: (i) das características do nó de conexão (relação X/R da impedância e tensão equivalentes); (ii) do carregamento do alimentador; (iii) do nó de conexão. Para os dois alimentadores foram considerados os casos da conexão de um e de dois parques eólicos, sendo que em todos os casos foram adotados parques eólicos idênticos. As análises realizadas mostraram grande influência da relação X/R da impedância equivalente tanto sobre a inserção quanto a penetração de geração eólica. O carregamento do alimentador influenciou de maneira não linear e também em alguns casos de maneira inversa, significando que o aumento do carregamento pode tanto aumentar quanto reduzir a máxima inserção de geração eólica. A influência da tensão equivalente sobre a inserção e penetração de geração eólica não mostrou-se muito evidente nos testes realizados. A topologia do alimentador teve influência, pois em diversos casos os limites má- ximos de inserção e penetração de geração eólica foram determinados pela tensão em nós do alimentador distintos do nó de conexão do parque. De maneira geral, a conexão de dois parques eólicos mostrou atingir níveis superiores de penetração de geração eólica em comparação a um só parque, podendo ser mais ou menos expressiva conforme a característica dos nós de conexão envolvidos.

Two computationally fast fluid mechanical models for vertical axis turbines are the streamtube and the vortex model. The streamtube model is the fastest, allowing three-dimensional modeling of the turbine, but lacks a proper time-dependent description of the flow through the turbine. The vortex model used is two-dimensional, but gives a more complete time-dependent description of the flow. Effects of a velocity profile and the inclusion of struts have been investigated with the streamtube model. Simulations with an inhomogeneous velocity profile predict that the power coefficient of a vertical axis turbine is relatively insensitive to the velocity profile. For the struts, structural mechanic loads have been computed and the calculations show that if turbines are designed for high flow velocities, additional struts are required, reducing the efficiency for lower flow velocities.Turbines in channels and turbine arrays have been studied with the vortex model. The channel study shows that smaller channels give higher power coefficients and convergence is obtained in fewer time steps. Simulations on a turbine array were performed on five turbines in a row and in a zigzag configuration, where better performance is predicted for the row configuration. The row configuration was extended to ten turbines and it has been shown that the turbine spacing needs to be increased if the misalignment in flow direction is large.A control system for the turbine with only the rotational velocity as input has been studied using the vortex model coupled with an electrical model. According to simulations, this system can obtain power coefficients close to the theoretical peak values. This control system study has been extended to a turbine farm. Individual control of each turbine has been compared to a less costly control system where all turbines are connected to a mutual DC bus through passive rectifiers. The individual control performs best for aerodynamically independent turbines, but for aerodynamically coupled turbines, the results show that a mutual DC bus can be a viable option.Finally, an implementation of the fast multipole method has been made on a graphics processing unit (GPU) and the performance gain from this platform is demonstrated.

The number of large-scale wind farms integrated to the power system in Sweden is increasing. Two generator concepts that are widely used are Doubly-Fed Induction Generators (DFIG) and Full Power Converters (FPC). The study is of a quantitative character and the aim of the Master thesis is to compare DFIG-models with FPC-models integrated in an area with high concentration of hydropower. Then it is possible to examine how the dynamics in the power system change depending on the selection of technology (DFIG or FPC) when connecting a wind farm. The power system is simulated during a summer night, i.e., a low load is connected. The Master thesis covers stability analysis of the power system by using rotor angle stability that are split into small-signal stability and transient stability (time-domain simulations) and finally voltage stability to see how the hydropower generators react when varying the power production in the wind farm. The Master thesis concludes that independently of wind turbine technique, integration of a wind farm has slight impact on the stability in the power system compared to a power system without a wind farm, even though the load is low. Further, an integration of a wind farms affects the reactive power production in neighbouring hydropower plants. Finally, when increasing the size of the wind farm the neighbouring hydropower station consume less reactive power which can induce problem with the voltage stability.