Influence of soil stiffness on the dynamic response of an offshore wind turbine

La industria de la energía eólica marina ha crecido de forma significativa durante los últimos 15 años, y se espera que siga creciendo durante los siguientes. La construcción de torres en aguas cada vez más profundas y el aumento en potencia y tamaño de las turbinas han creado la necesidad de diseñar estructuras de soporte cada vez más fiables y optimizadas, lo que requiere un profundo conocimiento de su comportamiento. Este trabajo se centra en la respuesta dinámica de una turbina marina con cimentación tipo monopilote y sobre la que actúa la fuerza del viento. Se han realizado cálculos con distintas propiedades del suelo para cubrir un rango de rigideces que va desde una arena muy suelta a una muy densa. De este modo se ha analizado la influencia que tiene la rigidez del suelo en el comportamiento de la estructura. Se han llevado a cabo análisis estáticos y dinámicos en un modelo de elementos finitos implementado en Abaqus. El desplazamiento en la cabeza de la torre y la tensión en su base se han obtenido en función de la rigidez del suelo, y con ellos se ha calculado la amplificación dinámica producida cuando la frecuencia natural del sistema suelo‐cimentación torre se aproxima a la frecuencia de la carga. Dos diferentes enfoques a la hora de modelizar el suelo se han comparado: uno utilizando elementos continuos y otro utilizando muelles elásticos no lineales. Por último, un análisis de fiabilidad se ha llevado a cabo con un modelo analítico para calcular la probabilidad de resonancia del sistema, en el que se han considerado las propiedades de rigidez del suelo como variables aleatorias. Offshore wind energy industry has experienced a significant growth over the past 15 years, and it is expected to continue its growth in the coming years. The expansion to increasingly deep waters and the rise in power and size of the turbines have led to a need for more reliable and optimized support designs, which requires an extensive knowledge of the behaviour of these structures. This work focuses on the dynamic response of an offshore wind turbine founded on a monopile and subjected to wind loading. Different soil properties have been considered in order to cover the range of stiffness from a very loose to a very dense sand. In this way, the influence of stiffness on the structure behaviour has been assessed. Static and dynamic analyses have been carried out by means of a finite element model implemented in Abaqus. Head displacement and stress at the tower base have been obtained as functions of soil stiffness, and they have been used to calculate the dynamic amplification that is produced when the natural frequency of the system soil‐foundation‐tower approaches the load frequency. Two different approaches of soil modelling have been compared: soil modelled as a continuum and soil simulated with non linear elastic springs. Finally, a reliability analysis to assess the probability of resonance has been performed with an analytical model, in which soil stiffness properties are considered as stochastic variables.

Basic statistics of the Community. Comparison with some European countries, Canada, the United States of America and the Union of Soviet Socialist Republics 1965. Sixth edition

Population; labour force; national product; agriculture; energy; industry; transport; external trade; social statistics; standard of living; trends of major economic indicators in the countries of the Community; supplementary statistics on iron and steel-trends from 1959-64.

Basic Statistics for Fifteen European Countries. Comparison with the United States of America and with the Union of Socialist Soviet Republics. 3rd Edition, November 1961

Population; national product; agriculture; energy; industry; transport; external trade; standard of living; trends of major economic indicators in the six

Basic Statistics of the Community. Comparison with some European countries, the United States of America and with the Union of Socialist Soviet Republics. Fourth Edition. November 1963

Population; national product; agriculture; energy; industry; transport; external trade; standard of living; trends of major economic indicators in the six; supplementary statistics on iron and steel-trends from 1952-62; supplementary statistics in an social field-employment, earnings, expenditure, social security

Basic Statistics of the Community. Comparison with some European countries, the United States of America and with the Union of Socialist Soviet Republics. Fifth Edition. November 1964

Population; labour force; national product; agriculture; energy; industry; transport; external trade; social statistics; standar5d of living; trends of major economic indicators in the countries of the community; supplementary statistics on iron and steel-trends from 1956-63

Benevolent sexism at work:gender differences in the distribution of challenging developmental experiences

The current research draws from ambivalent sexism theory to examine potential gender differences in the quantity and quality of developmental work experiences. In a sample of managers in the energy industry, men and women reported participating in a similar number of developmental experiences (with comparable levels of support), but men rated these experiences as more challenging and received more negative feedback than did women. Similarly, a sample of female managers in the health care industry reported comparable amounts, but less challenging types, of developmental experiences than their male counterparts'. The results of three complementary experiments suggest that benevolent sexism is negatively related to men's assignment of challenging experiences to female targets but that men and women were equally likely to express interest in challenging experiences. Taken together, these results suggest that stereotype-based beliefs that women should be protected may limit women's exposure to challenging assignments, which in turn may partially explain the underrepresentation of women at the highest levels of organizations. © The Author(s) 2012.

The value of indirect ties in citation networks:SNA analysis with OWA operator weights

This paper seeks to advance the theory and practice of the dynamics of complex networks in relation to direct and indirect citations. It applies social network analysis (SNA) and the ordered weighted averaging operator (OWA) to study a patent citations network. So far the SNA studies investigating long chains of patents citations have rarely been undertaken and the importance of a node in a network has been associated mostly with its number of direct ties. In this research OWA is used to analyse complex networks, assess the role of indirect ties, and provide guidance to reduce complexity for decision makers and analysts. An empirical example of a set of European patents published in 2000 in the renewable energy industry is provided to show the usefulness of the proposed approach for the preference ranking of patent citations.

Prospecção tecnológica para geração de energia eólica

The acceleration of technological change and the process of globalization has intensified competition and the need for new products (goods and services), resulting in growing concern for organizations in the development of technological, economic and social advances. This work presents an overview of the development of wind energy-related technologies and design trends. To conduct this research, it is (i) a literature review on technological innovation, technological forecasting methods and fundamentals of wind power; (ii) the analysis of patents, with the current technology landscape studied by means of finding information in patent databases; and (iii) the preparation of the map of technological development and construction of wind turbines of the future trend information from the literature and news from the sector studied. Step (ii) allowed the study of 25 644 patents between the years 2003-2012, in which the US and China lead the ranking of depositors and the American company General Electric and the Japanese Mitsubishi stand as the largest holder of wind technology. Step (iii) analyzed and identified that most of the innovations presented in the technological evolution of wind power are incremental product innovations to market. The proposed future trends shows that the future wind turbines tend to have a horizontal synchronous shaft, which with the highest diameter of 194m and 164m rotor nacelle top, the top having 7,5MW generation. The materials used for the blades are new materials with characteristics of low density and high strength. The towers are trend with hybrid materials, uniting the steel to the concrete. This work tries to cover the existing gap in the gym on the use of technological forecasting techniques for the wind energy industry, through the recognition that utilize the patent analysis, analysis of scientific articles and stories of the area, provide knowledge about the industry and influencing the quality of investment decisions in R & D and hence improves the efficiency and effectiveness of wind power generation

Os limites constitucionais ao exercício de direito de patente e seus reflexos na indústria do petróleo, gás natural e biocombustíveis

This dissertation deals with the constitutional limits on the exercise of patent rights and its effects on the oil, natural gas and biofuels. Held with the support of ANP / PETROBRAS, It seeks to show how the law will limit the exercise of industrial property, based on a reinterpretation of private law by the constitutional development perspective . Today it is a fact that Petrobras, a Brazilian joint venture, has the latest technology in various sectors of the oil industry, and is one of the highest investments in developing new technologies. The overall objective of this thesis is to establish the relationship between the public interest of the Petroleum Industry, Natural Gas and Biofuels and constitutional limits to the free exercise of patent rights, then confirm or refute our hypothesis that Article 71 on Industrial Property Law is contrary to the existing objectives in Article 3 of the Constitution of the Federative Republic of Brazil. The research aims to examine the relevant aspects of the legal nature attributed to IPGN constitutionally confronting the constitutional limits on the free exercise of patent rights, with the purpose to outline the state of the performance limits in the regulation of the economy, in particular the application of feasibility limitations on the right of property in favor of national interest on the strategic energy industry. The aim is to confront the fundamental rights to property and economic development, against the public interest, limiting these first. As to the objectives, the research will be theoretical and descriptive and harvest of industrial property, respect the possible impact of regulatory standards and limiting the right of ownership in the oil industry. To establish how the state will mitigate the intellectual property right, we discuss, at first, a definition of public interest from the general theory of state and sovereign character in order to establish a new concept of national interest and popular interest, which will in turn the definition of our concept of public interest. In the second phase, will be addressed the issue of industrial property rights and how to will be free exercise thereof, in the constitutional sphere, infra, and demonstrating the use of industrial property rights with examples of market and IPGN . After situating the industrial property rights in the constitution and national legislation, establish their relationship with the national and regional development, will be addressed in this chapter in particular the patent law, as most usual form of intellectual property protection in IPGN. Used a study highlighting the number of patents in the area of the analyzed industry, demonstrating with hard data the importance of a sector for industrial development. The relationship between the social function of intellectual property and the constitutional objective of development was characterized to demonstrate the strategic nature of oil to Brazil in the national and international scene, and put into question the hypothesis of the research which provides that even with large investments the lack of legal certainty in the sector turns out not to have a considerable volume of investment as it could.

Coordenação dos sistemas antioxidantes da catalase e da ascorbato peroxidase durante o envelhecimento acelerado de sementes de cártamo e girassol

World consumption of vegetable oils has increased in recent years because of its application in food, chemical, pharmaceutical and, more recently, energy industry. However, oilseeds, which these oils are extracted, have low viability, affecting the cultivation and productivity of these species. The aim of this study was to analyze the effect of aging on the coordination of catalase (CAT) and ascorbate peroxidase (APX) antioxidant systems in safflower and sunflower. . Therefore, seeds were subjected to accelerated aging for 3, 6 and 9 days and grown in moistened paper towel for 72 hours. Additionally, before accelerated aging, sunflower seeds were pretreated by osmopriming with 10 mM ascorbate (ASC) or 3 amino 1,2,4 triazol (3-AT), a specific inhibitor of CAT activitie. The method of artificial aging used was efficient in both species, because it caused a decrease in germination, seedling development and growth, especially in safflower. The aging caused inhibition of CAT activity for both species and to compensate for such inhibition , sunflower increased mRNA expression of this enzyme , while safflower mobilized over the activity of APX. Analysis of the expression of malate synthase and sugar content demonstrated that sunflower seeds consumes lipid reserves in quiescent state, while the safflower is more dependent on carbohydrate. Pretreatment with 3-AT inhibited CAT activity and stimulated the APX, though with ASC acted reverse on these systems. None of the treatments recovered the physiological decline aging. It is concluded that aging change the oilseeds antioxidant metabolism, despite interspecies variations in response to this process, the depletion of the CAT antioxidant system was common. Because of this we propose that the measurement of CAT activity can be used to identify aging seed lots.

Essays in Macro Finance

I study the link between capital markets and sources of macroeconomic risk. In chapter 1 I show that expected inflation risk is priced in the cross section of stock returns even after controlling for cash flow growth and volatility risks. Motivated by this evidence I study a long run risk model with a built-in inflation non-neutrality channel that allows me to decompose the real stochastic discount factor into news about current and expected cash flow growth, news about expected inflation and news about volatility. The model can successfully price a broad menu of assets and provides a setting for analyzing cross sectional variation in expected inflation risk premium. For industries like retail and durable goods inflation risk can account for nearly a third of the overall risk premium while the energy industry and a broad commodity index act like inflation hedges. Nominal bonds are exposed to expected inflation risk and have inflation premiums that increase with bond maturity. The price of expected inflation risk was very high during the 70's and 80's, but has come down a lot since being very close to zero over the past decade. On average, the expected inflation price of risk is negative, consistent with the view that periods of high inflation represent a "bad" state of the world and are associated with low economic growth and poor stock market performance. In chapter 2 I look at the way capital markets react to predetermined macroeconomic announcements. I document significantly higher excess returns on the US stock market on macro release dates as compared to days when no macroeconomic news hit the market. Almost the entire equity premium since 1997 is being realized on days when macroeconomic news are released. At high frequency, there is a pattern of returns increasing in the hours prior to the pre-determined announcement time, peaking around the time of the announcement and dropping thereafter.

Dynamic effects of anchor positional tolerance on tension moored floating wind turbine

For water depths greater than 60m floating wind turbines will become the most economical option for generating offshore wind energy. Tension mooring stabilised units are one type of platform being considered by the offshore wind energy industry. The complex mooring arrangement used by this type of platform means that the dynamics are greatly effected by offsets in the positioning of the anchors. This paper examines the issue of tendon anchor position tolerances. The dynamic effects of three positional tolerances are analysed in survival state using the time domain FASTLink. The severe impact of worst case anchor positional offsets on platform and turbine survivability is shown. The worst anchor misposition combinations are highlighted and should be strongly avoided. Novel methods to mitigate this issue are presented.

Description of an 8 MW reference wind turbine

An 8 MW wind turbine is described in terms of mass distribution, dimensions, power curve, thrust curve, maximum design load and tower configuration. This turbine has been described as part of the EU FP7 project LEANWIND in order to facilitate research into logistics and naval architecture efficiencies for future offshore wind installations. The design of this 8 MW reference wind turbine has been checked and validated by the design consultancy DNV-GL. This turbine description is intended to bridge the gap between the NREL 5 MW and DTU 10 MW reference turbines and thus contribute to the standardisation of research and development activities in the offshore wind energy industry.

Do Changes in Current Flow as a Result of Arrays of Tidal Turbines Have an Effect on Benthic Communities?

Arrays of tidal energy converters have the potential to provide clean renewable energy for future generations. Benthic communities may, however, be affected by changes in current speeds resulting from arrays of tidal converters located in areas characterised by strong currents. Current speed, together with bottom type and depth, strongly influence benthic community distributions; however the interaction of these factors in controlling benthic dynamics in high energy environments is poorly understood. The Strangford Lough Narrows, the location of SeaGen, the world’s first single full-scale, grid-compliant tidal energy extractor, is characterised by spatially heterogenous high current flows. A hydrodynamic model was used to select a range of benthic community study sites that had median flow velocities between 1.5–2.4 m/s in a depth range of 25–30 m. 25 sites were sampled for macrobenthic community structure using drop down video survey to test the sensitivity of the distribution of benthic communities to changes in the flow field. A diverse range of species were recorded which were consistent with those for high current flow environments and corresponding to very tide-swept faunal communities in the EUNIS classification. However, over the velocity range investigated, no changes in benthic communities were observed. This suggested that the high physical disturbance associated with the high current flows in the Strangford Narrows reflected the opportunistic nature of the benthic species present with individuals being continuously and randomly affected by turbulent forces and physical damage. It is concluded that during operation, the removal of energy by marine tidal energy arrays in the far-field is unlikely to have a significant effect on benthic communities in high flow environments. The results are of major significance to developers and regulators in the tidal energy industry when considering the environmental impacts for site licences.

Modelling of an efficient dynamic smart solar photovoltaic power grid system

A smart solar photovoltaic grid system is an advent of innovation coherence of information and communications technology (ICT) with power systems control engineering via the internet [1]. This thesis designs and demonstrates a smart solar photovoltaic grid system that is selfhealing, environmental and consumer friendly, but also with the ability to accommodate other renewable sources of energy generation seamlessly, creating a healthy competitive energy industry and optimising energy assets efficiency. This thesis also presents the modelling of an efficient dynamic smart solar photovoltaic power grid system by exploring the maximum power point tracking efficiency, optimisation of the smart solar photovoltaic array through modelling and simulation to improve the quality of design for the solar photovoltaic module. In contrast, over the past decade quite promising results have been published in literature, most of which have not addressed the basis of the research questions in this thesis. The Levenberg-Marquardt and sparse based algorithms have proven to be very effective tools in helping to improve the quality of design for solar photovoltaic modules, minimising the possible relative errors in this thesis. Guided by theoretical and analytical reviews in literature, this research has carefully chosen the MatLab/Simulink software toolbox for modelling and simulation experiments performed on the static smart solar grid system. The auto-correlation coefficient results obtained from the modelling experiments give an accuracy of 99% with negligible mean square error (MSE), root mean square error (RMSE) and standard deviation. This thesis further explores the design and implementation of a robust real-time online solar photovoltaic monitoring system, establishing a comparative study of two solar photovoltaic tracking systems which provide remote access to the harvested energy data. This research made a landmark innovation in designing and implementing a unique approach for online remote access solar photovoltaic monitoring systems providing updated information of the energy produced by the solar photovoltaic module at the site location. In addressing the challenge of online solar photovoltaic monitoring systems, Darfon online data logger device has been systematically integrated into the design for a comparative study of the two solar photovoltaic tracking systems examined in this thesis. The site location for the comparative study of the solar photovoltaic tracking systems is at the National Kaohsiung University of Applied Sciences, Taiwan, R.O.C. The overall comparative energy output efficiency of the azimuthal-altitude dual-axis over the 450 stationary solar photovoltaic monitoring system as observed at the research location site is about 72% based on the total energy produced, estimated money saved and the amount of CO2 reduction achieved. Similarly, in comparing the total amount of energy produced by the two solar photovoltaic tracking systems, the overall daily generated energy for the month of July shows the effectiveness of the azimuthal-altitude tracking systems over the 450 stationary solar photovoltaic system. It was found that the azimuthal-altitude dual-axis tracking systems were about 68.43% efficient compared to the 450 stationary solar photovoltaic systems. Lastly, the overall comparative hourly energy efficiency of the azimuthal-altitude dual-axis over the 450 stationary solar photovoltaic energy system was found to be 74.2% efficient. Results from this research are quite promising and significant in satisfying the purpose of the research objectives and questions posed in the thesis. The new algorithms introduced in this research and the statistical measures applied to the modelling and simulation of a smart static solar photovoltaic grid system performance outperformed other previous works in reviewed literature. Based on this new implementation design of the online data logging systems for solar photovoltaic monitoring, it is possible for the first time to have online on-site information of the energy produced remotely, fault identification and rectification, maintenance and recovery time deployed as fast as possible. The results presented in this research as Internet of things (IoT) on smart solar grid systems are likely to offer real-life experiences especially both to the existing body of knowledge and the future solar photovoltaic energy industry irrespective of the study site location for the comparative solar photovoltaic tracking systems. While the thesis has contributed to the smart solar photovoltaic grid system, it has also highlighted areas of further research and the need to investigate more on improving the choice and quality design for solar photovoltaic modules. Finally, it has also made recommendations for further research in the minimization of the absolute or relative errors in the quality and design of the smart static solar photovoltaic module.