The growing interest around offshore wind power, providing at the same time better wind conditions and fewer visual or environmental impacts, has lead many energy suppliers to consider the installation of offshore wind farms. However, the marine environment makes the installation and maintenance of wind turbines much more complicated, raising the capital and operation costs to an undesirable level and preventing the fast progression of this technology worldwide. Availability of offshore wind turbines varies between 65 and 90% depending on location, whereas onshore turbines range between 95 and 98% in most cases. In 2009, the ETI launched a research project aiming to improve economical efficiency of offshore wind farms by increasing their availability and decreasing their maintenance costs (partly through replacing corrective maintenance by preventive maintenance). This project named “Inflow” involves the development of a condition monitoring system, a system designed to monitor the state of different wind turbine components, and to analyze this data in order to determine the wind turbines overall condition at any given time, as well as its potential system ailments   This paper describes two different approaches to perform the condition monitoring of offshore wind farms, the first one involves thresholds-based analysis, while the other involves pattern recognition.

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The application of wind power in various fields of energy requirements has been examined. Specific applications of the three broad classes of wind machines - Small, Intermediate and Large-scale, have been evaluated. Two methodologies were developed which could compute the amount of wind power required of existing Wind Turbine Generators (WTG) when placed in two sites in Virginia. The impacts of placing multiple WTG's in clusters to get higher power levels have been examined in details. A wake interference model has been included to calculate the amount of power reductions in downwind WTG rows. The advantages evolving out of site dispersal were also investigated. In general terms, arrays of wind farms produce some firm capacity because of the diversity of wind at the dispersed sites. Mostly, arrays of multiple sites tend to fill up the low power output levels of an individual site during the day. Besides, the output from an array consisting of a total of N wind machines, will be more than the output from an identical number of machines in a single site. These aspects of site dispersal have been discussed. The studies of Clusters and Arrays have been extended to utility interface. Two separate models - an Individual Site model and a Dispersed Site model have been considered for integration. Capacity credit earned for each case was investigated in details using a Reliability model. Wind power was also looked at from the competition against conventional expansion plants point of view. The economics of wind power in terms of capacity and operational cost savings were also examined. The problems arising out of a possible integration of wind machines have been pointed out and some solutions have been suggested. Computational results are presented in details from the major studies and recommendations for further work have been discussed. / M.S.

The electrical-producing windmill industry boomed during 1983. It was estimated that"unit sales during 1983 would be twice those of the prior 10 years combined." Most of the activity has been in the development of windfarms in the western states and Hawaii. The boom is largely due to (1) tax breaks given to alternative energy producers and (2) the Public Utilities Regulatory Policies Act (PURPA) of 1978. PURPA requires public utilities to purchase electricity from small producers. In many instances, the investors main interest was the tax break and as a result the development was of inferior quality.⁴⁰ Electrical-producing windmills are delicate machines in that lightweight components are used to move large forces. Domestically, there are about 50 manufacturers of electrical-producing windmills. Most of these manufacturers have just entered the field. As such, they have not had time to perfect their machines. And as a result, 50% downtimes are not uncommon and failures are frequent.⁴⁰ In the mid-70's, the U.S. Department of Energy (DOE) embarked on a large scale program for the research and development of windmills. In 1982 the program was drastically cut by the Reagan administration. While the program was in full swing, significant steps were made in 129 130 developing safe, reliable wind energy systems. Wind energy systems could probably supply up to ten percent of the nation's annual electrical demands, but one to two percent is a more reasonable goal. For this to happen the government must not cut its existing financial incentives, existing windfarms must prove to be economical, private manufacturers must develop high quality wind energy systems, and windfarms must be developed at sites throughout the country. / Master of Engineering

When wind power and other intermittent renewable energy (IRE) sources begin to supply a significant part of the load, concerns are often raised about the inherent intermittency and unpredictability of these sources. In order to study the impact from higher IRE penetration levels on the power system, integration studies are regularly performed. The model package presented and evaluated in Papers I–IV provides a comprehensive methodology for simulating realistic time series of wind generation and forecasts for such studies. The most important conclusion from these papers is that models based on coarse meteorological datasets give very accurate results, especially in combination with statistical post-processing. Advantages with our approach include a physical coupling to the weather and wind farm characteristics, over 30 year long, 5-minute resolution time series, freely and globally available input data and computational times in the order of minutes. In this thesis, I make the argument that our approach is generally preferable to using purely statistical models or linear scaling of historical measurements. In the variability studies in Papers V–VII, several IRE sources were considered. An important conclusion is that these sources and the load have very different variability characteristics in different frequency bands. Depending on the magnitudes and correlations of these fluctuation, different time scales will become more or less challenging to balance. With a suitable mix of renewables, there will be little or no increase in the needs for balancing on the seasonal and diurnal timescales, even for a fully renewable Nordic power system. Fluctuations with periods between a few days and a few months are dominant for wind power and net load fluctuations of this type will increase strongly for high penetrations of IRE, no matter how the sources are combined. According to our studies, higher capacity factors, more offshore wind power and overproduction/curtailment would be beneficial for the power system.

Wind power is a rapidly growing industry worldwide, both on- andoffshore. Most of the good locations onshore in continental Europeare in use today, which has prompted a move offshore in recentyears. Europe has by far the most offshore wind turbinesinstalled, mostly located in the North sea.The low hanging fruits are locations with relatively shallowwaters (up to 45-50 meters), a high and steady wind speed and isclose to grid connections onshore. Big parts of the North Sea aresuitable for this, but many places with good wind conditionsworldwide are too deep. The next step for the industry is to moveto these deeper waters, with the help of floating wind turbines.The first prototype floating turbines have been running for acouple of years, with even larger, albeit still pretty small, windfarms in the planning stage.This thesis looks on the possibility of building large floatingwind farms in the future, specifically in the eastern most part ofthe North Sea - Skagerrak. Several different factors andstakeholders have been mapped out and important factors such aswater depth, wind speed and seabed conditions considered to createfour different future scenarios. Each scenario has been evaluatedtechnically and Levelized Cost of Energy (LCOE) has beencalculated to be able to compare the different locations.Since the technology is very new and under development, theinitial costs are high. This gives the lower LCOE of 149 €/MWh.Many new developments are however expected in the years to come,which would lower the investment cost considerably, by up to 40%according to some sources. This would lower the LCOE to under 100€/MWh.It is however also found that these investments carry many otherpositive effects, such as developing a new carbon neutraltechnology in Scandinavia which could become a big exportworldwide. The social acceptance of bottom fixed foundationoffshore (close to shore) and onshore wind power is also falling,and this would also be a big plus for floating offshore wind as itcan be built so far offshore it can't be seen from land. BothSweden and Denmark have big power plants closing in the comingdecades, nuclear power in Sweden and coal fired power plants inDenmark. These need to be replaced either by import or by newcarbon neutral power production.

Wind power is variable, uncertain, intermittent and site specific. The operating capacity credit associated with a wind farm is therefore considerably different from that assigned to a conventional generating unit and as wind penetrations in conventional power systems increase, it is vital that wind power be fully integrated in power system planning and operating protocols.<p> The research described in this thesis is focused on the determination of the operating capacity benefits associated with adding wind power to a conventional power system. Probabilistic techniques are used to quantify the risk and operating capacity benefits under various risk criteria. A short term wind speed probability distribution and short term wind power probability distribution forecasting model is presented and a multi-state model of a wind farm is utilized to determine several operating performance indices. The concepts and developed model are illustrated by application to two published test systems. The increase in peak load carrying capability attributable to added wind power is examined under a range of system operating conditions that include the effects of seasonality, locality and wind parameter trends. The operating capacity credit associated with dependent and independent wind farms is also examined. The dependent and independent conditions provide boundary values that clearly indicate the effects of wind speed correlation. Well-being analyses which incorporate the accepted deterministic criterion in an evaluation of the system operating state probabilities is applied to the wind integrated test systems using a novel approach to calculate the operating state probabilities. Most modern power systems are interconnected to one or more other power systems and therefore have increased access and exposure to wind power. This thesis examines the risk benefits associated with wind integrated interconnected power systems under various conditions using the two test systems.<p> The research described in this thesis clearly illustrates that the operating capacity benefits associated with wind power can be quantified and used in making generating capacity scheduling decisions in a wind integrated power system.

Wind power is variable, uncertain, intermittent and site specific. The operating capacity credit associated with a wind farm is therefore considerably different from that assigned to a conventional generating unit and as wind penetrations in conventional power systems increase, it is vital that wind power be fully integrated in power system planning and operating protocols.<p> The research described in this thesis is focused on the determination of the operating capacity benefits associated with adding wind power to a conventional power system. Probabilistic techniques are used to quantify the risk and operating capacity benefits under various risk criteria. A short term wind speed probability distribution and short term wind power probability distribution forecasting model is presented and a multi-state model of a wind farm is utilized to determine several operating performance indices. The concepts and developed model are illustrated by application to two published test systems. The increase in peak load carrying capability attributable to added wind power is examined under a range of system operating conditions that include the effects of seasonality, locality and wind parameter trends. The operating capacity credit associated with dependent and independent wind farms is also examined. The dependent and independent conditions provide boundary values that clearly indicate the effects of wind speed correlation. Well-being analyses which incorporate the accepted deterministic criterion in an evaluation of the system operating state probabilities is applied to the wind integrated test systems using a novel approach to calculate the operating state probabilities. Most modern power systems are interconnected to one or more other power systems and therefore have increased access and exposure to wind power. This thesis examines the risk benefits associated with wind integrated interconnected power systems under various conditions using the two test systems.<p> The research described in this thesis clearly illustrates that the operating capacity benefits associated with wind power can be quantified and used in making generating capacity scheduling decisions in a wind integrated power system.