Volume 2 wind energy 2 21 – trends prospects, and rd directions in wind turbine technology

Volume 2 wind energy 2 21 – trends, prospects, and rd directions in wind turbine technology Volume 2 wind energy 2 21 – trends, prospects, and rd directions in wind turbine technology Volume 2 wind energy 2 21 – trends, prospects, and rd directions in wind turbine technology Volume 2 wind energy 2 21 – trends, prospects, and rd directions in wind turbine technology Volume 2 wind energy 2 21 – trends, prospects, and rd directions in wind turbine technology

2.21 Trends, Prospects, and R&D Directions in Wind Turbine Technology JK Kaldellis and DP Zafirakis, Technological Education Institute of Piraeus, Athens, Greece © 2012 Elsevier Ltd All rights reserved 2.21.1 Brief Description of Wind Power Time Evolution 2.21.2 The Current Wind Turbine Concept 2.21.3 Size Evolution of Wind Turbines 2.21.4 Pitch versus Stall and Active-Stall Wind Turbines 2.21.5 Direct-Drive versus Gearbox 2.21.6 Blade Design and Construction 2.21.7 Innovative Concepts 2.21.8 Environmental Impact Reduction 2.21.9 Offshore Wind Parks 2.21.10 Vertical-Axis Wind Turbines 2.21.11 Small Wind Turbines 2.21.12 Building-Integrated Wind Turbines 2.21.13 Wind Energy Cost Time Evolution 2.21.14 Research in the Wind Energy Sector 2.21.15 Wind Energy Technological Problems and R&D Directions 2.21.16 Financial Support of Wind Energy Research Efforts 2.21.16.1 1998–2002 (FP5) 2.21.16.2 2002–06 (FP6) 2.21.16.3 2007–Today (FP7) 2.21.17 Conclusions References Further Reading Relevant Websites Glossary Capacity factor The capacity factor of a wind turbine refers to the ratio of the actual energy production of the machine for a given time period to the respective potential energy production of the same machine if it had operated at its rated power for the entire time period Embodied energy The energy consumed throughout the various life cycle stages of a system, for example, a wind turbine, equally well restricted to a single stage such as manufacturing Embodied energy amounts are usually compared with the useful energy amounts produced by the system in order to investigate whether they can be compensated by the latter Feed-in tariff A policy mechanism developed for the support of renewable energy technologies, through the award of a certain payment per kilowatt hour for electricity produced by a renewable resource and fed into the grid Feed-in tariffs may vary on the basis of technology, geographical location, and installation size Framework programs Framework programs for research and technological development, also abbreviated as FPs on the basis of Framework Programmes alone, comprise Comprehensive Renewable Energy, Volume 671 675 676 679 680 682 685 687 688 693 696 699 702 706 709 710 710 711 711 712 720 723 724 funding programs that have been created by the European Union so as to support and encourage research in various sectors, including also wind energy Pitch control In pitch-controlled machines, the angle of the blades is adjusted through signaling and the use of a pitch actuator, so as to capture the energy from the wind in the most efficient way Power (aerodynamic) coefficient A measure of the wind turbine rotor’s ability to exploit the available kinetic energy of wind Its maximum theoretical value corresponds to the Betz limit, being equal to 16/27 R&D The term is used to describe research and development, and refers to creative work undertaken on a systematic basis in order to increase the stock of knowledge and the use of this stock of knowledge to devise new applications Stall control In stall-controlled machines, the angle of the blades is fixed, while the blades are designed so that they can increasingly stall the angle of attack with the increase of wind speed Tip speed ratio The ratio of the linear speed at the tip of the blade to the wind speed upstream of the rotor doi:10.1016/B978-0-08-087872-0.00224-9 671 672 Trends, Prospects, and R&D Directions in Wind Turbine Technology 2.21.1 Brief Description of Wind Power Time Evolution Wind energy development counts thousands of years, that is, from the starting point of the very first vertical-axis wind machines operating on the basis of drag forces, up until the current time, during which wind turbines under development have reached the scale of tens of MW (Figure 1) Constant evolution of the wind power concept throughout this period may be reflected in the most straightforward way by the fact that we are now arguably entering the time of fourth-generation wind power machines (Figure 2) [1] From the early times of wind power exploitation, when the first vertical-axis windmills were used for grinding, to the times that electricity power generation lies on the rotation of huge epoxy-based blades reinforced with carbon fiber and the exploitation of offshore potential, humankind has encountered numerous types of wind machines and designs, which have always found an important place in the puzzle of technological development It was in fact centuries ago when the technology of wind energy made its first actual steps – although simpler wind devices date back thousands of years – with the vertical-axis windmills found at the Persian–Afghan borders around 200 BC and the horizontal-axis windmills of the Netherlands and the Mediterranean following much later (AD 1300–1875) (Figure 3) [2–4] Further evolution and perfection of these systems was performed in the United States during the nineteenth century, when over six million small machines were used for water pumping between 1850 and 1970 (Figure 4) Figure Wind power evolution: From the very first vertical-axis machines to large-scale contemporary wind turbines Uses: Power generation Type: Electric, geared or gearless generators, auxiliary excitation, Wind blades: Plastics, pitch control Towers: Steel or concrete Erection: High-rise crane Twentieth century Uses:Power generation−grinding mills Type: Electric/mechanical Wind blades: Wood/metal, stalled Towers: Wood (handycraft) Erection: Manual Nineteenth century Uses: Water pumping−grinding mills Type: Mechanical Wind blades: Wood and cloth, hand adjusted or stalled Towers: Wood (carpentry) Erection: Manual From BCE to 1800 Third generation Second generation First generation Figure Wind power evolution: From the first to the fourth generation of wind power machines Uses: Power generation Type: Electric, gearless generators, permanent magnets, no slip rings Wind blades: Plastics (epoxy) or bioplastics, fail safe pitch control Towers: Extruded concrete (selfmounting) Erection: self erecting Twenty-first century Fourth generation Trends, Prospects, and R&D Directions in Wind Turbine Technology 673 Figure The vertical-axis grain machines of the Persians and the horizontal-axis windmills of the Netherlands Figure From water pumping to the California outbreak On the other hand, the first ‘large’ wind machine to generate electricity (a low-speed and high-solidity wind turbine of 12 kW) was installed in Cleveland, Ohio, in 1888, while during the late stages of World War I, the use of 25 kW machines throughout Denmark was widespread Much later, the first wind turbine feeding a local grid was installed in 1931 in the USSR in Balaklava, with the electricity generated being fed into a small grid that was supplied by a 20 MW steam power station Further development of wind generators in the United States was inspired by the design of airplane propellers and monoplane wings, while subsequent efforts in Denmark, France, Germany, and the United Kingdom during the period between 1935 and 1970 showed that large-scale wind turbines could work Note that during this period, emphasis was mainly given to the development of horizontal-axis wind machines (i.e., the shaft of rotation is parallel to the ground) operating on the top of adequately high towers and using a small number of blades (normally two or three) Meanwhile, it was in 1931 that Georges Darrieus invented the vertical-axis wind turbine known as the ‘eggbeater’ windmill, introducing a new power generation concept for wind machines (Figure 5) European developments continued after World War II In Denmark, the Gedser mill 200 kW three-bladed upwind rotor wind turbine operated successfully until the early 1960s [5], while in Germany, a series of advanced horizontal-axis designs were developed, with both of the aforementioned concepts dictating the future horizontal-axis design approaches later emerging in the 1970s One of the most important milestones of wind energy history coincides with the US government involvement in wind energy R&D after the oil crisis of 1973 [6–8] Following this, in the years between 1973 and 1986, the commercial wind turbine market evolved from domestic and agricultural (1–25 kW) to utility-interconnected wind farm applications (50–600 kW) In this context, the first large-scale wind energy penetration outbreak was encountered in California [9], where over 16 000 machines ranging from 20 to 350 kW (a total of 1.7 GW) were installed between 1981 and 1990, as a result of the incentives (such as the federal investment and energy credits) given by the US government (Figure 4) In northern Europe, wind farm installations increased steadily through the 1980s and 1990s (Figure 6), with the higher cost of electricity and the excellent wind resources leading to the creation of a small but stable market After 1990, most market activity shifted to Europe [10], with the last 20 years bringing wind energy to the front line of the global scene, with major players from all world regions Nevertheless, both the revival of interest in the United States and the recent dynamic introduction of the Chinese in the wind energy sector have much altered the up-to-now wind energy market situation In summary, during these past 20 years, the wind energy sector has met tremendous growth, not only in terms of market share but also in terms of technological developments, with the latest achievements bringing about the era of offshore wind power 674 Trends, Prospects, and R&D Directions in Wind Turbine Technology Figure Aspects of Darrieus vertical-axis wind machines Figure Danish stamp of 1989 and a present-day offshore wind farm generation (Figure 6) [11] At this point, it should be noted that important advancements met in the field comprise the result of constant and unceasing research efforts, aiming at the development of innovative clean energy technologies In fact, according to the latest figures, systematic efforts recorded throughout this period of growth correspond to a galloping global wind power capacity that recently managed to exceed 200 GW (Figure 7) and that is, according to market experts, anticipated to reach 450 GW by 2015 [12] As already implied (Figure 7), the cumulative installed wind power is (a) (b) Installed capacity (GW) 210 180 4.0 5.2 150 120 3.8 44.7 26.7 5.7 90 5.8 60 13.1 40.2 30 20.7 19 19 97 19 19 99 20 20 0 20 02 20 20 04 20 20 06 20 20 08 20 09 20 10 Year Figure (a) Time evolution of installed wind power and (b) 2010 cumulative wind capacity distribution 27.2 China Spain France Denmark USA India UK Rest Germany Italy Canada Trends, Prospects, and R&D Directions in Wind Turbine Technology 675 nowadays mainly concentrated in the European Union, the United States, China, and India, while what should also be noted is that there is aremarkable activity recently recorded in offshore installations, with contemporary machines now reaching or even exceeding MW 2.21.2 The Current Wind Turbine Concept Being the result of strong competition among different design schools, techniques and manufacturers from all around the world, the vast majority of today’s wind turbines comprise the following main parts [13] (Figure 8): A ‘rotor’ of diameter D, using three relatively thin blades placed upstream of the tower and rotating on the basis of a horizontal axis that is almost parallel to both the ground and the wind direction Rotational speed of the rotor nR is kept relatively low in order to limit development of strong centrifugal stresses upon the blades [14], while it is the rotor that at the same time determines the power of wind to be exploited Pw (see also eqn [1]): Pw ¼ 0:5⋅ρ⋅ π⋅D2 ⋅V ½1Š where ρ is the air density passing through the rotor and V is the vertical to the rotor component of wind speed upstream of the rotor (normally at a distance approximately equal to the rotor diameter D) A ‘tower’, being normally of solid geometry and determined by a height H that is related to the rotor diameter (usually Η ≈ D) ine Design Project acronym: UPWIND EC contribution: €14.56 million Duration: March 2006 to February 2011 (60 months) Abstract: UPWIND looks toward wind power tomorrow, toward the design of very large turbines (8–10 MW) standing in wind farms of several hundred megawatts, both on- and offshore It will develop the accurate, verified tools, and component concepts the industry needs to design and manufacture this new breed of turbine It will focus on design tools for the complete range of turbine components It will address the aerodynamic, aeroelastic, structural, and material design of rotors Critical analysis of drivetrain components will be carried out in the search for breakthrough solutions Prediction of Waves, Wakes and Offshore Wind Project acronym: POWWOW EC contribution: €1.05 million Duration: October 2005 to September 2008 (36 months) Abstract: Currently, a good number of research projects are underway on the European and national level in the fields of short-term forecasting of wind power, offshore wind and wave resource prediction, and offshore wakes in large wind farms The purpose of this action is to coordinate the activities in these related fields, to spread the knowledge gained from these projects among the partners and colleagues, and to start the work on some roadmaps for the future 718 Trends, Prospects, and R&D Directions in Wind Turbine Technology Dissemination Strategy on Electricity Balancing for large Scale Integration of Renewable Energy Project acronym: DESIRE EC contribution: €1.2 million Duration: June 2005 to May 2007 (24 months) Abstract: DESIRE will disseminate practices that will integrate fluctuating renewable electricity supplies, such as wind power, into electricity systems using combined heat and power This will allow an increase in pan-European trade in electricity, improve the economic competitiveness of both combined heat and power production (CHP) and wind power, and allow the proportion of renewable electricity that can be absorbed by the system to increase Distant Offshore Wind Farms with No Visual Impact in Deepwater Project acronym: DOWNVIND EC contribution: €6.0 million Duration: September 2004 to September 2009 (60 months) Abstract: The R&D program will conduct research into the factors of environmental, electrical, operations and maintenance and wind turbine substructure pertinent to the installation and operation of large-capacity wind farms offshore in deepwater The Demonstrator Project will install two MW wind turbine generators (WTGs) in deep water near the Beatrice Alpha oil production platform in the Moray Firth, offshore north-east Scotland, then monitor their operation for an extended period to gather data on the WTG and substructure performance Standardization of Ice Forces on Offshore Structures Design Project acronym: STANDICE EC contribution: €0.24 million Duration: June 2004 to December 2007 (43 months) Abstract: The main objective of this project is to contribute to the development of an international standard for the design of marine structures such as offshore wind energy converters (OWECs) against ice loads with special emphasis on European subarctic ice conditions To achieve this objective, the project will take advantage of an international standardi­ zation effort Hogsara Island Demonstration Project Project acronym: HISP EC contribution: €1.7 million Duration: April 2004 to July 2007 (39 months) Abstract: The objective of the project is to gain experience and to build up a track record of a small wind farm with multi-megawatt wind turbines built on an island, to demonstrate high availability, and to verify the low-cost foundation design with as little alteration on the nature and inhabitants of the islands as possible The electrical conversion system will be designed for a cluster of turbines in order to minimize the number of components and to optimize costs, thus contributing to the objectives mentioned Appendix C Wind Energy Projects Funded by FP7 (Since 2007) Off-Shore Renewable Energy Conversion Platforms – Coordination Action Project acronym: ORECCA EC contribution: €1.6 million Duration: March 2010 to August 2011 (18 months) Abstract: The objectives of the projects are to create a framework for knowledge sharing and to develop a research roadmap for activities in the context of offshore renewable energy (RE) In particular, the project will stimulate collaboration in research activities leading toward innovative, cost-efficient, and environmentally benign offshore RE conversion platforms for wind, wave, and other ocean energy resources, for their combined use, as well as for the complementary uses Trends, Prospects, and R&D Directions in Wind Turbine Technology 719 Marine Renewable Integrated Application Platform Project acronym: MARINA PLATFORM EC contribution: €8.7 million Duration: January 2010 to June 2014 (54 months) Abstract: MARINA is a European project dedicated to bringing offshore renewable energy applications closer to the market by creating new infrastructures for both offshore wind and ocean energy converters It addresses the need for creating a cost-efficient technology development basis to kick-start growth of the nascent European marine renewable energy (MRE) industry in the deep offshore Multi-Scale Data Assimilation, Advanced Wind Modeling and Forecasting with Emphasis to Extreme Weather Situations for a Secure Large-Scale Wind Power Integration Project acronym: SAFEWIND EC contribution: €3.99 million Duration: September 2008 to August 2012 (48 months) Abstract: The aim of this project is to substantially improve wind power predictability in challenging or extreme situations and at different temporal and spatial scales Going beyond this, wind predictability is considered as a system design parameter linked to the resource assessment phase, where the aim is to take optimal decisions for the installation of a new wind farm Pilot Demonstration of Eleven MW-Class WEC at Estinnes in Belgium Project acronym: MW-WEC-BY-11 EC contribution: €3.27 million Duration: August 2008 to August 2012 (48 months) Abstract: This action focuses on demonstrating the development of a cost-effective, large-scale, high-capacity wind park using new state-of-the-art multi-megawatt turbines coupled with innovative technology used to stabilize the grid A key objective of the ‘7­ MW-WEC-by-11’ project is to introduce a new power class of large-scale wind energy converters, the MW WEC, into the market The new MW WEC will be designed and demonstrated at a large scale: 11 such WECs will be demonstrated in a 77 MW wind park close to Estinnes (Belgium) Northern Seas Wind Index Database Project acronym: NORSEWIND EC contribution: €3.95 million Duration: August 2008 to August 2012 (48 months) Abstract: NORSEWIND is a program designed to provide a wind resource map covering the Baltic, Irish, and North Sea areas The project will acquire highly accurate, cost-effective, physical data using a combination of traditional meteorological masts, ground-based remote sensing instruments (LiDAR and SoDAR), and satellite-acquired synthetic aperture radar (SAR) winds The resultant wind map will be the first stop for all potential developers in the regions being examined, and as such represents an important step forward in quantifying the quality of the wind resource available offshore PROcedures for TESTing and Measuring Wind Energy Systems Project acronym: PROTEST EC contribution: €1.98 million Duration: March 2008 to December 2010 (30 months) Abstract: The objective of this pre-normative project is to set up a methodology that enables better specification of design loads for the mechanical components The design loads will be specified at the interconnection points where the component can be isolated from the entire wind turbine structure (for gearboxes, for instance, the interconnection points are the shafts and the attachments to the nacelle frame) The focus will be on developing guidelines for measuring load spectra at the interconnection points during prototype measurements and to compare them with the initial design loads 720 Trends, Prospects, and R&D Directions in Wind Turbine Technology Reliability Focused Research on Optimizing Wind Energy Systems Design, Operation and Maintenance: Tools, Proof of Concepts, Guidelines & Methodologies for a New Generation Project acronym: RELIAWIND EC contribution: €5.18 million Duration: March 2008 to March 2011 (36 months) Abstract: The RELIAWIND consortium, for the first time in the European wind energy sector, and based on successful experiences from other sectors (e.g., aeronautics) will jointly and scientifically study the impact of reliability, changing the paradigm of how wind turbines are designed, operated, and maintained This will lead to a new generation of offshore (and onshore) wind energy systems that will hit the market in 2015 Future Deep Sea Wind Turbine Technologies Project acronym: DEEPWIND EC contribution: €2.99 million Duration: October 2010 to October 2014 (48 months) Abstract: The objectives of this project for new wind turbines are (1) to explore the technologies needed for development of a new and simple floating offshore concept with a vertical-axis rotor and a floating and rotating foundation, (2) to develop calculation and design tools for development and evaluation of very large wind turbines based on this concept, and (3) to evaluate the overall concept with floating offshore horizontal-axis wind turbines High Altitude Wind Energy Project acronym: HAWE EC contribution: €1.92 million Duration: October 2010 to April 2014 (42 months) Abstract: The aim of this project is to develop a wind power system capable of harnessing the energy potential of high-altitude wind (actually wind towers mainly use low-altitude wind, which is slow and intermittent and means that most wind farms operate at only 25–35% of their capacity) through R&D in technology fields such as materials, aerodynamics, and control High Power, High Reliability Offshore Wind Technology Project acronym: HIPRWIND EC contribution: €11.0 million Duration: November 2010 to November 2015 (60 months) Abstract: The aim of the HIPRWIND project is to develop and test new solutions for very large offshore wind turbines at an industrial scale The project addresses critical issues such as extreme reliability, remote maintenance, and grid integration, with particular emphasis on floating wind turbines, where weight and size limitations of onshore designs can be overcome References [1] Grob GR (2011) Wind Power Evolution International Sustainable Energy Organization for Renewable Energy and Energy Efficiency http://www.uniseo.org/documents/ (accessed June 2011) [2] Fleming PD and Probert SD (1984) The evolution of wind-turbines: An historical review Applied Energy 18: 163–177 [3] Musgrove P (2010) Wind Power, 1st edn Cambridge: Cambridge University Press [4] Pasqualetti MJ, Righter R, and Gipe P (2004) History of wind energy In: Cleveland C (ed.) Encyclopedia of Energy, pp 419–433 San Diego, CA: Academic Press [5] Meyer NI (1995) Danish wind power development Energy for Sustainable Development 2: 18–25 [6] Carmoy D (1978) The USA faces the energy challenge Energy Policy 6: 36–52 [7] Thomas RL and Robbins WH (1980) Large wind-turbine projects in the United States wind energy program Wind Engineering and Industrial Aerodynamics 5: 323–335 [8] Gipe P (1991) Wind energy comes of age California and Denmark Energy Policy 19: 756–767 [9] Righter RW (1996) Pioneering in wind energy: The California experience Renewable Energy 9: 781–784 [10] Ackermann T and Söder L (2002) An overview of wind energy-status 2002 Renewable and Sustainable Energy Reviews 6: 67–127 [11] Esteban MD, Diez JJ, López JS, and Negro V (2011) Why offshore wind energy? Renewable Energy 36: 444–450 [12] Global Wind Energy Council (GWEC) (2010) Global Wind Report http://www.gwec.net/ (accessed June 2011) [13] Kaldellis JK (2005) Wind Energy Management, 2nd edn Athens, Greece: Stamoulis Trends, Prospects, and R&D Directions in Wind Turbine Technology [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] 721 Ronold KO and Larsen GC (2000) Reliability-based design of wind-turbine rotor blades against failure in ultimate loading Engineering Structures 22: 565–574 Ahmed MR and Sharma SD (2005) An investigation on the aerodynamics of a symmetrical airfoil in ground effect Experimental Thermal and Fluid Science 29: 633–647 Tar K (2008) Some statistical characteristics of monthly average wind speed at various heights Renewable and Sustainable Energy Reviews 12: 1712–1724 Gasch R and Twele J (2002) Wind Power Plants Fundamentals, Design, Construction and Operation, 1st edn Berlin, Germany: Solarpraxis AG; London, UK: James & James Science Publishers Ltd Gardner P, Garrad A, Hansen LF, et al (2009) Wind Energy the Facts, Part I: Technology http://www.wind-energy-the-facts.org/documents/download/Chapter1.pdf (accessed June 2007) Lenzen M and Munksgaard J (2002) Energy and CO2 life-cycle analyses of wind turbines-review and applications Renewable Energy 26: 339–362 Crawford RH (2009) Life cycle energy and greenhouse emissions analysis of wind turbines and the effect of size on energy yield Renewable and Sustainable Energy Reviews 13: 2653–2660 Tremeac B and Meunier F (2009) Life cycle analysis of 4.5MW and 250W wind turbines Renewable and Sustainable Energy Reviews 13: 2104–2110 Kaldellis JK and Vlachou DS (2002) Analyzing the historical evolution of contemporary wind turbines In: Global Windpower Conference Paris, France, 2–5 April 2002 ENERCON (2011) Wind Turbines, E126/7.5MW http://www.enercon.de/en-en/66.htm (accessed June 2011) Repower Systems (2011) Products, Wind Turbines, 6M http://www.repower.de/produkte/windenergieanlagen/6M/?L=1 (accessed June 2011) Li N (2008) Size matters: Installed maximal unit size predicts market life cycles of electricity generation technologies and systems Energy Policy 36: 2212–2225 UPWIND (2011) Finding Solutions for Very Large Wind Turbines http://www.upwind.eu/ (accessed June 2011) Ragheb M (2009) Control of Wind Turbines University of Illinois at Urbana-Champaign https://netfiles.uiuc.edu/mragheb/www/NPRE%20475%20Wind%20Power% 20Systems/Control%20of%20Wind%20Turbines.pdf (accessed June 2011) Spruce CJ (2004) Power control of active stall wind turbines In: European Wind Energy Conference 2004 London, UK, 22–25 November 2002 Khadraoui MR and Elleuch M (2008) Comparison between OptiSlip and Fixed Speed wind energy conversion systems In: 5th International Multi-Conference on Systems, Signals and Devices Amman, Jordan, 8–10 August 2008 Urban A (2010) With or without gearbox? Drive train development for wind turbines In: Technologie-Workshop “Windenergie – Quo Vadis?” Vienna, Austria Polinder H, van der Pijl FFA, de Vilder G, and Tavner PJ (2006) Comparison of direct-drive and geared generator concepts for wind turbines IEEE Transactions of Energy Conversion 21: 725–733 Musial W, McNiff B, and Butterfield S (2007) Improving wind turbine gearbox reliability In: European Wind Energy Conference 2007 Milan, Italy, 7–10 May 2007 Siegfriedsen S and Bohmeke G (1998) Multibrid technology – A significant step to multi-megawatt wind turbines Wind Energy 1: 89–100 Li H, Chen Z, and Polinder H (2009) Optimization of multibrid permanent-magnet wind generator systems IEEE Transactions of Energy Conversion 24: 82–92 US Department of Energy (2010) Advanced Wind Turbine Drivetrain Concepts: Workshop Report http://www.nrel.gov/docs/fy11osti/50043.pdf (accessed June 2011) Busmann HG, Kensche C, Berg-Pollack A, et al (2007) Fraunhofer-Center für Windenergie und Meerestechnik, Testing of Rotor Blades DEWI Magazin 30: 5–9 LM Wind Power, Press Release (2011) LM Wind Power Marks Global Wind Day with Some ‘Big’ News June 15 http://www.lmwindpower.com/ (accessed June 2011) Griffin DA (2000) Advanced Research Turbine (ART) Aerodynamic Design of ART-2B Rotor Blades National Renewable Energy Laboratory http://www.nrel.gov/docs/fy00osti/ 28473.pdf (accessed June 2011) Griffin DA (2009) Blade System Design Study, Part II: Final Project Report (GEC) Sandia National Laboratories, SAND2009-0686 http://prod.sandia.gov/techlib/access­ control.cgi/2009/090686.pdf (accessed June 2011) Griffin DA (2001) WindPACT Turbine Design Scaling Studies Technical Area 1-Composite Blades for 80- to 120-Meter Rotor National Renewable Energy Laboratory http:// www.nrel.gov/docs/fy01osti/29492.pdf (accessed June 2011) Griffin DA (2001) WindPACT Turbine Design Scaling Studies Technical Area 2: Turbine, Rotor, and Blade Logistics National Renewable Energy Laboratory http://www.nrel gov/docs/fy01osti/29439.pdf (accessed June 2011) Hau E (2006) Wind Turbines: Fundamentals, Technologies, Application, Economics, 2nd edn Berlin; Heidelberg, Germany: Springer-Verlag Engels W, Obdam T, and Savenije F (2009) Current Developments in Wind – 2009 Going to Great Lengths to Improve Wind Energy Energy Research Centre of the Netherlands (ECN) http://www.ecn.nl/docs/library/report/2009/e09096.pdf (accessed June 2011) Manwell JF, McGowan JG, and Rogers AL (2002) Wind Energy Explained: Theory, Design and Application, 1st edn New York: John Wiley & Sons Sandia National Laboratories (2003) Cost Study for Large Wind Turbine Blades: WindPACT Blade System Design Studies ftp://ftp.ecs.umass.edu/pub/rerl/outgoing/ MIE_697W/Readings/WindPact/WindPact31428.pdf (accessed June 2011) MAGENN (2011) Technology http://www.magenn.com/technology.php (accessed June 2011) Maglev Wind Turbine (2011) http://magturbine.com/ (accessed June 2011) Argatov I, Rautakorpi P, and Silvennoinen R (2009) Estimation of the mechanical energy output of the kite wind generator Renewable Energy 34: 1525–1532 Argatov I and Silvennoinen R (2010) Energy conversion efficiency of the pumping kite wind generator Renewable Energy 35: 1052–1060 Canale M, Fagiano L, and Milanese M (2009) KiteGen: A revolution in wind energy generation Energy 34: 355–361 Aerotecture International Inc Products Available at: http://www.aerotecture.com/ (accessed 15 July 2011) Windpods Technology Available at: http://www.windpods.com/technology.html (accessed 15 July 2011) Badawy MTS and Aly ME (2000) Theoretical Demonstration of Diffuser Augmented Wind Turbine Performance World Renewable Energy Congress VI, pp 2300–2303 Fletcher CAJ (1981) Computational analysis of diffuser-augmented wind turbines Energy Conversion and Management 21: 175–183 FloDesign (2011) FloDesign Wind Turbine http://www.flodesign.org/ (accessed June 2011) ARISTA Power (2011) WindTamer 8.0 GT http://aristapower.com/wind/our-systems/windtamer-8-0-gt/ (accessed June 2011) Morrison ML and Sinclair K (2004) Wind energy technology, environmental impacts of In: Encyclopedia of Energy 6: 435–448 European Commission, Special Eurobarometer (2006) Attitudes Towards Energy http://ec.europa.eu/public_opinion/index_en.htm (accessed June 2011) European Commission, Special Eurobarometer (2007) Energy Technologies: Knowledge, Perception, Measures http://ec.europa.eu/public_opinion/index_en.htm (accessed June 2011) Björkman M (2004) Long time measurements of noise from wind turbines Sound and Vibration 277: 567–572 Bailey H, Senior B, Simmons D, et al (2010) Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals Marine Pollution Bulletin 60: 888–897 Bishop ID and Stock C (2010) Using collaborative virtual environments to plan wind energy installations Renewable Energy 35: 2348–2355 Desholm M (2009) Avian sensitivity to mortality: Prioritising migratory bird species for assessment at proposed wind farms Environmental Management 90: 2672–2679 Bright J, Langston R, Bullman R, et al (2008) Map of bird sensitivities to wind farms in Scotland: A tool to aid planning and conservation Biological Conservation 141: 2342–2356 Josimović B and Pucar M (2010) The strategic environmental impact assessment of electric wind energy plants: Case study ‘Bavanište’ (Serbia) Renewable Energy 35: 1509–1519 Jolivet E and Heiskanen E (2010) Blowing against the wind – An exploratory application of actor network theory to the analysis of local controversies and participation processes in wind energy Energy Policy 38: 6746–6754 Gross C (2007) Community perspectives of wind energy in Australia: The application of a justice and community fairness framework to increase social acceptance Energy Policy 35: 2727–2736 722 Trends, Prospects, and R&D Directions in Wind Turbine Technology [68] Musial W and Ram B (2010) Large-scale offshore wind power in the United States Assessment of Opportunities and Barriers, National Renewable Energy Laboratory http:// www.nrel.gov/wind/pdfs/40745.pdf (accessed June 2011) [69] 4C Offshore (2011) Global Offshore Wind Farms Database http://www.4coffshore.com/windfarms/ (accessed June 2011) [70] Smit T, Junginger M, and Smits R (2007) Technological learning in offshore wind energy: Different roles of the government Energy Policy 35: 6431–6444 [71] Markard J and Petersen R (2009) The offshore trend: Structural changes in the wind power sector Energy Policy 37: 3545–3556 [72] European Environmental Agency (2009) Europe’s Onshore and Offshore Wind Energy Potential An Assessment of Environmental and Economic Constraints http://www.energy eu/publications/a07.pdf (accessed June 2011) [73] European Wind Energy Association (2009) Oceans of Opportunity Harnessing Europe’s Largest Domestic Energy Resource http://www.ewea.org/fileadmin/ewea_documents/ documents/publications/reports/Offshore_Report_2009.pdf (accessed June 2011) [74] European Wind Energy Association (2009) Pure Power, Wind Energy Targets for 2020 and 2030 A Report by the European Wind Energy Association http://www.ewea.org/ fileadmin/ewea_documents/documents/publications/reports/Pure_Power_Full_Report.pdf (accessed June 2011) [75] Scholz-Reiter B, Luten M, Heger J, and Schweizer A (2010) Planning and control of logistics for offshore wind farms In: 12th WSEAS International Conference on Mathematical and Computational Methods in Science and Engineering Faro, Portugal, 3–5 November 2010 [76] Hameed Z, Vatn J, and Heggset J (2001) Challenges in the reliability and maintainability data collection for offshore wind turbines Renewable Energy 36: 2154–2165 [77] Riegler H (2003) HAWT versus VAWT: Small VAWTs find a clear niche Refocus 4: 44–46 [78] Peace S (2004) Another approach to wind (cover story) Mechanical Engineering 126: 28–31 [79] Darrieus GJM (1931) Turbine Having Its Rotating Shaft Transverse to the Flow of the Current US Patent 1,835,018 [80] Can K, Feng Z, and Xuejun M (2010) Comparison study of a vertical-axis spiral rotor and a conventional Savonius rotor In: Power and Energy Engineering Conference (APPEEC), 2010 Asia-Pacific Chengdu, China, 28–31 March 2010 [81] Price TJ (2006) UK large-scale wind power programme from 1970 to 1990: The Carmarthen Bay experiments and the Musgrove vertical-axis turbines Wind Engineering 30: 225–242 [82] Sandia National Laboratories (2011) Vertical Axis Wind Turbine: The History of the DOE Program http://windpower.sandia.gov/topical.htm (accessed June 2011) [83] Morgan CA, Gardner P, Mays ID, and Anderson MB (1989) The demonstration of a stall regulated 100 kW vertical axis wind turbine In: 1989 European Wind Energy Conference Glasgow, UK, 1–5 March 1989 [84] Morcos VH and Abdel-Hafez OME (1996) Testing of an arrow-head vertical axis wind turbine model Renewable Energy 7: 223–231 [85] Migliore PG, Wolfe WP, and Fanucci JB (1980) Flow curvature effects on Darrieus turbine blade aerodynamics Energy 4: 49–55 [86] Ham ND, Soohoo P, Noll RB, and Drees HM (1979) Analytical and experimental evaluation of cycloturbine aerodynamic performance In: AIAA Terrestrial Energy Systems Conference Orlando, FL, USA, 4–6 June 1969 [87] Eriksson S, Bernhoff H, and Leijon M (2008) Evaluation of different turbine concepts for wind power Renewable and Sustainable Energy Reviews 12: 1419–1434 [88] Sharpe T and Proven G (2010) Crossflex: Concept and early development of a true building integrated wind turbine Energy and Buildings 42: 2365–2375 [89] Müller G, Jentsch MF, and Stoddart E (2009) Vertical axis resistance type wind turbines for use in buildings Renewable Energy 34: 1407–1412 [90] Marsh G and Peace S (2005) Tilting at windmills: Utility-scale VAWTs: Towards 10 MW and beyond? Refocus 6: 37–42 [91] Wind Power Ltd (2011) Aerogenerator X http://www.windpower.ltd.uk/ (accessed June 2011) [92] All Small Wind Turbines (2011) All the World’s Small Wind Turbines in One Overview http://www.allsmallwindturbines.com/ (accessed June 2011) [93] American Wind Energy Association (AWEA) (2010) AWEA Small Wind Turbine Global Market Study http://www.awea.org/learnabout/smallwind/upload/ 2010_AWEA_Small_Wind_Turbine_Global_Market_Study.pdf (accessed June 2011) [94] RenewableUK (2011) Small wind systems UK Market Report http://www.bwea.com/small/index.html (accessed June 2011) [95] Kaldellis JK and Kavadias KA (2007) Cost–benefit analysis of remote hybrid wind–diesel power stations: Case study Aegean Sea islands Energy Policy 35: 1525–1538 [96] American Wind Energy Association and Northwest Sustainable Energy for Economic Development (2003) Permitting Small Wind Turbines – A Handbook http://www rpdmohesr.com/uploads/custompages/awea_permitting_small_wind%2012.pdf (accessed June 2011) [97] American Wind Energy Association (AWEA) (2009) AWEA Small Wind Turbine Performance and Safety Standard http://www.awea.org/learnabout/smallwind/upload/ AWEA_Small_Turbine_Standard_Adopted_Dec09.pdf (accessed June 2011) [98] Walker SL (2011) Building mounted wind turbines and their suitability for the urban scale-A review of methods of estimating urban wind resource Energy and Buildings 43: 1852–1862 [99] Kaldellis JK (2002) Optimum autonomous wind–power system sizing for remote consumers, using long-term wind speed data Applied Energy 71: 215–233 [100] Kaldellis JK and Vlachos GTh (2006) Optimum sizing of an autonomous wind–diesel hybrid system for various representative wind-potential cases Applied Energy 83: 113–132 [101] Kaldellis JK (2010) Stand-Alone and Hybrid Wind Energy Systems: Technology, Energy Storage and Applications, 1st edn Cambridge, UK: Woodhead Publishing [102] Bahaj AS, Myers L, and James PAB (2007) Urban energy generation: Influence of micro-wind turbine output on electricity consumption in buildings Energy and Buildings 39: 154–165 [103] Peacock AD, Jenkins D, Ahadzi M, et al (2008) Micro wind turbines in the UK domestic sector Energy and Buildings 40: 1324–1333 [104] Ledo L, Kosasih PB, and Cooper P (2011) Roof mounting site analysis for micro-wind turbines Renewable Energy 36: 1379–1391 [105] Yassin MF (2011) Impact of roof shape and its height of building on air quality in urban street canyons Atmospheric Environment 45: 5220–5229 [106] Warwick Wind Trials (2011) Microwind – A Catalyst for Change in UK Energy Culture? http://www.warwickwindtrials.org.uk/index.html (accessed June 2011) [107] WINEUR (2011) Wind Energy Integration in the Urban Environment http://www.urbanwind.net/wineur.html (accessed June 2011) [108] Syngellakis K and Robinson P (2006) Urban wind turbines: Development of the UK market In: European Wind Energy Conference 2006 Athens, Greece, 27 February–2 March 2006 [109] Cace J, Horst E, Syngellakis K, et al (2007) Urban Wind Turbines: Guidelines for Small Wind Turbines in the Built Environment http://www.urban-wind.org (accessed June 2011) [110] Encraft (2008) Warwick Wind Trials Fourth Interim Report http://www.warwickwindtrials.org.uk/resources (accessed June 2011) [111] Shaw S (2008) Progress Report on Small Wind Energy Development Projects Receiving Funds from the Massachusetts Technology Collaborative (MTC) http://www.ualberta ca/~mtyree/SWIEP/Docs/CadmusGroupReport20041408.pdf (accessed June 2011) [112] Zhang A, Gao C, and Zhang L (2005) Numerical simulation of the wind field around different building arrangements Wind Engineering and Industrial Aerodynamics 93: 891–904 [113] Blocken B, Carmeliet J, and Stathopoulos T (2007) CFD evaluation of wind speed conditions in passages between parallel buildings – Effect of wall-function roughness modifications for the atmospheric boundary layer flow Wind Engineering and Industrial Aerodynamics 95: 941–962 [114] Heagle ALB, Naterer GF, and Pope K (2011) Small wind turbine energy policies for residential and small business usage in Ontario, Canada Energy Policy 39: 1988–1999 [115] American Wind Energy Association (AWEA) (2010) Policies to Promote Small Wind Turbines A Menu for State and Local Governments http://www.awea.org/learnabout/ smallwind/upload/Policies_to_Promote_Small_Wind_Turbines.pdf (accessed June 2011) [116] Marsh G (2008) No child’s play? Making small wind pay Renewable Energy Focus 9(5): 30–36 [117] Junginger M, Faaij A, and Turkenburg WC (2005) Global experience curves for wind farms Energy Policy 33: 133–150 [118] Morthorst PE, Auer H, Garrad A, and Blanco I (2009) Wind Energy the Facts, Part III: The Economics of Wind Power http://www.wind-energy-the-facts.org/documents/ download/Chapter3.pdf (accessed June 2011) [119] Department of Trade and Industry (2007) Study of the costs of offshore wind generation A Report to the Renewables Advisory Board (RAB) & DTI URN Number 07/779, UK ... Policy 36: 22 12 22 25 UPWIND (20 11) Finding Solutions for Very Large Wind Turbines http://www.upwind.eu/ (accessed June 20 11) Ragheb M (20 09) Control of Wind Turbines University of Illinois at Urbana-Champaign... https://netfiles.uiuc.edu/mragheb/www/NPRE %20 475 %20 Wind %20 Power% 20 Systems/Control %20 of %20 Wind %20 Turbines.pdf (accessed June 20 11) Spruce CJ (20 04) Power control of active stall wind turbines In: European Wind Energy Conference 20 04... Management, 2nd edn Athens, Greece: Stamoulis Trends, Prospects, and R&D Directions in Wind Turbine Technology [14] [15] [16] [17] [18] [19] [20 ] [21 ] [22 ] [23 ] [24 ] [25 ] [26 ] [27 ] [28 ] [29 ] [30]