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Executive SummaryOver the past 30 years, wind energy has evolved from a small industry active in a few countries to a large international industry involving major players in the manufacturing, development, and utility sectors. Coinciding with the industry growth, significant innovation in the technology has resulted in larger sized turbines with lower associated costs of energy and more complex designs in all subsystems-from the rotor to the drivetrain to the electronics and control systems. However, as the deployment of the technology grows and its role within the electricity sector has become more prominent, so have the expectations of the technology in terms of performance, reliability, and cost. For the industry to continue to succeed and become a sustainable source of electricity, innovation in wind energy technology must continue to improve performance and lower the cost of energy while supporting seamless integration of wind energy into the electric grid without creating significant negative impacts on local communities and environments. At the same time, the nature of the issues associated with wind energy design and development are noticeably more complex than in the past due to a variety of factors such as, for example, large turbines sizes, offshore deployment or complex terrains. Looking toward the future, the industry would benefit from an integrated approach that simultaneously addresses turbine design, plant design and development, grid interaction and operation, and mitigation of adverse community and environmental impacts. These activities must be integrated in order to meet this diverse set of goals while recognizing trade-offs that exist between them.In order to address these challenges, National Renewable Energy Laboratory (NREL) has embarked on the Wind Energy Systems Engineering (WESE) initiative to evaluate how methods of systems engineering can be applied to the research, design, and development of wind energy systems. Systems engineering is a field within engineering that has a long history of application to complex technical systems such as aerospace. As such, the field holds much potential for addressing critical issues that face the wind industry today. This paper represents a first step for understanding this potential and lays out a conceptual design for the development of a WESE framework and tool. It reviews systems engineering methods as applied to related technical systems and illustrates how these methods can be combined in a WESE framework to meet the research, design, and development needs for the future of the industry. Subsequent efforts will focus on developing and implementing a framework based on the conceptual design illustrated in the last chapter of this report.In general, systems engineering approaches have the following four characteristics: holistic, multidisciplinary, integrated/value-driven, and long-term/life-cycle oriented. The approach is holistic in that it considers the full technical system, including any number of performance criteria, as well as potential...

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A test of a 0.658-scale V-22 rotor and wing was conducted in the 40x80 Foot Wind Tunnfl at Ames Research Center. One of the principal objectives of the test was to measure the wing download in hover for a variety of test configurations. The wing download and surface pressures were measured for a wide range of thrust coefficients, with live dimrent flsp andes, two nacelle angles, and both directions of rotor rotation. This paper presents there results, and describes a new method far interpreting wing surface pressure data in hover. This method shows that the wing flsp can produce substantial lift loads in hover. Notation A = rotor disc area, .rrR2, m2 C, = wing surface pressure coefficient in hover, ( pp.,,,,,)l VIA) C, = rotor thrust coefficient, TlpAR2R2 c = wing chord, m DL = wing download, N p = wing surface pressure, Nlm2 p,,,. = atmospheric pressure, Nlm2 R = rotor radius, m r = radial distance from rotor axis, m T = rotor thrust, N x = chordwise distance from wing leading edge, m p = air density, Kg/m3 R = rotor rotation speed, radls

An experimental investigation of rotorlwing aerodynamic interactions in hover is described. The investigation consisted of both s large-scale and a small-scale test. A 0.658-scale V-22 rotor and wing wss used in the largescale test. Wing download, wing surface pressure, rotor performance, and rotor downwash data from the largescale test are presented. A small-scale experiment was conducted to determine how changes in the rotorlwing geometry afieted the aerodynamic interactions. These geometry variations included the distance between the rotor and wing, wing incidence angle, wing nap angle, rotor rotation direction, and configurations both with the rotor axis at the tip of the wing (tilt rotor configuration) and with the rotor axis at the center of the wing (compound helicopter configuration). Nomenclature A = rotor disc area, .rrR2, m2 C, = rotor thrust coefficient, TIPAV,:,,~ c = wing chord, m DL = wing download, N P = pressure. Nlm2Pa,, = ~tmospheric pressure, Nlm2 AP = differential pressure, P -P.,,, Nlm2 = rotor radius; rn = rotor thrust, N = maximum wing thickness, m = rotor downwash velocity, rnls = ideal induced velocity in hover, m, mls = rotor tip speed, rnls = wing chordwise location, m = distance between rotor and wing, m = wing incidence angle, angle between wing chord line and horizontal, positive nose up, degrees = flap deflection angle, degrees = air density, kg/m3