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Effects of flow curvature on the aerodynamics of Darrieus wind turbines

Description: A theoretical and experimental investigation was conducted which clearly showed the effects of flow curvature to be significant determinants of Darrieus turbine blade aerodynamics; qualitatively, these results apply equally to straight or curved bladed machines. Unusually large boundary layer radial pressure gradients and virtually altered camber and incidence are the phenomena of primary importance. Conformal mapping techniques were developed which transform the geometric turbine airfoils in curved flow to their virtual equivalents in rectilinear flow, thereby permitting the more accurate selection of airfoil aerodynamic coefficients from published sectional data. It is demonstrated that once the flow idiosyncracies are fully understood, they may be used to advantage to improve the wind energy extraction efficiency of these machines.
Date: July 1, 1980
Creator: Migliore, P. G. & Wolfe, W. P.
Partner: UNT Libraries Government Documents Department

Feasibility study of pultruded blades for wind turbine rotors

Description: In work performed under subcontract to the National Renewable Energy Laboratory (NREL), a preliminary design study and proof-of-concept field test were conducted to evaluate the feasibility of using pultruded blades for wind turbine rotors. A 400 kW turbine was selected for the design study, and a scaled 80 kW rotor was fabricated and tested as a demonstration of the concept. To examine the feasibility of pultruded blades, several issues were addressed, including power performance, tower strikes, yaw stability, stall flutter, fatigue, and rotor cost. Results showed that with proper design, rotors using pultruded blades demonstrate acceptable fatigue life and stable yaw behavior without tower strikes. Furthermore, blades using this technology may be manufactured for approximately half the cost of conventional blades. Field tests of the scaled rotor provided experimental data on power performance and loads while verifying stable yaw operation.
Date: February 28, 2000
Creator: Migliore, P.G. & Cheney, M.C.
Partner: UNT Libraries Government Documents Department

U.S. Department of Energy Wind Turbine Development Projects

Description: This paper provides an overview of wind-turbine development activities in the Unites States and relates those activities to market conditions and projections. Several factors are responsible for a surge in wind energy development in the United States, including a federal production tax credit, ''green power'' marketing, and improving cost and reliability. More development is likely, as approximately 363 GW of new capacity will be needed by 2020 to meet growing demand and replace retiring units. The U.S. Department of Energy (DOE) is helping two companies develop next-generation turbines intended to generate electricity for $0.025/kWh or less. We expect to achieve this objective through a combination of improved engineering methods and configuration advancements. This should ensure that wind power will compete effectively against advanced combined-cycle plants having projected generating costs of $0.031/kWh in 2005. To address the market for small and intermediate-size wind turbines, DOE is assisting five companies in their attempts to develop new turbines having low capital cost and high reliability. Additional information regarding U.S. wind energy programs is available on the internet site www.nrel.gov/wind/. E-mail addresses for the turbine manufacturers are found in the Acknowledgements.
Date: April 26, 1999
Creator: Migliore, P. G. & Calvert, S. D.
Partner: UNT Libraries Government Documents Department

Vertical axis wind turbine development. Final report, March 1, 1976-June 30, 1977

Description: Theoretical and experimental research accomplished in evaluating an innovative concept for vertical axis wind turbines (VAWT) is described. The concept is that of using straight blades composed of circulation controlled airfoil sections. The theoretical analysis has been developed to determine the unsteady lift and moment characteristics of multiple-blade cross-flow wind turbines. To determine the drag data needed as input to the theoretical analysis, an outdoor test model VAWT has been constructed; design details, instrumentation, calibration results, and initial test results are reported. Initial testing was with fixed pitch blades having cross-sections of conventional symmetrical airfoils. Costs of building the test model are included, as well as cost estimates for blades constructed with composite materials. These costs are compared with those of other types of wind turbines.
Date: July 1, 1979
Creator: Walters, R. E.; Fanucci, J. B.; Hill, P. W. & Migliore, P. G.
Partner: UNT Libraries Government Documents Department

Vertical axis wind turbine development. Executive summary. Final report, March 1, 1976-June 30, 1977

Description: Information is presented concerning the numerical solution of the aerodynamics of cross-flow wind turbines; boundary layer considerations for a vertical axis wind turbine; WVU VAWT outdoor test model; low solidity blade tests; high solidity blade design; cost analysis of the WVU VAWT test model; structural parametric analysis of VAWT blades; and cost study of current WECS.
Date: July 1, 1979
Creator: Walters, R. E.; Fanucci, J. B.; Hill, P. W. & Migliore, P. G.
Partner: UNT Libraries Government Documents Department

Wind turbine trailing edge aerodynamic brakes

Description: Five trailing-edge devices were investigated to determine their potential as wind-turbine aerodynamic brakes, and for power modulation and load alleviation. Several promising configurations were identified. A new device, called the spoiler-flap, appears to be the best alternative. It is a simple device that is effective at all angles of attack. It is not structurally intrusive, and it has the potential for small actuating loads. It is shown that simultaneous achievement of a low lift/drag ratio and high drag is the determinant of device effectiveness, and that these attributes must persist up to an angle of attack of 45{degree}. It is also argued that aerodynamic brakes must be designed for a wind speed of at least 45 m/s (100 mph).
Date: April 1, 1995
Creator: Migliore, P G; Miller, L S & Quandt, G A
Partner: UNT Libraries Government Documents Department

Innovative wind turbines. Circulation controlled vertical axis wind turbine. Progress report, March 1-December 31, 1976

Description: Theoretical and experimental research efforts in evaluating an innovative concept for vertical axis wind turbines (VAWT) are described. The concept is that of using straight blades composed of circulation controlled airfoil sections. The theoretical analysis has been developed to determine the unsteady lift and moment characteristics of multiple-blade cross-flow wind turbines. To determine the drag data needed as input to the theoretical analysis, an outdoor test model VAWT has been constructed; design details, instrumentation, and calibration results are reported. Initial testing is with fixed pitch blades having cross-sections of conventional symmetrical airfoils. Costs of building the test model are included, as well as estimates for blades constructed with composite materials. These costs are compared with those of other types of wind turbines.
Date: October 1, 1978
Creator: Walters, R. E.; Fanucci, J. B.; Hill, P. W.; Migliore, P. G.; Squire, W. & Waltz, T. L.
Partner: UNT Libraries Government Documents Department