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At least 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Large wind turbine generators

The large wind turbine portion of the Federal Wind Energy Program consists of two major project efforts: (1) the Mod-0 test bed project for supporting research technology, and (2) the large experimental wind turbines for electric utility applications. The Mod-0 has met its primary objective of providing the entire wind energy program with early operations and performance data. The large experimental wind turbines to be tested in utility applications include three of the Mod-0A (200 kW) type, one Mod-1 (2000 kW), and possibly several of the Mod-2 (2500 kW) designs. This paper presents a description of these wind turbine systems, their programmatic status, and a summary of their potential costs.

Thomas, R. L.↗
NASA NTRS1978

Stable boundary layer wind shear model for aircraft flight hazard definition

It is pointed out that wind shear, particularly at the lower altitudes in the terminal area, has been identified as being hazardous to aircraft operations. Accurate and reliable wind profiles are required for use in fast time and manned flight simulation studies aimed at fully defining and understanding the wind shear hazard. A description is presented of wind speed profiles for neutral and stable atmospheric conditions developed for the simulation studies to improve the safety and reliability of operations in the terminal area. The wind shear is mathematically modeled and the mathematical scenarios are presented in a format for direct application to wind shear hazard/flight simulation studies.

Frost, W.↗
NASA NTRS1979

Wind study for high altitude platform design

An analysis of upper air winds was performed to define the wind environment at potential operating altitudes for high-altitude powered platform concepts. Expected wind conditions of the contiguous United States, Pacific area (Alaska to Sea of Japan), and European area (Norwegian and Mediterranean Seas) were obtained using a representative network of sites selected based upon adequate high-altitude sampling, geographic dispersion, and observed upper wind patterns. A data base of twenty plus years of rawinsonde gathered wind information was used in the analysis. Annual variations from surface to 10 mb (approximately 31 km) pressure altitude were investigated to encompass the practical operating range for the platform concepts. Parametric analysis for the United States and foreign areas was performed to provide a basis for vehicle system design tradeoffs. This analysis of wind magnitudes indicates the feasibility of annual operation at a majority of sites and more selective seasonal operation for the extreme conditions between the pressure altitudes of 100 to 25 mb based upon the assumed design speeds.

Strganac, T. W.↗
NASA NTRS1978

The radial evolution of the bulk properties of the solar wind

Simultaneous solar-wind proton data obtained at several heliocentric distances during radial alignments are compared. The radial variations associated with two high-speed streams in the solar wind are studied as examples of the radial evolution of the solar-wind speed distribution and of high-speed streams in the solar wind as observed in the ecliptic plane in 1973. Pioneer 11 data on high-speed streams in the solar wind observed at about 1.5 and 3.7 AU are compared with the corresponding high-speed-stream data obtained at earth. These analyses indicate that as these high-speed streams propagated to these extended heliocentric distances, there was an erosion of the highest speeds and a general narrowing of the speed distribution. These observations are consistent with the exchange of momentum in the solar wind between high-speed streams and low-speed streams as they propagate outward from the sun.

Intriligator, D. S.↗
NASA NTRS1979

Relationship between hurricane surface winds and L-band radar backscatter from the sea surface

High-altitude, airborne, L-band synthetic aperture radar (SAR) data were collected in Hurricane Gloria on 28 and 30 September 1976. The backscattered power levels (proportional to the surface scattering coefficient) averaged over a few square kilometers of surface area were found to vary with surface wind speed and the angle of the wind relative to the radar. Comparisons between the backscatter from the eye and eye-wall regions of the hurricane were made with low-level aircraft wind measurements that were nearly coincident in space and time. The SAR has the potential advantage over other radar types because of its higher spatial resolution. It also appears to have the ability to penetrate rainfall, with a reduction in the echo from the surface. One difference when compared with higher frequency microwave radars is a decrease in the sensitivity of the backscatter to changes in wind speed. This dependence of L-band radar backscatter on surface winds suggests that the winds associated with hurricanes can be measured with airborne or spaceborne radars.

Weissman, D. E.↗
NASA NTRS1979

Wind Loads on Flat Plate Photovoltaic Array Fields

The aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays were investigated. Local pressure distributions and total aerodynamic forces on the arrays are shown. Design loads are presented to cover the conditions of array angles relative to the ground from 20 deg to 60 deg, variable array spacings, a ground clearance gap up to 1.2 m (4 ft) and array slant heights of 2.4 m (8 ft) and 4.8 m (16 ft). Several means of alleviating the wind loads on the arrays are detailed. The expected reduction of the steady state wind velocity with the use of fences as a load alleviation device are indicated to be in excess of a factor of three for some conditions. This yields steady state wind load reductions as much as a factor of ten compared to the load incurred if no fence is used to protect the arrays. This steady state wind load reduction is offset by the increase in turbulence due to the fence but still an overall load reduction of 2.5 can be realized. Other load alleviation devices suggested are the installation of air gaps in the arrays, blocking the flow under the arrays and rounding the edges of the array. A wind tunnel test plan to supplement the theoretical study and to evaluate the load alleviation devices is outlined.

Miller, R.↗
NASA NTRS1979

The magnetospheric electric field and convective processes as diagnostics of the IMF and solar wind

Indirect measurements of the convection field as well as direct of the ionospheric electric field provide a means to at least monitor quanitatively solar wind processes. For instance, asymmetries in the ionospheric electric field and ionospheric Hall currents over the polar cap reflect the solar wind sector polarity. A stronger electric field, and thus convective flow, is found on the side of the polar cap where the y component of the IMF is parallel to the y component of the geomagnetic field. Additionally, the magnitude of the electric field and convective southward B sub Z and/or solar wind velocity, and thus may indicate the arrival at Earth of an interaction region in the solar wind. It is apparent that processes associated with the convention electric field may be used to predict large scale features in the solar wind; however, with present empirical knowledge it is not possible to make quantitative predictions of individual solar wind or IMF parameters.

Kaye, S. M.↗
NASA NTRS1979

Modified power law equations for vertical wind profiles

In an investigation of windpower plant siting, equations are presented and evaluated for a wind profile model which incorporates both roughness and wind speed effects, while retaining the basic simplicity of the Hellman power law. These equations recognize the statistical nature of wind profiles and are compatible with existing analytical models and recent wind profile data. Predictions of energy output based on the proposed profile equations are 10% to 20% higher than those made with the 1/7 power law. In addition, correlation between calculated and observed blade loads is significantly better at higher wind speeds when the proposed wind profile model is used than when a constant power model is used.

Spera, D. A.↗
NASA NTRS1980

The winds of the comparison data set for the Seasat Gulf of Alaska Experiment

Ship and data buoy winds used for comparison in the validation of Seasat-derived winds are described in terms of the time series of hourly wind observations from the buoys and in terms of the techniques used to produce 20- and 30-min average winds from the ships. Attention is given to the comparison data, the synoptic scale wind, turbulence concepts, the data buoy winds, Ocean Weather Station PAPA, the oceanographer data, and the results from Ocean Station PAPA Ship Quadra and from the oceanographer. Sources of scatter in the comparison data are reviewed.

Pierson, W. J.↗
NASA NTRS1980

Pilot-aircraft system reponse to wind shear

The nonlinear aircraft motion and automatic control model is expanded to incorporate the human pilot into simulations of aircraft response to wind to wind shear. The human pilot is described by a constant gains lag filter. Two runs are carried out using pilot transfer functions. Fixed-stick, autopilot, and manned computer simulations are made with an aircraft having characteristics of a small commuter type aircraft flown through longitudinal winds measured by a Doppler radar beamed along the glide slope. Simulations are also made flying an aircraft through sinusoidal head wind and tail wind shears at the phugoid frequency to evaluate the response of manned aircraft in thunderstorm wind environments.

Turkel, B. S.↗
NASA NTRS1980

An empirical model of the Venusian outer environment. I - The shape of the dayside solar wind-atmosphere interface. II - The shape and location of the bow shock

Solar wind plasma and magnetic field data and ionospheric data obtained from the Pioneer Venus orbiter are discussed. The variation in the magnetic field pressure within the magnetic barrier is shown to be similar to that expected for the solar wind pressure variations along an obstacle's boundary when a more realistic approximation of the shape of the ionosphere is included. Simultaneous solar wind pressure, ionospheric pressure, and magnetic barrier pressure data reveal that the ionospheric pressure below the ionopause is approximately equal to the solar wind pressure. The magnetic barrier pressure is found to be equal to approximately 2/3 to 3/4 of both the solar wind pressure and the ionospheric pressure. Estimates of the hot plasma pressure contribution to the total pressure in the magnetic barrier vary from 1/4 to 1/3. Just below the ionopause the ionospheric pressure deviations from the mean ionospheric pressure are significant, especially below approximately 400 km; they appear to be indicative of the adjustment of the ionospheric structure to changeing solar wind conditions. A first-order model of the ionopause pressure variations as a function of height and solar-zenith angle is proposed. Venera 9 and Venera 10 bow shock crossings are then analyzed for solar zenith angles in the range from approximately 25 deg to approximately 153 deg. A comparison of Venera 9 and Venera 10 bow shock crossings with those observed by the Pioneer Venus orbiter suggests that both the secular variation and the latitudinal asymmetry may be responsible for the closer shock crossings of the Venera 9 and Venera 10 spacecraft.

Vaisberg, O. L.↗
NASA NTRS1980

Observation of the Venus mantle, the boundary region between solar wind and ionosphere

For three orbit paths of the Pioneer Venus orbiter the interaction between the solar wind and the Venusian ionosphere has been studied. Results of the retarding potential analyzer and the magnetometer are described for the boundary region between the solar wind and the planetary ionosphere. These are the first measurements that show that a transition region exists between the two plasmas of different origin. The observed magnetic field and current system producing it appear strong enough to stop the solar wind flow in front of the ionosphere and to separate the shocked solar wind from the ionosphere. The transition region between the ionosheath and the ionosphere is called the 'mantle'. The observed mantle electron energy spectra close to the ionopause show ionospheric character. With increasing height the number of electrons that have ionospheric energies decreases, and the number of electrons that have solar wind energies gradually increases toward the ionosheath boundary, where only solar wind energy spectra are observed. The mantle surrounds the frontside of the ionosphere and extends probably more than eight Venus radii downstream.

Spenner, K.↗
NASA NTRS1981

The wind-speed measurement capability of spaceborne radar altimeters

This study represents an attempt to quantitatively assess the capability of a spaceborne radar altimeter to infer ocean surface wind speeds from a measurement of the backscattered power at vertical incidence. The study uses data acquired during 184 near overflights of NOAA data buoys with the GEOS-3 satellite radar altimeter and encompasses a wind-speed range from less than 1 to 18 m/s. An algorithm is derived from the data comparison for converting measurements of the normalized scattering cross section of the ocean surface at 13.9 GHz into estimates of the surface wind speed at the standard anemometer height of 10 m. The algorithm is straightforward and potentially useful for on-board processing of raw altimeter data for the purpose of providing real-time estimates of surface wind speed. For winds in the range of 1 to 18 m/s, the mean difference between the altimeter-inferred winds and the buoy measurements is negligible while the standard deviation of the difference is 1.74 m/s.

Brown, G. S.↗
NASA NTRS1980

Rare gases in the past and present solar wind

The elemental abundances, fluxes and isotopic compositions of rare gases in the past and present-day solar wind are discussed on the basis of direct measurements and fossil evidence in lunar and meteorite samples. Spacecraft measurements of the abundances of He, O, Si, Fe, Ne, and Ar with respect to H in the solar wind are shown to agree with relative abundance measurements of these elements in the solar photosphere and corona, while the lack of evidence of systematic depletion with increasing ionic mass suggests solar abundances of the much less abundant Kr and Xe in the solar wind. Relative He, Ne and Ar abundances in the ancient solar wind as derived from lunar ilmenite and the Pesyanoe meteorite are similar to present-day values, except for a factor of two underabundance of He, while the heavy rare gases appear to be enriched by up to a factor of five. The isotopic compositions of solar wind Ar, Kr and Xe have apparently been fairly constant over most of the solar lifetime, whereas He and possibly Ne show evidence of an increasing abundance of their heavy isotopes with increasing solar wind age.

Pepin, R. O.↗
NASA NTRS1982

Theoretical design study of the MSFC wind-wheel turbine

A wind wheel turbine (WWT) is studied. Evaluation of the probable performance, possible practical applications, and economic viability as compared to other conventional wind energy systems is discussed. The WWT apparatus is essentially a bladed wheel which is directly exposed to the wind on the upper half and exposed to wind through multiple ducting on the lower half. The multiple ducts consist of a forward duct (front concentrator) and two side ducts (side concentrators). The forced rotation of the wheel is then converted to power through appropriate subsystems. Test results on two simple models, a paper model and a stainless steel model, are reported. Measured values of power coefficients over wind speeds ranging from 4 to 16 m/s are given. An analytical model of a four bladed wheel is also developed. Overall design features of the wind turbine are evaluated and discussed. Turbine sizing is specified for a 5 and 25 kW machine. Suggested improvements to the original design to increase performance and performance predictions for an improved WWT design are given.

Frost, W.↗
NASA NTRS1981

Horizontal wind estimates deterministically derived from the STS-1 entry flight date--a comparison with available meteorology data

Two wind profiles were determined from STS-1 entry flight data based on preliminary best estimate trajectory (BET). The deterministic process used in deriving the atmospheric winds requires inertial estimates of the spacecraft angle-of-attack (alpha) and side-slip angle (beta) from the BET in conjunction with some air data system measurements of the actual angles. The current orbiter air data system (OADS) provides the necessary alpha information. Two beta profiles were adopted. The first profile assumed that the spacecraft would weathervane into any prevailing wind. The second assumed a conservative side-slip history computed from measured accelerations in the spacecraft body axes. It is shown that there are no major differences between the deterministic winds computed using both methods. Further, comparisons of these winds with raw measurements from Tehachapi, California, and preliminary winds obtained from the LaRC LAIRS file and the JSC/TRW descent BET are presented.

Kelly, G. M.↗
NASA NTRS1981

Comparison of upwind and downwind rotor operation of the DOE/NASA 100-kW MOD-0 wind turbine

Tests were conducted on a 38m diameter horizontal axis wind turbine, which had first a rotor downwind of the supporting truss tower and then upwind of the tower. Aside from the placement of the rotor and the direction of rotation of the drive train, the wind turbine was identical for both tests. Three aspects of the test results are compared: rotor blade bending loads, rotor teeter response, and nacelle yaw moments. As a result of the tests, it is shown that while mean flatwise bending moments were unaffected by the placement of the rotor, cyclic flatwise bending tended to increase with wind speed for the downwind rotor while remaining somewhat uniform with wind speed for the upwind rotor, reflecting the effects of increased flow disturbance for downwind rotor. Rotor teeter response was not significantly affected by the rotor location relative to the tower, but appears to reflect reduced teeter stability near rated wind speed for both configurations. Teeter stability appears to return above rated wind speed, however. Nacelle yaw moments are higher for the upwind rotor but do not indicate significant design problems for either configuration.

Glasgow, J. C.↗
NASA NTRS1982

Experience and assessment of the DOE-NASA Mod-1 2000-Kilowatt wind turbine generator at Boone, North Carolina

The Mod 1 program objectives are defined. The Mod 1 wind turbine is described. In addition to the steel blade operated on the wind turbine, a composite blade was designed and manufactured. During the early phase of the manufacturing cycle of Mod 1A configuration was designed that identified concepts such as partial span control, a soft tower, and upwind teetered rotors that were incorporated in second and third generation industry designs. The Mod 1 electrical system performed as designed, with voltage flicker characteristics within acceptable utility limits. Power output versus wind speed equaled or exceeded design predictions. The wind turbine control system was operated successfully at the site and remotely from the utility dispatcher's office. During wind turbine operations, television interference was experienced by the local residents. As a consequence, operations were restricted. Although not implemented, two potential solutions were identified. In addition to television interference, a few local residents complained bout objectionable sound, particularly the 'thump' as the blade passed behind the tower. To eliminate objections, the sound generation level was reduced by 10 dB by reducing the rotor speed from 35 rpm to 23 rpm. Bolts in the drive train fractured. A solution was identified but not implemented. The public reaction toward the Mod 1 wind turbine program was overwhelmingly favorable.

Collins, J. L.↗