5,777 research outputs found
Algorithm for sea surface wind retrieval from TerraSAR-X and TanDEM-X data
No full textA Geophysical Model Function (GMF), denoted XMOD2, is developed to retrieve sea surface wind field from Xband
TerraSAR-X/TanDEM-X (TS-X/TD-X) data. In contrast to
the previously developed XMOD1, XMOD2 consists of a
nonlinear GMF, and thus, it depicts the difference between
upwind and downwind of the sea surface backscatter in X-band SAR imagery. By exploiting 371 collocations with in situ buoy measurements which are used as the tuning dataset together with analysis wind model results, the retrieved TS-X/TD-X sea surface wind speed using XMOD2 shows a close agreement with buoy measurements with a bias of -0.32 m/s, an RMSE of 1.44 m/s and a scatter index (SI) of 16.0%. Further validation using an independent dataset of 52 cases shows a bias of -0.17 m/s, an RMSE of 1.48 m/s, and SI of 17.0% comparing with buoy measurements. To apply XMOD2 to TS-X/TD-X data acquired at HH polarisation, we validate three X-band SAR Polarisation Ratio (PR) models that were tuned using TS-X dual polarisation data by comparing the retrieved sea surface wind speed with buoy measurements
Modelling the aerodynamics of vertical-axis wind turbines in unsteady wind conditions
No full textMost numerical and experimental studies of the performance of vertical-axis wind turbines have been conducted with the rotors in steady, and thus somewhat artificial, wind conditions - with the result that turbine aerodynamics, under varying wind conditions, are still poorly understood. The Vorticity Transport Model has been used to investigate the aerodynamic performance and wake dynamics, both in steady and unsteady wind conditions, of three different vertical-axis wind turbines: one with a straight-bladed configuration, another with a curved-bladed configuration and another with a helically twisted configuration. The turbines with non-twisted blades are shown to be somewhat less efficient than the turbine with helically twisted blades when the rotors are operated at constant rotational speed in unsteady wind conditions. In steady wind conditions, the power coefficients that are produced by both the straight- and the curved-bladed turbines vary considerably within one rotor revolution because of the continuously varying angle of attack on the blades and, thus, the inherent unsteadiness in the blade aerodynamic loading. These variations are much larger, and thus far more significant, than those that are induced by the unsteadiness in the wind conditions
Wind reduction patterns around isolated biomass for wind erosion control in a desertified area of Central Sudan
No full textThe aim of this study was to assess the effectiveness of sparse vegetation, feature common in arid zone, to reduce wind force (velocity) and hence protect the surface and regions downwind from drifting sand and their consequences. Respectively 4 (with heights h of 4, 3.2, 2 and 1.66 m), 2 (with h of 3 and 2.5 m) and 3 (with h of 1.04, 0.9 and 0.8 m ) well established single biomass configurations of Leptadenia pyrotechnica trees, Prosopis juliflora trees and Panicum turgidum grass, were selected in the field. Solar powered cup anemometer wind measurements with a data logger system were taken at heights of 0.25 and 0.5 h, at distances 0.5 and 1 h, at four sides of the tree in the prevailing wind direction and perpendicular to it, and additionally at 2, 4 and 6 h windward and leeward. The protection effectiveness of the biomass was calculated as a wind reduction ratio and in terms of objects protection, which was evaluated using the dimensionless protection index (É). The study showed that windward protection provided by Leptadenia and Prosopis at level 0.25h and distance 0.5 h was similar, w ith a wind reduction ratio R0.8, while Panicum showed comparably higher R-values. Even at the 0.5 h level, Panicum showed an R of 0.65 at 0.5 h distance. Leew ard, at 0.25 h level differences were small, R increasing from 0.6/0.7 to 0.8/1 with distance, Leptadenia protecting best. At higher level (0.5 h) at distances 0.5 and 1 h Prosopis gave better protection than the other two at distances 0.5, 1 and 2 h. The research is an exam ple of simple experimental work under difficult environmental conditions in Africa. It was part of studies in which additional attention was paid to quantification aspects under such conditions as well as to the problems it helped solve in the African societies concerned as agrometeorological service
System-wide inertial response from fixed speed and variable speed wind turbines
Get PDFIEEE PES 2011 General Meeting, Detroit, Michigan, USA, July 24-28, 2011As wind penetration levels on power systems increase worldwide, the dynamic characteristics of these systems are changing due to the displacement of synchronous generation. One issue, of particular concern, is the resulting reduction in system inertia. Modern, variable speed wind turbines are controlled
by power electronics and so do not inherently contribute to the inertial response of the system. Such devices can however be fitted with a control loop which provides an active power response to significant frequency deviations, similar to the inertial response of fixed speed wind turbines and synchronous generation.
However, the response of variable speed turbines is dependent on local wind speeds and so cannot be quantified deterministically
by system operators. This paper examines the potential for wind generation to contribute to system inertial response and considers the aggregated inertial response capabilities of fixed speed and variable speed wind generation.Science Foundation Irelandti, ke, ab, co - TS 23.02.1
Producer responsibility : defining the incentive for recycling composite wind turbine blades in Europe
Get PDFCurrent global commitments to tackle climate change and reduce greenhouse gas emissions are resulting in increasing demand for wind energy technologies as a secure, affordable supply of energy. However, the recent expansion of wind energy generation is creating a growing waste disposal issue associated with the decommissioning of wind turbine (WT) blades in the future.
Whilst the average recyclability across the components of a modern WT has been calculated to be 80% by mass, the composite WT blades present a challenge for waste management. There is currently little legislation present for the regulation of end-of-life waste management for the wind energy industry in Europe. However, a review of European waste management policy has shown that landfill bans effectively divert waste from landfill and drive towards energy recovery.
This paper considers the producer responsibility scenarios for manufacturers to recycle WT blades. This will include an investigation into the current and future methods of WT blade disposal and specifically the potential of carbon fibre (CF) to add to the recyclability of blade systems
Suppression of the Pth(Ts) phenotype mediated by the overproduction of tRNA maintains moderate levels of the Pth(Ts) protein
No full text<p><b>Copyright information:</b></p><p>Taken from "Excess of charged tRNA maintains low levels of peptidyl-tRNA hydrolase in (Ts) mutants at a non-permissive temperature"</p><p>Nucleic Acids Research 2006;34(5):1564-1570.</p><p>Published online 15 Mar 2006</p><p>PMCID:PMC1408313.</p><p>© The Author 2006. Published by Oxford University Press. All rights reserved</p> () Depicts the cellular growth of the (Ts) mutant strain AA7852 separately transformed with pVH124 (ΔU, ΔV), pVH125 (U, ΔV) or pVH119 (U, V) incubated at different temperatures. Isolated colonies of the independent transformants were streaked onto LB-Ap plates and incubated overnight at the indicated temperatures. () Presents the immunodetection of Pth(Ts) in the (Ts) mutant strain AA7852 separately transformed with pVH124, pVH125, pVH119, ptRNACCA (X, R, T, M) or pTH2 (W) and grown at 32°C prior to transfer at time = 0 min at 41 or 43°C. The concentration of Pth(Ts) protein was estimated by immunoblot analysis. The left lane shows purified wild-type Pth protein, which migrates slightly faster in SDS–PAGE than the Pth(Ts) variant (arrowed) ()
Impact of wind power on the unit commitment, operating reserves and market design
No full textPaper presented at the 2011 IEEE Power and Energy Society General Meeting, San Diego, CA, 24-29 July 2011This article highlights and demonstrates the new requirements variable and partly unpredictable wind power will bring to unit commitment and power system operations.
Current practice is described and contrasted against the new requirements. Literature specifically addressing questions about wind power and unit commitment related power system operations is surveyed. The scope includes forecast errors, operating reserves, intra-day markets, and sharing reserves across interconnections. The discussion covers the critical issues arising from the research.Science Foundation Irelandau, ti, ke, ab, co - TS 10.04.1
Análise dos efeitos decorrentes de tormentas TS em estruturas reticuladas
Get PDFTCC (graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Civil.Este trabalho foi elaborado com o objetivo de propor o modelo mais adequado de perfil de velocidades de ventos para obtenção de forças oriundas de linhas de tormenta TS ou ThunderStorm em uma estrutura reticulada além de uma comparação com o modelo atual de norma ABNT NBR 6123:1988 – Forças devidas ao vento em edificações. Tormentas TS são fenômenos atmosféricos causados por nuvens do tipo cúmulo-nimbo ou no latim cumulonimbus, que causam fortes jatos verticais descendentes de vento localizados e em contato com o solo se deslocam para todas as direções e com velocidades variadas. O dimensionamento de estruturas reticuladas, em relação aos efeitos do vento segue a norma ABNT NBR 6123:1988 – Forças devidas ao vento em edificações, porém o tratamento de uma Tormenta TS requer uma análise mais sofisticada, pois uma Tormenta TS possui características singulares que a diferem de outros eventos de ventos. Será desenvolvido neste trabalho um estudo comparativo entre um modelo probabilístico que descreve uma tormenta TS e o modelo da NBR 6123:1988 em uma estrutura reticulada e uma análise dos possíveis perfis de velocidade de uma tormenta TS. A estrutura será submetida a dois diferentes carregamentos, de acordo com os modelos descritos anteriormente. Os resultados dos dois carregamentos são apresentados e discutidos além da análise dos possíveis perfis de velocidades apresentados
A study of optimal non-firm wind capacity connection to congested transmission systems
Get PDFAs wind is a low capacity factor source of power generation, a non-physically-firm connection strategy is key to its cost-effective and timely integration to presently constrained transmission networks. This paper therefore outlines the design and study of an optimal non-firm wind capacity allocation model. While a precise statistical representation of wind power variations and geographical inter-dependency requires a significant number of data samples, the structured very-large-scale linear programming problem that results is shown to be exploitable by the Benders’ decomposition scheme. Various wind capacity target levels are considered, and important sensitivity analyses performed for multiple load profiles, wind profiles, and fuel price parameter values. Interestingly, the optimal wind capacity allocation is found to be reasonably robust to sizeable load and fuel price deviations, and while the effect of a limited historical wind data profile is more influential, the associated cost-function penalty is not significantly critical. The economic value of combining wind connection with advanced post-contingency network remedial action schemes is also highlighted.Science Foundation Irelandti, la, ke, ab, co - TS 13.04.1
Rotor angle stability with high penetrations of wind generation
No full textThis paper explores the relationship between wind generation, particularly the control of reactive power from variable speed wind turbine generators, and the rotor angle stability of the conventional synchronous generators in the system. Rotor angle stability is a dynamic phenomenon generally associated with changes in active power flows that create angular separation
between synchronous units in the system. With larger penetrations of wind generation being introduced into power systems, there will be large flows of active power from asynchronous generation in the system. These asynchronous active power flows can aid in maintaining the rotor angle stability of the system. However, the manner in which wind generation injects reactive power into the system can be critical in maintaining angular
stability of the synchronous units. Utilizing wind generation to control voltage and reactive power in the system can ease the
reactive power burden on synchronous generators, and minimize angular separation in the system following a contingency event
and can provide a significant level of support which will become increasingly important in future power systems.Science Foundation Irelandti, ke, ab, jo, vo, is, st, en - TS 17.04.1
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