Search

Wind energy supply has grown rapidly over the last decade. However, the long-term contribution of wind to future energy supply, and the degree to which policy support is necessary to motivate higher levels of deployment, depends - in part - on the future costs of both onshore and offshore wind. Here, we summarize the results of an expert elicitation survey of 163 of the world's foremost wind experts, aimed at better understanding future costs and technology advancement possibilities. Results suggest significant opportunities for cost reductions, but also underlying uncertainties. Under the median scenario, experts anticipate 24-30% reductions by 2030 and 35-41% reductions by 2050 across the three wind applications studied. Costs could be even lower: experts predict a 10% chance that reductions will be more than 40% by 2030 and more than 50% by 2050. Insights gained through expert elicitation complement other tools for evaluating cost-reduction potential, and help inform policy and planning, R&D and industry strategy.

Zircon and monazite laser-ablation inductively coupled plasma mass spectrometry U-Pb geochronological data for two metasediment samples from the Westing Group, northern Shetland Islands, Scottish Caledonides yield ages between 938 [+ or -] 8 and 925 [+ or -] 10 Ma (Tonian) for upper amphibolites-facies metamorphism. Texturally early metamorphism is recorded by a migmatitic garnet + sillimanite + plagioclase + muscovite + biotite assemblage, which formed at c. 650-700 [degrees]C and 7 kbar. Subsequent reworking resulted in the growth of a secondary garnet + kyanite + plagioclase + muscovite + biotite assemblage at c. 650[degrees]C and 8-9 kbar. In situ electron probe microanalysis (EPMA) U-Th Pb chemical dating of monazite hosted within garnet grains and the matrix of one sample also give Tonian ages, apparently indicating that all the metamorphism occurred during the Neoproterozoic. However, the dominant structural fabrics appear to have formed during the Ordovician-Silurian Caledonian orogeny, suggesting that the reworking was substantially younger despite the apparent absence of Caledonian monazite or zircon ages. Detrital zircons are consistent with Laurentia-Baltica provenance. Deposition of the Westing Group is constrained to between c. 1030 and 930 Ma. The timing of Tonian metamorphism suggests possible correlations with sequences elsewhere in the northern Caledonides, including the Krummedal Succession of East Greenland and Laurentian-derived successions in Svalbard and northern Norway. Supplementary material: U-Pb LA-ICPMS and EPMA data are available at http://www.geolsoc.org/SUP18379. doi: 10.1144/0016-76492009-006.

The Tia Complex is located in the southern New England Orogen of eastern Australia and provides a detailed record of the structural-metamorphic evolution of an ancient accretionary prism. This record is characterized by six stages of deformation that were accompanied by a transition from moderate-pressure-low-temperature to low-pressure high-temperature metamorphism. The composition of jadeitic pyroxene (subduction), magnesioriebeckite (exhumation), and actinolite (heating) have been used to model P-T conditions during these structural events, which range from P = 6.3-6.7 kbar and T = 320-350[degrees]C (subduction) to 1.5-2.0 kbar and 400-420[degrees]C (heating). On the basis of new structural and metamorphic data combined with preexisting age data, the evolution of this accretionary prism can be divided into two main stages: (1) blueschist formation and exhumation and (2) elevated heat flow and anatexis. To explain these features, a new model is presented that requires (1) wedge underthrusting and rear wedge extension associated with a stationary subduction hinge and (2) subduction hinge migration resulting in the relocation of the accretionary wedge onto the upper plate and heating during exposure to the mantle wedge. To explain the event chronology preserved in the Tia Complex, both extensional collapse and subduction hinge migration models are required.

We present electron microprobe-based in situ (Th + U)-Pb monazite chemical age data from granulite-facies metapelites in Prydz Bay, East Antarctica. The monazite age data define two distinct age populations, Late Neoproterozoic to Early Palaeozoic (c. 570-520 Ma) and Neoproterozoic (c. 950-820 Ma), that confirm the polytectonic nature of Prydz Bay. Our data suggest that similarity in lineation orientation along the Prydz Bay coast is not sufficient to necessarily indicate time-equivalance. The minimum duration of Early Palaeozoic tectonism, spanning at least 60 Ma, is constrained from an Mg-Al-rich metapelite: monazite hosted by coarse-grained orthopyroxene defines the oldest Early Palaeozoic population, whereas cordierite + orthopyroxene symplectites define the youngest Early Palaeozoic population. The spatial distribution of monazites and their ages is correlatable with the inferred mineral assemblage evolution. We are able to characterize the evolution of Early Palaeozoic tectonism in quantitative P-T-t-mineral assemblage space, demonstrating that ultrahigh-temperature tectono-metamorphism in Prydz Bay is of Early Palaeozoic age. The survival of Neoproterozoic inheritance in Fe-Al-rich metapelites has implications for high Pb retentivity in monazite when chemical and kinetic conditions are favourable. The approach and logic applied herein are entirely and directly transferable to the interrogation of any other metamorphic terrane.

To maximize wind power extraction, a variable-speed wind turbine (VSWT) should operate as close as possible to its optimal power coefficient. The generator torque is used as a control input to improve wind energy capture by forcing the wind turbine (WT) to stay close to the maximum energy point. In general, current control techniques do not take into account the dynamical and stochastic aspect of both turbine and wind, leading to significant power losses. In addition, they are not robust with respect to disturbances. In order to address these weaknesses, a nonlinear approach, without wind speed measurement for VSWT control, is proposed. Nonlinear static and dynamic state feedback controllers with wind speed estimator are then derived. The controllers were tested with a WT simple mathematical model and are validated with an aeroelastic wind turbine simulator in the presence of disturbances and measurement noise. The results have shown better performance in comparison with existing controllers. [DOI: 10.1115/1.2356496]

Sm-Nd isotopic and geochemical data from Neoproterozoic to Cambrian sedimentary rocks in the intracratonic eastern Officer Basin in central Australia highlight the evolving provenance roles of the basement complexes that underlie and bound the basin. Initial [epsilon]Nd values of around -12 for the basal units indicate that both were largely derived from the late Archaean to Mesoproterozoic Gawler Craton, which bounds the basin to the south. At c. 720 Ma an influx of juvenile, glacially derived sediment indicates partial uplift of the Mesoproterozoic Musgrave Block along the basin's northern margin, in a regime interpreted to be broadly extensional. At around 600 Ma, synchronous with the development of a foreland architecture, there was a large influx of Musgrave Block-derived sediments. This is interpreted to mark the onset of the intracratonic Petermann Orogeny, which was a long-lived event or series of events, spanning more than 70 Ma. Subsequent to c. 600 Ma, the Nd isotopic composition of sequences within the Officer Basin indicates an increasing contribution from the Gawler Craton despite up to 45 km of denudation of part of the Musgrave Block. This suggests that the majority of sediment derived from the Petermann Orogen bypassed the eastern Officer Basin for much of the history of the Petermann Orogeny. Keywords: Officer Basin, Petermann Orogeny, Neoproterozoic, Sm-Nd isotopes, provenance.

Horizontal axis wind turbines routinely suffer significant time varying aerodynamic loads that adversely impact structures, mechanical components, and power production. As lighter and more flexible wind turbines are designed to reduce overall cost of energy, greater accuracy and reliability will become even more crucial in future aerodynamics models. However, to render calculations tractable, current modeling approaches admit various approximations that can degrade model predictive accuracy. To help understand the impact of these modeling approximations and improve future models, the current effort seeks to document and comprehend the vortex kinematics for three-dimensional, unsteady, vortex dominated flows occurring on horizontal axis wind turbine blades during non-zero yaw conditions. To experimentally characterize these flows, the National Renewable Energy Laboratory Unsteady Aerodynamics Experiment turbine was erected in the NASA Ames 80 ftx120 ft wind tunnel. Then, under strictly-controlled inflow conditions, turbine blade surface pressures and local inflow velocities were acquired at multiple radial locations. Surface pressure histories and normal force records were used to characterize dynamic stall vortex kinematics and normal forces. Stall vortices occupied approximately two-thirds of the aerodynamically active blade span and persisted for nearly one-fourth of the blade rotation cycle. Stall vortex convection varied dramatically a long the blade radius, yielding pronounced dynamic stall vortex deformation. Analysis of these data revealed systematic alterations to vortex kinematics due to changes in test section speed, yaw error, and blade span location. [DOI: 10.1115/1.1408307]

The role of glutamate residue, E699, in mouse anion exchanger 1 (AE1) on anion translocation and Cl-/sulfate transport was analyzed during the expression of AE1 in the Xenopus oocyte cytoplasmic ribonuleic acid. Xenopus oocytes that expressed murine AE1 mutated at residue E699 exhibited reduced Cl- transport while oocytes with the E699Q mutant exhibited increased sulfate transport. The effects of recombinant mutant AE1 on sulfate transport indicated the role of E699 as a proton binding site during H+sulfate/Cl- exchange.