Evaluation of the wind shear at a site in the North-West of the Yucatan Peninsula, Mexico

Extrapolations from 10m above the ground up to the wind turbine hub height are frequently made to the data available for wind power assessments. Because of its simplicity, the power law profile has been one of the most popular mathematical formulations to predict the vertical wind shear. This paper presents an analysis of wind speed and wind shear in terms of the directional, diurnal and seasonal patterns for a site at the Autonomous University of Yucatan which experiences the tropical conditions of the Yucatan Peninsula in Mexico. This analysis takes a detailed look at frequency distributions to facilitate a comprehensive understanding of the local climatic conditions. Diurnal wind speed variations are shown to be affected in particular by the differing wind conditions associated with fetches over two distinct offshore regions. Seasonal behaviour suggests some departure from the oscillations expected from temperature variation. In addition, the use of rate of change of temperature at one height is proposed as an alternative to vertical temperature gradient inferred from two heights as an indicator of atmospheric stability which will affect the wind shear. The work presented is part of a regionally funded research program to evaluate the onshore and offshore wind potential in the north of the Yucatan Peninsula

Study of the offshore wind and its propagation inland of the northern zone of the Yucatan Peninsula, Eastern Mexico

A preliminary study of the wind characteristics of the northern zone of the Yucatan Peninsula, Eastern Mexico was undertaken for offshore and coastal sites using data measured from three measurement sites. Ten minutes averages of wind speeds, wind directions and ambient temperatures at two different heights were recorded from data measured over a year. The usual wind statistics analysis was undertaken to evaluate the atmospheric stability and the relation between the offshore and onshore winds. The results were compared with the models previously proposed by Monin-Obukhov and by Hsu

Statistical evaluation of SCADA data for wind turbine condition monitoring and farm assessment

Operational data from wind farms is crucial for wind turbine condition monitoring and performance assessment. In this paper, we analyse three wind farms with the aim to monitor environmental and operational conditions that might result in underperformance or failures. The assessment includes a simple wind speed characterisation and wake analysis. The evolution of statistical parameters is used to identify anomalous turbine behaviour. In total, 88 turbines and 12 failures are analysed, covering different component failures. Notwithstanding the short period of data available, several operational parameters are found to deviate from the farm trend in some turbines affected by failures. As a result, some parameters show better monitoring capabilities than others, for the detection of certain failures. However, the limitations of SCADA statistics are also shown as not all failures showed anomalies in the observed parameters

Integration of low-cost accelerometers for condition monitoring of wind turbine blades

Wind turbine blades are structurally composed of different types of materials. Some of which include; wood and/or steel used for constructing the main-spar and glass reinforced plastic (GRP) for building the downwind and upwind sides of the blade. During manufacture and over the operation lifetime of wind turbine blades, they are subject to defects and degradation which can result to deformation/fault occurrence (such as cracks) and subsequent failure. The wide-spread of materials used in their construction makes it difficult for predictions on lifetime health to be made, thus the importance of condition monitoring. Condition monitoring of wind turbines is an effective method for improving the maintenance and subsequent operation of wind turbine systems. In this paper, non-destructive evaluations were conducted using vibration/modal analysis, low-cost MEMS (Micro Electro-Mechanical Systems) accelerometers and signal processing techniques to detect defects and variations in the health of small wind turbine blades. A healthy (new) and an unhealthy (old) Rutland 913 Windcharger blade were tested in a small scale experiment and comparisons were made. Results showed that the presence of a crack and the overall deterioration in the structural health of the old blade increased its modal frequency from that of the new blade and an edge crack decreased the local stiffness of the wind turbine blade. Experiments were conducted on a 4.5m blade to show how the results extend to larger blades. In conclusion, these low-cost accelerometers have the ability to detect high and low blade resonance frequencies and have the potential to be integrated easily either retrofitted externally or embedded in blades at manufacture for condition monitoring at marginal cost

Dye-sensitised solar cells using high mobility, transparent conducting oxides for tandem solar cell applications

Dye-sensitised solar cells are suitable for use as a top cell in a tandem solar cell structure, with a bottom CIGS solar cell, because their transmission characteristics can be adjusted by changing the particle size of the mesoporous TiO2 layer, and the photosensitising dye used. However, optical losses also occur from the fluorine doped tin oxide electrode, due to free carrier absorption in the NIR region of the solar spectrum, and lower the light available to the bottom cell. To solve this problem, a high mobility transparent conducting oxide (titanium doped indium oxide) has been used as the conducting layer to lower the optical loses in the near infrared through the cell. This increases light transmission from 800nm onwards, whilst maintaining high conductivity in the layer, which could be used in a tandem device. A device efficiency of 6.77% has been fabricated, whilst problems of porous layer delamination, and low temperature stability of the conducting layer have been solved

Open reading frame structure and phylogenetic analysis of the human papillomavirus genome identified in this study.

<p>Analysis and graphical presentation was performed as described in the legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093269#pone-0093269-g007" target="_blank">Figure 7</a>. The HPV reference genomes are from reference <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093269#pone.0093269-deVilliers2" target="_blank">[45]</a>, For the phylogenetic analysis, the ORFS for E6-E7-E1-E2-L2-L1 were concatenated.</p

Kinked Tensile Behavior of Cold Worked Nitinol

To characterize the decrease in ductility caused by an induced stress concentration as a function of various levels of cold work and heat treatment, Nitinol medical guide wires with a .004″ diameter were tested using both a standard, straight tensile test and a modified, bent tensile test. The ratio of the two break loads (bent:straight) for identically processed samples was used as a proxy for measuring the ductility of the guide wires: the higher the ratio, the more ductile the sample. The average break load ratio as a function of increased cold work, decreased from 1.27 to 0.91 for the heat treated samples, and decreased from 1.28 to 1.13 for the non-heat treated samples. The heat treated wires had lower break load ratios - a difference of 0.105 on average - compared to the similarly cold worked, non-heat treated wires. The magnitude of the decrease in break load ratio between heat treated and non-heat treated wires is dependent on the level of cold work; there was a difference of 0.01 for the lowest level of cold work, and a difference of 0.22 for the highest level of cold work. The decrease in break load - and ductility by proxy - from increased cold work and heat exposure is caused by the suppression of the austenite-martensite phase transformation as a result of these processes

Quantitation of specific virus reads in each of the 20 samples.

<p>All reads for each sample (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093269#pone-0093269-t001" target="_blank">Table 1</a> for total number of reads per samples) were mapped to the indicated viral genomes using MUMmer <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093269#pone.0093269-Delcher1" target="_blank">[31]</a>. The number of reads mapped to each virus (normalized for total reads in each sample) is depicted by color (see color bar scale to right of figure).</p

An overview of the SLIM read classification process.

<p>An overview of the SLIM read classification process.</p

An overview of the ViSeq process.

<p>An overview of the ViSeq process.</p