Quarterly published "Inventi Impact: Wind & Waves" publishes high quality unpublished as well as high impact pre-published research and reviews related to all the areas involving wind and waves including power generation, navigation, climate change etc.
In this paper, a stand-alone hybrid microgrid consisting of wind turbines,\nphotovoltaic (PV) arrays and storage battery banks is developed for use in\nQinghai Province, China. With the help of Software Homer and Matlab, different\nvariables such as annual average wind speed, annual average load demand,\nand annual capacity shortage are considered. The net present value is\nthen used during an entire project lifetime for the optimization solution....
This study aims to estimate the wind loads acting on a tower structure by comparing and reviewing design codes and the results of
wind tunnel tests. To this end, the modal properties of the tower were identified through short-term on-site measurements of the
Busan Tower in Korea. -e wind load acting on the tower was calculated using four design codes: KBC2009 (Korea), ASCE7-10
(USA), EUROCODE (Europe), and AIJ2004 (Japan). Additionally, force measurement tests and aeroelastic model tests were
conducted for comparison. -e results obtained indicated that the design wind velocity of each design code differed slightly,
reflecting the individual characteristics of each country. -e base shear force, base moment, and maximum displacement obtained
from each design code were similar to those obtained in the wind tunnel tests.-emagnitudes of the base moments and maximum
displacements calculated by each design code were in the order of KBC > AIJ ≈EUROCODE > ASCE7. -e overall results indicate
that each design code reasonably estimates the wind forces and the responses of the tower and also has an appropriate safety
margin. -e scatter in the predicted wind loads occurs primarily from the variations in the design wind velocity in the respective
This paper describes a new actively controlled multi-fan wind tunnel that generates\nnatural wind as a type of turbulence wind tunnel at a reduced cost.\nThe driving section of the wind tunnel has 100 PC cooling fans that are controlled\nby an original embedded system. The fluctuating velocity wind is successfully\ngenerated with a mean velocity of 7 m/s and two turbulent intensities\nof 2% and 3% based on Karmanâ??s power spectrum density function. The\ncase of 2% has the integral scales of 5 m, 10m and 20 m, and the case of 3%\nhas the integral scales of 3 m, 6 m and 15 m with a turbulence grid. In particular,\nthe wind with the turbulent intensity of 2% satisfies the Kolmogorovâ??s\n-5/3 multiplication rule of inertial subrange with the frequency range from\n0.01 Hz to 2.0 Hz. Consequently, the new wind tunnel can be used for studying\nengineering technology and research regarding conditions with natural\nwind....
Dual-Doppler lidar is a powerful remote sensing technique that can accurately measure\nhorizontal wind speeds and enable the reconstruction of two-dimensional wind fields based on\nmeasurements from two separate lidars. Previous research has provided a framework of dual-Doppler\nalgorithms for processing both radar and lidar measurements, but their application to wake\nmeasurements has not been addressed in detail yet. The objective of this paper is to reconstruct\ntwo-dimensional wind fields of wind turbine wakes and assess the performance of dual-Doppler lidar\nscanning strategies, using the newly developed Multiple-Lidar Wind Field Evaluation Algorithm\n(MuLiWEA). This processes non-synchronous dual-Doppler lidar measurements and solves the\nhorizontal wind field with a set of linear equations, also considering the mass continuity equation.\nMuLiWEA was applied on simulated measurements of a simulated wind turbine wake, with two\ntypical dual-Doppler lidar measurement scenarios. The results showed inaccuracies caused by the\ninhomogeneous spatial distribution of the measurements in all directions, related to the ground-based\nscanning of a wind field at wind turbine hub height. Additionally, MuLiWEA was applied on a\nreal dual-Doppler lidar measurement scenario in the German offshore wind farm Ã¢â?¬Å?alpha ventusÃ¢â?¬Â.\nIt was concluded that the performance of both simulated and real lidar measurement scenarios\nin combination with MuLiWEA is promising. Although the accuracy of the reconstructed wind\nfields is compromised by the practical limitations of an offshore dual-Doppler lidar measurement\nsetup, the performance shows sufficient accuracy to serve as a basis for 10 min average steady wake\nmodel validation....
By the increase of the penetration of power-electronic-based (PE-based) units, such as\nwind turbines and PV systems, many features of those power systems, such as stability, security,\nand protection, have been changed. In this paper, the security of electrical grids with high wind\nturbines penetration is discussed. To do so, first, an overview of the power systemsâ?? security\nassessment is presented. Based on that, stability and security challenges introduced by increasing\nthe penetration of wind turbines in power systems are studied, and a new guideline for the security\nassessment of the PE-based power systems is proposed. Simulation results for the IEEE 39-bus test\nsystem show that the proposed security guideline is necessary for PE-based power systems, as the\nconventional security assessments may not be able to indicate its security status properly....
A novel and robust active disturbance rejection control (ADRC) strategy for variable speed wind turbine systems using a doubly\nfed induction generator (DFIG) is presented in this paper. The DFIG is directly connected to the main utility grid by stator, and its\nrotor is connected through a back-to-back three phase power converter (AC/DC/AC).............................
Wind power is one of the important renewable energy sources. Currently, many\nresearches are focusing on improving the aerodynamic performance of wind turbine blades\nthrough simulations and wind tunnel testing. In the present study, the aerodynamic\nperformance of the perforated Eqwin blade (shell type blade) is investigated by using\nnumerical simulation. Three types of slots namely circular, horizontal rectangular and vertical\nrectangular were evaluated. It was found that the optimum angle of attack for a perforated shell\ntype blade was 12Ã?Âº with maximum Cl/Cd value of 6.420. In general, for all the perforated blade\ncases, Cl/Cd tended to decrease as the slot size increased except for the circular slot with 5 mm\ndiameter. This was due to the disturbance of the airflow in lower side region which passed\nthrough the bigger slot size. Among the modified slots; the circular slot with diameter of 5 mm\nwould be the best slot configuration that can be considered for blade fabrication. The Cl/Cd\nobtained was 6.46 which is about 5% more than the value of the reference blade. Moreover, the\nintroduced slot would also reduce the overall weight of the blade by 1.3%....
This paper illustrates how the penetration of electromagnetic waves in lossy media\nstrongly depends on the waveform and not only on the media involved. In particular, the so-called\ninhomogeneous plane waves are compared against homogeneous plane waves illustrating how the\nfirst ones can generate deep penetration effects. Moreover, the paper provides examples showing how\nsuch waves may be practically generated. The approach taken here is analytical and it concentrates\non the deep penetration conditions obtained by means of incident inhomogeneous plane waves\nincoming from a lossless medium and impinging on a lossy medium. Both conditions and constraints\nthat the waveforms need to possess to achieve deep penetration are analysed. Some results are\nfinally validated through numerical computations. The theory presented here is of interest in view of\na practical implementation of the deep penetration effect....
In this study, we proposed an empirical algorithm for significant wave height\n(SWH) retrieval from TerraSAR-X/TanDEM (TS-X/TD-X) X-band synthetic aperture radar (SAR)\nco-polarization (vertical-vertical (VV) and horizontal-horizontal (HH)) images. As the existing\nempirical algorithm at X-band, i.e., XWAVE, is applied for wave retrieval from HH-polarization\nTS-X/TD-X image, polarization ratio (PR) has to be used for inverting wind speed, which is treated as\nan input in XWAVE.Wind speed encounters saturation in tropical cyclone. In our work, wind speed is\nreplaced by normalized radar cross section (NRCS) to avoiding using SAR-derived wind speed, which\ndoes not work in high winds, and the empirical algorithm can be conveniently implemented without\nconverting NRCS in HH-polarization to NRCS in VV-polarization by using X-band PR. A total of\n120 TS-X/TD-X images, 60 in VV-polarization and 60 in HH-polarization, with homogenous wave\npatterns, and the coincide significant wave height data from European Centre for Medium-Range\nWeather Forecasts (ECMWF) reanalysis field at a 0.125Ã¢â??Â¦ grid were collected as a dataset for tuning\nthe algorithm. The range of SWH is from 0 to 7 m. We then applied the algorithm to 24 VV and 21\nHH additional SAR images to extract SWH at locations of 30 National Oceanic and Atmospheric\nAdministration (NOAA) National Data Buoy Center (NDBC) buoys. It is found that the algorithm\nperforms well with a SWH stander deviation (STD) of about 0.5 m for both VV and HH polarization\nTS-X/TD-X images. For large wave validation (SWH 6Ã¢â?¬â??7 m), we applied the empirical algorithm\nto a tropical cyclone Sandy TD-X image acquired in 2012, and obtained good result with a SWH\nSTD of 0.3 m. We concluded that the proposed empirical algorithm works for wave retrieval from\nTS-X/TD-X image in co-polarization without external sea surface wind information....
Wind energy is one of the fastest growing renewable energy sources. Wind speed forecasting is essential to enhance the utilization
of wind energy. Various prediction models have been developed to improve the prediction accuracy of wind speed. However, wind
speed time series has nonlinearity, fluctuation, and intermittence, which makes the prediction difficult. Existing prediction models
ignore data decomposition and feature reduction and suffer from the deficiency of individual models. /is paper proposes a novel
ensemble prediction model, which integrates data preprocessing, feature selection, parameter optimization, three intelligent
prediction models, and an ensemble strategy. To improve prediction performance, a highly efficient optimization algorithm is
applied to determine the individual models’ optimal parameters. Furthermore, partial least square regression is used to calculate
combination weight. Additionally, two 10 min datasets from the National Renewable Energy Laboratory (NREL) are employed for
� Copyright©2013. Inventi Journals Pvt.Ltd. All Right Reserved.