Presentation on theme: "WIND RESOURCE ASSESSMENT TECHNIQUES"— Presentation transcript:
1 WIND RESOURCE ASSESSMENT TECHNIQUES Dr.S.GomathinayagamExecutive DirectorCentre for Wind Energy TechnologyChennaiK.BoopathiScientist & Wind Resource AssessmentUnit Chief,WRAWind Resource AssessmentCentre for Wind Energy TechnologyChennai
2 WIND Air in motion i.e. motion of air relative to the earth’s surface. Free, clean and inexhaustible energyIt is intermittent sourceOne day it calm, howling nextIt will vary place to place and time to time
3 WIND RESOURCE-GLOBAL WIND SYSTEM All renewable energy (except tidal and geothermal power), and even the energy in fossil fuels, ultimately comes from the sun. About 1–2% of the energy coming from the sun is converted into wind energyThe region around equator at 0 deg latitude are heated more by the sun than the rest of the globe. Due to this flow of air takes place from the cold regions to hot regions.
4 Wind speed characteristics Horizontal and Inter annual VariabilityTemporal and Inter annual VariabilityVertical Wind Variability
5 Atmospheric boundary layer and Vertical wind profile Vertical wind profile for different roughness lengths z0, assumed “geostrophic wind” of15 m/s
6 Wind Regime in IndiaWind climatology in India is influenced by the strong monsoon circulationsSouth west monsoon during May to Sept brings the best windsWind speed during November to March is low, except in Southern tip of Tamil NaduBest Windy Sites are in Kerala, Karnataka, Tamil Nadu, Gujarat, Andhra Pradesh and Maharashtra
7 POWER IN THE WIND From Wind to Electric Power Power (translation) = Force x Velocity (P=F V) orPower (rotation) = Torque x rotational speed (P=T x co)P= KE*mKE - Kinetic Energy ,=1/2mV 2 m - mass flow rate=pAVPwind = Cp 1/2 pV3 ACp efficiency (“Betz” max. = 16/27)1/2 pV2 Dynamic pressure at 1 m2p Air density (~1.22 kg/m3)V Wind speedA Gross rotor area
8 Wind Resource Assessment Main objective is to identify potentially windy areas that also possess other desirable qualities for wind project development
9 WIND RESOURCE ASSESSMENT TECHNIQUESProspecting (Large area Screening & Field visits).Validation (Wind measurements & Data Analysis)Micro Survey & Micrositing.
11 PROSPECTING STEPS Preliminary area identification Ranking of candidate sitesSelection of tower location(s)Development of a monitoring planQuality assurance
12 Preliminary Area Identification Objective is to determine or verify whether sufficient wind resources exist within an area to justify further site-specific investigationLarge area screening- wind resource map look upuse of existing wind data-nearby airporttopographic indicatorsfield surveysflagged treesaccessibilityland use– obstructionsavailable land area
13 Large area Screening and Existing data large-area screening usually begins with a review ofexisting wind resource maps, data andother meteorological informations (pressure, temperature etc.)analysis of the climatology of the region along with the topographical maps (such as terrain form, land use and land cover, and other logistics like accessibility, grid availability etc.).use of existing wind data-nearby airportnearby airport measurement wind dataLong term re analysis data (NCEP/NCAR/MERRA)
17 Field visitsTo look for physical evidence to support the wind resource estimate developed in the large-area screening.Another purpose of the site visit is to select a possible location for a wind monitoring station. Consistently bent trees and vegetation, for example, are a sure sign of strong winds.
18 Ranking of Candidate Sites Objective is to compare areas to distinguish relative development potentialIn addition to accessibility, land use, obstructions, and available land area, siting criteria could include:proximity to transmission linespotential impact on local aestheticscellular phone service reliability for data transferspotential avian interactions
19 Standard Wind Class US Wind Class A site can be classified as one of the Standard seven classes depending on Wind Power Density/Wind Speedavailable at 50 m above ground.ClassSpeed(m/s)WPD(W/Sq.m)10-5.60-200234567
20 Site Selection A number of effects have to be considered : The power output of a wind rotor Increases with the cube of the wind speed. This means that the site for a windmill must be chosen very carefully to ensure that the location with the highest wind speed in the area is selected. The site selection is rather easy in flat terrain but much more complicated in hilly or mountainous terrains.A number of effects have to be considered :1. winds hear; the wind slows down, near the ground, to an extent determined by the surface roughness.2. turbulence; behind building, trees, ridges etcacceleration; (or retardation) on the top of hills, ridges etc.Inflow windExtreme windGustsWake effects
21 Turbulence and Acceleration of ridge and Obstacle The flow inclination must not exceed ± 8 degree for any wind directionTurbulence is variations in wind speedBack ground turbulenceWake turbulenceClose to an obstacle such as a building the wind is strongly influenced by the presence of the obstacle. The effect extends vertically to approximately three times the height of the obstacle, and downstream to 30 to 40 times the height. If the point of interest is inside this zone, it is necessary to take the sheltering effects into account, whereas if the point is outside the zone the building should be treated as a roughness element.The buildings and rows of trees shelter the met. mast in the centre of the drawing.tops of ridges experience higher wind speeds due to the effect of wlndshearThe ideal slope angle is said to be 16° (29 m rise per 100 m horizontal distance) but angles between 6° and 16° are good
24 Instruments for Measuring wind speed and Direction cup anemometervane anemometerultrasonic anemometerhot-wire anemometerother “high-tech” device (SODAR,LIDAR)
25 Instruments small vertical axis wind wheel Direction of wind is an important factor in the siting of a wind energy conversion system. If we receive the major share of energy available in the wind from a certain direction, it is important to avoid any obstructions to the wind flow from this side. Wind vanes were used to identify the wind direction in earlier day’s anemometerssmall vertical axis wind wheelrotational speed proportional to wind speedtwo ways taco generator (analogue signal)frequency signal (optoelectronic)most commonly used,sufficient for most tasks in wind technologywide range of qualitieslogging of time series (10-minute or 1-hour averages)channels for 3 or more wind speeds and wind vanes,air pressure, 2 or more temperatures, humiditypower supply by solar panel and batterysafety system for data storage in case of break down of power supplydata storage capacity minimum of 2 months
27 Analysis Monthly variation Diurnal variation number of manipulations with these data, basically looking at two aspects:time distributionfrequency distributionPlotting the monthly averages of each hour of the day shows the diurnal fluctuations of the wind speed in that particular monthMonthly variationDiurnal variation
28 TECHNIQUES FOR ESTIMATING WIND RESOURCES These techniques can be used screen candidate resource areas for sites with high potential or to estimate wind energy characteristics at a specific location.numerical modeling of flow over terrainphysical modeling of flow over terraintopographical indicators of wind energy potentialbiological indicators of wind energy potentialgeomorphol ogi cal indicators of wind energy potentialsocial and cultural indicators of wind energy potential.Numerical ModelingSynoptic scale -is a horizontal length scale of the order of 1000 kilometres (about 620 miles) or moreMeso-about 5 kilometers to several hundred kilometersMicro-1 km or less, smaller than mesoscale
29 WIND RESOURCE ASSESSMENT UNIT Offshore Wind MappingStudy based on coastal wind monitoring stations.Study based on data from data buoy deployed by NIOT.Study based on SAR in association with RISO –DTUStudy based on QUICK SCATT in association with INCOISSDI, Scotland has been encaged for preparing feasibility study.Measurements are being initiated at Dhanushkodi in Ramanathapuram, Tamil Nadu
30 SAR windsENVISAT ASAR WSM images from the European Space Agency (ESA). The WSM – Wide Swath Mode – scenes each cover 400 km x 400 km. As examples two of the wind maps are shown in Figure. The figure 1(top) shows an example from 4 December characterized by strong winds whereas the Figure 2 (bottom )shows much weaker winds on 25 September 2010.A total of 164 WSM scenes are used. Most of the 164 scenes are from ESA’s ordering system EOLISA and sent on DVD to Risø DTU but a few are taken from ESA’s rolling archive.There are a total of 164 ocean wind maps out of which 72 are observed in the morning and 92 in the eveningOcean wind map from ENVISAT ASAR WSM from 4 December 2010 at UTC in South India.Ocean wind map from ENVISAT ASAR WSM from 25 September 2010 at UTC in South India.
31 OFFSHORE WINDFARM (PROPOSED) AT DHANUSKODI RAMESHWARAM AND KANYAKUMARI
34 What is micro siting ?Micro siting is a way to optimize the park layout in any given site to give the optimum production on site.- Wind measurements- Roughness, Obstacles, Orography- Wind resource estimate- Turbine layout- Production estimate, incl. wake losses to other turbines- Load calculation to ensure a 20 year design lifetime- Calculate sound emission from the turbines to thenearest neighbor.- Create a visualization of the park.- Calculate shadow flickeringRecommend another turbine type, turbine layout, hub height, wind sector management or measurement campaignAll this is something that is done before the park is erected so you can calculate the feasibility of the project.
35 Analyze and reduce risks Benefits of sitingOptimize productionAnalyze and reduce risksThe most important aspect in the siting is to optimize the production capacity so the customer gets the most out of the project. But not less important to minimize the risks for Vestas that comes with choosing the wrong turbine for the project. Minimizing loads and making the project as feasible for Vestas as possible. Bad siting causes at times turbines to break down and not being able to withstand the 20 years lifetime as it should. This is very expensive for Vestas both in hard cash but not least in the bad reputation it brings along.
36 Conclusions The wind resource drives project viability. Wind conditions are site-specific and time/height variable.Accuracy is crucial. Wind resource assessment programs must be designed to maximize accuracy.Combination of measurement and modeling techniques gives the most reliable result.Know the uncertainties and incorporate into decision making.Good financing terms depend on it.
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