Anemometer interstellar

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<ul><li><p>Anemometers: Measuring Wind SpeedDebajyoti BoseLt. Col. Ashis KharePravin Badarayani</p></li><li><p>Anemometer: BasicsA commonweather stationinstrument</p><p>The term is derived from the Greek wordanemos, meaning wind</p><p>Describe any air speed measurement instrument used in meteorologyoraerodynamics</p><p>Invented in 1846 byJohn Thomas Romney RobinsonImage:National Weather Service(NWS) Collection, Baltimore, Image ID: wea00920</p></li><li><p>Anemometer: Reason For UseTwo primary reasons to measure wind speed:</p><p>To determine feasibility of wind power development at a siteAs part of a wind turbine control system</p><p>Is it worthwhile to turn the turbine into the wind and start it?</p><p>Animation: How the air moves forming Winds, V. Ryan 2005</p></li><li><p>Anemometer: TypesMechanical Type:Cup AnemometerNon-Mechanical Type:Hot Wire AnemometersUltrasonic AnemometersLaser/Doppler AnemometersPressure AnemometersPlate AnemometersTube Anemometers</p><p>Propeller Type Anemometers</p><p>Image: Digital Anemometer, www.everflowscientific.com</p></li><li><p>Cup AnemometersMost common wind speed measurement device</p><p>It consists of hemisphericalcups, each mounted on one end of horizontal arms</p><p>And the arms were mounted at equal angles to each other on a vertical shaftImage: www.directindustry.com</p></li><li><p>Cup Anemometers: ContinuedThe air flow past the cups in any horizontal direction turned the shaft in a manner that is proportional to the wind speed</p><p>On counting the turns of the shaft over a set time period produced the average wind speed for a wide range of speedsAnimation: Anemometer 2 from Barani Design and Wind101.net</p></li><li><p>In a Nutshell: Cup AnemometersMany cup anemometers have a vane attached to measure wind direction</p><p>Image: http://www.photolib.noaa.gov/nssl/nssl0161.htm</p><p>AdvantagesDisadvantagesLow PriceFlexible DesignSimple Installation</p><p>Most technicians understand operating principles and necessary connectionsMoving parts wear outWithout provisions for heating, they dont work well in snow or freezing rain</p><p>They dont work well in rapidly fluctuating winds</p></li><li><p>Hot Wire AnemometersUses a very fine wire (on the order of several micro-metres)Electrically heated up to some temperature above the ambientAir flowing past the wire has a cooling effect on the wire</p><p>The electrical resistance of most metals is dependent upon the temperature of the metal</p><p>Using above a relationship can be obtained between the resistance of the wire and the flow speed</p></li><li><p>Probe SpecificationsTungstenis a popular choice for hot-wiresTungsten or Platinum filament~1 mm long4-10 mm diameter</p><p>BenefitsGood spatial resolutionFlat frequency response</p><p>LimitationsFragileRequires clean flowCost (start at $300-400)</p><p>Image: www.tungstenringsco.com</p></li><li><p>Typical SpecificationsSource: http://www.extech.com/instruments/product.asp?catid=1&amp;prodid=43</p><p>ParametersHandheld/EconomyIndustrial GradeMeasurable velocities0.2-20 m/s0.2-90 m/sOperating temp ranges0-50 C-40-200 CVelocity Accuracy 3% reading 1% readingTime constant200 ms100 msInterfacing optionsHandheld reader, RS232RS232, RS485, voltage, 4-20 mA, Modbus, Profibus, etc.</p></li><li><p>Ultrasonic AnemometersFirst developed in the 1950sUse ofultrasonic sound wavesto measure wind velocityThey measure wind speed based on the time of flight of sonic pulses between pairs oftransducersMeasurements from pairs of transducers can be combined to yield a measurement of velocity in 1-, 2-, or 3-dimensional flowFigure: 2D ultrasonic anemometer with 3 paths Image: Anmomtre / girouette ultrasonique trois chemins</p></li><li><p>Ultrasonic Anemometers Figure: 3D ultrasonic anemometerImage: Google</p><p>AdvantageDisadvantageThe lack of moving parts makes them appropriate for long-term use in exposed automated weather stations and weather buoys where the accuracy and reliability of traditional cup-and-vane anemometers is adversely affected by salty air or large amounts of dustMain disadvantage is the distortion of the flow itself by the structure supporting the transducers, which requires a correction based upon wind tunnel measurements to minimize the effect</p></li><li><p>Laser/Doppler AnemometersLaser/Doppler anemometers use a beam of light from alaserthat is divided into two beams, with one propagated out of the anemometerParticulates (or deliberately introduced seed material) flowing along with air molecules near where the beam exits reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beamWhen the particles are in great motion, they produce aDoppler shiftfor measuring wind speed in the laser light, which is used to calculate the speed of the particles, and therefore the air around the anemometer</p></li><li><p>Plate AnemometersModern anemometers</p><p>Are simply a flat plate suspended from the top so that the wind deflects the plateThe pressure of the wind on its face is balanced by a spring</p><p>The compression of the spring determines the actual force which the wind is exerting on the plateThis is either read off on a suitable gauge, or on a recorder</p></li><li><p>Plate Anemometers: ContinuedImage: www.stormdebris.net</p><p>AdvantageDisadvantageThey are used on these high places because they are in a plate shape; has a good measurement status on higher altitudesInstruments of this kind do not respond to light winds, are inaccurate for high wind readings, and are slow at responding to variable winds.</p></li><li><p>Tube AnemometersAtube anemometer uses air pressure to determine the wind pressure, or speedA tube anemometer measures the air pressure inside a glass tube that is closed at one endBy comparing the air pressure inside the tube to the air pressure outside the tube, wind speed can be calculatedFigure: Invented by William Henry Dines in 1892, The movable part (right) to be put on top of the fixed part (left)Image: Wikipedia</p></li><li><p>Propeller Type/Vane AnemometersThe axis on the vane anemometer is parallel to the direction of the wind and therefore horizontal</p><p>Since the wind varies in direction and the axis has to follow its changes</p><p>Combines a propeller and a tail on the same axis to obtain accurate and precise wind speed and direction measurements from the same instrumentImage: nssl0161, National Severe Storms Laboratory (NSSL) Collection</p></li><li><p>Output from AnemometersSignal conditioning is usually done within the instrumentThe output can be an electrical signal to a data-logger or readout device:Pulse signalVoltage signalFor example, 0-10 V corresponds to the velocity measurement range of the instrument.</p><p>Current signalTypically, 4-20 mA corresponding to the instrument range.Eliminates voltage drop when the signal is transmitted over larger distances.</p></li><li><p>Importance of Accurate Wind Speed MeasurementsThe power obtained from the wind goes with the cube of the wind speedA small error in the measurement results in a much larger error in the predicted wind power</p><p>For example, a 5% error at a wind speed of 10 meters/sec leads to a 16% error in predicted wind power10% anemometer error leads to 33% errors in power prediction</p><p>This could be disastrous if one is monitoring a site for feasibility of wind power development!</p></li><li><p>Thank You Very Much Indeed !!!</p><p>A Presentation by M. Tech Renewable Energy Engineering </p><p>Debajyoti Bose: R120214007Lt. Col. Ashis Khare: R120214006Pravin Badarayani: R120214005</p><p>Department of Electrical Engineering</p></li></ul>