Presentation on theme: "Wind Energy in the Classroom"— Presentation transcript:
1 Wind Energy in the Classroom This slide show is a basic outline. We often make changes to this template depending on the time and location of the event.The Kidwind Project and WindWise
2 What is KidWind?The KidWind Project is a team of teachers, students, engineers and practitioners exploring the science behind wind energy in classrooms around the US. Our goal is to introduce as many people as possible to the elegance of wind power through hands-on science activities which are challenging, engaging and teach basic science principles.KidWind Project |KidWind Project |
3 Yesterday & Today Holland & Colonial America First documented windmill: Afghanistan (900AD)Wind PumperGreeceFirst windmills were found in Persia. They were vertical axis and were used to grind grains and seeds. Reeds form blades. They were kind of like a waterwheel turned on its side. Most of the paddles were covered by a wall and wind would run through a narrow opening to push the blades. Many have seen the Dutch windmills.Used to grind grains, seeds, pump water, saw lumber…these were fairly sophisticated devices. Used to cover much of New England coastline.
4 Very Low Maintenance Requirements Proven: ~ 5,000 On-Grid Wind Energy Technology in the World Today: Modern Small Wind Turbines: Horizontal AxisDownwindRotor10 kWTechnically AdvancedMinimal Moving PartsVery Low Maintenance RequirementsProven: ~ 5,000 On-GridAmerican Companies are the Market and Technology Leaders50 kWUpwindRotors400 W900 WWhen teachers build their Basic PVC Turbines they are more like a small wind turbine, simple direct drive systems.Emphasize high RPM…these things spin fast RPM.Many of these are sent to villages offshore as they can provide power for an entire village…here in the US is hard to justify the cost for one household. $$ on small wind turbines 10K-100K(Not to scale)
5 Vertical Axis Wind Turbines? AdvantagesOmnidirectionalAccepts wind from any angleComponents can be mounted at ground levelEase of serviceLighter weight towersCan theoretically use less materials to capture the same amount of windDisadvantagesRotors generally near ground where wind poorerCentrifugal force stresses blades & componentsPoor self-starting capabilitiesRequires support at top of turbine rotorRequires entire rotor to be removed to replace bearingsOverall poor performance and reliability/less efficientHave never been commercially successful (large scale)WindspireSee testing on early Mariah Windspire at NREL – test was discontinued due to failures.Spire seen swaying in the wind. Beware “Hope & hype” huckstersSavonious
6 Large Wind Turbines 450’ base to blade Each blade 112’ Span greater than 747163+ tons totalFoundation 20+ feet deepRated at 1.5 – 5 megawattSupply at least 350 homesUpwind rotors
7 Wind Energy is a Growing Industry US total installed wind energy capacity now over 43,635 MW as of Sept 2011 per WindPoweringAmerica.comEnough electricity to power the equivalent of over 7 million households!KidWind Project |
9 Costs are Decreasing 1979: 40 cents/kWh 2000: 4 - 6 cents/kWh NSP 107 MW Lake Benton wind farm4 cents/kWh (unsubsidized)Increased Turbine SizeR&D AdvancesManufacturing ImprovementsThe rapid growth in wind power can be attributed to two things….reduction in cost of the electricity produced and more interested in Green Power.I usually ask people here what they pay for their electricity by kwh….typical # are 7-20 cents. Wind has come way down in terms of cost over the last 40 years. The cheapest power out there is coal and wind cannot compete with that…Natural Gas and coal are comparable. The costs for wind listed above are the wholesale rate…do not include transmission etc.On this slide I often ask the crowd how we generate most of our electrical power in the US.Coal 50%Nuclear 20%Natural Gas 17%Hydro 7%Oil 3%Renewables 3% Wind less than 1%2004:3 – 4.5 cents/kWh
10 Issues Today: Costs & Benefits We also need to change students perceptions about what the future may look like and the limits of this technology.Wind will never be “base load” for the grid. The wind farm above is capable of generating 15-20Mw of electricity at full capacity. The oil fired facility below is at 300Mw. Most Nuclear plants are at Mw…Must keep the scale in mind….a very aggressive wind program can generate 10-20% of our power needs. To move towards a green future we are going to need mix of sources and also a great deal of energy efficiency….Wind cannot do it all.
11 Where do we get our electricity? KidWind Project |11
12 Fighting windmills has a long history! Don Quixote fighting “Giants”
13 KidWind Project | www.kidwind.org Accidents & Troubles“So far no evacuation zone has been declared. There are no threats to sea life, and the fallout from the disaster was not detectable thousands of miles away. Cleanup efforts are in progress, and will not include covering the area in a giant concrete dome. No workers have been asked to give their lives in order to save their countrymen from the menace of this fallen wind turbine.”– Christopher MimsKidWind Project |
14 Impacts of Wind Power: Noise Modern turbines are relatively quietRule of thumb – stay about 3x hub-height away from housesMany people think wind turbines are noisy.While this may have been true in the past (it is still somewhat true on older smaller devices)…newer larger devices are much quieter.
15 Impacts of Wind Power: Wildlife It is a common complaint that wind turbines kill birds. While it is true that turbines kill birds, this graph puts that in perspective with other human technologies.
16 In the November-December Audubon Magazine, John Flicker, President of National Audubon Society, wrote a column stating that Audubon "strongly supports wind power as a clean alternative energy source," pointing to the link between global warming and the birds and other wildlife that scientist say it will kill.National Audubon Society endorses wind power…
17 Prospecting the Right Site: Lessons Learned 1980’s California Wind FarmOlder Technology+ Higher RPMs+ Lower Elevations+ Lattice Towers+ Poorly Sited= Bad News!Altamont Pass Wind Farm in California…This wind farm was built in the 1980’s. Without doing an Environmental Impact Assessment, they built the wind farm in a raptor migration path. This wind farm had a major problem with avian mortality, and scarred the industry.Today this farm is being repowered. This means they are taking down the old turbines and replacing them with new. With one new turbine, they can replace 10 old turbines. Still poorly sited, but this is an improvement.
18 Prospecting the Right Site: Off-Shore On the Farm On a Mountain Many developers would like to move windfarms offshore because the wind are faster, smoother and they can be close to major population centers on the coast. This is very controversial in the US….we have a few planned offshore farms…CapeWind and Long Island…but nothing installed.Major complaints about offshore are related visual impact, navigation impact and lack of history.Check
19 The Transmission Challenge Where is the wind?Where are the population centers?Where are the wind farms?How do we get wind energy from the wind farms to the population centers?Probably the largest issue facing Commercial Wind Energy is transmission. It is typically windy where people don’t want to live so how will you get the power from where it is generated to where the people live? Most people oppose new power line construction vehemently….so this will be a touchy issue for a very long time.Quick Fact: 1 mile of High Voltage transmission line can cost upwards of $1 million!
20 KidWind Project | www.kidwind.org Where is the Wind?Note the Wind BeltKidWind Project |
22 Importance of Wind Speed No other factor is more important to the amount of power available in the wind than the speed of the windPower is a cubic function of wind speedV X V X V20% increase in wind speed means 73% more powerDoubling wind speed means 8 times more power
23 Calculation of Wind Power Power in the windEffect of swept area, AEffect of wind speed, VEffect of air density, Power in the Wind = ½ρAV3RThis is the equation for the power in the wind. (Don’t fear – there are only 2 equations in this presentation.) Each of the terms in this equation can tell us a lot about wind turbines and how they work. Lets look at wind speed (V), swept area (A), and density (Greek letter “rho,” ) one at a time.First, let’s look at wind speed, V. Because V is cubed in the equation, a small increase in V makes for a increase in power. (illustrated on next slide)(Click on the links at the bottom to get the values of both k and .)Swept Area: A = πR2 Area of the circle swept by the rotor (m2).
24 TechnologyPart of a turbine…all turbines from our little models to the biggest in the world have these parts.
25 KidWind Project | www.kidwind.org The “guts” of a wind turbineKidWind Project |
27 Airfoil ShapeJust like the wings of an airplane, wind turbine blades use the airfoil shape to create lift and maximize efficiency.The Bernoulli Effect
28 Lift & Drag ForcesThe Lift Force is perpendicular to the direction of motion. We want to make this force BIG.The Drag Force is parallel to the direction of motion. We want to make this force small.α = lowα = medium<10 degreesα = HighStall!!
30 Twist & TaperSpeed through the air of a point on the blade changes with distance from hubTo optimize angle of attack all along blade, it must twist from root to tipFastFasterFastest
31 Tip-Speed Ratio ΩR TSR = V R Ω = rotational speed in radians /sec Tip-speed ratio is the ratio of the speed of the rotating blade tip to the speed of the free stream wind.There is an optimum angle of attack which creates the highest lift to drag ratio.Because angle of attack is dependant on wind speed, there is an optimum tip-speed ratioRΩRVTSR =Where,Ω = rotational speed in radians /secR = Rotor RadiusV = Wind “Free Stream” Velocity
32 Performance Over Range of Tip Speed Ratios Power Coefficient Varies with Tip Speed RatioCharacterized by Cp vs Tip Speed Ratio Curve
33 Betz LimitAll wind power cannot be captured by rotor or air would be completely still behind rotor and not allow more wind to pass through.Theoretical limit of rotor efficiency is 59%Most modern wind turbines are in the 35 – 45% range
34 Rotor SoliditySolidity is the ratio of total rotor planform area to total swept areaLow solidity (0.10) = high speed, low torqueHigh solidity (>0.80) = low speed, high torqueRaASolidity = 3a/A
35 Over-Speed Protection During High Winds Upward Furling: The rotor tilts back during high windsAngle Governor: The rotor turns up and to one side
36 Yawing – Facing the Wind Active Yaw (all medium & large turbines produced today, & some small turbines from Europe)Anemometer on nacelle tells controller which way to point rotor into the windYaw drive turns gears to point rotor into windPassive Yaw (Most small turbines)Wind forces alone direct rotorTail vanesDownwind turbines
39 KidWind Project | www.kidwind.org Many Topics AddressedUse of Simple Tools & EquipmentApplied Mathematical RelationshipsPractices of Engineering & ScienceForces and ChangeEnergy Transformations (Forms of Energy)Circuits/Electricity/MagnetismProperties of AirWeather PatternsImpacts on ecosystems, wildlife & humansRenewable – Non Renewable EnergyKidWind Project |
40 Scientific & Engineering Practices New National Frameworks Asking questions & defining problemsDeveloping & using modelsPlanning & carrying out investigationsAnalyzing & interpreting dataUsing mathematics & computational thinkingDeveloping explanations & designing solutionsEngaging in argument from evidenceObtaining, evaluating & communicating information
41 Upper Elementary/Middle Building Wind TurbinesAssessing Wind ResourceMathematicsballoon~3mstreamersKite or balloon string41
43 Secondary Advanced Blade Design School Siting Projects Data Analysis Mathematics -Download lessonsMath lessons – free downloads on topics such as gear ratios, tip speed ratio & tower height estimation.43
44 Wind Turbine Blade Challenge Students perform experiments and design different wind turbine bladesUse simple wind turbine modelsTest one variable while holding others constantRecord performance with a multimeter or other load deviceGoals: Produce the most voltage, pump the most water, lift the most weightMinimize DragMaximize LIFTHarness the POWER of the wind!