Wind Energy Basics The Kidwind Project www kidwind

Wind Energy Basics The Kidwind Project www. kidwind. org

What is Electricity? Electricity is energy transported by the motion of electrons **We do not make electricity, we CONVERT other energy sources into electrical energy** Conversion is the name of the game Kid. Wind Project | www. kidwind. org

Faraday Effect • Basic Concepts • Voltage – V – Potential to Move Charge (volts) • Current – I – Charge Movement (amperes or amps) • Resistance – R – V = Ix. R (R in =ohms) • Power – P = Ix. V = I 2 x. R (watts) Kid. Wind Project | www. kidwind. org

How Does a Generator Work? Kid. Wind Project | www. kidwind. org

Where do we get our electricity? Kid. Wind Project | www. kidwind. org

What is a Fossil Fuel? ? ?

What is “Renewable Energy? ”

2009 8

2030 Power Required Doubles ! 9

Environmental Challenges 1875 Pasterze Glacier, Austria 2004 • Increasing atmospheric CO 2 is warming the planet • Power generation is leading cause of CO 2 emissions Carbon constraints increase demand for renewable energy 10

Types of Electricity Generating Windmills Small ( 10 k. W) Intermediate (10 -250 k. W) • Homes • Farms • Remote Applications • Village Power • Hybrid Systems • Distributed Power (e. g. water pumping, telecom sites, icemaking) Large (250 k. W - 2+MW) • Central Station Wind Farms • Distributed Power Kid. Wind Project | www. kidwind. org

Offshore Wind … GW Scale Renewable • US East Coast, Great Lakes, BC, UK, Germany, … • Proximity to Population & Load Centers • 10 -20 Km Offshore, Water Depths to 10 -40 M Offshore Construction, 7. 2 GW RFP’s in UK Challenges • Hurricane Exposure, Waves, Sea Bed Stability • Deep Water Foundations > 40 m Can Open Vast Resource • Tough Service Environment, Need Autonomous Operation GE 7 x 3. 6 MW – Arklow Banks, Irish Sea 20 GW Potential off NE Coast, Capacity Factors to 50%

Parts of a Wind Turbine

Wind Turbine Perspective Workers Blade 112’ long Nacelle 56 tons Tower 3 sections Kid. Wind Project | www. kidwind. org

Large Wind Turbines • • 450’ base to blade Each blade 112’ Span greater than 747 163+ tons total Foundation 20+ feet deep Rated at 1. 5 – 5 megawatt Supply at least 350 homes

Kid. Wind Project | www. kidwind. org

Importance of Wind Speed • No other factor is more important to the amount of power available in the wind than the speed of the wind • Power is a cubic function of wind speed – VXVXV • 20% increase in wind speed means 73% more power • Doubling wind speed means 8 times more power Kid. Wind Project | www. kidwind. org

• Major Factors: Air density, area of wind rotor and wind velocity • The most important factor is Wind Speed (Power varies cubic power of velocity) - As the velocity doubles, the power is increased by 8 times. - The rotor area is reduced by a factor of 8. • The selection of site is very critical for the success of a wind power

Calculation of Wind Power • Power in. Wind the wind Power in the = ½ρAV 3 Effect of air density, – Effect of swept area, A – Effect of wind speed, V R Swept Area: A = πR 2 Area of the circle swept by the rotor (m 2).

• The power coefficient or the power picked up by the wind turbine rotor is influenced by many factors: - profile of the rotor blade - number of blades - blade arrangement

Number of Blades – One • Rotor must move more rapidly to capture same amount of wind – Gearbox ratio reduced – Added weight of counterbalance negates some benefits of lighter design – Higher speed means more noise, visual, and wildlife impacts • Blades easier to install because entire rotor can be assembled on ground • Captures 10% less energy than two blade design • Ultimately provide no cost savings

Number of Blades - Two • Advantages & disadvantages similar to one blade • Need teetering hub and or shock absorbers because of gyroscopic imbalances • Capture 5% less energy than three blade designs

Number of Blades - Three • Balance of gyroscopic forces • Slower rotation – increases gearbox & transmission costs – More aesthetic, less noise, fewer bird strikes

Why 3 Blades? Blade calculations include realistic airfoils, L/D, and tip losses. Each point along a curve represents an optimized airfoil for given tip speed ratio. Ideal curve is zero drag optimum with rotational wake. = Vtip / V 1 - 4 blades cost more than 3 – provide marginal performance benefit - 2 blades provides loads balancing issue - requires teetered hub/downwind rotor - 3 blades (tripod) provides solution to loads resolution Actual Cp is constrained by Betz limit Also: noise (tip speed), loads, blade geometry 27

Betz’ Law • States theoretical limit for the conversion of wind energy in wind turbine • According to this law maximum possible wind turbine efficiency is less than 59. 3 % • Derived assuming a thin rotor from a fluid at a speed Major assumptions: - Rotor without any hub - Infinite number of blades with no drag - axial flow in and out

Blades • Aerofoil design Trailing Edge Angle of Attack • Air flow over the blade develops lift force and causes the blade to rotate

Lift & Drag Forces • The 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 = low α = medium <10 degrees α = High Stall!!

Airfoil in stall • Stall arises due to separation of flow from airfoil • Stall results in decreasing lift coefficient with increasing angle of attack • Stall behavior complicated due to blade rotation

Power Regulation • Turbine starts generating power at lower set wind speed. • Power increases with increase in Rated Power, 250 k. W 5 m/s 15 m/s Wind Speed wind speed up to a rated wind speed and rated power. • Power output remains constant at rated power between the rated wind speed and the cut-out speed • Turbines stops operating speeds higher than the rated speed due to safety reason. 25 m/s