KidWind Learning to build a Wind Turbine By Willem Scholten The Learning Access Institute

KidWind Learning about harnessing the power of the wind and generate energy (electrical) from it in the most efficient way.

Windmills and Wind Turbines What are they? Session #1 Windmills and Wind Turbines What are they?

“Windmills have fascinated us for centuries and will continue to do so “Windmills have fascinated us for centuries and will continue to do so. Like campfires or falling water, they’re mesmerizing; indeed, entrancing.” Paul Gipe, Wind Power for Home, Farm, & Business

What things are called Wind Machine Wind System Windmill Wind Turbine Kinetic device used to capture the wind and put it to work Wind System Wind machine, tower, and all ancillary equipment Windmill Wind machine that generates mechanical motion (ie. water pumping, grain grinding, saw mill, etc) Wind Turbine A device that produces electricity from kinetic energy of wind

Wind Energy has been popular for a long time The pilgrims arrived under the power of wind. Cape Cod was home to America’s first wind mill. Wind helped fuel our country’s early economy.

A long history.... Don Quixote fighting “giants” Fighting Windmills A long history.... Don Quixote fighting “giants”

Early “WINDMILL” in Afghanistan (900AD)

Dutch style windmills used for 100’s of years!

Kinderdijk, the Netherlands Serial Wind Power...... Kinderdijk, the Netherlands

Water pumping windmill helped settle the American West

Early Electric Wind Turbines helped Electrify Remote Farms

Birth of the Modern Wind Turbine Smith-Putnam 1.25MW Turbine, Vermont, 1940 California Wind Turbines, 1980

Wind Farms

Wind Farms

Session #2 Wind what is it?

How Wind Works Wind energy is created by uneven heating of the earth’s surface.

Wind Energy Wind is moving Air Anything that moves has energy in the form of Kinetic Energy Wind contains a lot of Kinetic energy The more the Wind blows the more Kinetic Energy it contains

Sea Breeze

Valley Breeze

Mountain Breeze

Mountain-Valley Breezes Typically strongest in summer Nighttime mountain breezes are stronger than daytime valley breezes Mountain-Valley winds can be enhanced by prevailing winds - wind flows between the interior and the coast

Where is the Wind?

Power in the Wind Wind Energy Calculations Advanced Topic Session #3 Power in the Wind Wind Energy Calculations Advanced Topic

Kinetic Energy in the Wind Kinetic Energy = Work = 1/2 mV2 Where: M = mass of moving object V = Velocity of moving object What is the mass of moving air? = density (ρ) x volume (Area x distance) = (ρ) x A x d = (kg/m3)(m2)(m) A V d

Calculation of Wind Power Power in the wind = 1/2 ρ A V3 = Effect of air density, ρ = Effect of swept area, A = Effect of wind speed, V Swept Area: A = ∏ R2 Area of the circle swept by the rotor (m2)

Importance of Rotor Diameter Swept area is proportional to square of the rotor. 20% increase in rotor diameter increases area by 44% Doubling diameter increases area 4 times

Importance of Wind Speed No other factor is more important then 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

Wind Speed and Height

“Micro-Siting”

Turbulence Top View Side View

Introduction to Energy Concepts Session #4 Introduction to Energy Concepts

Four basic forms of Energy Kinetic = 0.5 x mass x speed2 Thermal - energy of vibrating molecules within a material Electrical - force between electrical charges Chemical - electrical energy that holds molecules together Gravitational - also known as “potential energy” - force x distance = weight x height = m x g x h Nuclear - force that holds atoms together

Units of Energy Energy requires a force. Each form of energy has it’s own force: gravity, strong & weak nuclear forces, electrical, and kinetic forces. Kinetic Force = Mass x Acceleration Unit of Force = 1 Newton = 1 Kilogram x 1m/s Energy is a measurement of work accomplished by a force Energy = Force x Distance 1 Joule = 1 Newton x 1 Meter

Energy and Power Energy is a quantity, like distance. 1 kilowatt-hour = 1000 Watts x 1 hour 1 kilowatt-hour = 3.6 x 106 Joules Power is a rate, like speed, it is the rate that energy is converted from one form to another. 1 Watt = 1 Joule / second

Laws of Thermodynamics First Law: In any transformation of energy from one to another, the total quantity of energy remains unchanged. “Energy is neither created nor destroyed, it only changes forms.” Second Law: In all energy changes, the potential energy of the final state will be less than that of the initial state - (useful energy is always lost.) “Lost” energy is usually energy that has been converted to heat, could be noise (kinetic energy of air), or other forms of wasted energy.

Efficiency The ratio of the amount of useable energy obtained to the amount of energy input is the efficiency of a process. This is usually expressed as a percent and is always less then 100%.

Energy definitions Primary Energy - amount of energy contained in the initial source of energy Delivered Energy - amount of useable energy delivered to the “customer” Useful Energy - amount of energy attributed to the amount of work accomplished

Wind Energy to ...... Conversion Pumping Water, Wind Energy Sawing Wood, Grinding Grain Wind Energy Efficiency ??

Wind Energy to .... Conversion Wind Energy Electricity Efficiency ??

Converting Wind Energy into Electrical Energy The Rotor Blades Session #5 Converting Wind Energy into Electrical Energy The Rotor Blades

Wind Energy to Electricity Conversion Wind Energy Electricity Efficiency

The Turbine.....

Many different rotors

Parts of a Wind Turbine

Wind Turbine Workers Blade 112’ long Nacelle 56 tons Tower 3 sections

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

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

Blade Composition - Wood Strong, light weight, cheap, abundant, flexible Popular on do-it yourself turbines Solid plank Laminates Veneers Composites

Blade Composition - Metal Steel Heavy & expensive Aluminum Lighter-weight and easy to work with Expensive Subject to metal fatigue

Blade Construction - Fiberglass Lightweight, strong, inexpensive, good fatigue characteristics Variety of manufacturing processes Cloth over frame Pultrusion Filament winding to produce spars Most modern large turbines use fiberglass

Converting Wind Energy into Electrical Energy Optimum Blade Design Session #6 Converting Wind Energy into Electrical Energy Optimum Blade Design

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 Shape Just like the wings of an airplane, wind turbine blades use the airfoil shape to create lift and maximize efficiency.

Blade Engineering

Lift/Drag Forces Experienced by Turbine Blades Lift and Drag Forces Lift/Drag Forces Experienced by Turbine Blades

Twist and Taper Speed through the air of a point on the blade changes with distance from hub Therefore, tip speed ratio varies as well To optimize angle of attack all along blade, it must twist from root to tip Fast Faster Fastest

Betz Limit All 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

Experimental Classroom Blades Cardboard Tube for twisted blades Airfoil Blades

KidWind Challenge Students perform experiments and design different wind turbine blades Use simple wind turbine models Test one variable while holding others constant Record performance with a multimeter or other load device

KidWind Challenge Goals: Produce the most voltage, pump the most water, lift the most weight Minimize Drag Maximize LIFT Harness the POWER of the wind!

Generating the Electricity Session #7 Generating the Electricity

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!

Faraday Effect Voltage – V – Potential to Move Charge (volts)  Basic Concepts Voltage – V – Potential to Move Charge (volts) Current – I – Charge Movement (amperes or amps) Resistance – R – V = IxR (R in =ohms) Power – P = IxV = I2xR (watts)

How does a generator work?

Electrical Generator Mechanical Energy Electrical Energy G

KidWind Turbine Test We will measure: Voltage Current We will measure: Voltage - using Vernier Computer Sensor (V) Current - using Vernier Computer Sensor (A) Windspeed - using Vernier Computer Sensor (m/s) We will calculate: Power - P = V2/ R - calculated in (W) R = 10 Ohm in our setup

Experiment Templates

Making theWindmill Cut out the square Cut on each of the dotted lines from the corners towards the little hash marks (no further!) Fold a corner of each cut part toward the middle making sure it stays ‘rounded’ not folded flat, and glue down with a little bit of glue Do this 4 times Take a pencil with an eraser top, and stick a thumbnail through the Windmill in the center (black little square) and into the eraser Now experiment -- does it move better if the wind comes from the site or from the front? What happens if there is to much wind....

A B

Making the Airfoil Fold side ‘A’ over side ‘B’, side “B” is shorter so side ‘A’ should create a curved surface. (The line in the middle is the fold line) Tape the two sides together, so that the ‘B’ side is flat Use a pencil to make a hole where the black dot is, so that it can slide from one side to the other Stick a straw through the hole, and attach it to the top and the bottom of the wing with a small piece of tape Cut the straw so that is little as possible is above and below the wing Feed some string through the wind, and tie a paper clip to the end of the string which is coming through the flat part of the wing (the ‘B” side) Now hold the top and and the bottom of the string tight in front of a box fan, and notice what happens You can also do this as you run down the hallway or playground