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Windmill Project: The Windthrill

EF152 Section A1

4-23-09

Team 8:

Zach Jacob John Greer Trey Coates Boyd Culver Gage Craig

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-Overview

Our project goal was to create a functioning windmill that could light up a small

light bulb using only wind generated by a fan. We had to loop enough wire around a

rotating magnet moving fast enough to in turn generate this electricity. Along with this,

our device must act by itself with now outside interference. It must not be built from a

kit, and the materials cost must be less than forty dollars.

-Description of Wind Power

Man has been harnessing wind power since the Ancient Persians used it to

pump water. Since then, we’ve had all sorts of windmills, from vertical axis windmills, to

quaint Dutch windmills, to today’s modern turbines. Though windmills are used heavily,

especially out west, they are not very efficient at all. According to one source, to replace

just one power plant with wind power, you would need 300 square miles (roughly an

area the size of New York City) of land covered in wind turbines! This is because wind

turbines only take in energy from a small area (the circular area covered by the blades).

As such, wind power only generates about 1.5% of the world’s energy.

(Sources)

• http://www.wwindea.org/home/images/stories/worldwindenergyreport2008_s.pdf

• http://www.capecodtoday.com/blogs/index.php/2006/01/02/the_cost_and_efficien

cy_of_wind_power?blog=49

• http://www.telosnet.com/wind/early.html

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-Design Process

To start out, we immediately decided on a horizontal axis windmill, as opposed to

one that rotated on a vertical axis. Since this is how you typically see it done in wind

farms and such, we surmised that this was the superior design. Ours would have the

typical ‘flower’ design you see so often on windmills.

Of course, as often happens, our actual device would look much different than this

model. We decided on four blades, because they would be easier to space than three

blades. We actually looked to pictures of windmills to determine what we wanted our

final product to look like. We took ideas from two notable examples. A four bladed

‘modern’ windmill and an old Midwestern farm windmill.

These two windmills were inspirations for own device.

We took the four-bladed design from the turbine on the

left, and added a rudder similar to the one on the right.

This rudder would ideally direct the windmill blades into

the wind, so the maximum energy can be harnessed from

the powerful breezes.

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We quickly determined that our generator would need a box or casing of some sort for it

to rotate in. We also determined that a wooden frame would work better for that than a

plastic one, as there would be much less friction on the rotating axle. We would also

need a strong, sturdy base on which our large contraption could balance easily. In

addition, we played with the angle of the blades until we achieved an angle that worked

best to capture wind. We wrapped wire around the magnet box both vertically and

horizontally for maximum coverage. Ideally, this magnet would spin at a high enough

speed amongst the wires to generate enough electricity to power our small light bulb.

The majority of our design is made from wood, with the axles (the blade axle, and the

vertical rotational axle) being small metal poles. The wire is 30 gauge copper wire, and

the fan blades are made from cut PVC pipe. We have a group of magnets in the center

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of our generator, and our rudder is made of poster board and duct tape. To help prop up

the generator, we also used a small amount of actual U.S. coins.

To determine the amount of energy we are creating, we used two equations.

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1vAKE ×××= ρ

This is the first. KE is kinetic energy, ρ is the density of air, A is the circular area

covered by the windmill blades when they spin, and v is the wind speed. Since we do

not know the wind speed, we cannot solve this equation.

R

VKE

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=

However, using a volt meter, we can solve the above equation.

Using hypothetical wind speeds, we can see how our numbers, particularly our

efficiency and voltage, change as our speed increases.

Windspeed(mph) 10 12 14 16 18 20

Windspeed(m/s) 4.4704 5.36448 6.25856 7.15264 8.04672 8.9408

Resistance (ohm) 116 116 116 116 116 116

Voltage (volt) 1 1.2 1.5 1.9 2.2 2.5

Input Watts 8.983365 15.52325 24.65035 36.79586 52.39098 71.86692

Generator Watts 0.008621 0.012414 0.019397 0.031121 0.041724 0.053879

Windswept Area (m^2) 0.16417 0.16417 0.16417 0.16417 0.16417 0.16417

air density (kg/m^3) 1.225 1.225 1.225 1.225 1.225 1.225

efficiency 0.096 0.08 0.079 0.085 0.08 0.075

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-Bill of Materials

Scrap Wood $2.00

PVC Pipe $5.00

Nails, Screws, Metal poles $2.00

Magnets $5.00

Posterboard $1.00

Duct Tape $1.00

Copper Wire $12.00

Spare Change 50 cents _______________________________________ Total $28.50

-Conclusions

In the end, we did actually generate some electricity. However, we had many

problems. Unfortunately for us, we were reading the volt meter incorrectly. Also, our

light bulb that we were given was broken from the start. So we had no way to see if it

would light up or not. Friction of our axle against our box was also a problem, as this

limited the amount of useful energy. We also had to make a box small enough so the

wire was close to our rotating magnet, but big enough so the magnet wouldn’t catch on

the sides of the box. We had difficulty finding our wire. We also were originally using

metal nails on the box, but the magnets kept sticking, so we had to find a different way

to hold the box together. If we could do it differently, we would’ve made sure we were

using the volt meter correctly. We also would’ve added gears to increase the speed at

which the magnet is rotated amongst the wire, since a quicker rotation generates more

electricity. Perhaps we would have even switched our design to a vertical axis design,

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as these seemed to work quite well. But we did have a unique and interesting design.

Our rudder was a unique idea, and our incorporation of both modern and nostalgic

design into our device was noble. Overall, I would call our project a success, because

some electricity was generated and our design was ingenious.

-References

• http://www.mdpub.com/Wind_Turbine/index.html

• http://www.otherpower.com/toymill.html

• http://ezinearticles.com/?How-to-Build-a-Wind-Turbine---Step-by-Step-

Instructions&id=1414596

• http://www.wonderhowto.com/how-to/video/how-to-construct-a-model-windmill-

and-calculate-its-power-259781/

• http://monsterguide.net/how-to-build-a-windmill