Ellie Glover, Darby Nelson, Olivia Mihelick
Ms. Nuñez
Introduction to Engineering
6 April 2016
Research Statement
Wind Turbines are an innovative form of technology that harness the power of wind—the movement of
air resulting from differences in pressure within earth's atmosphere. There are a lot of benefits to using
wind energy. Wind energy is environmentally conscious since it does not pollute the air. It is also one of
lowest-cost sources of energy. Wind energy does not only have environmental benefits but it also helps
the economy of countries that use it by proving an increased opportunity for jobs and keeping energy
sources domestic to concentrate the wind energy transfer in a singular nation.
In this experiment, the task was to create a model wind turbine that would generate the highest power
efficiency while also remaining environmental and cost friendly, in addition to being aesthetically
pleasing. A box fan was placed in front of the wind turbine to mimic the effects of wind. The wind
turbine blades would be connected to a hub and allowed to rotate through a gear box, whose power
would be transferred into electricity using the help of a motor. The amount of electricity, in volts was
recorded by the multi-mater.
Before the blades could be designed, tests had to be performed in order to more clearly outline the
specifications necessary in order to maximize the blade's power output. A test was performed to
determine the ideal length of the blades by holding pieces of paper in front of the running fan and
letting go of them to see how far they flew away from the fan. At the location the pieces of paper flew
the farthest, this location should be near the end of the wind turbine in order to increases the amount
of torque (or rotational force) on the wind turbine blades. The wind turbines blades were made slightly
longer than this distance so that the torque would be near, but not on, the edge of the wind turbine
blades. Another test was performed by placing small pieces of paper at various distances away from the
fan and letting go to see which flew the farthest. At about a distance of ½ a foot, the pieces of paper
flew the farthest away from the fan, demonstrating that at this location the greatest wind force from
the fan was experienced. In testing , the wind turbine should be placed at this distance so that our wind
turbine would experience the greatest amount of wind force.
In order to choose the best material, the desired qualities of the material had to be determined. The fan
blades need curvature so that they can catch and move the wind in order to gain power. They need to
be able to bend easily but still be able to retain a rigid shape. If the blades bend too much, they will not
be strong enough to move the air a great distance. The blades need to have a smooth surface so that
minimal energy is lost to air friction. The material of choice needs to also be lower cost and
environmentally friendly. The material that best encompasses all of these desired characteristics is
cardboard. Carboard is capable of being bent and retaining its bent shape. It is stiff enough that it can
move air without losing its shape. Carboard has a flat, smooth surface so that the wind will not
encounter much friction with the surface of the blades. Carboard is also very environmentally friendly. It
is made out of 100% recyclable materials. Since the fan blades are recyclable, they will not take up room
in landfills and will have very little impact on the environment.
The shape of the blades needed to be considered and designed appropriately so that it will maximize
electric output. Each of the blades has a bend it in. This bend is meant to trap the wind so that it can
carry it around the fan. This also provides an angle for the wind to push off of and turn the turbine. This
bend is at an angle for that reason—there is more surface area for the blade to catch the wind and turn.
When making these blades there was a problem with the bends because the cardboard would flatten
out over time, decreasing the effectiveness of the blades. In order to fix this, a hole was poked on either
end of the bend and a string fed through. The tension in the string allowed the bend to stay in place.
In order to catch and move the most wind, the blades have to be rotated at an ideal angle. Rotating the
blades changes the amount of the blades that is facing the wind source. If the blades are turned too far,
there will not be enough area on the blade for the wind to push against it and spin, but if the blades are
not rotated enough the force of the wind will push the whole blade system backward instead of catching
the wind and rotating.
There are many forces of flight involved with the ability of the propeller blade to generate energy. One
of these forces is thrust. Thrust moves an aircraft through the air. This happens because the wind from
the box fan is being forced out the other end of the propeller which causes it to move forward. Another
force involved is drag. Drag is the force that acts opposite of thrust. As the propeller spins and moves
the air, drag is created. Drag is what slows down the propeller's rotation. With each blade added to the
wind turbine, there is a force of drag created. The other force which slows down the rotation of the
propeller is gravity. Gravity is the force that pulls an object down to the earth. The lighter the blades are,
the smaller the force of gravity that acts on the propellers and slows them down.
When designing a wind turbine there is a trade-off that has to be made between thrust and drag. Each
added blade to a turbine adds the force of drag that acts opposite the thrust and slows the propeller
down. On the other hand, each blade increases the surface area of the turbine that is exposed to the
air—there is a greater area for thrust to be created. Therefore, when designing and creating a wind
turbine, one has to determine the optimal number of blades, in order to create more thrust or to
minimize drag.
A wind turbine works the opposite way of a fan. A fan converts electrical energy into rotational,
mechanical energy. A wind turbine takes rotational, mechanical energy and converts it into electrical
energy. One of the most important concepts in this conversion fo energy is the law of conservation of
energy. In simple terms, the amount of rotational, mechanical energy should be equal to the amount of
electric energy generated. Since the blades rotate when they encounter wind, this is kinetic energy or
energy of motion, represented by the equation K= ½ (moment of intertia)(angular velocity)2. Therefore,
as the anglular velocity of the wind turbine increases, the amount of electric energy propduce will
increase also.
In this experiment, a test was performed to determine if three blades or six blades was better. When
three blades were used, the turbine was able to generate 2.3 volts. Three more identical blades were
created and added to the turbine, for a total of six blades. When six blades were used, the turbine was
able to generate 4.7 volts. Since the six blade turbine worked better, six blades will be used in the
design.
Combining all of the aspects of material, angle of rotation, bending, and number of blades, a final wind
turbine design was created.
Sources:
"Advantages and Challenges of Wind Energy." Energy.gov. Office of Energy and Renewable Energy.
https://energy.gov/eere/wind/advantages-and-challenges-wind-energy.
Foxnews.com. "Ask a science teacher: What creates the wind?" Fox News Science. Fox News.
http://www.foxnews.com/science/2013/12/10/ask-science-teacher-what-creates-wind.html.