Vernier MINI Wind Turbine User manual

MINI Wind Turbine
Instruction Manual

4
The MINI Wind Turbine
The MINI Wind Turbine wind turbine kits are perfect for demonstrating
how wind turbines function. They also allow you to perform experiemnts
with wind power. Check out all the kits at: www.KidWind.org/shop
The MINI Wind Turbine
The MINI Wind Turbine is an easy-to-build turbine that produces enough
electricity to power LED bulbs, a sound & light panel, and other load
devices.
The MINI Wind Turbine Blade Design kit
Be a blade engineer! With the KidWind MINI Blade Design kit you
will also be able to use your turbine to make and test blades that you
construct yourself. See what happens to wind turbine power output when
you change the number, pitch, and shape of the blades.
Why Study Wind Energy?
In 2009, wind power comprised 39% of all new energy installations
in the US. As investors and power producers look to build new power
infrastructure, they are choosing to build wind farms at an increasing rate.
Of our current electrical generation mix, about 2% of our energy is
produced by wind turbines. That is double what we had three years ago:
approximately 20,000 wind towers.
The current US wind power capacity of 36,700 MW is capable of
generating enough power for over 11 million US homes! Some industry
leaders believe that by the year 2030 we will get 15–20% of our energy
from the wind. Reaching this goal will take
great effort and lots of scientists, engineers,
and technicians.
The MINI Wind Turbine, and other KidWind
kits, will help you explore some of the science
and engineering behind the growing field of
wind power so you can one day help move
the US towards a sustainable energy future.
US annual and cumulative wind power capacity growth
Source: US Department of Energy’s Wind Powering America
0
5000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
Capacity (MW)
’10’09’08’07’06’05’04’03’02’00’99
Annual Capacity Additions
Cumulative Capacity
’01

5
Building the MINI Turbine
1. Unwrap the wires of your MINI nacelle and feed the wires down the
aluminum tower.
2. Feed the wires through the wooden base.
3. Insert the nacelle post into the end of the tower.
4. Slide the tower through the wooden base.
5. Feed the wires through the hole in the yellow cap and nsert the cap
into the end of the tower.
6. Stand up your MINI Turbine and push the red blade set onto the shaft
of the generator.
Converting to blade testing turbine
The MINI Wind Turbine Blade Design kit includes a 12-hole crimping hub
and blade materials. The KidWind Hub makes it easy to change blades
and try your own designs.
Pull off the red plastic blade set. The best way to do this is to pry it off
slowly using a screwdriver or something similar. Replace it with the
KidWind Hub and you are ready to make and test your own blades. See
page 10 for tips on how to make and test blades.
Connecting to Devices and Loads
KidWind MINI
The MINI Wind Turbine comes with a sound & light panel that you can
connect to your turbine to demonstrate power output. Be sure to connect
red wires to red and black wires to black.
The MINI Wind Turbine can power a variety of electrical devices
beyond the included sound & light panel (especially if you build a mini
wind farm)!
For more fun experiments, try pumping water with the KidWind water
pump, electrolyzing water in a hydrogen fuel cell, or storing energy in a
super capacitor. You can also connect it to another DC motor, which
can spin a small propeller. All of these items can be found at
www.KidWind.org/shop
The MINI Wind Turbine Blade Design Kit
The MINI—Blade Design Kit comes with a simple multimeter so you
can quantify how much power your turbine generates. The following
directions will help you connect your MINI to the meter and record
voltage and amperage.
Carefully remove blades, using a screwdriver to pry
against the motor.
Unwrap wires and pass
them through the tower.
Feed the wires through
the hole in the wooden
base.
Feed the wires through
the plastic plug and
insert it into the tower.
Stand up the tower and
attach the red blades
or the KidWind Hub.

6
Measuring voltage
Attach the wires from the generator to the multimeter. Polarity is not
relevant at this point.
To check the voltage, select DC volt (V) and set the number to 20.
Place your turbine out in the wind or in front of a fan and let it spin. It is
normal for the voltage readings to fluctuate because of the inconsistent
nature of the wind or unbalanced blades.
Voltage is related to how fast the DC generator is spinning. The faster it
spins, the higher the voltage. With no load on the generator, it has little
resistance and can spin very fast.
You can measure voltage with no load, but it is more realistic to place
a resistor in the circuit and measure the voltage across the resistor. We
commonly use 10, 30, 50 or 100 ohm resistors.
Measuring amperage
To calculate your turbine’s power output, you will need to measure current
as well. When measuring current you are monitoring how many electrons
are being pushed through the wire by the turbine. We measure current
from our turbine in milliAmperes.1A =1000 mA.
To measure current, place a load in series with the multimeter so the
generator is forced to do some work. Set the meter to 200 or 20 mA,
which is a typical range for our devices.
The current that your turbine produces depends on the load placed in the
circuit and the torque your blades are generating.
Voltage, Resistance and Currant
Voltage (measured in volts), is also called “potential difference” or
“electromotive force” (EMF). It is a measure of the amount of “potential
energy” available to make electricity flow in a circuit. It is the electric
“pressure” causing the current to flow.
Electric current is a measure of the rate at which electric charge
(electrons) are flowing through a circuit. It is given in the unit of amperes
(“amps”). Smaller amounts of current are often stated in milliAmps (mA). A
mA is 1⁄1000 of an amp.
Electrical resistance is the opposition to the flow of electricity. Measured
in ohms, it reflects how much electric “pressure” (voltage) is required to
push a given amount of current through part of an electric circuit.
To measure the power your turbine is producing, you need to do some
math with these values (see page 12).
Resistors are electrical components with a known resistance.
There is a standard system of colored bands to show what the
resistance of a resistor is.
The MINI Blade Design kit includes a 50 ohm resistor and a
100 ohm resistor.
RESISTORS
20
20
200
V
A
Resistor
Measuring DC Voltage Measuring Current

7
Experiments for your MINI Turbine
The MINI Wind Turbine was designed to demonstrate wind power
technology while helping you do some simple experiments!
Experiment 1: changing wind speed
This experiment can be done with the red blade set or your homemade
blades using the crimping hub. Place the turbine about three feet in front
of a fan, and turn it on high. What happens when you turn the fan to
medium or low? Does the LED bulb light up at any wind speed?
Now leave the fan on medium and move your turbine away from the fan
by about a foot. Continue moving the turbine away from the fan, one foot
at a time, until the LED bulb no longer works. How far away can you get?
Why is the turbine unable to power the light bulb as you back away from
the fan?
The KidWind MINI—Blade Design includes a multimeter. What happens
to the voltage or current as you move your turbine further from the fan, or
decrease the wind speed?
Experiment 2: blade design
The amount of power your turbine can produce depends on blade
efficiency. To build efficient blades, you must capture the wind and
reduce drag as they spin around. Blade design experiments are a fun
and engaging way to explore how design affects power production.
The blades on modern turbines “capture” the wind and use it to rotate the
drive shaft of a generator. How well you design and orient your blades
can greatly impact how fast the blades spin and how much power your
turbine produces.
If you are doing this for a science fair or school project, you should focus
on just one of these variables at a time, as your results can get confusing
quite quickly.
You can do a lot of great experiments by isolating blade variables and
examining how they affect the power output of your turbine. Try these
variables to get started:
• blade pitch (angle)
• blade size
• blade shape
• number of blades
• blade materials
After attaching your new blades, try to light the LED bulb or measure your
voltage, current, or power with a multimeter. How has the efficiency of
your turbine changed? Try a few blade designs to learn what makes
blades more efficient.
To make an electrical circuit, the conductive metal wires of each
element must be in direct contact with those of the next. Make
sure the ends of the wires are stripped, then connect them with
clip cords or by twisting them together.
CONNECTING WIRES
Try graphing the relationship between voltage and
wind speed or amperage and wind speed.
a
V
Wind speed
Wind speed
Graph your Data
The red blade set is designed to be very efficient. If you are
able to design a blade set that is better than our red blades, we
want to hear about it! Send us a note at www.KidWind.org.
CAN YOU BEAT THE ENGINEERS?

8
Experiment 3: building a MINI wind farm
A wind farm is a collection of wind turbines in the same location. This
may also be called a “wind power plant,” because many wind turbines
working together can produce a lot of electricity—just like coal or nuclear
power plants. Wind turbines are often grouped together in wind farms
because this is the most economical way to generate electricity from the
wind.
Two or more KidWind MINIs can be wired together to make a MINI
Wind Farm!
Connecting turbines
When you connect your various components together (KidWind MINIs,
load, meter, etc.), you can make more complicated electrical circuits.
There are two ways of connecting components in a circuit: series and
parallel.
A circuit wired in series has components connected end to end, like a
chain. The electrons must travel a single path through all of the various
parts of the circuit.
A circuit wired in parallel provides a different path for a current to travel
through each of the components. In parallel, each component has a
separate loop.
If you are connecting the KidWind MINIs in series, connect the wires of
the turbines from positive (red wire) to negative (black wire), making one
continuous loop through the circuit.
If you are connecting the turbines in parallel, connect each positive wind
turbine wire (red) individually to the red lead from the multimeter or load
device. Connect each negative wind turbine wire (black) individually to
the black lead from the multimeter or load device.
The wires you use to connect your MINI Wind Farm to various loads act
just like the high voltage transmission lines that bring the electricity of real
wind farms to our homes and schools!
If you use a multimeter to record voltage and current as you add wind
turbines to your wind farm, you will find some interesting results.
Experiment 4: How does turbulence affect wind turbines?
If multiple wind turbines are placed too close to one another or there are
obstructions near a wind turbine, the efficiency of the turbines will be
reduced.
Place some objects to act as trees or houses in front of your MINI and
see how the power output changes. How does this disturbance affect the
turbine output or performance? Some people want to put wind turbines
When you have multiple turbines wired in series, the voltage
should increase with each additional turbine, but the current
will stay the same.
If you wire the turbines in parallel, the current will increase
with each additional turbine, but the voltage will not change.
OUTPUT OF SERIES VS. PARALLEL
Examples of a modern electricity generating
turbine and a water pumping turbine (not to scale)
MINI wind farm wired in series
MINI wind farm wired in parallel
R = Red wireB = Black wire
RRR
BB B
RR
R
R
B
BB
B

9
on the roofs of homes. Do an experiment and see if you think this is a
good idea. Can you design a shroud around the turbine to collect more
wind? Some inventors think this might be a good idea. What do you
think?
Wind park effect
Each wind turbine extracts some energy from the wind, so winds directly
downwind of a turbine are slower and more turbulent. For this reason,
wind turbines in a wind farm are typically placed 3–5 rotor diameters
apart perpendicular to the prevailing wind and 5–10 rotor diameters
apart parallel to the prevailing wind. Energy loss due to the “wind park
effect” may be 2–5%.
What effect do you find when you move the turbines around in your
MINI wind farm? Place a few turbines very close together, or right behind
each other. Do you notice a reduction in the efficiency of your wind
farm?
CIRCUITS
Series circuitParallel circuit
Bulb
(or other
load)
DC Generator
(such as your
turbine)
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
G
+
This wind farm was designed to minimize
“wind park effect.”
Example of a shrouded wind turbine.
5
7

10
Tips on Making Blades
Efficient blades are key to maximizing power from a wind turbine. Sloppy
or poorly-made blades will never produce enough energy to power
anything. It takes time and thought to make good blades!
An important concept to keep in mind when making turbine blades is
drag. Drag, or wind resistance, is the force that opposes the rotation of
the blades. The amount of drag a blade experiences depends on how
fast it is moving through the air and the surface area of the blade. Faster
rotation means more wind resistance. More surface area means more
wind resistance. Ask yourself, “are my blades creating too much drag?”
If they are adding drag to your system it will slow down and—in most
cases—low RPM means less power output.
Tips on improving blades
• Shorten the blades: Wind turbines with longer blades tend to generate
more power. While this is also true on our small turbines, it is often
difficult for students (and teachers) to make large, long blades that don’t
add lots of drag and inefficiency. Try shortening them a few inches.
• Change the pitch: Try making the blades atter toward the fan (0°–5°).
Pitch dramatically affects power output, so play with it a bit and see
what happens. You can use a protractor to measure the pitch.
• Use fewer blades: To reduce drag, try using 2, 3, or 4 blades.
• Use lighter material: To reduce the weight of the blades, use less material
or lighter material.
• Smooth surfaces: Smooth blade surfaces create less drag. Try removing
excess tape or smoothing rough edges to reduce drag.
• Find more wind: Make sure you are using a decently sized box or room
fan with a diameter of at least 14”–18”.
• Blades vs. fan: If the tips of your blades are outside the fan wind, they
are not catching any wind; they are just adding drag!
• Blade shape: The tips travel much faster than the root and can travel
faster if they are light and small.
Caution!
Do not touch the blades while they are spinning! They are moving very
fast and will hurt your hand if they hit you.
Do not stand in the “plane of rotation” of the blades (to the side of the
blades) in case something hits them and flies off. Stand in front of or
behind the turbine.
Wear safety goggles when the turbine is spinning.
Twisting the blades (0° near the tip and around
10°–20° near the root) can improve performance.
More Drag Less Drag
0° 45° 90°

11
The Power in the Wind
If a large truck or a 250lb linebacker was moving toward you at a high
rate of speed, you would move out of the way, right?
Why do you move? You move because in your mind you know that this
moving object has a great deal of energy as a result of its mass and its
motion. And you do not want to be on the receiving end of that energy.
Just as those large moving objects have energy, so does the wind. Wind
is the movement of air from one place to another. That’s the motion part.
What is air though? Air is a mixture of gas molecules. It turns out that if
you get lots of them (and I mean lots of them) together in a gang and they
start moving pretty fast, they can definitely give you a serious push. Just
think about hurricanes, tornadoes, or a very windy day!
Why aren’t we scared of light winds while we stay inside during a
hurricane or wind storm? The velocity of those gangs of gas molecules
have a dramatic impact on whether or not we will be able to stay
standing on our feet. In fact, in just a 20 mph gust you can feel those gas
molecules pushing you around.
Humans have been taking advantage of the energy in the wind for ages.
Sailboats, ancient windmills, and their newer cousins the electrical wind
turbines, have all captured the energy in the wind with varying degrees
of effectiveness. They all use a device such as a sail or blade to “catch”
the wind. Sailboats use wind energy to propel them through the water.
Windmills use this energy to turn a rod or shaft.
A simple equation for the power in the wind is described below. This
equation describes the power found in a column of wind of a specific
size moving at a particular velocity.
P=½ ρ(πr2) V3
P = Power in the Wind (watts)
ρ= Density of the Air (kg/m3)
1.2 kg/m3at sea level and 20ºC
r = Radius of your swept area (m)
V = Wind Velocity (m/s)
π= 3.14
From this formula you can see that the size of your turbine and the velocity
of the wind are very strong drivers when it comes to power production.
If we increase the velocity of the wind or the area of our blades, we
increase power output.
The density of the air has some impact as well. Cold air is more dense
than warm air, so you can produce more energy in colder climates. Swept area is the area of the circle inscribed by
the tips of a wind turbine’s blades.
r
Swept
area

12
The power of wind farms
Recall the Power in the Wind equation:
P = ½ ρ(πr2) V3
What are we changing in this equation when we add wind turbines and
create a wind farm? The density of the air will not change. Adding more
turbines will not change the wind velocity, either. The part of the equation
you are changing is the swept area (r).
Advanced Calculations
Determining the power output of your KidWind MINI
These calculations are more advanced than just measuring voltage or
current alone and require you to have learned how to use your multimeter
properly. During these calculations, be mindful of the units to which your
multimeter is set. Make sure it is set to volts or amps, rather than millivolts
or milliamps. If you do not use the correct units, your calculations will
come out wrong.
The equation for electrical power is shown below:
P = V × I
P = Power in watts
V = Voltage in volts
I = Current in amps
Example:
Your MINI Wind Turbine is producing 3v at 50mA. How much power is
your turbine producing?
P = V × I
P = 3 × .050 A
P = .15 watts
Ohm’s law
Using Ohm’s law, multimeter measurements, and resistors, we can do
some simple calculations to determine current output. The foundation of
these basic electrical computations is referred to as Ohm’s law, after the
German physicist George Ohm. In 1827, Ohm described measuring
voltage and current through simple electrical circuits containing various
lengths of wire.
Ohm’s law:
V = I × R
V = voltage in volts
I = current in amps
R = resistance in ohms
Typical output for the MINI:
Voltage: 1–4 volts
Amperage: 20–100 milliamps (.020–.1 amps)
If your numbers have come out much higher than this,
something is amiss. Check your units!
TYPICAL OUTPUT

13
Using algebra we can rearrange this equation so we can determine the
current from voltage and resistance:
I = V/R
Current = Voltage/Resistance (ohms)
Resistor = 50 ohms
Voltage = 1 volt
I = V/R
I = 1/50 = 0.020 amps = 20 milliamps
Computing power using voltage, current, and resistance
It can be difficult to calculate power by measuring current and voltage
simultaneously. You need two multimeters and lots of clip cords. In certain
situations, we can make this a bit easier using Ohm’s law.
Remember: Power = Voltage × Current
Using substitution of Ohm’s law, we can replace the current measurement
I with V/R and derive the equation below.
P = V × I
P = V × (V/R)
P = (V × V)/R
P = V2/R
If we know the voltage that our turbine is producing and the resistance in the
circuit, we can determine our power output.
Examples:
V = 3 volts
R = 50 ohms
P = V2/R
Power = (32) /50
= 9/50
= 0.18 watt
= 180 milliwatts
Using these equations, you can now easily calculate how much power your
turbine is producing in different experiments.
Wind Turbine Information
Windmills have been used for centuries to pump water or move heavy rocks
to grind seeds into grain. A wind turbine is the modern advancement of the
windmill, using the wind to turn an electrical generator instead.
Wind turbine scale
The smallest production wind turbines have a rotor diameter of 1m and only
produce enough power to charge a few 12 volt batteries: about 100 watts.

14
You
1.8 m
24 m
Residential scale
12 m
Water pumper
80 m
Utility scale
Scale of wind machines
A wind turbine that could power your whole house is still considered
“small.” This wind turbine might have a rotor diameter of 7m and could
produce 10 kW (10,000 watts) in a 25 mph wind.
A typical “large” or utility scale wind turbine has a rotor diameter of
80m and stands on a tower 80–100m tall. This wind turbine could
produce 1.5 MW (1,500,000 watts)—enough electricity for about 400
American homes in a 30 mph wind.
Utility scale turbines are getting bigger and bigger. Some turbines today
can produce over 5 MW and have a rotor diameter of 126 meters!
Energy transformations
Wind turbines transform the kinetic energy of the wind into electricity.
The force of the wind on the blades causes them to move. Blades are
usually shaped like airfoils, using lift to spin the blades faster than the
wind.
The blades and the hub together are called the rotor. The blades on
large utility scale turbines change their pitch to react to wind speed. The
red blades on your MINI have a fixed pitch, more similar to a residential
scale turbine. With the crimping hub, you can manually change pitch.
As the rotor turns, it spins a drive shaft which is connected to a generator.
The spinning generator converts mechanical (rotational) energy into the
electrical energy we use every day. Many large wind turbines often have
a gearbox between the rotor and the generator, so that the generator
can spin much faster than the blades are spinning.
Generators on large grid-connected turbines spin at 1200 to 1800
revolutions per minute (RPM). On the smaller, residential turbines, the rotor
and the generator spin at the same speed, anywhere from 0–500 RPM
since there is no gearbox.
Your MINI does not have a gear box and is considered a “direct drive”
device. That means you have to get the blades spinning very fast to
create usable power. Large turbine manufacturers have started to make
turbines without gearboxes, but to do this they need generators with lots
of heavy magnets and wire. This makes the tower designers job much
more difficult.
At KidWind we have other kits which let you experiment with
gearboxes and winding your own generators. Check them out
in the at www.KidWind.org.
OTHER KIDWIND KITS
The airfoil shape of most wind turbine blades uses
lift to increase rotor speed.
Lift

15

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