ALTurbine
Adaptable Learning Turbine
Copyright ©2008
Kidwind Project
2093 Sargent Avenue
Saint Paul, MN 55105
http://www.kidwind.org
This work may not be reproduced by mechanical or electronic means without
written permission from KidWind, except for educational uses by teachers in a
classroom situation or a teacher training workshop. For permission to copy
portions or all of this material for other purposes, such as for inclusion in other
documents please contact Michael Arquin at the KidWind Project at
michael@kidwind.org.
We would like to thank the Wright Center for Science Education at Tufts University
for giving us the time and space to develop a nugget of an idea into a useful
project for hundreds of teachers.
We would also like to thank Trudy Forsyth at National Wind Technology Center and
Richard Michaud at the Boston Office of the Department of Energy for having the
vision and foresight to help establish the KidWind Project. Lastly we would like to
thank all the teachers for their keen insights and feedback on making these wind
turbine kits and materials first rate!
4/15/2009 — ALTurbine
2
Adaptable Learning Turbine Parts List (FULL KIT)
Wood Tower
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◊
(2)
(1)
2 x 4 Interlocking wood boards with drilled hole
2’ Wooden Monopole Tower
Nacelle Parts
◊
◊
◊
◊
◊
◊
◊
◊
◊
(1)
(2)
(4)
(2)
(4)
(4)
(8)
(2)
(2)
12-Hole Crimping Hub w/attached driveshaft
Molded plastic nacelle sections
Different sized gears + (1) gear key
4” Bolts
Wing nuts
Hex nuts
Small screws
Additional steel drive shafts
DC Generators with wires attached
Wires, Accessories, Output Devices & Blade Materials
◊
◊
◊
◊
◊
◊
◊
◊
◊
◊
◊
(2)
(1)
(2)
(1)
(1)
(1)
(25)
(5)
(5)
(1)
(1)
Alligator Clip Wires
Simple Multimeter
LED Bulb and Incandescent Bulbs
DC Motor w/ Yellow Mini Prop
Mini-Pump and Cylinder System
Ultra Capacitor
1/4” diameter poplar dowels
18” sheets of balsa wood
15” coroplast sheets
Protractor
Sheet Sandpaper
Tools
To build this turbine, you’ll need at minimum wire strippers a screwdriver, tape, and glue.
4/15/2009 — ALTurbine
3
Adaptable Learning Turbine
These instructions will show you how to
build the Adaptable Learning Turbine. While
some parts come pre-assembled, you will
have to put a few things together to finish
the job. This turbine allows for maximum
variability and experimentation while
dramatically increasing power output
through the use of gears.
Cool Features of the ALTurbine:
The ALTurbine is our most powerful, adaptable and experimental turbine. It is also
our most eco-friendly design!
Adaptable:
◊ Interchangeable gear ratios—up to 8:1
◊ Ability to test BOTH electricity production and weighlifting
◊ Interchangeable generators—test different DC motors
◊ Can easily be converted to a yawing wind turbine
◊ Can fit two generators and/or rotors at the same time (MORE power!)
Renewable:
◊ Forest Stewardship Council (FSC) Certified Renewable Wood Tower
◊ All plastic parts are made from 100% recycled plastic!
Awesome!
◊ Can produce upwards of 12+ Volts!
You can use your ALTurbine to power a variety of accessories, such as:
•
•
•
•
Fuel Cells
LEDs
Incandescent Bulbs
Mini Water Pumps
4/15/2009 — ALTurbine
•
•
•
Small Motors
Ultra Capacitors
Any other small applications
that you can think of
4
Building a Tower for the ALTurbine
Wood Tower
1. Connect the two 2 x 4 base boards to make an “X”
2. Slide in the 2 foot wood pole. If the pole is too tight,
you can sand it a little bit, but it should be a snug fit.
*NOTE* In humid weather, the wood may expand. It
will still fit, but will require a bit more sanding.
3. The pole will only fit if the 2x4 base boards are put
together a certain way. If it is not fitting, try reversing
one of the 2x4 boards.
4. Now simply attach the nacelle (head) to the top of the
tower.
The ALTurbine can also be mounted on a PVC tower.
Here is how to build it:
Parts Needed: (All 1” diameter)
♦ (4) 90° PVC fittings
♦ (6) 6” PVC pipe sections
♦ (3) PVC T fittings Drill a small hole in one “T”
♦ (1) 24” PVC pipe section
1. Using (4) 90° PVC fittings, (2) PVC Ts and (4) 6” PVC
pipe sections, construct the two sides of the PVC
turbine base. Make sure in this step to use the PVC
(2) Identical Base Sides
Ts that DO NOT have a hole drilled in them.
2. Fit the parts together without using glue (PVC glue is
really nasty stuff). To make them fit snuggly tap
them together with a hammer or bang them on the
floor once assembled.
3. Next, connect the two sides of the base using the
PVC T with the hole. The hole will allow you to snake
out the wires from the DC motor.
Sides joined
together.
Make sure to
use a PVC T
with a hole
drilled so you
can get the
wires out!
4. Slide the generator head (nacelle) onto the tower.
Run the wires down through the post and through the
hole in the PVC T at the center of the base. Attach
the tower to the base.
5. Attach alligator clips to the wires. Then straighten all
parts and make sure joints are secure.
4/15/2009 — ALTurbine
5
Building the Nacelle
1) Take the 2 identical molded nacelle parts and fit them together.
Each side has 3 small holes. Secure the two sides together by screwing
6 small screws into these holes.
2) Take a wing-nut* and screw it about 2/3 of the way up the
4” bolt. Next, slide the 2 motor mount sections up the bolt such
that the two concave sections are facing each other (see
picture). Then screw a hex-nut onto the bolt under the mounts.
3) Notice that the top of the nacelle has
cutouts shaped for the top of the bolts. Slide
the bolt (with nuts & mount) into the
cutouts. Then attach a wing-nut onto the
bottom of the bolt so that it is secured to the
molded nacelle.
4) Now take the second 4” bolt and screw a wing-nut about
1/3 of the way up. Slide that bolt into the top cutout and
through the motor mounts. Take a hex-nut and screw it onto
the bolt under the mounts. Move the wing-nut up the bolt so
that you can slide the bolt all the way down to the bottom cutout. Now secure the second bolt with another wing-nut as you
did with the first bolt.
5) Secure all the nuts and bolts so that the nacelle is tight and secure. Be careful not to
over-tighten the wing-nuts on the bottom of the nacelle, or you will bend the nacelle. Over
-tightening will probably not break anything, but it can make your turbine less efficient.
Too
tight!
Done!
*Note* When constructing the nacelle, the wing-nuts and hex-nuts may be used interchangeably. While wingnuts are easier to adjust, the smaller size of the hex-nuts allows for more variable configurations.
4/15/2009 — ALTurbine
6
ALTurbine Gears and Motors
6) Now you are ready to attach a generator to the nacelle.
Choose a DC motor to use as your generator and loosen the
motor mounts until you can fit the motor between them. Then
tighten the nuts down onto the motor mount to hold the motor
securely in place.
Optional: If you are using a PVC tower, you can snake the wires
from the motor through the slot in the nacelle behind the motor
mount. Then the wires can go down through the PVC pipe. On a
wood tower, the wires can go out the side of the nacelle. You can
attach the wires to the wood tower with zip-ties or tape.
7) Attach the smallest gear (pinion) to the driveshaft of
the DC motor. The small hole in this gear should friction
fit onto most small DC motor driveshafts.
8) Choose a gear to use and push it
onto the long driveshaft that is
connected to your 12-hole crimping
hub. Notice that the hub and the
gears both have small notches that
key into each other. Line up the
notches so that the hub and gear can
rotate together.
NOTE: The ends of the driveshaft may be
sharp. Use sandpaper to sand off edges.
9) Slide the driveshaft with attached hub into the
hole at the top of the nacelle. You will now need to
move your DC motor up or down so that the pinion
gear meshes with the gear on the hub.
Note: If you are using the largest gear size, you will
notice that it will only fit with regular nuts under the
motor mounts, as wing-nuts are too tall. If you are
using the smallest gear size, you will have to use
regular nuts above the motor mounts. Give the hub
a spin to make sure that the gear turns and rotates
the small pinion gear on the motor.
4/15/2009 — ALTurbine
7
10) Now slide the small gear key onto the
back of the driveshaft where it sticks out the
back of the molded nacelle. Slide it up pretty
close to the nacelle, but if it is too close it will
add friction as the turbine spins. This will
keep the driveshaft from sliding forward as
you are moving it around.
Remember to be careful since the end of the
driveshaft may be a bit sharp! Sanding the
end is a good idea.
Gearbox and
generator in
rear
The gear key allows you to move the whole
gearbox and generator to the back of the
turbine, leaving the hub and rotor in front.
Simply slide the main driveshaft out and slide
it in the opposite side. Next slide a gear onto
the back of the driveshaft, followed by the
gear key to hold the gear in place. Again, be
sure to line up the main drive gear with the
pinion attached to your DC motor.
Gearbox and
generator in
front
11) The completed nacelle will slide right onto your
tower! You can secure the nacelle in place by screwing
in one or two more small screws in the holes at the
bottom of the nacelle.
Now it’s time to build yourself some
blades and start exploring the wonders of
wind energy!
4/
More Important Notes on the ALTurbine
How to Make the ALTurbine a Weightlifter:
Lifting weights with your wind turbine is another
great way to explore wind energy. Before wind
turbines were used to generate electricity,
windmills were used to grind grain and pump
water. These windmills had very different
characteristics from the modern electricity
producing wind turbines.
The ALTurbine can easily be converted to a
weightlifting turbine. Remove the DC motor and
String (tie
its mount. Leave the hub and driveshaft
and tape on)
attached to the nacelle, and push the gear key
to the back of the driveshaft. Now tie a string
onto the driveshaft. It is a good idea to tape the
string down on the driveshaft so that it does not slip
on the shaft. Attach the other end of the string
securely to a cup. This cup will hold your weights—
nuts, bolts, anything you have laying around. With
blades on the hub, the rotation of the driveshaft
should draw up the cup. See how much weight you
can lift with wind power!
It is also a cool experiment to compare blades for
electricity and weightlifting. Do blades that work
well for making a lot of voltage also work well for
lifting a lot of weight? What is different about your
blades, and why does that make them better for
different applications?
Blade Strike: If your blades have a lot of pitch (high
angle), it is possible that the blades will hit the nacelle or
pinion gear and get stuck. If this happens, try a shallower
pitch (angle) or move the blade further down the dowel
so that the blades can freely rotate.
Blade Strike
4/
Add a spacer to the ALTurbine for more pitch variability
If you want to experiment with higher blade pitches, it is a
good idea to insert this plastic spacer behind the hub of
the ALTurbine. Without the spacer, the blades will strike
the nacelle or pinion gear if their pitch is too steep. The
addition of this spacer moves the blades further from the
nacelle so that they can be pitched all the way to a flat 90
degrees without striking any part of the turbine.
Remove the hub and driveshaft from the nacelle. If you have a gear attached to the hub,
you will have to remove this as well. Slide the
spacer down the driveshaft behind the hub.
You can choose where to locate the gears and
generator—on the front side or back side of the
nacelle. In either location, you will need to use
the small gear key to secure the larger gear in
place since the gear can no longer be attached
to the hub.
As you push the larger gear in place, be careful to make
sure that it lines up and meshes with the small pinion
gear. Once you have it set in place, the gear key should
hold it securely as the turbine rotates. If the gear key is
slipping when the turbine rotates and your gears are not
spinning, make sure there is not too much friction between the gears. You can also add a little bit of glue or
tape on the gear key to hold it in place.
4/15/2009 — ALTurbine
10
The ALTurbine Dual-Generator System
Dual generators
The ALTurbine can be set up with a dualgenerator system. If you buy another set
of motor mounts and nuts and bolts, you
can attach a DC motor to the front and
back of the nacelle. On the setup pictured,
the front motor was producing 12 volts and
the rear motor was producing 5 volts.
You can wire the two generators together in
series or in parallel. If you connect them in
series your voltage will increase. If you
connect them in parallel, your amperage
will increase.
Before you connect the generators, you
need to determine their polarity.
Finding Polarity:
To correctly connect two or more generators in a circuit, you will need to
find the polarity of the wires coming from each generator. Finding the
polarity means figuring out which wire is positive (+) and which is
negative (-).
Connect your wind turbine to a multimeter. Make sure that the
multimeter leads are in the correct ports, as shown in the picture (black
to the left, red in the middle). Place the turbine in front of a fan, and get
a voltage reading. If your voltage is a positive number, the wind turbine
wire connected to the RED multimeter lead is positive (+). If your
voltage reading is negative, the wind turbine wire connected to the RED
multimeter lead is negative (-). Once you have established which wire is
positive and which is negative, it is a good idea to mark them with some
tape so you remember.
The polarity of the wires is determined by the direction your blades are
spinning. By changing the direction of spin you will change the polarity
of your wires.
If you are connecting the generators in series, connect the wires from
positive to negative, making one continuous loop through the circuit.
If you are connecting the generators in parallel, connect each positive and negative wire
separately to the leads of the load or meter.
If you have another hub, you can even try a Dual-Rotor setup on your ALTurbine!
Slide the other hub onto the back of the driveshaft and attach another set of
blades to it. Make sure your blades are pitched correctly!
4/15/2009 — ALTurbine
11
Using Mini-Supercapacitors to Store Energy
A capacitor is similar to a battery because it can store
and release electrical energy. But the way that capacitors work is very different from the way batteries
work.
Small supercapacitors
Batteries are charged by chemical reactions. Every
battery has two terminals. The chemical reactions inside the battery produce electrons on one terminal and
absorb electrons on the other terminal. The chemical
reaction is reversed to deliver the energy of a battery.
A capacitor does not use chemical reactions at all. Instead, two metal plates separate negative charges from positive charges, creating voltage.
Supercapacitors (also called “ultracapacitors”) are different from normal capacitors because they are able to hold a much greater charge. Therefore, the potential
is greater, and the total energy stored can be much higher.
Chemical reactions can take some time, but releasing the energy stored in capacitors can be done very fast. For this reason, capacitors are able to release an enormous amount of power in a very short time. However, batteries can release steady
voltage for a longer period of time, while most small supercapacitors only store
enough energy for a few minutes of voltage.
Charging Supercapacitors:
Charging a supercapacitor with renewable energy is very easy, but
there are some important steps to follow. Supercapacitors are polarized, which means that they have positive and negative terminals. Because of this, you have to properly connect your electricity source
(wind turbine, solar cell, etc.) to the supercapacitor. Sometimes the
terminals are marked with (+) and (-) signs, but you can always be
sure that the longer lead from the supercapacitor is the positive terminal.
See the next page for instructions on determining polarity.
Larger supercapacitors are used in hybrid-electric vehicles. They are charged when
the vehicles brake, and discharged to enhance acceleration.
4/15/2009 — ALTurbine
12
Charging a Supercapacitor
You can use a renewable energy!
To determine the proper polarity of your turbine or solar cell, you will
need to connect it to a multimeter. Make sure the wires from the multimeter are correctly installed as shown in the picture (black wire goes in
COM port). If your voltage reading is positive, the lead connected to the
red multimeter wire comes from the positive terminal. If the voltage
reading is negative, the lead connected to the red multimeter wire comes
from the negative terminal. It is a good idea to mark your wires with
tape so you know which is positive and which is negative.
The positive lead from your wind turbine, solar cell, or battery should
attach to the long (+) lead on the supercapacitor. The negative lead
goes to the short (-) lead on the supercapacitor.
If you are sure you have the correct polarity, you can start to pump
some energy into the supercapacitor! Turn the fan on to start your turbine or shine some light on your solar panel. Then wait about 1 1/2—2
minutes. After this time the supercapacitor should be charged up pretty
well. Now you can use this stored energy to power small electrical
gadgets!
Experiments and Activities with Supercapacitors
Although these are relatively small supercapacitors with low overall power, they can still do a
good amount of work after you charge them up!
With the supercapacitor charged up, it will start
powering devices as soon as you complete a circuit. Remember that LED and incandescent bulbs
are also polarized, so you might have to switch
the leads before you can get them to light up.
4/15/2009 — ALTurbine
What Can Kidwind SuperCapacitors Power???
• Light LED bulbs
• Light incandescent bulbs
• Pump water (with KidWind
low-voltage water pump)
• Drive motors
• Cars
• Boats
• Planes/props
• Other?
13
Gear Ratios
You may have learned about the way an electric
generator works: A coil of wire is rotated in a
magnetic field to create a flow of electrons. This
is the basis of how a wind turbine makes
electricity. The blades spin, causing a driveshaft
to spin, which in turn rotates the coils in the
generator. The problem is that to make the type
of electricity we use every day, the generator
has to spin VERY fast. To simplify, the faster the
coils rotate near the magnet, the more electrons
will be pushed along.
If you’ve seen a real utility-scale wind turbine, you
probably noticed that the blades spin pretty slowly. So
how do they get the generators to spin fast enough?
They do this by using gears. You have probably used
gears on a bicycle before, so you know how they work.
Gears give a wind turbine a mechanical advantage.
This means that they multiply the mechanical force of
the turning blades. This is done by using gears with
different numbers of teeth. When the larger gear
makes one full revolution, the smaller gear has to spin
faster to keep up.
Routine maintenance on gears
A “Gear ratio” is the relationship between the number of teeth on two or more
gears that are meshed. So when you ride your bicycle, the gear in front might
have 48 teeth, while the gear in back has 16 teeth. That would mean every time
your pedals spin around once, the back wheel spins three revolutions (48/16 = 3).
This is called a 3 to 1 (3:1) gear ratio. Wind turbines
work the same way except that they have much
larger gear ratios. A modern wind turbine may have
a gear ratio of 100:1 or more. So every time the
blades make one revolution, the generator shaft
spins 100 times!
The Kidwind ALTurbine offers 3 different gear ratios.
The smallest gear attaches to the generator
driveshaft and is called the spindle. This gear has 8
teeth. The other 3 gears attach to the rotor. One has
16 teeth, one has 32, and the largest has 64 teeth.
What are the possible gear ratios of the ALTurbine?
Do some experiments to find out how different gear
ratios change the torque and power dynamics of
your Kidwind ALTurbine!
4/15/2009 — ALTurbine
ALTurbine Gearbox (8:1 ratio)
14
Building & Attaching Blades
Caution!!
Never make blades out of metal or any sharp edged material because they
could cause injury during testing. Blades tend to spin very fast (300-600
RPM) and can easily cut people if they have sharp edges.
1. To make blades, carve or cut different shapes and
sizes out of a variety of materials (wood, cardboard,
felt, fabric). Tape or hot glue them to the dowels.
Students have made blades out of styrofoam bowls,
pie pans, and paper and plastic cups. Anything
you find around the house or classroom can be made
into blades!
2. Before testing check that the blades are securely
attached to the dowel. If not secured properly, they
may detach or deform as you test your turbine in high
winds. We recommend using a combination of tape
and hot or regular glue.
3. Insert the dowels into holes on the crimping hub. It is
important to tighten the hub when inserting the blades
so that they do not come out at high speed.
4. When attaching the
blades to the hub
consider a few
important questions:
• How close is the
root of your blade to the hub? What do you think is
optimal?
• Are your blades about the same size and weight?
Blades that are not balanced will cause vibrations
that can reduce the efficiency of your turbine..
• Are the blades equally distributed around the hub?
If not you can also have a set up that is out of
balance.
• Have you secured the hub after you inserted the
blades? If not they can fly out at high speed!
• Want to know how fast your blades are
spinning? Get a Hangar 9 Micro
Tachometer.
Pie plate used to catch the wind.
As the crimping hub can be
separated into two parts you can
try different creative ways to
attach “blades” to the hub. One
of the best blades we ever saw
was made from a pizza pie box!
Again, DO NOT USE sharp metal or very hard plastic
to make blades, because blades can spin at very high
speeds (500RPM) and could cause injury.
4/15/2009 — ALTurbine
SAFETY & BLADE TESTING AREA
•
It is important to wear safety goggles testing blades.
•
NEVER make blades out of metal or any sharp edged material
as these could cause injury while spinning fast during testing.
SETUP FOR TESTING
Safely set up your testing area like the picture below. It is important to clear this
area of debris and materials.
Make sure the center of the fan matches up with
the center of the wind turbine. You may need to
raise your fan with some books or a container.
Stand In Front or Behind Turbine
Some things to note about fan wind that reduces
the efficiency. Fans create;
•
•
•
Highly Turbulent & Rotational Wind— Blades
may spin better one direction than another
Highly Variable Wind Speed— Wind speed is
about 10-13 MPH on high for a $20 circular
fan. Wind speeds near the middle will be
much different than the edges.
Limited Diameter— Blades bigger than the fan will not “catch” more wind—they
will just add drag and slow down your blades.
How to Clean Up Wind?
Want some more “professional wind”? You can try to build a simple wind
tunnel. Lots of plans can be found online (search term:classroom wind
tunnel or go to www.kidwind.org). One simple way to make more
laminar—smooth, straightened—flow is to build a honeycomb in front of
your fan using milk cartons, 2” PVC pipe or some other material.
Going Outside?
If you want to use your wind turbine outside, you must make sure that
it faces into the wind. Wind turbines are designed to YAW (or rotate)
to face the wind. If the wind shifts, and the turbine cannot rotate,
wind will hit the blades from the sides causing stress and inefficiency.
If you want to experiment outside with a yawing wind turbine, check
out the KidWind Yawing Add-On Tower. This yawing tower works great
with the ALTurbine.
4/15/2009 — ALTurbine
16
Some Blade Building Tips
KidWind model wind turbines are designed for use in science classes, or as a hobby or
science fair project. Their purpose is to give students an affordable way to perform various
blade design experiments quickly. Efficient blades are a key part of generating power
from a wind turbine. Sloppy or poorly-made blades will never make 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. Ask yourself,
“Are my blades creating too much DRAG?”. Your blades are probably catching the wind
and helping to spin the hub and motor driveshaft, but consider the ways that their shape or
design might be slowing the blades down as well. If they are adding DRAG to your system
it will slow down and in most cases low RPM means less power output.
Some 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. See what happens when you shorten them a few centimeters.
•
CHANGE THE PITCH - Students commonly set the angle of the blades to
around 45° the first time they try to use the turbine. Try making the blades
flatter 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. Finding a way to TWIST the blades (0° near the tips and around 10° - 20°
near the root) can really improve performance.
0°
45°
90°
Wind Source
•
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 - Are your blades bigger than your fan? If the tips of your
blades are wider than the fan you’re using, then they’re not catching any wind–
they are just adding drag!
•
BLADE SHAPE - Are the tips of your blade thin and narrow or wide and
heavy? The tips travel much faster than the root and can travel faster if they are
light and small, which means that if you have wide or heavy tips you may be
adding lots of drag.
4/15/2009 — ALTurbine
17
How to use the Multimeter
To accurately measure power production you should use a multimeter. Small DC motors like the
one you’re using do not produce much power when spun slowly. On the Geared PVC Wind Turbine,
gears cause the shaft of the generator to spin faster, increasing power output. Well designed
blades can produce around 3 volts at 1/2 amp. With this level of power output you can light small
bulbs, LEDs, small DC motors, fuel cells, and water pumps.
Power (Watts) = Voltage (V) x Current (A)
<—- Watch Your Units
Make sure you are recording volts and amps (not milli or microvolts unless you want to!) If your
readings are higher than 1— 2 watts you have done something wrong!
Voltage
1. Attach the wires from the generator to the
multimeter. Color does not matter!
2. To check the voltage select DC Volt (V) and
set the whole number to 20 volts.
Set to 20 DC Volts
3. Place your turbine out in the
wind or in front of a fan and let it run.
It is normal for the readings to
fluctuate. Power output is often unsteady because the
wind is inconstant or your blades are not balanced.
4. A set of very well designed blades may make around 2 — 4 volts.
Typical blades will be in the 1—2volt range.
5. When measuring voltage you are calculating how fast the DC generator is spinning.
The faster it spins the higher the voltage. Since there is no load on the generator it
has very little resistance and can spin very fast. If you look closely when you attach a
load (bulb, pump) the RPM will drop as will your voltage.
Amperage
1. To get a more accurate picture of the power output of
your turbine measure amperage as well. To accurately
measure the amperage you must hook up your
multimeter differently.
2. Place a load (a resistive object - small LED bulb, resistor,
pump etc.) in series with the meter so that the
generator is “loaded” and has to do work.
3. A set of very well designed blades will produce around
0.4 amps (400 milliamps) with this motor. Typical
blades will make .1-.3 amps (100 – 300 milliamps).
This will vary based on your resistive load (bulb, pump).
4. When measuring amperage you are gauging how many
electrons are being pushed through the wire by the
turbine. This relates to the torque your blades are
generating.
Wind Turbine
wires
meter
Probes from the
multimeter
load in series
To accurately record current you
need to put a load in series. In
this picture you can see the load
(bulb) between the connection
with the meter and the turbine.
DON’T FORGET TO TURN OFF THE METER WHEN YOU ARE DONE OR THE BATTERY
WILL DIE!!
4/
15
Factors that Affect Power Output
Now that you have a wind turbine, lets start exploring what factors affect the amount of
power your turbine produces. Here are a few places to start;
•
•
•
•
Wind Speed
Generator Type
Blades
Gear Ratio
Wind speed is an easy variable to change. Take your turbine and place it in front of a fan
at three different distances. How does the power output change. Think about this in
relation to the Power in the Wind equation on page 12. To more accurately measure the
wind speed of your fan get a wind meter from Kidwind (www.kidwind.org) or search some
ideas on the web to build your own.
Generators
The DC generator in your wind turbine is actually a DC motor
that spins using the energy in the wind. The magnets and wires
in the generator transform the energy in the wind into
electricity. By manipulating the strength of the magnets used
and coils of wire inside the generator we can affect the power
output. In this kit we provide you with a DC generator
preinstalled in the gearbox. If you wanted you could compare
this to a different DC generator that you harvest from some old
electronics in your house, but you would have to build another
gearbox. Old VCRs, electrical toys and CD players are good
places to start finding DC motors and gearboxes Do some
research on how generators work or electromagnetism to learn
more!
Blade Design
Blade design experiments are an entertaining place 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. As we mentioned above the spinning shaft of the generator
spins wires near magnets to generate electricity. How well you design and orient your
blades can greatly impact how fast these blades spin and how much power your turbine
produces.
Experiments with blades can be simple or very complicated, depending on how deeply you
want to explore. Some blade variables you can test include:
•
•
•
Length
Number
Pitch
•
•
•
Shape
Materials
Weight
If you are doing this for a science fair or project you should focus on just one of these.
variables at a time as your results can get confusing quite quickly.
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Powering items with your ALTurbine
This geared turbine puts out some serious power, so you can put it to use! Try hooking it
up to some different loads like the Kidwind Water Pump, a Fuel Cell, a buzzer or
noisemaker or a short string of Christmas lights.
Light Bulbs & LEDs
You can use the ALTurbine to light small incandescent bulbs or LEDs. LEDs
require much less current then incandescent so they are easier for the turbine to
light. You can also use other bulbs from flashlights just make sure they are
designed for low voltage and low current.
LED lights need at least 1.75 volts to light, but very little
amperage. LEDs also require that the electricity runs in the “right”
direction. If your turbine is making more than 2 volts, but the LED
is not lighting try reversing the turbine output wires that are
connected to the LED bulb and try again.
Small Motors
The power needs of most small DC motors are pretty minimal, especially if they happen to
have a low voltage rating. The Geared PVC Wind Turbine can easily power a variety of
small DC motors. Look for small DC motors in broken electrical toys. You can also find a
wide variety of at Kelvin.com, Pitsco or All Electronics online electronics store.
You need around .6 - .8 volts to power a small motor with propeller.
Low Voltage Water Pumps.
KidWind uses a low voltage water pump that works well with our wind
turbines. You need to produce around 2.0 volts for this pump to run
well and a good deal of torque as pumping water requires a great
deal of energy. This is one of our favorite demonstrations using wind
energy. We typically hook it up to some type of graduated cylinder
to see whose turbine blades can pump the most amount of water in 1
-2 minutes! Do not try to run 6V or 12V aquarium pumps using
our wind turbines it will not work!
Fuel Cells
Using this wind turbine you can generate enough electricity to
run a simple fuel cell. When you run electricity through the
fuel cell it will create hydrogen and oxygen in a storage
chamber which can be recombined to generate electricity.
You could use this stored electricity to run the mini-water
pump, a small DC motor or you can attach it to a fuel cell car
and see how far it travels on two minutes of wind produced
electricity-the ultimate in closed loop travel!
To run this device your turbine needs to produce at least 1.75 volts. More than 2.0
volts for sustained periods can also damage your fuel cell so be careful.
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20
Power in the Wind — A Simple Look
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.
air from one place on earth to another. That’s the motion part.
Wind is the movement of
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 sailboat or a windmill — 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, blade or
fabric 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 a
the power found in a column of wind of a specific size moving at a particular velocity.
P = Power in the Wind (watts)
ρ = Density of the Air (kg/m3)
r = Radius of your swept area (m2)
V = Wind Velocity (m/s)
∏ = 3.14
r
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.
P = 1/2 ρ (∏ r2)V3
How much wind power is coming
from a regular house fan?
V = 5 m/s (meters/sec)
ρ = 1.0 kg/m3 (kilograms/cubic meter)
r = .2 meters
A = .125 m2 (Area of Circle = ∏r2)
Power in the Wind = ½ρAV3
= (.5)(1.0)(.125)(5)3
The density of the air has some impact Power
= 7.85 Watts
as well. Cold air is more dense than
warm air so you can produce more
There are 7.85 watts of wind power coming
energy in colder climates (as long as
out typical house fan on high. Can our little
the air is not too thin!).
turbines capture all of this power? Do some
research on the BETZ LIMIT to find out.
4/15/2009 — ALTurbine
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ALTurbine FAQ
Why won’t the rotor spin when I put my turbine in front of the fan?
Check the orientation of the blades. Are your blades oriented in the same direction? Are
they flat? Are they hitting the tower? Look at some pictures of old and new windmills to
get some ideas about how to orient your blades.
Why does the gearbox seem to turn slowly or feel stiff? The addition of the gearbox
adds some friction to the system. Because of this you will need to make sure that your
blades generate enough TORQUE (turning force) to overcome this friction.
Why does the turbine slow down when I attach it to a load (pump, bulb, motor)?
Loading the generator forces it to do work. This makes it harder to push electrons through
the circuit. The more load you add the harder it is for the generator to turn and the more
torque you must generate from the blades. The only way to do this is to make bigger
blades or relocate your wind turbine to a place with higher wind speeds.
Why are the readings on my multimeter all over the place?
Your readings may be fluctuating because the wind coming out of your fan is fluctuating.
This can also be caused by blades that don’t spin smoothly or change shape as they spin.
Additionally, if your blades are not balanced, evenly distributed, or are producing unequal
amounts of drag your readings will be irregular.
I bent a driveshaft! How do I fix it?
If you (or your student) bent a driveshaft, don’t worry! Hold the driveshaft tightly with a
pair of pliers as you pull on the hub. The hub will pop off when you give it a good tug. Now
take one of the extra driveshafts included in your kit and push it into the hub. A little spot
of glue will secure it. Remember to sand any sharp ends of the driveshaft.
Is a fan a good wind source to test with?
Well, it is the best we’ve got, unless you have a wind tunnel handy! The wind that comes
out of a fan has a great deal of rotation and turbulence. It isn’t very smooth. While it will
still makes your turbine spin it is not exactly like the wind outside. To see this turbulence,
hold a short piece of thread in front of a fan and move it from the center out. It should
head out straight all the time...does it?
Can I take my turbine outside? Can I leave it there?
You can certainly take, use and test your wind turbine outside. But unless you have a
yawing tower (available from KidWind) it will not track the wind and may not perform
optimally. To make it work well you will have to continually face it into the wind. It is not
a good idea to leave your turbine outside for too long. It is designed for basic lab tests
and not to endure the rigors of the outdoor environment!
Based on the power in the wind equation it seems that longer blades should
make more power. On my turbine this is not true!! WHY??
The blades on your turbine may be bigger than the diameter of the fan. If that is the
case, the extra part is only adding drag so your blades will slow down. Additionally, if you
design large blades poorly they will have lots of drag near the tips and slow down. This
will negate any positive effect of the added length. Also, short blades spin faster than
4/15/2009 — ALTurbine
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