PicoTurbine Windmill Kit

PicoTurbine Windmill Kit

PicoTurbine makes an excellent small group project for grades 5 through College. For the younger grades (5 and 6), it is recommended that the teacher perform some of the construction in advance of the class in order to save time, for example bend the yoke wire into the U shape. Children below about grade 7 or 8 may not be able to do this accurately enough. It is also recommended for grades 5 that the teacher handle the screwdriver to screw the yoke to the wooden base and install the center screw.

By performing this as a small group project, it is possible to complete the project in about 30 to 40 minutes, as long as you use a paste or glue-stick to glue the paper templates to the cardboard, so they are dry enough to work with in about 10 minutes or less.

Alternatively, you could glue the parts in advance, or break the project across several periods (do the gluing and yoke in a 20 to 25 minute session in the morning, and complete the project in a 20 to 25 minute session in the afternoon when everything is dry). Of course, the project could also be broken across two school days.

A reasonable set of tasks that can be done simultaneously by a group would be:

• One person cuts out templates and glues them to cardboard.
• Simultaneously, another group member bends the yoke wire and prepares the base screws.
• After the above tasks are complete, one member attaches the blade coverings to the blades while another attaches the magnets to the rotor and a third attaches the wires to the stator.
• Finally, the project is assembled by the group.

Renewable Energy Education

PicoTurbine is an excellent project to supplement science and environmental lessons. It is especially relevant during Earth Day celebrations.Here are some fun facts about wind power as a renewable energy source that you can use in your curriculum.

• Germany is currently the number one producer of wind powered electricity in the world. As of 1999, Germany had 4,000 megawatts of installed wind capacity, as much as two large nuclear power plants. The United States has about 2,500 megawatts of installed wind capacity. Most “wind farms” in the USA are located in California, and they may have dozens, and in some cases thousands of windmills. The Netherlands and Denmark also have aggressive plans to increase wind power in their countries.
• Commercial sized wind electric generators can produce between 100,000 and 2 million watts of power, as compared with little PicoTurbine which produces only a fraction of a watt.
• Wind power has been used for thousands of years. Early designs were used in Mesopotamia to grind wheat. Grinding and pumping water were the two biggest uses of windmills before the 20th century. Even today, thousands of water pumping windmills are used in the central and western portions of the USA, saving millions of tons of pollution and providing water in remote areas.
• There is enough wind in two states (Texas and Oklahoma) to produce all the electricity used in the entire USA if it were fully developed.
• Wind power and hydro-electric power are currently the only alternative energy sources that are clearly competitive in cost with fossil fuel electricity generation. Solar electricity is still more expensive than fossil fuel power generation. However, fossil fuels cause pollution, so renewable energy proponents argue there is a hidden cost that will be paid by future generations for burning fossil fuel, and this hidden cost makes renewable energy more economical in the long run.
• Currently, hydro-electric generation produces about 10% of all power in the USA, however there are few remaining sites that can be developed for major amounts of power. For this reason, wind power has more potential for future clean energy production in the USA than hydro.
• Wind and Solar power are very complementary renewable electricity sources, and are often used in combination for power in remote areas. For example, the sun is less intense in the winter, but wind is usually stronger in the winter (cold air is denser, leaves that block wind are not on trees in winter, etc.). The sun doesn’t shine during rainstorms, but the wind is usually higher during storms.
• The United States has a goal to produce at least 2% of all electric power using Solar and Wind within 10 years. Some states have goals of 5%.
• Wind generators do not produce any chemical pollution, but they do produce some “noise pollution.” For this reason, large commercial wind farms are usually placed away from heavily populated areas. Scientists are working to reduce the noise levels of the whirling blades (great strides have been made in the last 10 years).
• Some environmentalists have worried in the past that wind power may be dangerous to birds (which may be killed when flying into the whirling blades.) However, studies have shown that the severity of this problem has been overstated. Wind power produces no air pollution and has minimal impact on the environment compared to most other forms of power generation.

Classroom Experiments and Activities

Here are some experiments and classroom ideas you can perform with PicoTurbine:

Lung Power

If you have a multimeter that displays AC millivolts, you can have a lung power contest. Allow each child to puff on PicoTurbine from a distance of several inches for up to 10 seconds. The teacher watches the multimeter, and whatever the highest reading was during the 10 seconds is the score for that child. Best lung-power wins!

Best Turbine

If several different PicoTurbine units have been built by a class, then you can have contests and award prizes. Some ideasare:

• Most electricity. Using a hair dryer and a multimeter, see whose model produces the most electricity under the same conditions. Make sure the dryer or fan is at the same distance for each contestant. If you don’t have a multimeter, judge which machine lights the LED the brightest.
• Smoothest motion. The teacher judges whose model has the smoothest operation and least wobble when spinning.
• Lowest start-up speed. See whose model will start up in the lowest wind speed. This is judged by using a hair dryer set at different distances from the PicoTurbine. The PicoTurbine that spins with the dryer the farthest away is the winner (the wind speeds drops quickly with distance from the dryer).
• Best construction. The teacher judges whose machine is the neatest looking and most finely crafted.
• Best Blade Coloring. The teacher judges whose machine has the nicest blade coloring design. Clever designs might look interesting when turning, for example a “barber pole” stripe design. This contest is good for younger children in mixed age level settings.

Alternative Designs for PicoTurbine

This section provides some design alternatives for PicoTurbine for experimenters and perhaps science fair projects.

Weatherproof PicoTurbine

PicoTurbine, as described in the main plans, is not weatherproof. The tape, glue, paper, and cardboard will quickly disintegrate in rain. Here are some ideas to produce a weatherproof PicoTurbine that can be left outdoors. It will be harder to build, but worth the effort. Adult supervision will be more necessary for this version of the project, especially if hot glue is used.

• Instead of tape and glue, use hot glue, or weatherproof tape. These can be purchased at hardware stores. Hot glue should only be used by adults.
• Instead of cardboard, use an old plastic CD for the rotor. You will need to build up the dowel using duct tape, a cork, or some other method because the hole in a CD is larger than the ¼ inch dowel thickness.
• Instead of paper, use a plastic soda bottle for the blades. Carefully cut the top and bottom off the bottle using scissors, leaving a four inch long cylinder with open top and bottom. Then cut this cylinder in half lengthwise, resulting in two half-cylinders. Use hot glue to affix these blades to the top of the CD used as the rotor. A second CD hot glued on top of the blade set will provide further stability.

High Power PicoTurbine

To make a higher power version of PicoTurbine, follow these instructions:

• Make the Blade coverings 8 inches tall instead of 4 inches, perhaps using the cut-soda bottle idea above.
• Use a 1 foot long ¼ inch threaded rod instead of a wooden dowel. Obtain 6 nuts and 6 large washers to use to attach the rotor and blade supports.
• Use 8 magnets instead of 4. Equally space the magnets and remember to alternate north and south poles.
• Attach the magnets to a 1 gallon paint can lid. This provides a metal backing to the magnets and increases the magnetic field strength somewhat. Use hot glue to affix the magnets. Only adults should use hot glue! Carefully poke a center hole by using a ten penny nail and hammer over a piece of scrap wood. Be careful of jagged edges in the hole when attaching to the threaded rod.
• Use 8 coils instead of 4.
• This version produces about 4 times as much power. Warning: the LED can’t handle the voltage that will be produced. Obtain a 3-volt flashlight lamp. To use the LED, you must put a small resistor in series with the LED to limit the current, otherwise you will burn it out as well. Use about a 200 to 500 ohm resistor.

Alternative Blade Designs

As shown in this document, PicoTurbine uses a traditional “barrel offset” Savonius blade design. But, blades can be offset more or less. Also, the curved portion can be a shallower or deeper curve. Play around with the shape of the blade support parts and test these to see which is more efficient. This would make an excellent science fair project. It would even be possible for an advanced student to look up patented designs for Savonius wind turbines (that’s the kind PicoTurbine is)and do a study of which one is best. To do this, go to the website: http://www.uspto.gov (the US Patent and Trademark Office) and search for “Savonius”. You will get quite a few patents back. Look at the blade design described in the 1996 patent by Benesh. It claims to be much more efficient than the blade design used in PicoTurbine. Put it to the test!

PicoTurbine Direct Current Kit

Concepts Required Before Building the Circuits

Before building these circuits, the teacher must be certain that some elementary electricity concepts are understood. The very minimum that needs to be understood is:

• "Voltage and Current"
  
  Students should understand the difference between voltage and current. The simplest way is to use a water pipe analogy. Voltage is similar to the pressure in the pipe. There can be pressure even with no water flowing (perhaps a valve is turned off). Current is similar to the volume of water flowing through the pipe. It is actually the amount of electric charge flowing through the circuit per unit time, or in other words the rate of charge flow.
  
  
• "Resistance"
  
  Resistance impedes the flow of electricity. In our water pipe analogy it might be the friction of the water along the pipe walls, or perhaps the pipe is flowing uphill. Voltage (pressure) is required to overcome resistance.
  
  
• "Ohm’s Law"
  
  The relationship between Voltage, Current, and Resistance is given by Ohm’s law: V = IR. In other words, voltage is current times resistance. The water pipe analogy also works well here. Thinner wire has higher resistance than thicker wire. Similarly, to put a given amount of water through a larger diameter pipe requires less pressure than if the pipe is very thin. Imagine trying to pump 1 gallon of water per second through a drinking straw! That would require a great deal of pressure. However, very little pressure would be required to pump 1 gallon per second through a six-inch diameter drainage pipe. Similarly, if you want to drive a large current through a high resistance, you must have a proportionally large voltage.
  
  
• "Functions of Basic Electronic Components"
  
  Students should understand the functions performed by diodes and capacitors. In our water pipe analogy, a diode is like a one-way valve. A capacitor is like a small storage container that can store water and later release it.
  
  
• "Alternating vs. Direct Current"
  
  Students should understand the difference between alternating and direct current. In the pipe analogy again, alternating current would be similar to water flowing in one direction, then stopping, then flowing in the other direction again. Direct current represents the more familiar situation where the “water” only flows in a single direction. It should be noted that in alternating current, both the voltage as well as the current (pressure as well as amount of water) are both varying over time.

Using the Kits in the Classroom

Kits can either be used for small group work or as a demonstration by the teacher. When demonstrating, it may be helpful to have more than one breadboard and wire up two circuits for comparison purposes. For example, wire up a simple half-wave circuit on one and a full wave with smoothing on the other. In this way it is easy to compare the sounds of the piezo buzzer.

If an oscilloscope is available, it can be used to directly display the voltage patterns. A dual-display oscilloscope is ideal because you can tap off the alternator directly for one display and tap off the place where the piezo buzzer or LED would be connected on the other display. In this way, you can show both the input AC voltage and the output DC voltage simultaneously.

It is not necessary to build the full PicoTurbine windmill to do these demonstrations. You need only build the alternator portion of the kit if the renewable energy aspect of the project is not relevant to the class. If spun by hand, the alternator will turn for a longer period of time if there is no blade attached, because there will be less air friction.

If renewable energy is relevant (we hope so!) then a small fan can keep the PicoTurbine spinning at a more consistent speed than turning by hand. This is especially desirable if using an oscilloscope so you get a nice clear wave pattern. Even though the text gives a way to demonstrate the voltage doubling circuit without the use of a multimeter, it is a far more convincing demonstration with such a meter, since the exact voltage can be measured.

The LED demonstration given in the text will, however, help drive home the reason why you might want to use a doubler circuit: with the doubler the LED will light in lower wind speeds than without.

Reasons for Alternating and Direct Current

Many students will ask, “Why bother with two kinds of electricity? Why not standardize on either alternating or direct current?”

This is a very astute question. This very debate spurred a rivalry in the early part of this century between two of the greatest inventors who have ever lived: Nichola Tesla and Thomas Edison. Edison wanted to simply run DC current through the distribution wires to everyone’s home, while Tesla argued for 60 cycle per second alternating current. Tesla won, and we still use 60 cycle alternating current today to transmit power to our homes and schools.

The reason is that alternating current has great advantages when you are transmitting current a great distance. It is a simpler matter to step up and step down alternating current. When transmitting electricity, you want to have a high voltage and a low current. This is because resistive losses are proportional to the square of the current. So, doubling voltage cuts resistive losses by a factor of 4.

Long haul power lines sometimes use 50,000 volts or more. However, high voltages like this are not safe. If we actually delivered 50,000 volts through wall outlets, thousands of people would be electrocuted to death every year! So, this high voltage is transformed down to 120/240 volts before being delivered to our homes. Even at 120 volts electricity is quite dangerous, by the way, and is not to be toyed with. But at 120 volts we at least don’t have to worry about the current spontaneously jumping out of the wall outlets! This could actually occur with very high voltages, since those voltages are enough to break down the very high resistance of air itself under the right circumstances and jump over a foot to nearby objects or people.

We need DC current because many devices require it to operate properly. So, rectification circuits are commonly used by devices to transform wall outlet power (or PicoTurbine power!) to DC for use by computers, radios, TV’s and other devices.

We will caution here, once again, that the components supplied with the PicoTurbine-DC kit are only capable of handling the low voltages and currents produced by PicoTurbine, and could cause injury or death if used with wall outlet power. Only qualified adults with specific training and certification in electrical design work should ever design or build circuits for use with wall outlet power.