Introduction: (Initial Observation)
Fossil fuels such as oil and coal are nonrenewable, that is, they draw on finite resources that will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve. In contrast, renewable energy resources – such as wind and solar energy – are constantly replenished and will never run out. Most renewable energy comes either directly or indirectly from the sun. Wind Turbines have a long history and they date back to the ancient times. They have been used through history and they are still in the process of developing.
Windmill is a machine that runs on the energy generated by a wheel of adjustable blades or slats rotated by the wind.
Windmills may be used to do a work such as grinding grain into flour or pumping water out of a water well. They may also be used to create electricity. In this project we will study the parts of a windmill and make a model of a windmill.
Adults help and supervision is required
Information Gathering:
Find out about renewable energy sources such as wind energy. Read books, magazines or ask professionals who might know in order to learn about using wind energy. Keep track of where you got your information from.
If you like to collect information from the Internet, you may start from www.WindPower.org for some general information. You can even use some parts of the same website for more details.
How about some cool pictures of windmills?
Introduction to wind energy
We have been harnessing the wind’s energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill’s modern equivalent – a wind turbine – can use the wind’s energy to generate electricity.
Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind’s energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.
A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind’s force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners or farmers in windy areas can also use wind turbines as a way to cut their electric bills. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form a wind plant. Several electricity providers today use wind plants to supply power to their customers.
To see a detailed diagram of a real windmill, you can visit the website of some windmill manufacturers.
The workings of a windmill:
Look at the diagram and fill in the blanks.
(a) A system of cogs change the turning movement from horizontal to ___________.
(b) The small wheel at the back acts as a sail and pushes the top of the windmill around so that it _________ into the wind.
(c) The __________ makes the sails turn in a big circle.
(d) The top of the windmill is separate from the rest of the mill and can move around on _________.
(e) The ____________ central column makes the grindstone turn.
(f) Grains of wheat, oats, barley or other cereals are __________ into the mill.
(g) _________ is produced when the grains are ground.
Modern Windmills:
1. Modern blades are specially designed to capture more energy from the wind. They are made from light (yet strong) composite materials to enable them to survive gusty winds, and they use aerodynamic controls or “brakes” to control speeds.
2. The latest rotor hub designs are flexible, allowing increased rotor efficiency, while minimizing damaging drivetrain and structural loads.
3. Innovative direct-drive low-speed generator and power train designs allow a wind turbine to produce power at variable rotor speeds. This allows designers to make machines more efficient and easier to control, while eliminating or reducing the size of expensive gearboxes.
4. Special tower designs and construction materials allow designers to use taller towers to place the turbine higher, where the wind is stronger and more energy is available.
5. Advanced power control systems improve the control of the wind turbine in constantly varying wind conditions, continually optimizing the power produced while minimizing fatigue damage.
More advanced and older students may make wind powered electric generators that really works. Making a working generator requires some craft and mechanical skills. Following link is a good sample and help for such project. http://www.otherpower.com/woodmill.html.
Wind Power, Components:
Blades
The blades or rotors catch the wind. When the wind blows against them, they change the horizontal movement of the wind into a rotational force turning the shaft. The generator then turns this movement into electricity. Blades come in many sizes; the longest blades in use today are over 50 meters long.
Generator
The generator converts the mechanical energy of the rotating shaft into electrical energy. This electricity is then sent to homes and businesses where machines change the electricity into forms that consumers can use such as heat and light.
Tower
The tower lifts the wind turbine up high so that it can take advantage of the stronger, more consistent winds which blow above the ground. The world’s tallest towers are more than ten stories high.
Batteries
Batteries are an important part of remote wind systems because they serve to stabilize the power fluctuations from the wind turbine and store the excess energy production. This stored energy is then available to supply the loads during low wind periods.
Wind Power Site
Finding the best site for a wind turbine is essential. The wind itself is rarely a steady, consistent flow, and obstructions such as nearby buildings or hills can reduce the performance of the turbine. Furthermore, wind speed varies naturally with the time of day, the season, and the height of the turbine above the ground.
Windmill using coat hangers
We received this creative design from Mr. Philippe Paul.
He has used coat hangers and a bicycle rim to make a windmill propeller. This is how he describes his design.
Using a coat hanger, I traced the inner enclosed area on a piece of ceiling Styrofoam. I then cut nine pieces with a razor blade to fill in the nine coat hangers that make up the windmill (27 spokes or 3 times 9 repeat patterns).
I used Styrofoam on the model that is shown in the picture, but later (shrink wrapped) covered the coat hangers with plastic. I used a sealer and a heat gun to make the plastic tight.
The other “ingredient” was scotch tape. I wrapped some tape around the corner of the hanger to hold the Styrofoam pieces in place. So far I taped the hanger corners that are near the rim and will not try to put any tape near the axle until a strong wind proves to me that it is needed.
I gently jammed the corner of a plastic coat hanger in a triangular opening created by two spokes connecting to the axle. The tip of the corner of the coat hanger itself could be touching the chrome shinny part of the axle. The next step is to wrap the hook of the coat hanger around a spoke that is connecting to the outer rim. After these two steps, the coat hanger will swing loosely but is already attached to the wheel. The next step is to gently push the other corner of the coat hanger (with the palm of your hand) as close to the rim as possible. This is when you decide what the angle of inclination of the blades will be relative to the plane of rotation of the wheel itself.
At the chosen angle, the coat hanger will make contact with the adjacent spokes at two locations. This is when I started to get the feeling that the thing was building itself. While holding the coat hanger at the proper angle, wrap five turns or more of shinny scotch tape around the two contact points where the coat hanger touches the adjacent spokes. Once you install the first coat hanger, count 1,2,3 and install another one. The shinny scotch tape can be as strong as you need it to be by adding more turns. However some kind of metal clip with chew the plastic in the long run. I prefer the tape.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to learn about the parts of a windmill. We will do it by gathering information and building a model of a windmill.
You have many choices for the design and construction of a windmill. What we introduce here are just samples. It is much better if you finally use your own ideas to design and construct a windmill model.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Many variables may affect the function of a windmill. Wind speed and the design factors are among the variables that can be studied, however since the purpose of this project is learning about the parts of a windmill we will not study any specific variable.
If you want to study the effect of any specific variable, you can simply make a windmill model similar to the one described in the experiments section and use that to perform some more experiments. For example if you want to know how does the speed of wind affect the energy production of a windmill, you can expose your model to the winds with different speeds and measure the amount of weight that can be lifted by the windmill.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
My hypothesis is that windmill is something like an electric fan with an opposite function. An electric fan gets energy (electricity) and creates wind, but wind mill gets wind and produces energy.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1: Make a simple windmill
SUPPLIES YOU NEED
* One wooden dowel (an old broom handle works great)
* One cardboard tube from a used paper towel roll
* One push tack or a small nail
* Thread or light string
* Scotch tape
With these supplies and the help of an adult, you can have fun building the windmill below.
(1) Cut the cardboard tube lengthwise into four equal parts.
(2) Tape two of the cardboard strips together into the shape of a plus sign.
(3) Cut each end to a partially rounded point. Be sure to keep the cuts equal and going in the same direction. This will allow your windmill to spin in one direction.
(4) Tack or nail the windmill to the end of your broom handle.
Once you’ve completed your windmill, it will want to spin in the wind. Try putting it in different areas outside to see where the wind is the strongest. If there is no wind at all or not enough to make it spin, run with it or wave it around. At different times of the day, there may be more wind. Usually in the mornings it is calm and, as the day goes on, the wind picks up. So experiment with this and see if you can find the best time to play with your windmill.
Experiment 2: Make a simple windmill and measure the power
In this experiment you will make another model of wooden windmill. This windmill can be used for some additional experiments such as measuring the power of windmill.
The way that this experiment is being proposed here requires adults help and supervision. If you don’t have an expert adult and proper tools, simply eliminate all cuttings and drillings and try to assemble all pieces just by glue. Even instead of a piece of wood, you can glue a few pieces of cardboard in a multi layer form to build a similar piece. You will have to wait a longer time for glue to dry, but being safe is better than being sorry.
Procedure:
Use about 3 feet long piece of 1 x 2 wood. (It is known as one by two, but it’s real size is 0.75″ x 1.5″)
Start by cutting a square piece of wood to be the center of the blades. Sample in the picture is 1.5″ x 1.5″ x 0.75″, but what you make can be larger or smaller.
Sand it so it will have smooth surface and edges.
Locate the center of the square and make a hole on that. This is the axis hole. I used a 1/8 inch drill bit, because the nail that I used as axis is slightly ticker than 1/8 inch. (10d 3 inch nail).
Secure the square wood by an adjustable clamp and use a saw to cut diagonal 0.25″ groves on all rectangular sides.
Sand one side of each Popsicle stick so it will fit the grove. Then apply some wood glue and insert the Popsicle sticks. Allow about 8 hours for the glue to dry.
Insert the nail in the center hole, so it goes trough and comes out of the other side. It should take some force and may cause your wood to break if it is not strong enough.
Make another hole using a larger drill bit (slightly larger than the thickness of the nail that you are using.) on the long piece of wood, about 1 inch from one end.
Inset the nail that is now the axis of your blades into this hole. It should spin freely. You may use a spacer between the blades and the long wood that is now your windmill tower. A few small metal washers can be used as spacers. Spacers will make sure that the body of the blades will not touch the tower and cause friction.
Now hold the windmill in a windy area and blades should start to spin.
You can make a wooden base for your windmill or insert it in an empty plastic or metal container and fill around that with sand. We temporarily used a clamp to hold it for taking a picture.
You can use your newly built windmill to do some tests and some more experiments.
For example you may want to use the windmill to do some work such as lifting a weight. We want to see what is the heaviest weight that the windmill can lift.
Tightly attach a string to the nail. You can use any glue or adhesive tape to attach the string to the rod. Now, attach the weight to the bottom of the string letting it hang from the string.
Next, expose the windmill to wind and see whether or not the weight gets coiled up. If there is no wind, you can run with the windmill so that the propellers turn causing the weight to be brought up. Do several tests with different weighted objects to see how much weight the windmills can lift.
Experiment 3: Make a windmill, measure the force directly
In this experiment you will use a spring scale to examine the force created by wind. This can be done using the previous setup and the nail, but nail is short and you may prefer to use a longer wood dowel instead of that. What you will see here includes a reconstruction of the previous windmill and replacing the nail with a 6″ x 1/4″ wood dowel.
Remove the nail that you inserted in the center of blades in previous experiment and use a 1/4″ drill bit to enlarge the hole. Then insert the wood dowel into the center piece and make it to be the axis of your blades. You may need to apply some glue to secure the axis in place. Insert the dowel into a small ball bearing with inside diameter of 1/4″ and then use a copper strap to secure the ball bearing at the top of a wooden tower.
Spin the blades by hand and make sure that they can spin freely. Now connect the string to the axis and secure it with a piece of tape. You should now be able to expose the windmill to the wind and it should coil up the string and pull it up even if you hang a weight to the string.
To find out what is the maximum weight that can be lifted by our windmill, we used a spring scale instead of the weight. That spring scale showed a force equal to 70 grams in a moderate wind.
Now we can use this value and calculate how much will be the power of a larger windmill. If we assume the surface of blades as a main factor (this can be tested), a wind mill that the surface of it’s blades is 1000 times more will have 1000 times more power.
Experimental Project Ideas:
Making a windmill is an engineering and craft project; however, after you make a windmill, you may study different design factors to determine how they affect the wind energy collected by the windmill. Factors such as the number of blades, the pitch of blades, the length of blades may be studied.
How does the pitch of the blade affect the efficiency of a windmill?
For this project you will need to make a propeller in which the pitch of blades are adjustable. 2 or 4 blades are enough for this experiment.
The adjustable blades can be made of a piece of balsa wood sheet inserted into a grove in one end of a short wooden dowel. Apply some glue to make a permanent connection.
The center block on the other hand must have one hole for each blade in its outer rim. While the center block is on flat surface, you may use a protractor and insert the blades at specific angles such as 10, 20, 30, 40, 50, 60, 70 an 80 degrees.
For each angle you may measure the wind energy and record it in a table like this:
| Propeller angle | collected wind energy |
| 20º | |
| 30º | |
| 40º | |
| 50º | |
| 60º | |
| 70º |
Make a graph:
You may finally use the above results table to make a graph. Click on the graph link at the footer of this page for general information about making graph.
Materials and Equipment:
List of material can be extracted from the experiment design section.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
You will not need any calculation for this project. However if you do some calculations, make sure to write them in your report.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
References:
I base my research on a helpful book American Windmills which has several windmill designs and I think that the bigger the blade, the more electricity produced.
Cosner, Sharon, “American Windmills, ”David McKay Company Inc., 1977
Gary, Chandler and Kevin Graham, “Alternative Energy Sources,” Fitzhenry and
Whiteside Ltd., 1996
Mike Eisele, “Which Blade Variable Has the Greatest Effect on Windmill Efficiency,” [Online] Available at http://www.selah.k12.wa.us/SOAR/SciProj99/MikeESciProj.html
Eric Jenkins, “Which Windmill Blades Angle is Most Efficient,” Copy is attached below.
Manwell, James E. “Windmill” Encarta 98
McDonald, Lucile “Windmills New and Old Energy Source” Eliever-Dutton Publishing Co. Inc.
Visich, Marian Jr. “Turbines” World Book Encyclopedia 1995 v.19 pg. 498-500
http://www.cogreenpower.org/Wind.htm
http://www.selah.wednet.edu/SOAR/SciProj2000/AshleighB.html
http://www.otherpower.com/danb_windmill.html
Sample Project
Which Blade Variable Has the Greatest Effect on Windmill Efficiency?
By Eric J.
Table of Contents
Abstract
The purpose of this experiment was to determine which variable, the number, length, or pitch of blades, has the greatest impact on windmill efficiency. I became interested in this idea when I realized how important wind-powered electricity will be in the future, and in conserving energy. The information gained will help people better understand what a windmill really is and how they can benefit humankind, if used properly and improved.
My hypothesis is that 6 blades, 20cm long with 10 degrees pitch, will capture the most energy from the wind. My hypothesis is based upon the work of R.A. Barris in his article “Propellers” and Dermot Mcguain in his article “Optimizing Windmill Blade Efficiency.” Specifically, referencing the effect of the number of blades, Barris noted, “…range from two to seven with the most common of four, five, or six.” He went on to discuss the effect of blade pitch, explaining “Plane propellers are set at ninety degrees to stop the windmill effect if an engine goes out.” Dermot Mcguain discussed the effect of blade size, indicating “larger blades have a greater swept area and thus catches more wind with each revolution.
The constants in the experiment were:
-
- the same friction on axle
- the same weight of the axle assembly, minus the blades
- the same wind speed
- the same design and height of windmill
- the same methods for each test
- the same shape and type of blade
The three manipulated variables were the number of blades, length of the blades, and the degree of pitch.
The responding variable was the power (measured in watts) generated from the each test of the windmill. To measure the responding variable a 40cm fish line was tied onto the axle, as the blades developed speed the axle turned and the string slowly wound up, raising a weight. Three trials of how long it took the weight to reach the marked height were timed in each setting, so an average time could be computed. The work (joules) is calculated by taking the distance (0.4 meters) and multiplying it by the amount of weight (0.4 Newtons). Once finished, to determine the power (watts) the amount of work (joules) is divided by the average time.
The results of this experiment were a windmill with 7 blades, at a 10 pitch and 15cm blade length yielded the greatest windmill efficiency.
The conclusion drawn from the results indicate the hypothesis should be rejected because it stated that with 6 blades, at 10 degrees, and with a blade length of 20cm, would be the most energy efficient. That test run had the power rating of 0.0211. The best run was with 7 blades, at 10 degrees and with a length of 15cm, this run had a power calculation of 0.213.
Purpose
The purpose of this experiment was to determine which variable, the number, length, or pitch of blades, has the greatest impact on windmill efficiency. I became interested in this idea when I realized how important wind-powered electricity will be in the future, and in conserving energy. The information gained will help people better understand what a windmill really is and how they can benefit humankind, if used properly and improved.
Hypothesis
My hypothesis is that 6 blades, 20cm long with 10 degrees pitch, will capture the most energy from the wind. My hypothesis is based upon the work of R.A. Barris in his article “Propellers” and Dermot Mcguain in his article “Optimizing Windmill Blade Efficiency.” Specifically, referencing the effect of the number of blades, Barris noted, “…rage from two to seven with the most common of four, five, or six.” He went on to discuss the effect of blades pitch, explaining “Plane propellers are set at ninety degrees to stop the windmill effect if an engine goes out.” Dermot Mcguain discussed the effect of blade size, indicating “larger blades have a greater swept area and thus catches more wind with each revolution.
Experiment Design
The constants in the experiment were:
-
- the same friction on axle
- the same weight of the axle assembly, minus the blades
- the same wind speed
- the same design and height of windmill
- the same methods for each test
- the same shape and type of blade
The three manipulated variables were the number of blades, length of the blades, and the degree of pitch.
The responding variable was the power (measured in watts) generated from the each test of the windmill. To measure the responding variable a 40cm fish line was tied onto the axle, as the blades developed speed the axle turned and the string slowly wound up, raising a weight. Three trials of how long it took the weight to reach the marked height were timed in each setting, so an average time could be computed. The work (joules) is calculated by taking the distance (0.4 meters) and multiplying it by the amount of weight (0.4 Newtons). Once finished, to determine the power (watts) the amount of work (joules) is divided by the average time.
Materials
1: weight, 0.4 Newtons
3: 3 .79 cm in diameter wooden dowels
1: 1 .32 cm in diameter wooden dowels
1: vinyl window blinds for blades
40 cm: fishing line
2: small nail brads
3: nylon washers
2: nylon nuts
2: wooden blocks to hold axle
1: wooden platform
1: rubber band
1: stick to release tension
1: hot glue gun
1: drill
1: nail
4: wooden wheels
25: wooden dowel pegs
1: drill press
1: band vise
1: yardstick
1: stopwatch
1: coping saw
1: fan
1: pair of pliers
1: dowel jig
1: compass and protractor
Procedures
1. Build windmill.
2. Cut out twenty-two 10cm long blades, twenty-two 15cm long blades, twenty-two 20cm long blades.
3. Put the 10cm long blades in dowel pegs and set at 10 pitch, using a protractor.
4. Turn fan on medium, time how long it takes the weight to pass the marked point, 40cm above. Do this two more times at the 10 pitch.
5. Take the three times and perform the mathematical calculations.
6. Compute the average time it takes the weight to reach the height by adding the three trial times and then dividing the sum by three.
7. Use the formula work (W) equals force (F) multiplied by distance (D). The force (0.4 Newtons) times the distance (40cm) yields the work. Then consider Power (P) equals work (W) divided by time (T). The work is expressed in joules. One joule equals one Newton moved a distance of one meter. In this experiment the joules generated are determined by multiplying 0.4 Newtons by 0.4 meters (40cm). The joules (work) is then divided by the time taken to reach the height in order to determine the power generated.
8. Switch the 10cm blades with the 15cm blades and repeat steps four and five. Once 15cm blades are recorded, switch them with the 20cm blades and repeat steps four and five
9. Once all length of blades are used at 10, adjust the blades to 30 using a protractor, and attach the 10cm long blades. Repeat steps four to six.
10. With all calculating done compare the generated power by the tests, and begin spreadsheets and graphs.
Procedures to Build Windmill
1. Buy supplies (see materials, pg. four).
2. Cut four .79cm diameter dowels into 60cm lengths.
3. Cut two .32cm diameter dowels into 28cm lengths.
4. Cut .48cm holes in each of the four 60cm dowels, 4cm up from the bottom.
5. Glue the 60cm dowels together in pairs with the 28cm dowels, by the holes.
6. Cut two blocks, drilling two .79cm holes in the bottom, holding the posts together and a .95cm hole down the middle to position the axle.
7. In the middle of both blocks, glue nylon washers.
8. Cut a .79cm diameter wooden dowel 40cm long for the axle.
9. Make base out of wood 81cm by 36cm. Drill holes in base to hold posts.
10. Take nylon nuts; drill 9.5cm holes down center of each, nail brad into them, to keep the axle from falling out.
11. Place rubber band around both post tops, keeping them upright.
12. Cut a 0.5cm by 33cm wooden stick to release some tension on the axle, enabling it to turn easier.
13. Make a support on back end with a 63cm long .79cm in diameter dowel by drilling a hole through the dowel and into the back block with a .2cm bit. This will enable a nail to hold the windmill upright.
14. With a dowel jig and bench vise take the four wooden wheels and drill a .79cm hole, at specific angles, the amount depends on the wheel. Once finished then drill a hole down the middle with a .79cm bit.
15. Take the wooden dowel pegs and stick them inside each hole, tapping with a hammer. With a coping saw, cut a straight line down the center of each dowel to hold the blades.
Research Report
Introduction
In this report the reader will find information about windmills, general information as well as specific to this project. Some of the topics include: the origin of the word windmill, its history, principles, improvements, the different types, and different functions windmills perform.
Windmills are one of the best low-cost energy producers. Wind is there for the taking, when we use it efficiency energy is produced without high pollution or toxins. If we improve them, the cost of energy for the common person would be decreased without harming the environment.
History
The first country to use windmills was Persia in the fifth century AD. The Persians used the windmills to irrigate the land and made the windmills turn grindstones in corn mills, where the word windmill originated. These windmills were horizontal, with a wheel and supported by a vertical shaft. Though hardly sufficient, this started the idea of harnessing the wind.
The popular windmill spread throughout Europe, and in the twelfth century was also used to pump water. In Holland the people used them to drain their polders after the dikes were built. Polder is a Dutch word meaning land reclaimed from the sea. Places such as the Netherlands have prospered from creating vast wind farms. These simple structures, called post mills, were made of wood and had a stretched canvas for blades, they were not very efficient; only half the sail rotation was utilized.
During the fourteenth century in France the tower mill was invented. It consisted of a stone tower topped by a rotating wooden cap that supported the wind shaft and the upper portion of the mill gearing.
All these structures shared similar features, a horizontal shaft with four to eight sails, about three to nine meters long, radiated from the shaft. The sails were either covered by canvas or fitted with wood shutters.
Turbines
A turbine is a rotary machine that converts the power of water into energy, like a windmill, but not with wind. The river flows through a rotor, a wheel mounted to a shaft. The fluid turns buckets, fins, or blades on the rotor, making the rotor spin. The Greek Hero Alexandria built the earliest known turbine in AD 75. His device was a hollow ball that spun due to jets of steam being released. His ball is like a turbine where the steam hit the rotator causing energy.
Today, many hydroelectric dams have many larger sized turbines to make power and redirect large amounts of river water for irrigation. This energy is turned into electricity, which powers the people’s homes, cutting back on the need for more pollution-causing forms of energy.
Bernoulli’s Law
Bernoulli’s law, by Daniel Bernoulli, explains the relationship between pressure and velocity of moving fluids. He said the narrower the horizontal tube for water to flow through there would be more pressure in the pipe, causing the water to go faster. This means water travels slower in bigger pipes, because the walls of the pipes must exert a force to accelerate the water on it’s way to the constriction.
Bernoulli’s law explains how vertical axis windmills turn, and how airplanes fly with lift, an upward force. Due to the curve on the top of a wing, air traveling across the wing, moves faster, making the pressure on the upper wing less. This causes the higher pressure to go to the bottom giving the plane lift.
Work, Force, and Power in Physics
Work
Work is the effort that is put into doing something. The specific definition for physics is: the product of a force and a distance, or displacement, along the direction of the force.
The amount of work it takes someone to do something like climbing a mountain depends on the person’s weight and the height of the mountain. Once climbing the mountain the person has gained potential energy from the Earth’s gravity, which can be turned into kinetic energy if the person falls or jumps.
The standard unit to measure work in the metric system is the joule. A joule is the work performed by a force of one Newton acting through a distance of one meter.
Force
Force is something that accelerates an object. Force has both direction and magnitude. When forces combine they make a net force, when is the objects mass and acceleration. Force is distinguished in Newtons second law of motion, an objects mass multiplied by acceleration equals the force of an object. If a large object is given the same amount of force as a smaller object the smaller object will accelerate faster. If the masses are the same but the objects are given a different amount of force push or pull, the object with more force will have a faster acceleration.
If forces combine to a net force of zero, the object will not move, or just move at the same speed it had been moving at.
A unit of force is the Newton, which is the force that moves an object with a mass of 1 kg an acceleration of 1 m/sec. In English units, the unit of force is the poundal, which is the amount of force that accelerates a 1-lb object 1ft.
Power
Power is the rate at which the work is done. If you were suppose to shovel snow in your neighbors’ driveways and you either have one day or one week, you would choose the week, because it takes less power than the day. The average power to do something is found by dividing the work by the how long it required. The amount of power is always written units of energy divided by units of time. Two possible units of power are horsepower, in the English system, and watts, in the metric. The amount of power used to lift thirty-three thousand pounds one foot is equal to one horsepower. One watt is the power needed to do one joule of work per second. There are 746 watts in one horsepower.
Improvements
There have been many improvements since the first windmills. No longer used just for milling and irrigation, they are now used for pumping seawater, sawing wood, making paper, and pressing oil from seeds.
Another improvement was the fantail, a mechanism invented in 1745 that rotated the blades into the wind. Which was an automatic way of getting the most wind, as opposed to having a person manually turning the windmill into the wind. Later, in 1772, the spring sail was invented which has wooden shutters on the sails, which open and shut.
The number of blades has been another major improvement. The old windmills have had four to eight blades on a windmill, the newer windmill are usually about two to three. Along with all these constructions the materials used for the blades have also changed.
The windmills have been equipped with air brakes, to control the wind speeds in strong winds. Some vertical axis windmills have had hinged blades to avoid stress at high wind speeds. Cyclo-turbine windmills have had a vane, which senses wind direction and causes rotor to rotate in the wind. Wind turbines have been equipped with gearboxes that control the shaft in wind speeds. The blades have also been changed in many ways, experimenting with airfoils.
Altitude has a tremendous negative effect on the power efficiency. Modern windmills are about twenty feet above the ground and at least three hundred feet from any obstruction, though the idealistic height is thirty feet above ground and five hundred feet from any near obstruction.
People have attempted to find the best places for wind farms. The British Isles have almost no inhabitants, but some of the best wind generators. In fact, the biggest wind farm is set in California, which makes about fourteen hundred megawatts of energy; in contrast to about a thousand, megawatts which a nuclear power plant generates.
The different geographical sites change the amount of wind in places. Up in the mountainous areas, there is convection current with the valleys, with the difference of hot air and cold air. The hot air rises above the valleys, cools and returns to the valley, where it heats up and rises, creating a breeze in the mountains. This effect is also found in the ocean and with the hot sand.
People also have made a bigger area to sweep with the blades. The bigger the sweep area the more wind caught, the more wind caught the faster the blades turn.
Differences in Windmills
Horizontal Axis Windmills
The horizontal axis windmills have a horizontal axle. These windmills use Bernoulli’s principle, using the lift like a airplanes wings, with a curved top. These kinds usually have two or three blades, are seen on farms and other places. The blades are shaped to take the air from the bottom of the blade to the top, creating lift. The blades utilize the lift to the rotation.
Vertical Axis Windmills
The vertical axis windmills use drag instead of lift. They act like a brick wall, using the resistance of the wind to create drag and to get pushed by the wind.
Types
There are many different types of windmills, each for a different purpose. The many types latitude: the tower mill, the sock mill, sail windmill, water pump, spring mill, multi-blade, Darrius savonis, cyclo-turbine, and the classic four arm windmill.
All these different types may be either horizontal or vertical windmills. The many jobs they perform include powering: hydraulic pumps, motors, air pumps, oil pumps, churning, cheating friction, heat directors, electric generators, Freon pumps, and centrifugal pumps.
Tip Speed Ratio
The tip speed ratio is how many times the blades of a windmill will turn for every mile an hour the wind speed is. A tip speed of 1:1 means that in a twenty-three mph wind, the blades rotate twenty-three times. Modern turbines have a tip speed ratio five to ten times faster. To calculate the tip speed ratio you calculate speed of rotation of the blade divided by the wind speed.
Summary
Why Wind Power?
Wind energy makes very little pollution, toxic by-products or greenhouse gasses; it is still not a sufficient supplement for non-renewable fuels, like oil. Although not as popular as Nuclear power plants, scientists estimate that by the twenty-first century, ten percent of the world’s electricity will be generated from windmills.
Although many questions still need to be answered, scientists are on the right track by trying to improve sufficiency of windmills. For example: Do materials of the blades affect the solidity of the windmill blades? Do different designs decrease solidity? Does the temperature affect the solidity of windmill blades? Does the length and width affect tip speed ratio or is it just length, or just width? If these questions are answered, the windmill may become a great weapon in the quest to find low-cost energy.
Results
The original purpose of this experiment was to determine which variable, the number, length, or the pitch of blades, has the greatest impact on windmill efficiency. The results of this experiment were a windmill with 7 blades, at a 10 pitch and 15cm blade length yielded the greatest windmill efficiency.
Conclusion
My hypothesis was that 6 blades, 20 cm long with 10 degrees pitch, would capture the most energy from the wind. The conclusion drawn from the results indicate the hypothesis should be rejected because it stated that with 6 blades, at 10 degrees, and with a blade length of 20cm, would be the most energy efficient. That test run had the power rating of 0.0211. The best run was with 7 blades, at 10 degrees and with a length of 15cm, this run had a power calculation of 0.213.
Because of the results of this experiment, I wonder if the length of the blades was less important than the pitch. If I were to conduct this project again I would test the size and also aerodynamics of the blades and maybe even shave the edges like airplane wings.
Bibliography
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- Dennis, Landt, Catch the Wind, New York, Four Winds Press, 1976.
- “Windmill and wind power,” Groliers Encyclopedia, 1995
- “Windmill” Encarta Encyclopedia, 1995
- Dermot, Mcguain, “Optimizing Windmill Blade Efficiency,” http://www.west.net/~csf/windmill.htm, 12-15-97.
- “HWP2 Horizontal Axis Windmill,” www.tequip.com, 12-15-97.
- Barris, R.A. “Propeller,” McGraw-Hill Encyclopedia of Science and Technology, 1982.
- “Turbine,” Groliers Encyclopedia, 1995
- “Turbine,” Encarta Encyclopedia, 1995
- “Power,” Grolier Encyclopedia, 1995
- “Power,” Encarta Encyclopedia, 1995
- “Work,” Grolier Encyclopedia, 1995
- “Work,” Encarta Encyclopedia, 1995
- “Bernoulli’s Principle,” Grolier Encyclopedia, 1995
- “Bernoulli’s Principle,” Grolier Encyclopedia, 1995
- “Force,” Grolier Encyclopedia, 1995
- “Force,” Encarta Encyclopedia, 1995
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Glossary
Power– the rate at which the work is done.
Work– a word that describes an effort that is put into doing something.
Bernoulli’s Principle– Bernoulli’s law, by Daniel Bernoulli, was about the relationship between pressure and velocity of moving fluids.
Lift– when there is less pressure on the top of the wing and more pressure underneath it due to a curved wing.
Tip speed ratio– the tip speed ratio is how many times the blades of a windmill will turn for every mile an hour of wind speed.
Horizontal axis windmills– when the axle is horizontal to the ground, uses lift.
Vertical axis windmill– when the axle is vertical to the ground, uses drag.
Turbine– a rotary machine that converts the power of water into energy that can be used for electricity, almost like a windmill but not driven by wind.
Force– something that accelerates an object.
Windmill – A windmill is a wind instrument that collects the force of wind and can turn it into electricity. The blade catches the wind, turning the axle, which can turn a generator, making electricity. They were originated in Persia and are still used in the world today.
