VIEWS: 3 PAGES: 4 POSTED ON: 10/3/2012
Overview The implementation of renewable energy practices has become more and more widespread in recent years. Of these alternative options, one of the most promising is that of wind energy. If you think about it, wind is everywhere – and up high, it is even more powerful. If we can effectively harness this force and use it for our own needs, then we will open up a door to the future. This exercise will introduce you to the wind turbine design process. In this lab, you will pick a blade design and build your own mini-turbine. Then, by using the NXT and a light sensor to count and log rotations, you will analyze the efficiency of your design and see how making certain changes will affect performance. Hopefully, by the time you complete this exercise, you will have a deeper understanding of how engineering designs are developed, troubleshot, improved. Objectives In this lab, students should accomplish the following: Learn the importance of picking a strong initial engineering design Understand how much time and energy is necessary for a wind turbine to generate a meaningful amount of power Understand how to examine quantitative data and make a qualitative assessment of it Introduce themselves to the concept of counter/encoder measurements Learn how to compare different engineering designs and make a good judgment call on which is the best option Learn how laboratory experiments can be scaled up and used to help us better understand real- world situations Familiarize themselves with renewable energy Activity Wind power is an area of sustainable energy utilization that is still in its relatively early stages of development. Because of this, it serves as a great platform for introducing students to the engineering design process. Not only will you familiarize yourselves with an industry that is growing in both size and importance, but you will also have the opportunity to get really innovative with your design ideas and then test out their viability in real life situations. Have fun during this lab – you have the opportunity to both be creative and contribute new ideas to an engineering area that is growing in importance every day. 1. Using the Legos that come with your NXT Robotics kit, construct a sturdy base for your turbine. If you need an example, take a look at the photograph on the next page to help you generate some ideas. 2. Add a shaft to the top of this base, similar to the one above. Secure it in place so that it does not move laterally, but does rotate with ease. 3. Now comes the fun part – designing your turbine blades. Use a gear to mount them to the shaft. Consider the following when deciding on a layout: How many blades do you need? What types of materials would be best to use? (You will need to use light colored materials, however.) What shape should the blades be? How should the blades be angled? How long/wide should the blades be? Keep weight and ability to catch the wind in mind as you determine your design. Remember, you want to harness the most energy possible from the incoming gusts. If you are at a loss for ideas, think about what fan-like structures exist all around you (for example, pinwheels, ceiling fans, propeller blades). 4. Once you have attached your blades to the base, mount an NXT light sensor behind the base so that the beam can shine through and hit the blades without any obstructions. Cut a piece of black electrical tape in half and stick it to the back of one of the blades, so that the NXT light sensor detects the tape each time the blades make one full rotation. 5. Tape your turbine down to the table, near the edge, so that it cannot be knocked over. Place a floor fan about two feet away from the turbine and use it to test out the rotational capacity of your blades. Make sure that they do rotate freely with the wind. 6. On your computer, open up the attached WindTurbine.VI and load it onto your NXT. Notice how this basic program works. The value of the light read by the sensor is logged every 10 milliseconds for ten seconds. This will return 6,000 values. We added a strip of black paper to one of the turbine blades during the construction process. Why did we need to do this? (Hint: You can look at this setup as a very basic encoder.) If we read 300 low values from the light sensor during these ten seconds, what is the average speed of the turbine? 7. Load the Wind Turbine VI onto your NXT, mount it to your base, and hook up the light sensor. Start the logging program at the same time you turn on the fan at a low sped. Once the NXT has finished logging, reconnect it to your computer so you can get the data off. 8. In LabVIEW, navigate to Tools >> NXT Applications >> DataViewer 9. Select the data you would like to import, and examine the data. 10. Open your dataset in LabVIEW, navigate to the block diagram, and replace the MEAN block in the for loop with the Detect Peak Threshold function (found in the functions panel under Signal Processing >> Signal Operation). Your block diagram should look like the one below. 11. Navigate to your front panel and run your program. This should give you the number of rotations your turbine completed in the 10 seconds that it was logging data. Your data should also be displayed in graphical form on the front panel – similar to how it looked in the Data Viewer. How many rotations did your turbine complete? How did this compare to your neighbor? What differences in design do you think contributed to higher/lower numbers of rotations? 12. Run the program several more times, with different fan speeds. Compare the data sets to one another in the Data Viewer. Make a chart (see Excel spreadsheet) that organizes the results based on blade type and fan speed. If time permits, run the tests again but start the logging only after the fan has been on a while and the turbine blades are rotating at optimal speed. Compare the data taken when the turbine was already rotating with that taken when the turbine started logging at a standstill. How much of a difference in number of rotations are between the two? What blades saw the lowest difference between these two tests? Why do you think that is? Challenge Now, take what you have learned in this exercise and scale it up to a real world situation. Take some time to consider the following: Wind gusts in real life are inconsistent and vary depending on weather conditions. How do you think this affects the viability of wind turbines? How would this impact the consumers of energy sourced by wind turbines? What could you do to prevent these consumers from having their electricity cut off? What factors must be taken into account when deciding how to design and place a turbine? (Consider such things as environmental factors, power transmission and storage, demand, cost.)
"Lesson Plan - Wind Turbine"