Wind Turbine Project Report

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San Jose State University *

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Mechanical Engineering

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Oct 30, 2023

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The Best of the Best Wind Turbine Design August Basuino, Vy Lam, Joshua Perez, Jack Wu San Jose State University, Charles W. Davidson College of Engineering ENGR 10: Introduction to Engineering Section 19, Team Group #2 Professor Javier Valencia April 6, 2023

1 Project Summary The objectives of the project were to build a wind turbine tower that can produce a power rating of at least 2 watt. The tower should have at most a stiffness of 20 Newton per millimeter (N/mm). In terms of height and weight constraint, the tower (excluding the bottom and top plate) should not exceed 200 g while the whole structure should not exceed 17 inches. With all these specifications in our mind, our team ensured that the wind turbine tower was built according to the guidelines with pre-made carbon fiber pipes (Cost: $18) and wood sticks (Cost: free). As tower testing data is finalized (process shown in figure 1 and 2), the tower (including the bottom and top plate) didn’t exceed 17 inches, meaning height requirement is fulfilled. Simultaneously, the tower reaches 20.547 N/mm at 2.4 kg, which means that it didn’t meet the stiffness expectation but it was overall acceptable. Meanwhile, the tower weighs exactly 200 grams and it has produced a maximum power of 2.9 watts. The tower was away from the wind blower by 368.3mm and the turbine has gained a speed of 7886 RPM. These results indicate that the turbine blade design improves power efficiency but materials choice didn’t fulfill the weight and stiffness expectation. While the blade design was successful, our team has concluded that weight and stiffness of our tower could have been improved by centering the carbon fiber pipe. Then the amount of wood stick should be cautiously applied as an excessive amount won’t be able to support the tower by much difference. Other than that, the overall test was consistent with other team groups along with consideration of the lab environment.

2 Figure 1. Wind turbine blade is being blown by Figure 2. Stiffness test setup from side wind velocity of 25 mph while its speed is view with hundred grams of weights being measure being added as measurement continues Table 1 - Group #2 Tower Specification Height 17 inches Weight 200g Maximum Output 2.7 watts Theoretical Power 6.5 watts Stiffness 20.547 N/mm Turbine Blade Speed 7886 RPM

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3 Table of Contents Project Summary ........................................................................................................................... 1 Table of Contents ........................................................................................................................... 3 Introduction .................................................................................................................................... 4 Background Information 1.1 ................................................................................................... 4 The Project 1.2 ......................................................................................................................... 6 Theories ........................................................................................................................................... 8 Design .............................................................................................................................................. 9 Design of the Blade 2.1 ............................................................................................................. 9 Design of the Tower 2.2 .......................................................................................................... 9 Build .............................................................................................................................................. 10 Building of the Blade 3.1 ....................................................................................................... 10 Building of the Tower 3.2 ...................................................................................................... 12 Test ................................................................................................................................................. 12 Testing of the Blade 4.1 .......................................................................................................... 12 Testing of the Tower 4.2 ......................................................................................................... 13 Performance of the Blade 4.3 ................................................................................................ 14 Performance of the Tower 4.4 ............................................................................................... 16 Conclusions ................................................................................................................................... 16 Recommendations ........................................................................................................................ 17 Reference ...................................................................................................................................... 18 Appendices .................................................................................................................................... 19 Appendix A ............................................................................................................................. 19 Appendix B ............................................................................................................................. 24

4 Introduction Background Information 1.1 Conservation of Earth’s natural resources has always been part of goals for humans in achieving sustainability. As limited resources will keep depleting over many decades, it’s essential for scientists and engineers to construct various methods to reduce waste while maintaining enough resources to keep human civilization advancing. Throughout the years, humans have evolved in countless ways to produce energy. Whether the energy is for commercial or industrial use, humans need to be cautious about the drawback in drawing energy from such sources. Therefore, renewable energy is now something that we need to consider. For example, wind turbines are one of the common renewable energy methods that convert kinetic energy produced by high speed wind into electricity. The typical structure is shown in figure 3 and components can be seen in figure 4. Figure 3. Wind Farm. Photograph by Inga Spence/Alamy Stock Photo

5 Figure 4. Standard wind turbine component A wind turbine generally consists of three blades, a tower and a generator which converts kinetic energy to electricity. Ideally, in order to create the most effective and efficient energy generator, blades have to be large enough to increase sweeping area, meaning more wind will be obstructed by their lengths. Besides the size of blades, the more blades a wind turbine can have, the more kinetic energy can be drawn from the wind. Also, each blade should be as thin as possible to reduce the tower’s overall weight. In reality, achieving an extreme in any aspect of a wind turbine tower results in failure. For example, the threshold of turbine blades decreases if they are too thin as they can’t withhold the pressure from the wind. Too many blades would be less cost effective and increase overall weight significantly, not to mention that energy production may not be significantly different. While larger blades can faster generate more electricity, the maintenance logistics may put workers a more difficult task to operate. The worst thing it can happen is that it may take the same amount of energy that it produces to be able to fix a blade. Therefore, every choice that our

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6 team needs to make are interconnected and they need to be adjusted accordingly to ensure a functional wind turbine tower. The Project 1.2 The purpose of this wind turbine project is to create the lightest, stiffest, most energy-efficient tower with materials provided in labs and ones that teams will acquire on their own. Since wind turbines have already been designed in the most efficient ways from the real-world, this project focuses on building professionalism and teamwork, rather than employing it for real life use. Each team is usually separated into four to six people. Every group member is responsible for various tasks such as designing blades using Solidwork, constructing the tower and testing its stiffness and power. The generator and 3D printer is included in the lab, thus teams won’t need to worry about the cost regarding those. However, groups must discuss the materials to build the tower. Materials vary from any since there is no restriction as long as they can fulfill the purpose of this project. The specification of the wind turbine construction can be seen in figure 5. Figure 5. Diagram of support structure with restriction in height, length and width (Youseffi, 2014)

7 Diameter of the carbon fiber pipe is 2 ¼ inches. Thickness of the pipe is about 1/20 of an inch. Tools used: hacksaw, vises, hot glue gun, yard stick, weighing balance, dry kitchen sponge that acted as sandpaper. Materials used for the tower: carbon fiber pipe, wooden popsicle sticks, thin rectangular wooden sticks, hot glue. Measuring equipment: (stiffness measuring) hooked weights, metal wire with loops tied on it, small table with a hollow center and a pulley, electronic drop indicator for measuring displacement, metal screw eye for attaching metal wire, (power measuring) air mover, digital tachometer for measuring rotations per minute, load box, power meter, electrical wires, the same type of table as was used for measuring stiffness.

8 Theories Formula for Force (F) = Stiffness (k) * Displacement (x) Formula rearranged for Stiffness k = F / x Formula for Efficiency of the Windmill 𝐸??𝑖?𝑖???? = 𝑀𝑎? 𝑃???𝑟 𝑃𝑟?????? 1 2 *𝑃*?*𝑉 3 *???? ?𝑖?𝑖? Betz limit = 59% Air Density P= 1.2 (kg/m 3 ) Area of the sweep area of the blade A = 𝞹 r 2 Wind Velocity V = 11.176 m/s Gravity = 9.8m/s 2

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9 Design Design of the Blade 2.1 Figure 6. Direct profile of an individual wind turbine blade on Solidworks Given the task to design a windmill blade on Solidworks (a 3D design software) that included a prefixed hub, with the restraints of a diameter of 6.0 inches, a blade width of maximum 0.7 inches, a blade height of .25 inches, and a maximum blade length of 2.5 inches. Through research considering the restraints a conclusion was determined that the optimum number of blades a wind turbine should include is 3. (Kerrigan, 2018) stated that 3 is the perfect number to have maximum output in power. Also, that including more blades would see a slight increase in power but not enough to balance the cost of more material. In Figure 6, you can see from the bottom left corner to the top right of the profile, there is a 12 degree angle of attack which was determined from (Mesa, 2019). The optimum angle of attack for a windmill is around 10-15 degrees. As for the restraints, optimizing the size of the blade would result in the largest sweep area, allowing a greater absorption of wind. Design of the Tower 2.2 The design of the tower consisted of the materials carbon fiber, wood, and hot glue. The first design of the tower was scrapped because the thin pieces of wood that were used would not

10 help much with stiffness because the angle of the wood was too similar to the vertical angle of the carbon fiber pipe. The carbon fiber pipe was not altered for the second design and the thin wood pieces were removed. The second design followed a shape more similar to that of a trapezoid on all four sides. The second design was able to be more structurally sound than the first design while using less hot glue. That was because the wood pieces were arranged in a way that allowed the tower to deflect more against the weights that would be placed against the tower during the stiffness testing. The carbon fiber pipe was not centered on the bottom plate of the tower because a drilling machine in class was used to drill into the bottom plate. The width of the bottom plate prevented the drill bit from reaching the center of the bottom plate because the back side of the drill machine blocked the edge of the bottom plate. Small craters were created in the bottom plate by the drill bit, and those were used to help support the carbon fiber pipe. That was done because the bottom of the pipe became more secure while it lay in the craters. The drill bit was round and so the craters were round and there was difficulty in placing the carbon fiber pipe flat against the bottom plate vertically. Hot glue was used to secure the carbon fiber pipe and much care was taken to do that because the tower would have tipped over if the pipe was not secure. The carbon fiber pipe was secured before the wood pieces were replaced. The hot glue and the wood pieces in the first design were removed and the wood in the second design was acquired from the array of free materials available in the classroom. The wood pieces used in the second design were rectangular wood dowels and tongue depressors. Build Building of the Blade 3.1 Upon the completion of the design, building the blade would require Solidworks. Using the hub, we would individually design a blade that will be replicated and evenly distributed

11 around the hub. Following the slide deck that was provided by Professor Valencia, tasked to create two planes, one connected from the hub and the second at the tip of the blade. Connecting the planes required a loft to line up individual points from the two different planes, creating a smooth surface. However the edges of the blade were still sharp. Filets were then added to smooth out the rough edges, which was followed by the replication of the blade and placing the replicas at 120 degrees around the hub. The model of the blade was placed on a USB flash drive belonging to the university during the class in which the models of the blades were created. The blade was later printed without cost to the students using a computer numeric control machine and 3D printing. The letter “G” with the number two and the letter “S” with the number nineteen were placed on the center of the blade so that the group of students knew which blade was theirs. Figure 7. Final design of the blade on Solidworks

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12 Building of the Tower 3.2 After gathering the materials of a carbon fiber pipe, wooden base plates, wood sticks, and hot glue, the tower was created. Firstly, a hole the size of the carbon fiber pipe was drilled into the base. Then the carbon fiber pipe was inserted into the hole and hot glued to secure it. In our first design, the wood sticks were hot glued into the carbon fiber pipe. The class provided wooden sticks that would be cut and used to the dimensions of our liking. At first the base wasn't strong enough. Our team decided to hot glue the wood sticks straight from top block to bottom plate in order to give the carbon fiber pipe more support. The next step was to prevent the tower from bending by the wind, so more wood sticks were used with hot glue to give the lower part of the carbon fiber pipe more cover. Figure 8. Drilling the base Figure 9. Cutting the wood sticks Figure 10. Process of hot glue

13 Test Testing of the Blade 4.1 Figure 11. Set-up of the testing for the windmill blade In Figure 11, the entire wind turbine is mounted to a small table using bolts and butterfly nuts. The wires connected from the back of the blade, are attached to a motor that is connected to a power meter, which will collect the currents (amps), the voltage (v), and the power (Watts). Also connected to the power meter is a potentiometer which will be used to vary the load. Lastly, directly in front of the blade is a fan, which acted as wind for the test. The number of rotations per minute of the blade while spinning was measured using reflective tape and a digital tachometer. A small square of white reflective tape was placed onto one blade of the blade. This

14 was done because the digital tachometer had a laser which allowed it to measure the rotations per minute while being accurately pointed at the reflective tape. The highest power setting of the fan was used, which was recorded at 25 miles per hour and maintained throughout the duration of the testing. Lastly, the task was given to vary the load to find the optimum power production. Testing of the Tower 4.2 Figure 12. Testing the stiffness of the tower In Figure 12, similar to the set up of the testing for the blade, the tower is mounted and stabilized by bolts and nuts. On the opposite side of the motor, a screw with a loop is drilled into the block to create a pulley system where weights were added. On the front side, a displacement meter was added to record the displacement from the front of the block to the reader. The

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15 weights on the opposite side of the displacement reader will cause the tower to move because of gravity. The pulley system creates a perpendicular force. Once the set-up was completed, weights were added in increments of 100g. After collecting the data, the task was given to graph the data in order to find the slope of the line, which resulted in the stiffness of the tower. Performance of the Blade 4.3 Graph 1. Voltage vs Current graph In graph 1, the voltage and current are inversely proportional because as voltage increases, current decreases, and vice versa.

16 Graph 2. Power vs Current graph In graph 2, the optimum power production can be seen between 1000 and 1200 amps which would most likely be around 2.75 Watts produced. =30.4% efficiency 𝐸??𝑖?𝑖???? = 2.7 1 2 *1.2*0.018*1395.92*.59 ? 100

17 Performance of the Tower 4.4 Graph 3. Stiffness graph In graph 3, the slope of the line corresponds to the stiffness of the tower. The stiffness of our tower would be roughly 20.55 N/m, which is greater than the required stiffness of 19. The relationship between force and displacement are directly proportional because as force increases so does the displacement. Conclusions In this project, we created a wind turbine and tested its performance. We designed the support tower and assembled it. We also used SolidWorks to design the blade for the wind turbine using knowledge from our research and the course material. The data for power generation from each group was collected and written on the board in class, and the turbine

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18 produced the most power according to those results. The tower did not visibly bend during stiffness testing. If it did bend then that would have been a result of the weights for testing gradually increasing in weight, which would have made bending of the tower not visible to the naked eye. The efficiency of the power generation was 28% lower than the Betz limit of 59%. Our wind turbine efficiency was .304, which is lower than the average of .42 (Arsie, Marano, Nappi, Rizzo, 2005). However, given the circumstances and knowledge that is now, slight tweaks in the tower and blade could easily result in a higher production of power. Recommendations The blade edges should have been more rounded because the lift of the edges allow the blade tips to move faster than the wind, generating more power and high efficiencies. The tower could have been centered on the bottom plate so that the weight of the tower would be distributed more evenly. The wood pieces located under the blades should have been positioned at a less extreme angle compared to the vertical position of the blades. That was because the angle of the wood almost stopped the blades from rotating. If that occurred then the blades would not be able to rotate at all. The tower could have been lighter because the weight was exactly 200 grams and the maximum weight for the highest value of points on the rubric was the value 200 grams. There should have been less hot glue used to reduce the weight.

19 Reference Arsie, Ivan & Marano, Vincenzo & Nappi, G & Rizzo, Gianfranco. (2005). A Model of a Hybrid Power Plant With Wind Turbines and Compressed Air Energy Storage. Proceedings of the ASME Power Conference, 2005. 10.1115/PWR2005-50187. https://www.researchgate.net/figure/Wind-turbine-efficiency-vs-wind-speed_fig11_228903334 E10 website. https://www.sjsu.edu/e10/labs/wind-turbine.php Kerrigan, Saoirse. “The Scientific Reason Why Wind Turbines Have 3 Blades.” Interesting Engineering, Interesting Engineering, 28 Mar. 2018, https://interestingengineering.com/science/the-scientific-reason-why-wind-turbines-have-3-blade s. MESA. Aerodynamics of Wind Turbine Blades - Nm Mesa. https://www.nmmesa.org/wp-content/uploads/2019/10/Aerodynamics-of-Wind-Turbine-Blades.p df.

20 Appendices Appendix A SJSU: ENGR10 LAB Project Wind Turbine and Support Tower Performance Data Section: 19, Team # 2, Date: 03-15-2023, Data collected by (Name): Joshua Perez 1. Stiffness (deflection) Measurements a. Tower Height: 17 in. b. Tower Net Weight: 200 g. (Total Assembly – Top/Bottom boards) c. Stiffness Measurements: grams and mm Table 1.0 – Tower stiffness data Data Points LOAD (Kg) LOAD (N) DISPLACEMENT (mm) Observations 1 0.100 0.981 0.03 - Weight was placed on the back side if the side with the blade is considered the front - 3 significant figures used - kg to N conversion factor used was 1 kg to 9.81 N 2 0.200 1.97 0.06 3 0.300 2.94 0.10 4 0.400 3.92 0.14 5 0.500 4.91 0.20 6 0.600 5.89 0.24 7 0.700 6.87 0.29 8 0.800 7.85 0.34 9 0.900 8.83 0.45 10 1.00 9.81 0.49 11 1.20 11.8 0.57 12 1.40 13.8 0.66 13 2.40 23.5 1.19 As weights were added, the visibility of the bending of the tower was difficult to determine the displacement solely upon the use of the naked eye

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21 d. Load vs Displacement Graph. Provide the stiffness value of your team’s tower from the graph. Graph 1. Stiffness graph 2. Power Measurements a. Blade to Fan Distance: (at ̴ 25 mph wind speed) : 368.3 (mm) b. Wind Speed: 25 mph (In front of the motor and prior to blade installation) c. Power Measurements: volts, amps, and watts (Note: Wait ~5 sec. between readings for reading stability)

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22 Table 2.0 – Power measurement data Data Points Voltage Volts (V) Current I (Amps) Power P (Watts) Blade Speed (RPM ) Notes 1 5.24 001 0.01 7886 - 3 significant figures used - 0 ohms 2 2.70 995 2.7 6651 1 ohms 3 5.8 011 0.07 8691 Varied data 4 5.6 102 .59 8516 5 5.30 198 1.04 8321 6 4.36 478 2.15 7717 7 3.86 1625 2.4 7394 8 3.22 807 2.7 6935 9 2.5 980 2.45 6355 10 2.49 946 2.41 6298 d. Power vs Current Graph. Provide the max value of power generated.

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23 Graph 2. Voltage vs Current graph

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24 Graph 3. Power vs Current graph NSPE Code of Ethics for Engineers: Engineers, … shall ….hold paramount the safety , … of the public... (This means you and your classmates.)

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25 Appendix B 1. Work distribution ● Joshua and Jack worked on designing the blade. ● August and Vy worked on designing the tower. ● Jack bought the material for the tower. ● Everyone participated in building the tower and testing the wind turbine performance. 2. Report contribution ● Jack worked on the summary, introduction, and table of contents. ● Vy worked on the references, building of the tower, and appendices ● Joshua worked on theories, design of the blade, build of the blade, testing of the tower, graphs, table of contents, and editing. ● August worked on gathering information on the tools, materials, measuring equipment used, conclusions, recommendations, design of the tower, and testing of the blade. 3. Challenge One challenge we faced was that the tower when we built turned out to be a little weaker than we had expected with our design. After discussing, our team decided to give it a makeover and removed all the previous wood sticks. We positioned the wood sticks differently in the new model and it appeared to be stronger. A lesson we learned is to do more research in modeling the base and be prepared to do it again until it’s satisfactory for all of us.

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26 4. Team performance Teamwork Skill Performance 1) Open and honest communication among members 5 2) Each individual carried his/her own weight 5 3) Collaboration in decision making 5 4) Team set goals and milestones 3 5) People listened to each other 5 6) Leadership was shared among the members 3

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