Problem Statement. Design and construct a small wind turbine to produce as much power as possible while

Transcription

1 Problem Statement Design and construct a small wind turbine to produce as much power as possible while still maintaining efficiency. One must be able to measure the output of the turbine, the design must be creative, must be powered by wind, and must be safe to use. Plexiglass, metal, and other heavy or dangerous blades are highly discouraged. The design must be economical, the maximum rotor blade diameter allowed is 200 cm, and premade turbine blades or airfoils may not be used. Research Statement Wind is caused by air flowing from high pressure to low pressure. Because the earth is rotating, the air does not flow directly from high to low pressure, and is deflected to the right in the northern hemisphere and to the left in the southern hemisphere. As a result, the wind flows around high and low pressure areas rather than simply directly from one to another. The closer the high and low pressure areas are the together, the stronger the winds. Wind plays a large role in the creation of electricity and is a primary renewable energy source. As a whole, electricity is considered to be a secondary energy source. Electricity is generated from the conversion of primary sources of energy such as fossil fuels (coal, natural gas, oil, etc.), nuclear power, and renewable sources (wind, solar, geothermal, etc.). The process of producing electricity is quite complex, but in simple terms, it starts with the initial energy source that creates movement in a turbine or piston which then rotates the rotor in a generator. The activation of a generator produces an electrical current that then gets carried into communities by power lines. Specifically regarding the transformation of wind power to electricity, certain devices such as windmills and wind turbines are used. Windmills harness wind energy to

2 produce mechanical power in the form of torque. This power is then used for the purposes of milling grain or pumping water. Windmills can also be modified for the purposes of providing heat and light. As opposed to producing mechanical energy, a modern type of windmill, using the kinetic energy of wind, produces electrical energy. This modern type of windmill is known as a wind turbine. Wind turbines are more advanced and efficient than windmills. Wind turbines transform wind power through the rotation of rotor blades around a central hub. The wind rotates the rotor blades on a wind turbine, which then turns a gearbox shaft that powers a generator to make electricity. Finally, the electrical generator converts the kinetic energy of the rotating blades into electrical energy that can be carried in electrical cables. For wind turbines there are two main types of designs: vertical axis turbine and horizontal axis turbine. The main rotor shaft of a vertical-axis wind turbine is set to be transverse to the wind whereas for horizontal-axis wind turbines the rotating axis is parallel to the ground. Airfoil shaped rotor blades are popular amongst modern wind turbines, however, windmills typically use flat blades or sails. The purpose of either variation of blades is to harness the combination of both lift and drag to cause the rotation of the blades. Wind power is one of the fastest-growing energy sources in the world as it offers many advantages. One significant advantage is that wind power is cost effective. Land-based utility-scale wind is one of the lowest-priced energy sources and costs between two to six cents per kilowatt hour. Wind energy also mitigates the price uncertainty that fuel costs add to traditional sources of energy. Furthermore, wind is a clean fuel source as it does not cause pollution and does not produce atmospheric emissions that cause things such as acid rain, smog, or greenhouse gases. Wind power is also sustainable as it does not exploit natural resources and its functionality is based simply on wind. Wind power has also contributed to industry growth in the U.S. as it has an annual economic impact of roughly $20 billion and has employed more

3 than 100,000 workers in With ever-growing environmental problems, the importance of harnessing wind power has grown as it can contribute to mitigating the impacts of climate change. While there are many advantages, there are also some disadvantages to wind power. Although wind power is relatively cost efficient, its high initial investment costs compared to fossil-fueled generators should be noted. Also, good wind sites are often located in rural and remote locations, far away from cities where the electricity is needed, so a means of transporting the electricity is needed. Another disadvantage is that wind power might not be the most profitable use of land resulting in high opportunity costs for those harnessing wind power. Turbine blades can also damage local wildlife as some birds have been killed by flying into spinning turbine blades. The power of wind is defined as follows: The variables that impact the power of wind are air density, wind speed, and the area swept which is affected by blade length. This affects the design and placement of turbines because they can be optimized by being located where air density and wind speeds are at a max and designed to have an efficient area swept value. There is a disadvantage to using wind power that traditional sources such as oil and coal do not have: the wind is not constant, but varies in direction and intensity with time. To deal with wind variability, the builders of wind turbines must adapt their turbines to be able to handle various wind conditions. Some designers are working on developing components within the turbine to store energy, so that excess energy produced in periods of high wind can be stored up and drawn away during periods of low wind, thus making the overall output of the turbine more regular and dependable. There remains the question of how we pay for wind power development. Currently, the

4 government subsidizes wind power production, which angers many who feel it is unfair for taxpayers to pay this price. However, it is projected that eventually these subsidies will lead to cheaper energy. As technology advances, wind turbines become less expensive to build and more efficient at producing power, which leads to lower energy prices. Additionally, wind power is not subject to the sort of price volatility that affects other sources of power, such as oil. It is therefore likely that, if wind technology continues to develop, its stability and efficiency will ultimately lead it to become become actually less expensive than coal or oil power, and thus be a worthwhile investment. However, beyond potential costs, there are some negative impacts of wind power that must be addressed if it is to be expanded further and used to meet a greater percentage of energy needs. For example, wind turbines can produce a great deal of sound, leading residents of local areas to complain about the effects of the sound on their lives and health. To deal with this problem, turbines can be built farther away from centers of human population. This can be achieved by building turbines offshore. Technology can also be developed which allows wind turbines to operate less noisily, such as serrations along the trailing edges of the blades which help control the air flow and reduce the noise produced by the turbine. Additionally, while the overall environmental impact of wind turbines is less than that of burning fossil fuels, there is an impact on the natural environment stemming from potential damage to local habitats and the killing of flying animals such as birds. In order to lessen this impact, the design and location of wind turbines could be modified. Again, turbines build over water might help to solve this problem, as fewer birds fly far offshore and there is not much of a local ecosystem above the surface of the water. Finally, there are some people who complain about the implementation of wind turbines because they see them as ugly, or damaging the landscape in some way. In order to address this concern, it is important to consider implementing local variability in design. This

5 variability would allow residents to have some say in which wind turbine design was installed in their community, rather than a standardized design which residents of a certain area may find unattractive being automatically installed. In order to implement this local variability, designers could develop a few different styles of wind turbine similar to one another in power production, efficiency, and ease to build, and allow residents to choose between them so that they are more satisfied with the aesthetics of the wind turbine. Despite these problems still to be worked out, the wind power industry offers a significant number of job opportunities to a great many people. Jobs in the industry include scientists and engineers, who research potential materials and designs for the turbine blades, and various machinists, assemblers, inspectors, and managers who work in the process of actually constructing the turbine. Specific types of engineers that often work in the wind power industry include aerospace engineers, who are experts in the behavior of air and thus qualified to work on designing blades, as well as electrical and mechanical engineers, who might deal with the internal components of the turbine, and environmental engineers, who help to mitigate any potential environmental damage caused by the turbines. Overall, wind energy displays a great deal of promise as a future large-scale source of energy. Projections for the future of wind energy generally predict successful expansion into a larger share of the global energy market. By 2050, according to the Wind Vision report conducted by the Department of Energy, wind energy could provide upwards of 600,000 jobs nationally and prevent over 12 gigatons of greenhouse gases by preventing the burning of fossil fuels. Currently, some of the areas of wind power that are being revolutionized include developing new coatings to protect the blades from the elements, allowing them to last longer and function more efficiently, as well as continuing to work on the development of offshore wind farms which have several advantages over land-based farms. All of these developments should only increase the

6 already immense potential that wind power has to sustainably meet our energy needs as we move into the future. Short Report To create our own wind turbine, we made use of a gearbox, four blades, and the Kidwind base. The wind turbine we created utilizes a pringle can cut into four separate curved blades attached to dowel rods as the main component of power generation. We used a pringles can due to the precurved nature of the can, which provided a way to make air foils without having to curve our own cardboard. We used the airfoil shape because this shape allows for a higher lift force while simultaneously decreasing the drag force on the blade. We also chose to use the pringles can because it is made of a very light weight cardboard material which decreases the drag force on the blades. We chose to use four blades because the KidWind kit we used as the stand for the turbine allowed only for a number of blades that 12 is evenly divisible by (it provided 12 blade locations, so to keep the blades evenly spaced the number of blades had to be a factor of 12). We felt that six blades added too much weight and therefore drag force to the blades so the power generated would not increase significantly. We decided that four blades was the correct amount over three because adding one blade would not increase the drag force significantly, but would increase the power generated. Our wind turbine utilizes a gearbox, a pringles can, and the kidwind kit to generate power. The wind turbine we designed and produced went through several changes in order to find the maximum power output possible. We tested both the effects of the pitch of the blades and lengths of the blades to generate the optimal amount of power. In order to find the best angle of attack for our turbine we conducted a series of tests to observe which angle generated the most power. We began by first facing the blades directly towards the fan and tested the power generated from this angle, and then we continued

7 to change the angle of attack and test

8 the power generated at the various angles until we found the highest power generated. This angle created the best rotational speed at the fan speed we were using. We tested the length of the blades in a similar way. With the knowledge that the length of the wind turbine blades may increase the power as length increases, but an increase in blade length will cause an increase in the drag force on the blades, we decided to increase the length of our blades slightly to see if the advantages of increasing the length outweighed the disadvantages. We decided to first increase the length by 5 cm, an increase of approximately 25%. After we increased the length we tested the amount of power generated by this increase. The increase in length produced about a 7% decrease in power. After analyzing the data it was clear that the optimal length was the original length of our blades (about 20 cm). We know this because the increase in length produced a drop in power and although we could have decreased the percentage we changed length by, we determined that any change in length lower than 25% would be too small to create a significant change in power and thus not be worth the excess material we would have to add to the blades. After conducting research and several tests we were able to maximize the power output of the wind turbine. Our wind turbine uses a pringles can as the blades in order to create the airfoil shape that is optimal for power generation. The pitch and length of the blades were changed several times and then tested to find the best possible blade arrangement. The final wind turbine we created has been built to use the wind generated by a box fan (wind speed of 3.0 m/s) to create a power of mw. Works Consulted The Cost of Wind Energy in the U.S. AWEA, American Wind Energy Association,

9 org/falling-wind-energy-costs. Hamilton, James, and Drew Liming. Overview of a Wind-Farm Project. U.S. Bureau of Labor Statistics, U.S. Bureau of Labor Statistics, Just Energy > Learning Center > Electricity. Just Energy, Just Energy, learning-center/electricity. National Geographic Society. Where Does Electricity Come From? National Geographic Society, National Geographic, 20 Feb. 2013, University of Texas at Austin. Dealing With Wind Variability On The Wind Farm. ScienceDaily, ScienceDaily, 24 Oct. 2007, The Way to More Efficient, Quieter Wind Turbines. Phys.org - News and Articles on Science and Technology, Phys.org, 1 Oct. 2015, phys.org/news/ efficient-quieter-turbines.html.

10 Wind Energy Converts the Winds Power into Electricity. Alternative Energy Tutorials, Alternative Energy Tutorials, html. Wind Vision. Department of Energy, Office of Energy Efficiency and Renewable Energy, Wolfe, Michael. Devices Used to Harness Wind Energy. Sciencing, Sciencing, 24 Apr. 2017, sciencing.com/devices-used-harness-wind-energy html.