Rooftop Wind Turbines

Team 3C: Wind turbines Presentation Video https://mediaspace.carleton.ca/media/CCDP%202100C%20Team3%20Rooftop%20Wind%20Turbines%20Presentation/1_j4qih2jy

Overview

Wind turbines built on rooftops (shown in figure 1 below) that use a renewable form of energy (wind energy) are known as rooftop wind turbines. This energy is eco-friendly unlike burning fossil fuels which releases harmful games that deteriorate the environment [2]. Furthermore, the wind energy market is one of the efficient energy sources since it is one of the cheapest sources of electricity. In Europe, for example, the costs of the wind energy are seen comparatively lower than coal and gas energy markets (shown in Figure 5 below) [3]. Additionally, wind energy was reported in 2017 to be one of the lowest cost electricity generating technology in the United States [4].

Figure 1: Rooftop wind turbine on Twelve West building located in Portland USA [1]

Figure 2: Electricity generating costs in the European Union, 2015 and 2030 [3]

Turbine Size: Abraham Paulose

Turbine size significantly affects the turbine’s efficiency as the size of the turbine is the deciding factor that determines how much energy is being transferred from the wind onto the turbine [5]. Figure 2 below shows the timeline of wind turbines built from 1980 to 2011 along with their blades’ diameter and the amount of power generated. As the blades’ diameter increases over the years, the power produced by the turbine increases with it as well. The bigger the blade’s diameter, the more wind the turbine can harvest [6].When these wind molecules hit the blades, the wind energy applies torque onto the turbine blades causing the blades to rotate [6]. Since the larger blades capture more wind, it experiences more torque thus increasing the turbine’s power production.

Figure 2: Turbine size [6]

Generation: Abdalrahman Shaheen

Wind force will reach the wind turbine blades and cause a rotation of 7-12 rpm (revolutions per minute). Attached to the blade’s hub is the drive shaft. The drive shaft rod is connected to a gearbox that increases the spinning speed inside the turbine. The generator (see Figure 3) takes the increased kinetic energy to rotate a metal conductor that spins around magnet poles. More magnet poles will allow the generator to spend less effort and be more efficient [7]. Generators can spin up to 1500 rpm, this high rotation speed produces current that will go to the computer system to control the current. The current then passes to a transformer which will raise the voltage and supply electricity to light up houses and power appliances.

Figure 3. Components of a wind turbine [Abdalrahman Shaheen][8]

Type of Wind Flow: Francisco De Grano

            Wind turbines need wind in order for them to operate and generate power there are two types of wind flow that turbines use. Laminar and turbulent wind flow see Figure 4, laminar flow is the predictable movement of air and turbulent flow is the chaotic movement of air [9]. Reynolds number is used to differentiate laminar flow and turbulent flow. Turbulent flow causes turbines to have mechanical stress which can lead to turbine failures in the future, in addition they also cause turbines to produce less output and be less efficient. What causes these turbines to produce less output and be less efficient is torque reversals [10]. A torque reversal is when the wind changes the direction in which the turbine is spinning.

Figure 4: Turbulent flow vs. Laminar Flow[Francisco De Grano]

Turbine Height: “Ethan” Thomas Ballantyne

Wind speed directly affects how fast the blades of the turbine can spin. Faster spinning blades result in more energy being produced [11]. Wind speed increases with height, starting at zero [12]. Wind has a velocity of 0 m/s when in contact with the ground, this is known as the no-slip condition. The no-slip condition is caused by friction between the wind and the ground being so strong that the wind is no longer in motion at that point. As altitude increases the friction force slowly weakens resulting in faster wind speed. So, the higher a wind turbine can be built, the more energy it can theoretically produce. Figure 5 below shows the height of wind turbines from 1995 - early 2018 with projections of turbine height up to roughly 2023 [13]. The turbine shown in the presentation had not been built at the time of this graph's publication.

Figure 5: Wind turbine hub height progression [13]

Pitch Control Systems: Jayanta Gunjal  

Canada ranks 6th in the world in terms of energy consumption with 3.14% of energy being produced by wind [14]. The main reason this number is so low is because wind turbines have many restrictions; they require wind, space and height among other things. For the purpose of maintaining a high efficiency, pitch control systems are needed to control the pitch of the turbine blades.

The pitch of a blade refers to how “twisted” the end of a blade is. There is a specific pitch angle for any given wind speed to optimize output power. Pitch angles greater or less than this value reduce power output, even to the point of zero rotation with high winds [15]. Figure 1 below depicts various pitch angles.

Figure 1: Various pitch angles: a) fine pitch angle, b) coarse pitch, c) feathered [16]

References

[1]“Project,” Solaripedia. [Online]. Available: http://www.solaripedia.com/13/297/3341/twelve_west_clouds.html. [Accessed: 25-Nov-2020].

[2]“Renewable Energy vs Fossil Fuels: 5 Essential Facts,” Amigo Energy, 25-Jan-2018. [Online]. Available: https://amigoenergy.com/blog/renewable-energy-vs-fossil-fuels/. [Accessed: 26-Nov-2020].

[3]R. Fares, “Wind Energy Is One of the Cheapest Sources of Electricity, and It's Getting Cheaper,” Scientific American Blog Network, 28-Aug-2017. [Online]. Available: https://blogs.scientificamerican.com/plugged-in/wind-energy-is-one-of-the-cheapest-sources-of-electricity-and-its-getting-cheaper/. [Accessed: 02-Nov-2020].

[4] P.-E. Morthorst and S. Awerbuch, “The Economics of Wind Energy,” ewea.org, 2009. [Online]. Available: https://www.ewea.org/fileadmin/files/library/publications/reports/Economics_of_Wind_Energy.pdf. [Accessed: 2020].

[5]"NZ Wind Energy", Windenergy.org.nz, 2020. [Online]. Available: http://www.windenergy.org.nz/improvements-in-technology. [Accessed: 01- Oct- 2020].

[6] G. Johnson, “WIND TURBINE POWER, ENERGY, AND TORQUE,” in Wind Energy Systems, University Reprints, 2006, pp. 72–145.

[7] Things you don't know about wind turbines. (n.d.). Retrieved November 25, 2020, from http://www.industrycrane.com/blog/How-wind-turbines-work.html

[8] Generac Power Systems, I. (n.d.). How Does a Home Backup Generator Work? Retrieved November 25, 2020, from https://www.generac.com/for-homeowners/home-backup-power/how-it-works

[9]“Laminar flow,” Applied Mathematics, 19-Jan-2015. [Online]. Available: < https://uwaterloo.ca/applied-mathematics/current-undergraduates/continuum-and-fluid-mechanics-students/amath-463-students/laminar-flow.>  [Accessed: 08-October-2020].

[10]Dvorak P. (2015). “How turbulent winds abuse wind drive trains,” [Online]. Available:

< https://www.windpowerengineering.com/how-turbulent-wind-abuse-wind-turbine-drivetrains/

> [Accessed: 25-October-2020].

[11]“Wind power,” Wind power - Energy Education. [Online]. Available: https://energyeducation.ca/encyclopedia/Wind_power. [Accessed: 01-Oct-2020].

[12] C. R. Hadlock and C. R. Hadlock, Supplementary material and solutions manual for Mathematical modeling in the environment. Washington, D.C.: Mathematical Association of America, 1998. [Accessed: 26-Oct-2020].

[13]   P. Dvorak and P. Dvorak, “Nabrawind Technologies begins installation of one of the tallest wind turbine towers in the world,” Windpower Engineering & Development. [Online]. Available: https://www.windpowerengineering.com/nabrawind-technologies-begins-installation-one-tallest-wind-turbine-towers-world/. [Accessed: 01-Oct-2020].

[14] “Chapter 1: Canadian energy consumption in the global context,” Canada's Energy Outlook, 22-May-2018. [Online]. Available: https://energyoutlook.ca/chapter-1/. [Accessed: 05-Nov-2020].

[15] A. Rezaeiha, I. Kalkman, and B. Blocken, “Effect of pitch angle on power performance and aerodynamics of a vertical axis wind turbine,” Applied Energy, 07-Apr-2017. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S0306261917303744. [Accessed: 05-Nov-2020].

[16] “fine pitch,” Academic Dictionaries and Encyclopedias. [Online]. Available: http://aviation_dictionary.enacademic.com/2793/fine_pitch. [Accessed: 05-Nov-2020].