--- title: "Wind sources, turbines, parks, power control" subject: "Energy Environment and Society" chapter: 3 key: "semester_7/energy_environment_and_society:wind-sources-turbines-parks-control" source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/wind-sources-turbines-parks-control site: BCT Engineering --- # Wind sources, turbines, parks, power control Energy Environment and Society · Chapter 3: Renewable Energy Sources - Asked in: 2074 Chaitra, 2+4 marks - Video: [How do wind turbines work? - Rebecca J. Barthelmie and Sara C. Pryor](https://www.youtube.com/watch?v=xy9nj94xvKA) — TED-Ed - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/wind-sources-turbines-parks-control - Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-3 ## Question What are the availabilities of wind energy sources? Explain wind turbines, wind parks and power control system of wind energy production. ## Short answer Good wind sources are coasts, open plains, hilltops, and mountain passes like the Kali Gandaki valley. Wind turbines convert wind to electricity; wind parks are groups of turbines connected to a common substation. Power is controlled by pitch, stall, yaw, variable-speed converters, and brakes. ## Answer #### Availability of wind energy sources Wind arises from uneven heating of the earth by the sun. Good wind sources are: - Coastal areas and offshore (sea breezes), open plains, and hill tops/ridges. - Mountain passes and valleys where wind speeds up (Kali Gandaki valley in Mustang, Nepal). - Average speed of at least 5–6 m/s at hub height is generally needed for economic power generation. - Availability is mapped using meteorological data, anemometer masts, and remote sensing. The world has a vast technical potential (many times current demand); Nepal's estimated commercial potential is about 3,000 MW (based on earlier studies). #### Wind turbines A wind turbine converts the kinetic energy of wind to electricity: wind turns the rotor blades, which drive a shaft, gearbox and generator located in the nacelle on a tower. Types are horizontal axis (common; two or three blades) and vertical axis (Savonius, Darrieus). Large turbines are rated 2–15 MW. Power extracted = Cp · ½ ρ A v³ (Cp ≤ 0.593, Betz limit). #### Wind parks (wind farms) A group of many wind turbines installed at one site, connected to the grid via a common substation. Turbines are spaced 5–10 rotor diameters apart to avoid wake losses. They can be onshore or offshore. Benefits: economies of scale in transmission, installation and maintenance. Requirements: good wind, enough land or sea area, and a grid connection. ```text T1 T2 T3 T4 \ | | / [Collector cables] | [Substation] --> grid ``` #### Power control systems Wind power must be limited at high speeds to protect the machine and to keep the output constant: 1. **Pitch control:** blades rotate about their axis to change the angle of attack; used in large modern turbines. Pitching out of the wind reduces power. 2. **Stall control (passive):** blade shape causes stall in high winds, so power is limited automatically; simple, but less accurate. 3. **Active stall control:** combination of both. 4. **Yaw control:** turns the rotor away from the wind in storms. 5. **Variable-speed operation with power electronics (converter)** to maximise Cp at low speeds. 6. **Brakes** (mechanical and aerodynamic) for emergency stop. Cut-in at about 3–4 m/s, rated at 12–15 m/s, cut-out at about 25 m/s. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What average wind speed at hub height is generally needed for economic generation? A. At least 5-6 m/s B. 1-2 m/s C. 3 m/s only D. Above 25 m/s Answer: A. Economic power generation needs at least about 5-6 m/s at hub height. (Key point: Economic wind speed) 2. Why are turbines in a wind park spaced 5-10 rotor diameters apart? A. To reduce cable length B. To avoid wake losses C. To raise air density D. To increase yaw angle Answer: B. Turbines behind others get slower, turbulent wind (wake), so spacing limits the loss. (Key point: Wind park spacing) 3. How do pitch and stall control differ? A. Pitch rotates blades to change angle of attack (active); stall control uses blade shape to stall automatically (passive) B. Pitch is passive and stall is active C. Both use brakes only D. Both change tower height Answer: A. Pitch control actively turns blades; stall control is passive and simple but less accurate. (Key point: Pitch vs stall control) 4. What are the typical cut-in, rated and cut-out wind speeds? A. 3-4, 12-15 and 25 m/s B. 10, 5 and 2 m/s C. 12, 25 and 3 m/s D. 1, 2 and 3 m/s Answer: A. Turbines start at 3-4 m/s, reach rated power at 12-15 m/s and shut down at about 25 m/s. (Key point: Operating speeds) ## Related in Energy Environment and Society - [Wind energy, factors and scope](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Awind-energy-factors-scope) — Energy Environment and Society, chapter 3 - [Hydrogen production and storage](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahydrogen-production-storage) — Energy Environment and Society, chapter 3 - [Electrochemistry basics, hydrogen production](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aelectrochemistry-hydrogen-production) — Energy Environment and Society, chapter 3 - [Classification of water turbines](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Awater-turbines-impulse-reaction) — Energy Environment and Society, chapter 3, asked 2× - [Characteristics of impulse and reaction turbines](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aimpulse-reaction-characteristics) — Energy Environment and Society, chapter 3 - [Wind availability factor and turbine components](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Awind-availability-components) — Energy Environment and Society, chapter 3 ## Related in other subjects - [Energy sources in Nepal and wind scope](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aenergy-sources-nepal-wind) — Power Plant Design, chapter 1, asked 2× - [Horizontal and vertical axis wind turbines](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Ahawt-vawt-types-characteristics) — Energy Resources, chapter 4 - [Wind turbine power, tip speed ratio and energy](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Awind-turbine-power-energy-numerical) — Energy Resources, chapter 4 - [Energy sources and solar power generation](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aenergy-sources-solar-power) — Power Plant Design, chapter 1