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What is the energy source that powers wind turbines?
What is the energy source that powers wind turbines?
The sun
Wind turbines are more efficient than windmills.
Wind turbines are more efficient than windmills.
True
What are the two main types of wind turbines based on their rotor axis?
What are the two main types of wind turbines based on their rotor axis?
What is the name for the structure that houses the wind turbine's components?
What is the name for the structure that houses the wind turbine's components?
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What is the name of the international standard that defines the design requirements for wind turbines?
What is the name of the international standard that defines the design requirements for wind turbines?
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The Weibull distribution is a mathematical tool used to model wind speed.
The Weibull distribution is a mathematical tool used to model wind speed.
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What two parameters are crucial for describing the Weibull distribution?
What two parameters are crucial for describing the Weibull distribution?
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A lower value of the shape factor (k) indicates less wind speed variability.
A lower value of the shape factor (k) indicates less wind speed variability.
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What is the general theory that provides a model for wind speed variation with altitude?
What is the general theory that provides a model for wind speed variation with altitude?
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What is the term used to describe the graphical representation of the wind direction and frequency at a specific location?
What is the term used to describe the graphical representation of the wind direction and frequency at a specific location?
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Wind turbines with fixed pitch blades are generally more efficient than those with variable pitch blades.
Wind turbines with fixed pitch blades are generally more efficient than those with variable pitch blades.
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What is the name of the theoretical limit for the power coefficient of a wind turbine according to Betz's law?
What is the name of the theoretical limit for the power coefficient of a wind turbine according to Betz's law?
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What is the term used to describe the ratio between the speed of the turbine's blade tip and the wind speed?
What is the term used to describe the ratio between the speed of the turbine's blade tip and the wind speed?
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The power coefficient of a wind turbine decreases as the tip-speed ratio increases.
The power coefficient of a wind turbine decreases as the tip-speed ratio increases.
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Wake losses are a major source of energy loss in wind turbines.
Wake losses are a major source of energy loss in wind turbines.
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What is the term used to describe the ratio of the lift force to the drag force on a blade element?
What is the term used to describe the ratio of the lift force to the drag force on a blade element?
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Blade twisting is often used to maintain a constant angle of attack along the entire blade length.
Blade twisting is often used to maintain a constant angle of attack along the entire blade length.
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What is the name of the mechanism where the blades are turned perpendicular to the wind to limit power output?
What is the name of the mechanism where the blades are turned perpendicular to the wind to limit power output?
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Active stall control is a mechanism for limiting power output by allowing the blades to stall.
Active stall control is a mechanism for limiting power output by allowing the blades to stall.
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What is the difference between the rated (nominal) power (Pn) and the rotor power (PRn) of a wind turbine?
What is the difference between the rated (nominal) power (Pn) and the rotor power (PRn) of a wind turbine?
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Wind turbines with variable rotation speeds eliminate the need for a speed multiplier.
Wind turbines with variable rotation speeds eliminate the need for a speed multiplier.
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What is the primary reason for limiting the tip speed of a wind turbine blade?
What is the primary reason for limiting the tip speed of a wind turbine blade?
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What is the term used to describe the ratio of the frontal area of the blades to the total area swept by the rotor?
What is the term used to describe the ratio of the frontal area of the blades to the total area swept by the rotor?
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A higher solidity value generally leads to a narrower and more pronounced peak in the power coefficient - tip-speed ratio (CPR - λ) curve.
A higher solidity value generally leads to a narrower and more pronounced peak in the power coefficient - tip-speed ratio (CPR - λ) curve.
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The choice of the number of blades for a wind turbine is solely determined by efficiency considerations.
The choice of the number of blades for a wind turbine is solely determined by efficiency considerations.
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What is the term used to describe the phenomenon where air flow separates from the blade's surface, reducing power output?
What is the term used to describe the phenomenon where air flow separates from the blade's surface, reducing power output?
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The maximum power output of a wind turbine is primarily limited by the maximum power output of its electric generator.
The maximum power output of a wind turbine is primarily limited by the maximum power output of its electric generator.
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What is the most common method of power control for wind turbines?
What is the most common method of power control for wind turbines?
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The rotation speed for fixed-pitch wind turbines directly depends on the wind speed.
The rotation speed for fixed-pitch wind turbines directly depends on the wind speed.
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What is the general term for the wind turbine's ability to turn itself into the wind to optimize power generation?
What is the general term for the wind turbine's ability to turn itself into the wind to optimize power generation?
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The design choice for a wind turbine's rotation speed influences its annual energy production.
The design choice for a wind turbine's rotation speed influences its annual energy production.
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Study Notes
Wind Energy
- Solar Irradiation: The sun irradiates Earth with 1.74 x 1014 kWh of energy per hour, with 1.22 x 1014 kW absorbed. Approximately 1-2% of this energy is converted into wind energy, which is significantly greater (50-100 times) than the energy converted into biomass by all plants on Earth.
Wind Rotor Operation
- Mechanism: Wind rotors operate similarly to windmills, with wind pushing the blades. In turbines, this rotational motion powers a generator that produces electricity. Aeromotors directly transmit turbine motion to the user as mechanical energy (e.g., water pumps in some areas).
Wind Turbine Characteristics
- Dimensions: A typical 600 kW wind turbine has a rotor with a 43-44 m diameter, covering an area of 1500 square meters.
Air Density and Kinetic Energy
- Air Density Dependence: The kinetic energy of moving air depends on its density. Density factors relating to air temperature and humidity are detailed. A one-meter thick slice of air passing through the rotor of a 600 kW turbine weighs 1.9 tonnes.
Available Power
- Relationship with Velocity: Available power from the wind increases proportionally with the cube of the wind velocity. The graph vividly demonstrates this relationship, illustrating the crucial importance of wind velocity. A key implication is that a small increase in wind velocity may correspond to a substantial increase in power output.
Types of Wind Motors/Generators
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Vertical Axis Wind Turbines (VAWTs): These do not require directional adjustments, offering operational simplicity. They can be Savonius, Darrieus, or H-Darrieus types. Lift rotors (most typical) have aerodynamic profiles that produce better efficiency than drag rotors.
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Horizontal Axis Wind Turbines (HAWTs): The most common type is the three-blade wind turbine, but other variations exist (e.g, Dutch four-blade, American multi-blade).
Weibull Distribution
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Probability Density Function: Used to describe the statistical distribution of wind speeds, enabling prediction of expected wind speeds. The formula for the probability density function and cumulative distribution function for Weibull distribution are shown.
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Scale and Shape Parameter: These factors determine the average wind speed and give an idea of windiness.
Weibull Statistics
- Median and Average Speed: These statistics along with maximum available energy speeds are shown in graphical representation.
Wind Resource Characterization
- Windiness Index: Provides an overview of the strength of wind at a given site, considering statistical analysis over time intervals.
Wind Rose
- Data Representation: A visual tool to show the frequency and direction of wind over one year at a specific location.
European Wind Atlas
- Regional Variation: Visualizes the average wind power density and speed across different European regions, which helps to assess local wind energy potential. Different types of terrain are described with specific roughness coefficients and equations
Wind Turbine Standards
- Design Considerations: International standards (IEC 61400, part 1) dictate design requirements to withstand extreme conditions, covering various aspects like protection mechanisms, electrical systems, and mechanical parts.
- Extreme Wind Speeds: Specified values for extreme wind conditions.
Wind Turbine Operation
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Power Output: The power output of an ideal wind turbine and available wind energy. The theory of Betz and how it leads to a theoretical maximum. Torque, thrust coefficient, power coefficient equations.
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Wake Losses: Wind turbine operation is not ideal, in practice, due to wake effects.
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Blade Angle and Aerodynamics: Rotor design for optimal power generation. Blade pitch optimization.
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Tip Speed Ratio: This factor is crucial for evaluating the power coefficient in the presence of wind turbine characteristics
Variable Rotation Speed
- Power Control: Methods for managing wind power input, including using variable pitch angles to influence the aerodynamic forces on the blades.
Fixed Pitch Wind Turbines
- Constant Rotation Speed Considerations: These turbines operate at fixed rotation speeds.
- Limitations of Fixed Pitch: Fixed pitch blades are limited by the maximum wind speed at which they operate safely and effectively
Wind Turbine Performance
- Factors Affecting Performance: Variable rotation speed and fixed pitch blade designs affect wind turbine performance. The graphs summarize how maximum power and yearly energy yield are impacted.
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Description
This quiz covers fundamental concepts of wind energy including solar irradiation, the operation of wind rotors and turbines, and the physical characteristics of wind turbines. Test your knowledge on how these systems convert wind energy into electrical power and the factors affecting their efficiency.
