Chapter 7 Flashcards
Equation for kinetic energy
Ke=half x m x v2
Why can’t 100% of the winds energy be extracted by a wind turbine
Because wind has velocity downstream
What is the betz limit
The amount of energy (59.3%) that can be extracted from the wind due to this required downstream velocity
Why can’t turbines ever reach the betz limit
Mechanical:(friction) which causes thermal losses
Electrical:(resistance) which causes thermal losses
State the relationship between pout and kA
Pout=kA
State the relationship between power output and swept area
Power output is directly proportional to swept area
Equation for swept area
A=pie x r2
State the relationship between power output and wind speed
Power output is directly proportional to the cube of wind speed
State the relationship between a wind turbines blade diameter and power output
Pout is directly proportional to the square of blade diameter
State the relationship between pout and air density
Pout is directly proportional to air density
How does temperature affect pout
Higher temperature=lower pout as higher temperature means lower air density and air density and pout are directly proportional
Lower temperature= higher pout as lower temperature means higher air density and pout and air density are directly proportional
What is altitude
Altitude is how a specific point is above the earth it is measure from the sea level
Higher altitude means lower air density
Lower altitude means higher air density
What 8 parameters affect maximum energy production in wind turbines
Wind speeds
Air density
Cop
Swept area
Obstructions
Hub height
Temperature
Altitude
Equation for repayment period of a wind turbine
Repayment period in years = project costs/ revenue produced per year
Four factors used to determine hub height
Wind resource assessment- seeing what the levels of wind are like in the area
Terrain- are there any obstructions
Wind turbine size
Visual impact - will it cause shadow flicker
Equation for the weight of a new wind turbine
Mn=Mo(BLn3/BLo3)
State the relationship between turbines performance and blade length, strength of materials and siting requirements
Bigger Blades = more power but larger blades mean higher cut in speed
Heavier materials mean in can withstand more but will have higher cut in speeds and vice versa
Siting requirements ideally you want a location with no obstructions
Definition of wind survival speed
The maximum wind speed that is designed to withstand before sustaining damage
Testing methods used to determine wind survival speed
Destructive testing product is tested under extreme conditions until it breaks
What name is given to the method of rotating the blades of a turbine to control the rate of power production
Pitching
What is yawing
The turning of a turbine to ensure it aligns with the wind this helps maximise power output
Issues affecting energy output of a wind turbine
The turbine selected
Topography
Orientation of the site
Available wind speeds
Altitude and air density
Issues affecting cost of wind turbines
Installation costs
Grid connection costs
Servicing
End of life costs
Surveys
Environmental and social issues of wind turbines
Visual issues
Noise pollution
Communication links
Environmental impact assessment
Local objections
