Module Nine: Wind Turbine Energy Output

In land wind turbines with fairly poor wind resources have a capacity factor of about: a. 50% b. 38% c. 27% d. 18%

18%

Most wind turbines are designed with performance standards based on the Weibull distribution with the shape parameter of: a. 1 b. 2 c. 3 d. 4

2

Wind turbine manufacturers usually provide annual energy production for a turbine based on Weibull shape parameter of: a. 1 b. 2 c. 3 d. 4

2

Optimal energy conversion takes place when the wind turbine reduces its windspeed to ________ of its original speed a. 1/4 b. 1/3 c. 1/2 d. 2/3

2/3

What is the common capacity factor range for wind turbines?

25% to 40% is common

According to Betz law the maximum energy that can be removed from the wind is: a. 50% b. 59% c. 75% d. 100%

59%

Modern wind turbines are available to produce power more than ________ % of the time a. 94 b. 96 c. 98 d. 100

98

Windspeed variations are important for the wind industry because: a. turbine designers can optimize their designs b. turbines can minimize generating costs c. investors can accurately estimate potential income d. all of the above

All of the above

Why is efficiency more important at higher windspeeds?

At High wind speeds, the turbine must waste any excess energy above what the generator was designed for.

Why efficiency not so important at low windspeeds?

At low windspeeds there's not much energy to harvest.

What term is used as a measurement of the reliability of a wind turbine and refers to the percentage of time that a plant is ready to generate

Availability

To determine the output power of a wind turbine you must reduce the power density available by: a. a factor for Betz law b. the efficiency of the turbine c. the efficiency of the drive train d. both A and B

Both A and B

What term is used to compare the turbines actual production over a given period of time with the amount of power the plant would have produced if they have run at full capacity for the same amount of time?

Capacity factor

As wind speed increases the wind power will increase proportionally. T/F

False

How much power or energy that will hit the wind turbine is determined by using the energy content in the average wind speed for that site. T/F

False

If you measure windspeeds throughout the year, you will notice that strong gale force winds are common, when moderate winds are rare. T/F

False

Once the power curve has been created for specific wind turbine model this power curve can be applied to this turbine at any location T/F

False

Outline how optimal turbine output is measured.

Harvest whatever energy you cancel keeping the costs per kilowatt hour at a minimum

Wind energy must be used in conjunction with other sources of energy generation because: a. Wind turbines have a low availability b. the wind is not consistent c. Wind turbines have a low capacity factor D. When turbines do not need a backup

The wind is not consistent

Explain why turbines do not always run at the rated output

The wind is not constant

Power curve is a line produced from an average of swarm of points. The reason the line must be the average is: a. the wind that flows through the rotor cannot be measured exactly b. the blade will stall differently as wind speed changes c. the blade pitch is always hunting d. the tower is flexing

The wind that flows through the rover cannot be measured exactly

A 3% error in the windspeed measurements will result in the energy in the Wind being 9% higher or lower. Consequently, there may be errors up to plus or minus 10% even in certified power curves. T/F

True

A wind speed of 17 M/S can save as much as 5000 times more power as a wind speed of 1 m/s T/F

True

Another way of finding the meeting windspeed is to balance the distribution T/F

True

Finding the windspeed, that provides the mean of the power in the wind, is equivalent to balancing the power distribution of the windspeeds T/F

True

Most wind turbine designers use the Rayleigh distribution to base their turbines performance on. T/F

True

The efficiency of the wind turbine varies with the windspeed T/F

True

The electrical energy placed by wind turbines onto a great Norwis supplied by conventional generation is known as "negative load" T/F

True

The energy content or power density available in the wind varies with the cube of the windspeed T/F

True

The more kinetic energy a wind turbine pulls out of the wind, the more the wind will be slowed down as it leaves the rotor T/F

True

The power density for a power weighted average wind speed of 8.7 m/s is almost twice as much as an average wind speed of 7 m/s T/F

True

There may be up to 10% error in confirmed power curves for wind turbines T/F

True

Wind turbine manufacturers often give standard turbine performance figures using the Rayleigh distribution T/F

True

Windspeed variations for a typical site are usually described using the _________

Weibull distribution

At what point can the variable output from wind energy affect the operation of the electrical grid?

When wind energy reaches approximately 20% of the total grid system

What effect does wind energy have on the electricity demand which has to be met by conventional generating plants?

Wind energy reduces the demand on conventional generating plants

The power curve is a curve that compares the power output of the turbine at various: a. wind speeds b. times of the year c. times of the day d. none of the above

Wind speeds