Wind Flashcards
What is wind
movement of air between areas of high and low-atmospheric pressure, created by uneven heating of the earths surface and rotation of the earth
greater the pressure difference, the ________ the wind blows
harder
define wind energy
wind being used to generate mechanical power through wind turbines, then either turn generator for electricity, or do other mechanical power lime milling or pumping
define wind farms
wind turbines grouped into a single wind power plant and generates bulk electrical power
what energy creator is the largest ghg emitter
coal
the operation of wind turbines in a cold climate such as Canada’s involves ___________ challenges not present in warmer locations
The challenges associated with cold climate on wind turbines include
accumulation of ice on wind turbine blades resulting in reduced power output and increased rotor loads
cold weather shutdown to prevent equipment failure
limited or reduced access for maintenance activities
are offshore wind turbines or onshore wind turbines generally larger
offshore
Advantages of offshore wind energy
higher speed and more consistent wind
stronger and more endurable turbine to produce power
disadvantages of offshore
more expensive to build
more difficult to maintain and access
advantages of onshore
comparatively cheaper
easier to install and lower maintenance cost
convenient access
disadvantages of onshore
wind inconsistency
environmental impact
offshore wind speed tend to be faster, which means __________ more power, and steadier, which means more reliable
exponentially
describe how offshore wind turbines get energy
1 capture wind energy and generate electricity.
2. Array cables transmit electricity
3. to an offshore substation
4. electricity then moves through export cables
5. reaches land
6. and transfers to the onshore grid
progression of expected wind turbine evolution to deeper water
land based, shallow water, transitional water, and deep water
Give the ranges of water depth for these wind turbines: shallow water, transitional water, and deep water
shallow water - <30 m
transitional water 30-60 m
deep water > 60 m
wind turns the propeller-like blades of the turbine around a _____, which spins its own _______, so _______ is generated directly
rotor, generator, electricity
the kinetic energy of wind power becomes _______ power and the ______ power
mechanical, electrical
list the components of a wind turbine
turbine, gearbox, generator, power interface, grid, and a control system
what is the max power output of a wind turbine in 2020
14 MW and 200 m tall
define cut-in speed
the minimum speed to initiate rotation
and produce power.
define cut-out speed
the maximum speed, and the turbine
must be shut down when it reaches this.
define operational wind
speed is the range between cut-in
and cut-out speeds.
define rated wind speeds
is the range the turbine will operate
at its peak
what is the equation for power extracted from wind
Pwind = 1/2 EpAv^3
The _______ of the wind turbine extracts kinetic energy from moving air and converts it to
__________ kinetic energy turning a _______.
rotor, rotational, shaft
define wind speed
the wind speed determines the kinetic energy of the air and the rate at which it strikes the blades of the rotor
define rotor area
the amount of wind captured by a rotor is the area swept out during its rotation
define density of air
the denser the air, the greater the impact wind will have when it strikes the blade
how much power does a small wind turbine produce
<= 100kW
how much power does a mid-size wind turbine produce
101kW-1MW
how much power does a large scale wind turbine produce
> = 1MW
The wind blows through the blades causing them to rotate. A _______
rotor is in place to turn the turbine towards the wind.
yaw
The rotor and blades of the horizontal wind turbine are connected
to the ___________ by a shaft
generator
what are the 4 types of horizontal axis wind turbines
single bladed, double bladed, triple bladed, farm wind-mill/multi bladed
The 4 different types of horizontal wind turbines can be directed in which two ways
upwind, downwind
are vertical-axis wind turbines used for cities or residential application
residential application, small wind projects
vertical-axis wind turbines: The design allows the blades to rotate at ______ speeds than the
wind, but needs a ________ to get started.
higher
motor
vertical-axis wind turbines: The blades are _______ to ground, and generator and gearbox can be
placed on the ________, so service is easy
closer
ground
vertical-axis wind turbines: It rotates and produces electricity regardless of wind direction (no
______ mechanism required).
yaw
vertical-axis wind turbines: The most common commercial types are the _________, with a
shape like an egg-beater and uses _______ forces on its blades to get
them to turn.
darrieus
lift
What are the 5 types of vertical axis wind turbines
Savonius, gyromill, darrieus, magnus, and vortex
What holds the blades and assists with the turning the blades
rotor
what locks down the system when it stops turning
brakes
what is the gear used to turn the nacelle
yaw drive
what is used to turn the nacelle
yaw motor
what receives the energy from the low speed shaft
high-speed shaft
what determines wind direction
wind vane
what determines the speed of the wind
anemometer
what transfers energy from the rotor
low speed shaft
what connects the high speed shaft to the generator
gear box
what produces electricity for use by customers
generator
what houses the generator and gearbox. It also supports the rotor, which connects the blades at the hub. It can be the length of a school bus
nacelle
what captures the wind and turns the low-speed shaft
blades
As the blades rotate, they convert the kinetic energy of the wind to rotational force called ________
torque
The torque from the blades is transmitted through the _________ to the gearbox
low-speed shaft
The gear set in the gearbox causes the output __________ to turn at a much higher speed
high-speed shaft
a generator connected to the other end of the high-speed shaft turns at to produce __________
AC electricity
what is the highest powered wind turbine and where is it located
in china they have an offshore wind turbine capable of producing 16MW. Has a 260 m rotor diameter
Name the two types of innovative wind turbines
wind trees, and harmony vertical axis wind turbines
what are the 4 environmental impacts of wind power
Noise, effect on land use, wildlife, aesthetics
explain the environmental impacts of wind power
noise in residential areas is annoying
effect on land use; deforestation
wildlife: birds and bats
aesthetics: changes the appearance of landscape
What is the power equation that a wind turbine can generate
P = 8/27 pv^3An
What do each of these variables represent. P = 8/27 pv^3An
P power
1/2pv^3 is available power density
a = swept area
n = efficiency
(16/27)(1/2)pv^3 is the available power density
The mean power output from the wind turbine over a period from 0 to T is proportional to the cube of the ____ ____ ___ ______
mean cubic wind velocity
The mean cubic velocity, v, must be calculated from velocity measurements taken at __________ __________
frequent intervals
is the arithmetic average of wind velocities a good way to calculate values
no
what is the best way to calculate Velocity
anemometers
what is the probability density function used for
used to specify the probability of the random variable falling within a particular range of values
the probability density function is non-__________ everywhere, and the area under the entire curve is equal to ____
negative
1
how do you find the probability of having a wind velocity larger than v1 and smaller than v2
Probability = integral from v1 to v2 of the pdf with respect to v
What are the two ways to examine probabilistic behavior
Cumulative distribution function and the complementary cumulative distribution function
Do I use cumulative or complementary cumulative: answers the question of how often a given random variable, v, is below a given value V
cumulative
Do I use cumulative or complementary cumulative: answers how often the variable v is above a given value V
complementary cumulative
how do cumulative and complementary cumulative equations differ?
there is 1 - the integral for commentary cumulative
describe why we would use the Rayleigh distribution
if all one knows about a site is its average wind velocity, the best one can do is to make the assumption that the wind obeyed a Rayleigh distribution
what is the pdf for a Rayleigh distribution
pdf(v)= (v/ σ ^2) e^(-0.5(v/ σ )^2)
what is σ
mode of the distribution - value at which the probability density function peaks
what is the ccdf for the Rayleigh equation
e^(-pie/4(V/v)^2)
The Rayleigh distribution, being a ______ parameter function is a poor representation of the wind behavior
single
what is the c value in the weibull distribution
very roughly equal to the average speed
what does the ccdf represent for the weibull distribution
that the wind velocity is equal to or larger than a chosen value v
what are the 4 types of forces a wind turbine experiences
drag force, lift force, centrifugal force, gravitational force
air on top of the airfoil travels ________ resulting in ________ pressure than ________ the foil
faster, lower, under
the difference between the two pressures creates the _________ force that rotates the wind turbine blade
lifting
lift force: wind generates a force _____ to the direction it is blowing
perpendicular
drag force: wind exerts a force ____ the direction it is blowing
in
what is the specific rated capacity/rotor loading equal to
the rated generator power / the swept area of the turbine
what are the modern rotor loadings range
300 to 500 W/m^2
what are the 2 solutions to synchronization problem
- maintaining the rotation of the turbine at a constant rate (changing the blade pitch)
- allowing the turbine to rotate at the speed dictated by load and wind velocity. DC is generated and inverted to AC. These variable-speed machines are more expensive, but more efficient and longer lifespans
what does P’’ represent
power density
define flux of a fluid
the number of molecules that cross a unit area in a unit time
what is the flux equal to
nv
where n is concentration of the molecules and n is bulk velocity of the flow
what is RTP
reference temp and pressure
1 atm, 25C or 298.3 K
what is STP
standard temp and pressure
1 atm and 0C
wind turbine in cold locations at low atmospheric altitude can generate ______ power than in warm locations at high altitude
more
what is dynamic pressure
the total energy per unit volume, total energy density, Wd
wind exerts pressure on ____ surface exposed to it
any
what assumption is made about a simplistic flow pattern
any molecule striking the surface is reflected and moves back against the wind without interfering with the incoming molecules
describe a more realistic flow pattern
the reflected molecules will disturb the incoming flow. This leads to a pressure smaller than that from the ideal flow case, a pressure that depends on the shape of the object. To deal with this we say the pressure is equal to the dynamic pressure and multiplied by the drag coefficient
what does the drag coefficient depend on
shape of the object, its size and flow velocity
