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ENER 305 > Wind > Flashcards

Wind Flashcards

(102 cards)

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1
Q

What is wind

A

movement of air between areas of high and low-atmospheric pressure, created by uneven heating of the earths surface and rotation of the earth

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2
Q

greater the pressure difference, the ________ the wind blows

A

harder

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3
Q

define wind energy

A

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

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4
Q

define wind farms

A

wind turbines grouped into a single wind power plant and generates bulk electrical power

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5
Q

what energy creator is the largest ghg emitter

A

coal

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6
Q

the operation of wind turbines in a cold climate such as Canada’s involves ___________ challenges not present in warmer locations

A
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7
Q

The challenges associated with cold climate on wind turbines include

A

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

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8
Q

are offshore wind turbines or onshore wind turbines generally larger

A

offshore

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9
Q

Advantages of offshore wind energy

A

higher speed and more consistent wind
stronger and more endurable turbine to produce power

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10
Q

disadvantages of offshore

A

more expensive to build
more difficult to maintain and access

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11
Q

advantages of onshore

A

comparatively cheaper
easier to install and lower maintenance cost
convenient access

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12
Q

disadvantages of onshore

A

wind inconsistency
environmental impact

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13
Q

offshore wind speed tend to be faster, which means __________ more power, and steadier, which means more reliable

A

exponentially

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14
Q

describe how offshore wind turbines get energy

A

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

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15
Q

progression of expected wind turbine evolution to deeper water

A

land based, shallow water, transitional water, and deep water

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16
Q

Give the ranges of water depth for these wind turbines: shallow water, transitional water, and deep water

A

shallow water - <30 m
transitional water 30-60 m
deep water > 60 m

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17
Q

wind turns the propeller-like blades of the turbine around a _____, which spins its own _______, so _______ is generated directly

A

rotor, generator, electricity

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18
Q

the kinetic energy of wind power becomes _______ power and the ______ power

A

mechanical, electrical

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19
Q

list the components of a wind turbine

A

turbine, gearbox, generator, power interface, grid, and a control system

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20
Q

what is the max power output of a wind turbine in 2020

A

14 MW and 200 m tall

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21
Q

define cut-in speed

A

the minimum speed to initiate rotation
and produce power.

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22
Q

define cut-out speed

A

the maximum speed, and the turbine
must be shut down when it reaches this.

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23
Q

define operational wind

A

speed is the range between cut-in
and cut-out speeds.

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24
Q

define rated wind speeds

A

is the range the turbine will operate
at its peak

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25
what is the equation for power extracted from wind
Pwind = 1/2 EpAv^3
26
The _______ of the wind turbine extracts kinetic energy from moving air and converts it to __________ kinetic energy turning a _______.
rotor, rotational, shaft
27
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
28
define rotor area
the amount of wind captured by a rotor is the area swept out during its rotation
29
define density of air
the denser the air, the greater the impact wind will have when it strikes the blade
30
how much power does a small wind turbine produce
<= 100kW
31
how much power does a mid-size wind turbine produce
101kW-1MW
32
how much power does a large scale wind turbine produce
>= 1MW
33
The wind blows through the blades causing them to rotate. A _______ rotor is in place to turn the turbine towards the wind.
yaw
34
The rotor and blades of the horizontal wind turbine are connected to the ___________ by a shaft
generator
35
what are the 4 types of horizontal axis wind turbines
single bladed, double bladed, triple bladed, farm wind-mill/multi bladed
36
The 4 different types of horizontal wind turbines can be directed in which two ways
upwind, downwind
37
are vertical-axis wind turbines used for cities or residential application
residential application, small wind projects
38
vertical-axis wind turbines: The design allows the blades to rotate at ______ speeds than the wind, but needs a ________ to get started.
higher motor
39
vertical-axis wind turbines: The blades are _______ to ground, and generator and gearbox can be placed on the ________, so service is easy
closer ground
40
vertical-axis wind turbines: It rotates and produces electricity regardless of wind direction (no ______ mechanism required).
yaw
41
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
42
What are the 5 types of vertical axis wind turbines
Savonius, gyromill, darrieus, magnus, and vortex
43
What holds the blades and assists with the turning the blades
rotor
44
what locks down the system when it stops turning
brakes
45
what is the gear used to turn the nacelle
yaw drive
46
what is used to turn the nacelle
yaw motor
47
what receives the energy from the low speed shaft
high-speed shaft
48
what determines wind direction
wind vane
49
what determines the speed of the wind
anemometer
50
what transfers energy from the rotor
low speed shaft
51
what connects the high speed shaft to the generator
gear box
52
what produces electricity for use by customers
generator
53
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
54
what captures the wind and turns the low-speed shaft
blades
55
As the blades rotate, they convert the kinetic energy of the wind to rotational force called ________
torque
56
The torque from the blades is transmitted through the _________ to the gearbox
low-speed shaft
57
The gear set in the gearbox causes the output __________ to turn at a much higher speed
high-speed shaft
58
a generator connected to the other end of the high-speed shaft turns at to produce __________
AC electricity
59
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
60
Name the two types of innovative wind turbines
wind trees, and harmony vertical axis wind turbines
61
what are the 4 environmental impacts of wind power
Noise, effect on land use, wildlife, aesthetics
62
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
63
What is the power equation that a wind turbine can generate
P = 8/27 pv^3An
64
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
65
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
65
The mean cubic velocity, v, must be calculated from velocity measurements taken at __________ __________
frequent intervals
66
is the arithmetic average of wind velocities a good way to calculate values
no
67
what is the best way to calculate Velocity
anemometers
68
what is the probability density function used for
used to specify the probability of the random variable falling within a particular range of values
69
the probability density function is non-__________ everywhere, and the area under the entire curve is equal to ____
negative 1
70
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
71
What are the two ways to examine probabilistic behavior
Cumulative distribution function and the complementary cumulative distribution function
72
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
73
Do I use cumulative or complementary cumulative: answers how often the variable v is above a given value V
complementary cumulative
74
how do cumulative and complementary cumulative equations differ?
there is 1 - the integral for commentary cumulative
75
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
76
what is the pdf for a Rayleigh distribution
pdf(v)= (v/ σ ^2) e^(-0.5(v/ σ )^2)
77
what is σ
mode of the distribution - value at which the probability density function peaks
78
what is the ccdf for the Rayleigh equation
e^(-pie/4(V/v)^2)
79
The Rayleigh distribution, being a ______ parameter function is a poor representation of the wind behavior
single
80
what is the c value in the weibull distribution
very roughly equal to the average speed
81
what does the ccdf represent for the weibull distribution
that the wind velocity is equal to or larger than a chosen value v
82
what are the 4 types of forces a wind turbine experiences
drag force, lift force, centrifugal force, gravitational force
83
air on top of the airfoil travels ________ resulting in ________ pressure than ________ the foil
faster, lower, under
84
the difference between the two pressures creates the _________ force that rotates the wind turbine blade
lifting
85
lift force: wind generates a force _____ to the direction it is blowing
perpendicular
86
drag force: wind exerts a force ____ the direction it is blowing
in
87
what is the specific rated capacity/rotor loading equal to
the rated generator power / the swept area of the turbine
88
what are the modern rotor loadings range
300 to 500 W/m^2
89
what are the 2 solutions to synchronization problem
1. maintaining the rotation of the turbine at a constant rate (changing the blade pitch) 2. 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
90
what does P'' represent
power density
91
define flux of a fluid
the number of molecules that cross a unit area in a unit time
92
what is the flux equal to
nv where n is concentration of the molecules and n is bulk velocity of the flow
93
what is RTP
reference temp and pressure 1 atm, 25C or 298.3 K
94
what is STP
standard temp and pressure 1 atm and 0C
95
wind turbine in cold locations at low atmospheric altitude can generate ______ power than in warm locations at high altitude
more
96
what is dynamic pressure
the total energy per unit volume, total energy density, Wd
97
wind exerts pressure on ____ surface exposed to it
any
98
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
99
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
100
what does the drag coefficient depend on
shape of the object, its size and flow velocity
101

ENER 305 (9 decks)

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