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EGR 1301 > Energy And Electricity > Flashcards

Energy And Electricity Flashcards

0
Q

Where does wind come from?

A

It’s solar.

The earth continuously released into the atmosphere the heat received by the sun but unevenly

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1
Q

Types of renewable sources of energy

A 
Nuclear
Hydroelectric
Waves
Geothermal
Biomass
Wind
Solar
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2
Q

How wind turbines work

A
  1. When the blades start moving, they spin a shaft that leads to s generator
  2. The generator consists of a conductor (ex. A coiled wire surrounded by magnets)
  3. The rotating shaft turns the magnets around the conductor and generates an electrical current
  4. Sensors cause the top of the turbine to rotate to face the wind and the blades change their angle to best catch the wind ️n the blades are flexible and stop spinning if there is too much wind
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3
Q

Wind miss application

A
  1. Wind turns the turbine blades
  2. Spinning the shaft
  3. Generating electricity
  4. An inverter converts electricity from DC to AC
  5. Electricity is connected directly to the mains power
  6. Or connected to a battery bank
  7. Or connected to the electrical grid
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4
Q

Advantages of wind energy

A
  1. Available and free
  2. Renewable
  3. Costs are decreasing
  4. No pollution
  5. Works all day/night
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5
Q

Disadvantages of wind energy

A
  1. Still uses land
  2. Wind fluctuates
  3. Mostly in rural areas
  4. Electricity storage?
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6
Q

Windmill packing density

A

As a windmill extracts energy from the wind, the turbine leaves behind it a wake characterized by reduced wind speeds and increased levels of turbulence
A turbine operating in the wake of a turbine will produce less energy and suffer greater structural loading

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7
Q

Rule of thumb: windmills cannot be spaced closer that ___times their diameter without losing significant power

A

5

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8
Q

Kinetic energy of a windmill

A

KE= 1/2ρAtv^3

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9
Q

Wind power density (per unit area and per second)

A

P= 1/2ρv^3

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10
Q

Power output from a wind turbine

A

P= 1/2(Cp)ρAv^3

Cp= the power coefficient= the fraction of the power in the wind that may be converted by the turbine into mechanical work

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11
Q

Where does solar energy come from?

A

Sun (a star)
Thermonuclear fusion
Entire EM spectrum

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12
Q

The amount of solar energy that reaches the surface of the earth every hour is greater than…

A

Humankind’s total demand for energy in one year

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13
Q

Non electric solar energy

A 
Water heating
Heating living spaces
Day lighting
Drying 
Agriculture
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14
Q

Solar energy generating electricity

A

Photovoltaics
Power tower
Concentrated and remote (ex. Asteroid rover)

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15
Q

About how much of the sun’s energy makes it to the surface of the earth?

A

47%

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16
Q

___% of solar energy comes from the middle 6 months

A

70%

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17
Q

Basics of solar powered water heaters

A
  1. Collector absorbs energy
  2. Heats water
  3. Water circulates (passive or active)
  4. Tank stores water
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18
Q

Color absorption

A

Dark colors absorb a lot and reflect a little

Light colors absorb little and reflect a lot

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19
Q

Power tower basics

A
  1. Collect light/energy from many reflectors
  2. Heat water
  3. Parabolic (parallel rays converge)
  4. Track the sun
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20
Q

Disadvantages of solar power

A

Inefficient and costly equipment
Part time
Reliability depends on location
Environment impact of PV cell production

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21
Q

A mill uses…

A

Mechanical rotational energy for work and processing

From water or wind

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22
Q

Breast shot wheel

A

One type of traditional water wheel

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23
Q

Overshot wheel

A

More efficient than breast shot wheel

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24
What are dams for?
``` Recreation Drinking water Flooding Irrigation Energy ```
25
Hydroelectric power system
Flowing water is directed at a turbine (advanced water wheel) The flowing water causes the turbine to rotate, converting the water's KE to ME
26
The amount of electricity that can be generated by a hydropower plant depends on:
1. Flow rate: the quantity of water flowing at a given time 2. Head: the height from which the water falls The greater the flow and the head, the more electricity produced
27
Standard equation for calculating energy production hydraulically
P= (head)*(flow)*(efficiency)*11.8 ``` 11.8= index that converts units of feet and seconds to kW kW= ft*ft^3/s*% ```
28
How useful is dam energy?
Moderate to high net useful energy yield Fairly low operating and maintenance costs Low pollution Rarely shut down Help control flooding Supply a regulated flow of irrigation water to lowlands below the dam
29
Highest producers of renewable energy
Solar and hydroelectric
30
Disadvantages to hydroelectricity
``` Flood vast areas Destroys wildlife habitats Uproots people Keeps nutrients from settling downstream Keep fish from migrating upstream Kills lots of fish ```
31
What makes the tile floor feel colder than the carpet?
Thermal conductivity
32
Temperature
Quantitive measure of "hotness" Described on the atomic scale Vibrational KE Measure of the INTENSITY of internal energy in a system
33
Heat
A measure of the total QUANTITY of thermal energy FLOW into or out of a system Is the energy transferred between a system and its environment because of a temperature difference that exits between them
34
Joule determined...
The amount of work needed to produce one unit of energy | The equivalence between ME and internal energy (heat)
35
1 cal= __J
1 cal= 4.186J
36
Specific heat capacity
The amount of thermal energy needed to raise a unit mass of a substance a unit of temperature Q Energy in calories Q= mcΔT
37
Specific heat
c Different materials require different amounts of heat to produce the same temperature change c= Q/(mΔT)
38
2 mechanisms for heat transfer due to a temperature difference
1. Conduction 2. Convection 3. Radiation
39
Natural flow of heat is a,ways from....
Higher temperature regions to cooler ones
40
Conduction
Heat flowing through matter Hotter atoms collide with cooler ones, transferring some of their energy Direct, physical contact is required Cannot occur in a vacuum Poor conductors= insulators (styrofoam, wool, air...)
41
Convection
Energy transfer through the bulk motion of hot material Ex. Space heater, gas furnace "Hot air rises"
42
Radiation
``` Radiant energy: energy associated with electromagnetic waves CAN operate through a vacuum All objects Osborn and emit radiation Temperature determines: 1. Emission rate 2. Intensity of emitted light 3. Type of radiation given off Temperature is determined by the balance between rates if emission and absorption ```
43
Converting work into heat: Joule's experiment
``` U= W Q= W mcΔT= FΔx mcΔT= maΔx ```
44
Thermal linear expansion
ΔL= L0*α*ΔT α= coefficient of linear expansion
45
Thermal volume expansion
ΔV= V0*β*ΔT ``` β= coefficient of volume expansion β= 3α ```
46
Latent heat of fusion
(Solid/liquid) ΔHfus (kJ/kg) If T⬆️, melting point If T⬇️, freezing point
47
Latent heat of vaporization
(Liquid/gas) ΔHvap (kJ/kg) If T⬆️, boiling point If T⬇️, condensation point
48
Latent heat of sublimation
(Solid/gas) If T⬆️, sublimation point If T⬇️, sublimation point
49
Transition between phases is a _______ process
Constant temperature process Melting/solidification: Qfus= mΔHfus Boiling/condensation: Qvap= mΔHvap
50
Heat and combustion
Qcomb= mΔHcomb ``` Qcomb= energy released m= mass (kg) ΔHcomb= specific heat of combustion (MJ/kg) ```
51
Motors and engines yield...
Circular motion
52
Engines use
Combustion or steam
53
Motors use
Electricity
54
2 types of electric motors
AC and DC
55
2 types of DC motors
Separately excited | Self excited
56
Types of self excited motors
Series Compound Shunt
57
2 types of AC motors
Synchronous | Induction
58
Types of induction motors
Single phase | Three phase
59
Who designed the modern AC electricity supply system?
Tesla
60
Two wires carrying electric current...
Exert a force on each other (magnetic force)
61
Two wires carrying electric current in the same direction...
Attract
62
Two wires carrying electric current in the opposite directions...
Repel
63
Force, current, and magnetic field are all...
Perpendicular to each other | Righthand rule
64
A magnetic field of loops/coils with many "turns" is a ____
Solenoid
65
Magnetic field=
B= (2*10^-7)*(N*I)/R ``` N= number of turns I= current R= radius in meters ```
66
A magnetic field coil is identical to...
Magnetic field of a disk-shaped permanent magnet
67
Reversing current in a magnetic field coil...
Reverses the polarity | Changes N and S
68
In a stationary (magnetic) field...
A permanent magnet is added Electromagnet rotates and poles line up Switch poles of electromagnet and it will rotate to line up again
69
Stationary part of motor
Stator | Permanent magnet
70
Rotating part of motor
Rotor | Electrically controlled "brushes" to change polarity and reverse rotation to rotate the shaft
71
Generator
Essentially a motor working in reverse Electromagnetic induction Power supplied by wind, water, or fuel
72
Electromagnetic induction
If you move a magnet near a coil of wire, a current will be produced
73
Other magnetic uses
Levitation | Transformer: power in-power out

EGR 1301 (16 decks)

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