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Electrical > Sustainable Power Systems > Flashcards

Sustainable Power Systems Flashcards

1
Q

What is greenhouse effect

A

Process where heat leaving the earth is partially reflected back onto the earth surface by atmospheric gases

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2
Q

Global warming

A

excessive concentrations of greenhouse gases cause changes in climate, as more heat is reflected back by the atmosphere

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3
Q

Hierarchy of gases that cause global warming

A

Water vapour and clouds
CO2
Methane CH4
Nitrous Oxide N2O
Ozone O3
Chlorofluorocarbons CFC

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4
Q

Sources of Energy Supply in Australia ( Highest to lowest)

A

Petroleum
Coal
Natural gas
Renewable Energy
Nuclear

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5
Q

What is sustainable Energy ?

A

Energy that can be used without having an overall detrimental effect on the environment

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6
Q

What is MEPs ( Minimum Energy Performance Standards )

A

MEPS specify the minimum level of energy performance required for various appliances and equipment sold in Australia.

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7
Q

Renewable Energy are sourced from ?

A

Natural resource that do not become depleted

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8
Q

What happens when batteries are connected in series and parallel

A

Series = increased voltage
Parallel = increased current

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9
Q

What is the Ah capacity of a battery ?

A

It is the quantity and duration of current battery can supply.

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10
Q

What is an inverter ?

A

Is an electronic device that converts a DC current input into an AC current

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11
Q

What is the basic operation of an inverter?

A

It rapidly switches the dc input in different directions for varying amounts of time. (By using a bridge)

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12
Q

What is Pulse Width Modulation (PWM)?

A

Is a technique of rapidly switching the current in series of pulses with same magnitude but different duration.

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13
Q

What is the use of a charge controller (battery charger) ?

A

It enables safe and functional charging, discharging and interconnection with installations.

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14
Q

What is irradiance (G)

A

The quantity of solar power available at the surface at any instant in time. ( W/m^2)

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15
Q

What is Irradiation (H) ?

A

The quantity of solar energy available at the surface over a given time period. ( kWh/m^2)

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16
Q

What is extraterrestrial irradiation ?

A

The quantity of solar energy available at the top of the earth’s atmosphere

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17
Q

What is sunshine hours ?

A

The average hours of sunshine received at a location over a given period of time.

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18
Q

What is Declination angle ?

A

angle is the angle between the horizontal plane of the earth (known as the equator) and the horizontal plane of the sun.

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19
Q

What is Equinox ?

A

is when the horizontal plane of the sun and earth are aligned (i.e. the declination angle is 0⁰), occurring twice a year.

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20
Q

What is Solstice ?

A

Is when the declination angle is at its maximum value, occurring twice a year:

The winter solstice is the day of the year with the least hours of sunlight.

The summer solstice is the day of the year with the most hours of sunlight.

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21
Q

What is Radiance ?

A

Radiance is the quantity of energy emitted from a source :

Direct radiation is solar radiation that comes straight from the sun, casting shadows on a clear day.

Diffuse radiation is indirect sunlight that is scattered from air molecules, dust and water vapour.

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22
Q

What is Reflectance ?

A

Reflectance is the ratio of reflected radiation to incident radiation arriving at a surface.

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23
Q

What is solar window ?

A

The area of the sky through which the sun moves throughout each yearly cycle.

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24
Q

What is Latitude

A

Is a coordinate indicating the north-south position of a point on the earth.

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25
Q

What is Longitude ?

A

Is a coordinate indicating the east-west position of a point on the earth.

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26
Q

What is Zenith ?

A

Is a point directly above a location.

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27
Q

What is Azimuth angle ?

A

The angle between the sun and true north in a clockwise direction. Applied to a PV array, a 180 degree azimuth angle indicates that the array faces due south.

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28
Q

What is altitude angle ?

A

The angle between the horizon and the sun.

29
Q

What is Tilt angle ?

A

Isthe angle btw the horizontal plane and the plane of a photovoltaic module.

30
Q

Describe photovoltaic cell.

A

A cell is a single PV unit, typically producing a nominal output voltage of 0.5 V.

31
Q

Describe a photovoltaic module

A
32
Q

What is a PV string ?

A
33
Q

What is a PV array ?

A
34
Q

What is the purpose of Bypass diodes in PV array ?

A
35
Q

Function of PV blocking diode ?

A

Allows current to leave shaded strings but prevent current from back feeding into it.
Connected in series with string.

36
Q

What is are contour maps ?

A
37
Q

What is potential energy (E) in MHS

A

The stored energy that exists due to gravity acting on the water that is held in the forebay/dam.

38
Q

What is Gross / Static Head (H) ?

A
39
Q

List the 5 basic arrangement of a Micro-Hydro System (MHS).

A
40
Q

What is flow rate Q ?

A

The volume of water passing through a point or pipe at a given time, measured in litres per second (L/s) or cubic metres per second (m3/s).

41
Q

What is Hydraulic Losses ?

A

Losses caused by turbulence in the water and friction between the water and the walls of the pipework/fittings.

A water velocity of 1 m/s is generally maintained to minimise turbulence. Friction losses are directly proportional to pipe length, so hydraulic losses are expressed in metres (m).

42
Q

What is equivalent Pipe Length ?

A

Is the length of straight pipe (of the same size as the fitting) that would cause the same hydraulic loss as the fitting.
Measured in “m”

43
Q

What is Net/ Dynamic Head (h) ?

A

The ‘effective’ head, taking the total hydraulic losses into account, measured in metres (m).

Net Head = Gross Head – Hydraulic Losses

44
Q

What are the 3 primary method of measuring flow rate ?

A
  • Volume and time method
  • Area and velocity method
  • Notched weir method
45
Q

What is the volume and time method of calculating flow rate ?

A
46
Q

Compare low head and high head system characteristics.

A
47
Q

What are impulse turbines ?

A
48
Q

Name the following impulse turbines.

A
49
Q

What are reaction turbines ?

A
50
Q

Name the following reaction turbines.

A
51
Q

How does wind move ?

A

The natural phenomenon we know as ‘wind’ is simply the movement of air. The reason air moves from one place to another is due to a difference in pressure between the two locations – the air moves from the higher pressure location to the lower pressure location until equilibrium is reached.

52
Q

What is vertical wind speed profile ?

A

A profile indicating the variation in wind speeds at different heights above the ground.

53
Q

What is Temperature Inversion Layer ?

A

A layer of cold dense air in the atmosphere that resists the transfer of wind energy from above to below.

54
Q

What is the basic arrangement of a wind turbine ?

A
55
Q

What is Specific Wind Power (P0)

A

The available wind power per unit of wind capture area, measured in watts per square metre (W/m2).

56
Q

What is Cut-in Wind Speed (Vc)

A

The minimum wind speed required for the WECS to produce useable electrical energy.

57
Q

What is Rated Wind Speed (vR)

A

The wind speed required for optimal WECS operation, i.e. to achieve maximum power output.

58
Q

What is Furling Wind Speed (vF)

A

The wind speed which causes the turbine to furl or feather (i.e. shut down) to prevent damage.

59
Q

What is Rated Power (PR) (WECS)

A

The maximum power output of the WECS. The rated power is achieved at the rated wind speed.

60
Q

What is Power Co-efficient (cP)

A

A factor of how efficiently the wind turbine converts the kinetic wind energy into mechanical energy.

61
Q

What is Output Co-efficient (cO)

A

A factor of how efficiently the WECS converts wind energy into an electrical output.

62
Q

What is Tip Speed Ratio (λ)

A

A ratio of the wind speed to the resulting speed of the tip of the turbine blade.

63
Q

What does Isobar mean on this weather map ?

A

The isobars indicate levels of atmospheric pressure in hectopascals (hPa), in a similar way that contour lines indicate height above sea level on topographic maps. Winds tend to blow from higher pressure regions to lower pressure regions.

64
Q

At what positions should WECS be placed uphill and downhill an obstacle ?

A
65
Q

What instrument is used for measuring wind ?

A

Anemometer

66
Q

What are the 2 main types of wind turbines ?

A

Vertical Axis Wind Turbine (VAWT)

· Horizontal Axis Wind Turbine (HAWT)

67
Q

What are the names of these vertical wind turbines ?

A
68
Q

What are the 2 types of Horizontal Axis Wind Turbines (HAWT)

A
69
Q
A

Electrical (7 decks)

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