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Energy From The Wind Flashcards

1
Q

Describe the differences between HAWTs and VAWTs in regards to wind direction, speed and RPM

A

HAWT
* Wind Direction - Consistent
* Wind speed - High
* RPM - high

VAWT
* Wind direction - Any
* WInd speed - Low
* RPM - Low

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2
Q

List the components of a wind turbine starting at the rotor

A
  1. Blades
  2. Hub
  3. Low speed shaft
  4. Gearbox
  5. High speed shaft
  6. Generator
  7. Wind Vane and Anemometre
  8. Tower and Nacelle
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3
Q

Equation for Kinetic Energy

A

Ke = ½mv²

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4
Q

Define what is meant by the Betz Limit and state the value

A
  • The maximum amount of the winds Ke that can be converted into mechanical energy in a rotor
  • Calculated to be 59.3%
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5
Q

Define Rotor Collected Energy

A

The total energy from the wind extracted by a turbine

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6
Q

Explain why the betz limit can’t be reached

A
  1. Friction: moving parts rub together lose Ke to thermal energy, can be minimsed with lubrication and bearings but never eliminated
  2. Resistance: Any current moving through a wire will encounter resistance, causing the wire to heat up and electrical energy is lost to thermal energy
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7
Q

Define Rated Energy Output

A

The energy an appliance (like a wind turbine) could generate under ideal test conditions

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8
Q

Describe the relationship between Pout and swept area

A

Directly proportional

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9
Q

Describe the relationship between Pout and density

A

Directly proportional

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10
Q

Describe the relationship between Pout and COP

A

Directly proportional

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11
Q

Describe the relationship between Pout and velocity of the wind

A

Pout is proportional to velocity cubed

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12
Q

Describe the relationship between Pout and diametre of the blades

A

Pout is proportional to diametre squared

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13
Q

List and explain the factors that affect air density

A
  1. Temperature: thermoexpansion causes particles to become further apart, therefore decreasing density
  2. Altitude: as altitude increases, air density decreases
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14
Q

Equation for a CBA

A

Repayment Period in Years = Project costs/Revenue produced (savings) a year

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15
Q

Factors that affect hub height

A
  1. Wind Resource Assessment: Most critical factor to find velocity
  2. Terrain: Obstructions cause a decrease in wind speed for a large area
  3. Turbine Size: The larger a wind turbine the higher the hub, average hub height : rotor diametre = 1 - 1.4 : 1
  4. Visual Impact: A larger visual impact will mean having to lower the hub height
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16
Q

Mass of a turbine proportional to blade length cubed

A

Mn = Mo(BLn/BLo)³

BL = Blade Length

M = Mass
BL= Blade Length

17
Q

Describe the factors that influence turbine performance

A
  1. Blade Length: directly proportional to r²
  2. Strength of Materials
  3. Siting Requirements: Exposed, no obstructions (to avoid turbulent air)
18
Q

Define wind survival speed

A

The maximum wind speed a turbine is designed to withstand before sustaining damage

19
Q

Why might passive pitching be used and give an example

A
  • For small scale projects to keep costs to a minimum
  • complex solutions not justified
  • Springs to pitch
20
Q

Why might active pitching be used and give an example

A
  • Large scale projects that want energy output to be at a maximum
  • Hydraulic ram/ electric motors
21
Q

What is passive yawing and why might it be implemented

A
  • Involves a wind vane at back of turbine
  • This moves with the wind
  • Doesnt cost anything to turn
22
Q

What is active yawing and why might it be implemented

A
  • Larger turbines require more to turn them
  • Hydraulic rams/ electric motors may have to be used
23
Q

List the factors that affect the E out of a turbine

A
  1. Turbine selected
  2. Topography
  3. Orientation
  4. Wind speeds
  5. Altitude
24
Q

List the factors that affect the costs of a turbine

A
  1. Installation
  2. Grid connection
  3. Servicing
  4. End of life/ injury costs
  5. Surveys
25
Q

List the environmental and social issues with a turbine

A
  1. Visual issues
  2. Noise pollution
  3. communication links
  4. Local environments
  5. Local objections

Env Tech (7 decks)

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