Wind energy

Question 1

What are the percieved problems with wind energy?

Answer 1

1. Levelised cost
2. public opinion (noise, visibility, environmental damage)
3. Availability (dependent on weather)
4. componenet transport constraints on land (blades need to be transported in one piece

Question 2

How much of the energy in the UK was generated by renewables in 2017?

Answer 2

25%

Question 3

How much of the energy in the UK was generated by wind in 2019?

Answer 3

often as high as 50%

Question 4

What is the installed capacity based off for wind turbines?

Answer 4

• nameplate capacity

- rated capacity

Question 5

What is the rated capacity?

Answer 5

the clamed output at a specified wind sepped and is the maximum power that can continuously be delivered

Question 6

How do you calculate the capacity factor?

Answer 6

= (actual MWh pa)/(ratedx 24x365)

It is usually betweeen 20 and 40 %

23. 5% for UK farms in 09
24. 8 in 11

Question 7

What is the effect of auctions on energy price?

Answer 7

Drastically reduces it

Question 8

What was the first trigger for wind energy development in the modern era?

Answer 8

governemnt funding becasue of the 1973 oil price increase

Question 9

When was the first idea of generating energy from wind developed?

Answer 9

1890s

Question 10

How do modern wind turbines work?

Answer 10

• convert kintetic energy of wind to electricity
• power is porportional to swept area nad cube of wind speed
  wind speed is site specific
• power coefficient varies with the tip speed ratio

Question 11

What is the theoretical maximum for the fraction of wind power that may be converted?

Answer 11

0.593

Question 12

How much area would be needed to power the UK?

Answer 12

20,000 km^2

roughly 50,000 5MW rated turbines

Question 13

How do we accurately measure wind speed?

Answer 13

• An anemometer mast

Question 14

What helps better the accuracy of wind speed assesment>

Answer 14

• number and distribution of anometer masts depedning on size and topography
• boundary layar thickness
• take measurements from the hub height
• take readings at hourly or half hourly intervals
• calculate the max 3 second gust speed
• find the standard deviation
• find the mean wind direction
• measure the mean temperature

Question 15

Why is average wind speed not a good way of determining wind speed?

Answer 15

as if it is too hgih wind turbines shut off

Question 16

What are the challenges of wind power?

Answer 16

The wind speed varies with the time of day, the weather etc.

• there is no phase relationship between the variations in available wind power and variations in demand - non dispatchable
• flexible generating capcacity is required

Question 17

What is drag?

Answer 17

The force in the direction of the relative wind

Question 18

What is lift?

Answer 18

the force normal to the direction of the relative wind

Question 19

Are onshore wind turbines in a regular or irregular away?

Answer 19

irregular

Question 20

Are offshore wind turbines in a regular or irregular array?

Answer 20

regular

Question 21

What is betz analysis?

Answer 21

using a 1 dimensional momentum and energy balance

The energy balance is carried out along a streamtube, which constitutes the flow which passes through the rotor

Question 22

What does the betz limit show?

Answer 22

The maximum extractable mechanical energy

Question 23

What is the assumption we make when dealing with blades and turbines?

Answer 23

That they form an actuator disc - large number of bleeds, and they form an annulus of uniform resistance to the flow

Question 24

What are the current problems with the wind energy industry?

Answer 24

1. scaling up, flexibility, gravitational lloads, etc.
2. wake effects in wind farms
3. offshore deployment
4. public perception