Wind Energy

Question 1

How is wind created?

Answer 1

The sun hits the earth and energy is absorbed by the atmosphere. More energy is absorbed near the equator and less towards the poles. This causes variations in pressure and temperatures that results in movement of air around the planet.

Question 2

When and why does a sea or land breeze occurs?

Answer 2

Sea breeze occurs during the day: High pressure above the sea because it’s cooler, air moves from higher to lower pressure area on land (onshore breeze).
Land breeze occurs during the night: Land cools more quickly than the ocean and the air above it, creating a cool, offshore breeze.

Question 3

Where does the wind power density increases?

Answer 3

At higher altitudes and off-shore compared to on-shore.

Question 4

What types of wind technologies exist?

Answer 4

1. Large scale on shore (1-7.6 MW)
2. Small scale on shore (1.5 - 999kW)
3. Micro wind (<1.5 kW)
4. Airborne wind (30-600 kW)
5. Fixed offshore (3-8.4 MW)
6. Floating offshore (2-7 MW)

Question 5

What types of drivetrains exist?

Answer 5

1. Gearbox + Doubly-Fed Induction Generator (DFIG)
2. Direct Drive (Electrically Excited Synchronous generator or Permanent Magnet Synchronous Generator)
3. Gearbox + Full scale converter (PMSG or SCIG)

Question 6

What does REEs stands for?

Answer 6

Rare Earth Elements

Question 7

What does SCIG stands for?

Answer 7

Squirrel Cage Induction Generator (asynchronous generator)

Question 8

How is a wind turbine characterized?

Answer 8

By its power curve: the power produced in function of the wind speed

Question 9

What is required for low-wind sites to increase the capacity factor of wind turbines?

Answer 9

Rotor diameter increase is beneficial at low wind speeds.

Question 10

What is required for high-wind sites to increase the capacity factor of wind turbines?

Answer 10

Rated power increase is beneficial at high wind speeds.

Question 11

What can increase the OPEX of wind turbines?

Answer 11

Failure rates are often higher than anticipated. Condition monitoring and early fault detection can reduce unforeseen maintenance costs.

Question 12

What impact does wind turbines have on the environment?

Answer 12

When using permanent magnets in generators, rare-earth materials are needed. The extraction of these materials may lead to pollution concerns.

Question 13

What does AEP stands for?

Answer 13

Annual Energy Production

Question 14

What impact could wind turbines have on people?

Answer 14

1. Ice form on turbine blades can be thrown off during operation
2. Flicker and visual disturbance
3. Noise pollution

Question 15

What are advantages of offshore wind farms?

Answer 15

1. Higher average speed
2. Higher annual load factor
3. Lower visual and auditive impact => better acceptance by public
4. Large potential for development

Question 16

What are disadvantages of offshore windfarms?

Answer 16

1. Difficulties regarding access, logistics, supply chain, O&M
2. Marine activities cause constraint for development (ship routes, fishery, …)
3. Higher risks, technical, health and safety
4. Higher CAPEX due to difficult works at sea
5. Higher OPEX due to difficult access for O&M, more aggressive marine environment

Question 17

What are advantages of floating offshore wind turbines?

Answer 17

1. Not dependent on depth of water (Large share of offshore wind resource is in deep waters => not possible for fixed wind turbines)
2. Installation process can be done at quay side
3. Easily dis/reconnect for large repairs onshore, relocation
4. Not dependent on the sea bed

Question 18

Why are floating wind turbines an emerging technology?

Answer 18

They take advantage of the improved wind conditions in deep waters

Question 19

In what four parts can the floating support structure be broken down?

Answer 19

1. Floater: Maintains buoyancy (opwaartse kracht) and structural integrity
2. Mooring: connects the floater to the seabed with chains or cables
3. Anchoring: Attaches the mooring lines to the seabed
4. Electrical & data cable: export of power and communication

Question 20

What does AWEC stands for?

Answer 20

Airborne Wind Energy Converters

Question 21

How does Airborne Wind Energy Converters work?

Answer 21

It consists of tied up aircrafts that extract high density wind energy at high altitudes (200-600m) with 90% material savings compared to horizontal axis wind turbines (HAWT).

Question 22

What two type of generation systems exist for AWE?

Answer 22

1. On board generation
2. On ground generation

Question 23

What is on board generation?

Answer 23

The aircraft has a generator that produces electrical power and transports it via a cable to the ground.

Question 24

What is on ground generation?

Answer 24

The generator is located at the ground and produces electricity due to the movement of the aircraft.

Question 25

What two types of AWE systems exist?

Answer 25

1. Static floating system using helium or H2
2. Dynamic flying systems (aircraft)

Question 26

What are advantages of AWE?

Answer 26

1. High capacity factor (50-70%)
2. Considerable material savings compared to HAWT
3. Low environmental impact (GWP)
4. Flexible (easy transport, installation, decommissioning, maintenance)
5. Can be complementary to HAWT (low wind sites, low flight areas, less radar interference)
6. Lower visual and auditive impact => better social acceptance

Question 27

What are disadvantages of AWE?

Answer 27

1. Risky flying device (uncertain certification and regulations at the moment)
2. High wear rate components (requires regular maintenance)

Question 28

What is the onshore capacity of wind?

Answer 28

780 GW (World Wide)
208 GW (Europe)
China, USA and Germany own 64% of the global market

Question 29

How much onshore wind need to be installed per year to limit global warming to 1.5 by 2050?

Answer 29

180 GW => urgent improvements needed