Wind Energy Flashcards
How is wind created?
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.
When and why does a sea or land breeze occurs?
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.
Where does the wind power density increases?
At higher altitudes and off-shore compared to on-shore.
What types of wind technologies exist?
- Large scale on shore (1-7.6 MW)
- Small scale on shore (1.5 - 999kW)
- Micro wind (<1.5 kW)
- Airborne wind (30-600 kW)
- Fixed offshore (3-8.4 MW)
- Floating offshore (2-7 MW)
What types of drivetrains exist?
- Gearbox + Doubly-Fed Induction Generator (DFIG)
- Direct Drive (Electrically Excited Synchronous generator or Permanent Magnet Synchronous Generator)
- Gearbox + Full scale converter (PMSG or SCIG)
What does REEs stands for?
Rare Earth Elements
What does SCIG stands for?
Squirrel Cage Induction Generator (asynchronous generator)
How is a wind turbine characterized?
By its power curve: the power produced in function of the wind speed
What is required for low-wind sites to increase the capacity factor of wind turbines?
Rotor diameter increase is beneficial at low wind speeds.
What is required for high-wind sites to increase the capacity factor of wind turbines?
Rated power increase is beneficial at high wind speeds.
What can increase the OPEX of wind turbines?
Failure rates are often higher than anticipated. Condition monitoring and early fault detection can reduce unforeseen maintenance costs.
What impact does wind turbines have on the environment?
When using permanent magnets in generators, rare-earth materials are needed. The extraction of these materials may lead to pollution concerns.
What does AEP stands for?
Annual Energy Production
What impact could wind turbines have on people?
- Ice form on turbine blades can be thrown off during operation
- Flicker and visual disturbance
- Noise pollution
What are advantages of offshore wind farms?
- Higher average speed
- Higher annual load factor
- Lower visual and auditive impact => better acceptance by public
- Large potential for development
What are disadvantages of offshore windfarms?
- Difficulties regarding access, logistics, supply chain, O&M
- Marine activities cause constraint for development (ship routes, fishery, …)
- Higher risks, technical, health and safety
- Higher CAPEX due to difficult works at sea
- Higher OPEX due to difficult access for O&M, more aggressive marine environment
What are advantages of floating offshore wind turbines?
- Not dependent on depth of water (Large share of offshore wind resource is in deep waters => not possible for fixed wind turbines)
- Installation process can be done at quay side
- Easily dis/reconnect for large repairs onshore, relocation
- Not dependent on the sea bed
Why are floating wind turbines an emerging technology?
They take advantage of the improved wind conditions in deep waters
In what four parts can the floating support structure be broken down?
- Floater: Maintains buoyancy (opwaartse kracht) and structural integrity
- Mooring: connects the floater to the seabed with chains or cables
- Anchoring: Attaches the mooring lines to the seabed
- Electrical & data cable: export of power and communication
What does AWEC stands for?
Airborne Wind Energy Converters
How does Airborne Wind Energy Converters work?
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).
What two type of generation systems exist for AWE?
- On board generation
- On ground generation
What is on board generation?
The aircraft has a generator that produces electrical power and transports it via a cable to the ground.
What is on ground generation?
The generator is located at the ground and produces electricity due to the movement of the aircraft.
What two types of AWE systems exist?
- Static floating system using helium or H2
- Dynamic flying systems (aircraft)
What are advantages of AWE?
- High capacity factor (50-70%)
- Considerable material savings compared to HAWT
- Low environmental impact (GWP)
- Flexible (easy transport, installation, decommissioning, maintenance)
- Can be complementary to HAWT (low wind sites, low flight areas, less radar interference)
- Lower visual and auditive impact => better social acceptance
What are disadvantages of AWE?
- Risky flying device (uncertain certification and regulations at the moment)
- High wear rate components (requires regular maintenance)
What is the onshore capacity of wind?
780 GW (World Wide)
208 GW (Europe)
China, USA and Germany own 64% of the global market
How much onshore wind need to be installed per year to limit global warming to 1.5 by 2050?
180 GW => urgent improvements needed
