Wind Energy Flashcards
(34 cards)
How do wind turbines work?
They convert kinetic energy of wind into electrical energy
What is the relationship between power, swept area and wind speed?
The power is proportional to the swept area and cube of the wind speed
What is the theoretical maximum fraction of wind power that can be converted into mechanical work?
0.593 which is the Betz limit
What are some of the perceived problems of wind energy?
- Cost –> Expensive to implement and operate
- Planning Permissions & Public Opinion (Noise, Visibility, Environmental/Ecosystem Damage)
- Availability –> Wind energy usually harnessed in winter months so not reliable for all year round energy
- Difficult to transport components of the wind turbine by land –> Blades are very big + End of life cycle leaves excess material from very large components
What are the potential solutions to the perceived problems?
- Cost –> UK renewable energy is subsidised by the government
- Availability –> Combined with solar energy (Summer months there’s more sun)
What are the benefits of wind energy?
- Renewable Energy
- Doesn’t produce any CO2 after implemented
- Investment in wind energy is gradually increasing
- This is attractive to smaller companies/players in the industry
- Viable to build in small scale
How do you find the Wind Energy Penetration?
Total amount of wind energy produced (GWh) / Total annual electricity demand (GWh)
How do you find the Wind Power Capacity Penetration?
Installed Wind Power Capacity (GW)/ Peak load (GW)
What is the capacity credit of wind?
Capacity of conventional plants displaced by wind power whilst maintaining the same degree of system security/ reliability
What is the installed capacity?
The installed capacity is based on the “nameplate capacity” or “rated capacity” of the wind turbines
What is the rated capacity?
The rated capacity is the manufacturers claimed output at a specific wind speed and is the maximum power that can be continuously delivered.
The actual delivered capacity is usually 20-40% of the rated capacity
How do you find the capacity factor?
Actual MWh pa/ (rated capacity x 24 x 365)
How much energy is generated by wind in the UK in 2019?
More than 50% of the electricity generated by renewables is by wind energy
Where should Wind farms be located?
Located near the coast and further up longitudinally.
Near the equator the potential for wind energy is very low due to low winds speeds from global wind circulation patterns.
Near the coasts and sea there’s a lower friction factor so wind speeds are higher
How do you find the Kinetic Power Flux?
ρ0.5u^3
ρ = 1.225 kg/m^3
units = W/m^2
What is the UK’s potential for wind energy and what’s the current average electricity production from wind energy?
UK technical potential ~ 610GW
Current UK average electricity production ~ 50GW
Describe the problem with integration for wind energy in UK?
More than 15% of energy used for wind farms crosses one or more borders.
There can be political problems between different regions for energy supply and demand
What factors affect wind conditions?
- Terrain and geographical location
- The latitude of the location
- The presence of land mass and mountains
- Obstacles like trees and buildings
What is used to measure accurate wind speeds?
An anemometer
Describe the atmospheric boundary layer
Wind speeds generally increase as elevation increases away from the ground
This is because there’s less friction from obstacles near the ground/ friction from the ground
How would you accurately measure wind speed?
- Anemometer mast numbers and placement vary based on site size and topography.
- The Earth features a boundary layer (wind shear profile).
- Boundary layer’s thickness (gradient height) spans several hundred meters.
- Ideal measurement occurs at hub height, typically above 100 meters.
- Minimum recommended measurement height is at least 75% of hub height.
- Weather station data is commonly recorded at 10 meters.
- Typically, data should be collected hourly or half-hourly for a minimum of one year.
Are wind speed statistics accurate?
- An annual mean wind speed is not accurate as the wind speeds can vary greatly throughout the year
- Mean wind speed variation usually follows a Weibull distribution
Explain why wind variation is a problem for wind power
Wind speed varies with time of day, weather, time of year. There’s no phase relationship between variations in available wind power and variations in demand
- Wind power is non-dispatchable
What is dispatchable power?
Power than can be turned on and off by grid operators to match the demand - neither base load (e.g: nuclear) nor intermittent sources (e.g: wind) fit the bill
