Wind Flashcards
What is the generic power formula for wind
P = 0.5pA(V^3)
How are the UK trying to incentivise investors to get into the wind sector
Contracts for difference. Implements a strike price that means when the electricity price is below, the generators are paid a top-up and when the electricity price is above the generators pay the difference back. This helps with the reliability of investment back to the generators as they can expect at least a guaranteed price.
What types of wind turbine are there
Horizontal or vertical axis.
Horizontal can be downwind or upwind
vertical can use drag forces (savonius)
or lift forces (Darrieus)
Formula for Total energy entering a turbines CV
= (massflowrate)*0.5(V^2)
mass flow rate equation
= pAV
How can flow be analysed through 1-D turbine
Betz analysis
Formula for velocity at a turbine rotor
V1 = (V(enter)+V(exit))/2
Value for the ideal Cp
0.593
Why can wind turbines not function at Ideal power curve
- Losses in the drive train and generator
- finite number of blades
Tip-speed ratio formula
= (tip speed of blade)/wind speed
= wR/v
What happens when the number of turbine blades is increased
The turbine blades slow down
How to find the annual energy capture
The area under a power curve, with cut-in, cut-out and Prated as limits
What is the capacity coefficient
(annual energy capture)/rated power *time
What happens when rated wind speed is increased
- energy capture increases, capacity coefficient would decrease, capital cost rises
List the disadvantages of wind turbines
- Variable power output. Wind dependant can cause issues with the grid.
- low efficiency
- Noisy
- Visual effect
- Birds
- Environmental impact, destruction of land and nature, transmission implementation
