Wave power Flashcards
What 3 properties affect linear waves?
- Amplitude
- Period
- Still water depth
How can the energy in a wave be estimated?
By integrating the potential and kinematic energy in the wave over a wavelength
The potential energy is a result of the displacement of mass from a position of rest.
Ep = rhoga^2/4. The potential energy is proportional to the square of the amplitude
The kinetic energy is total kinetic energy contained in all the water from the free surface to the bottom. However, in airy theory we can only integrate up to the still water level
Ek = rhoga^2/4
Total energy per unit surface area is thus:
E = Ep+Ek = rhoga^2/2
P = E*Cg since the energy propagates with the group velocity, at which the group velocity is smaller than the phase velocity
What is the main reason that the LCOE of wave is high?
Non-commercial designs. All designs are different meaning that no large scale production can take place
Which three main wave energy converter (WEC) categories exist?
- Oscillating water columns
- Wave activated bodies
- Overtopping
Why is resonance of importance?
Since it can increase the energy contained in the waves. By manipulating the device to move in relation to the excitation force, it is possible to generate resonance
Where is the most wave power capacity located?
Africa & south-west south america
What is the assumption made in airy waves (linear water waves)?
That the wave slope is small (has a low amplitude) –> hard to analyze extreme waves
How does the velocity profile vary with depth?
In shallow waters, the velocity profile is uniform
In deep water, the velocity profile is exponential
What is latch reactive control?
- Hold you buoy until it will move in phase
- Get out more energy, but get large mechanical forces
How does an oscillating water column work?
An OWC extracts wave energy using the rise and fall of waves into airflow through turbines to generate power. As the water column moves with the waves, it will cause the trapped air to become compressed or decompressed and thus increase in velocity which will drive the turbine
How does a wave activated body work?
Wave activated bodies extract wave energy directly. They can be of the types point absorber or rotational absorber. In a point abosrber, a buoy moves together with the waves and the converter system forces the generator to produce electricity. One way of fulfilling this is by having a hydraulic piston pump that will deliver high pressure water which can be driven through turbines
