Tidal Energy Flashcards
How can a tide be described as?
The periodic vertical rise and fall of water in the oceans
What is tidal range?
The difference in sea level between high and low tide
What is a tidal current?
Tides are accompanied by an incoming (flood) or outgoing (ebb) horizontal flow of water
What is the reference point called that is used to measure tidal oscillations?
Mean Sea Level (MSL)
What causes the sea level oscillation over time?
The sea level oscillation is a superposition of the semi-diurnal cycle and the cycle of spring/neap tides
What drives the hydroelectric turbine?
The gravitational potential energy difference between the two bodies (sea and basin)
How is electricity generated from tidal range?
By capitalizing on the artificial height differential between two bodies of water created by a dam or barrier
Where are tidal currents typically accelerated?
headlands or through constrictions such as channels between islands
Where is the energy potential of tidal currents usually located?
Typically located in areas with the greatest tidal range; the higher the tidal range, the stronger the current.
What is the estimated technical potential of tidal energy?
438-876 TWh/year
What are the two forms of tidal range power plants?
Tidal barrage and tidal lagoon
What are the main components of a tidal range power plant?
- Sluice gates
- bulb turbines
- impoundment
What is a tidal barrage and which power plant was the largest of its kind until 2014?
- A tidal barrage is a structure that spans an entire river estuary in a straight line to generate electricity from tidal energy.
- La Rance
What defines a tidal lagoon structure and what is an example of such a project?
- A tidal lagoon is a structure that encloses an area of coastline with a high tidal range behind a breakwater.
- Swansea Bay Lagoon Project
What are the different types of tidal stream devices classified by their working principle?
- Horizontal-axis turbine
- Vertical-axis turbine
- Oscillating hydrofoil
- Archimedes screw
- Tidal kite
Can you give examples of vertical axis tidal turbines?
Examples include the Norront AS turbine and the GCK technology
What is the advantage of a tidal kite?
The increased relative velocity felt by the turbine, unlocking energy potential at low-energy sites
What is currently the largest planned tidal stream project in the world?
The MeyGen project in Pentland Firth
List some environmental consequences of tidal energy schemes?
- Ecosystem Alteration
- Fish and Marine Mammal Impact
- Sediment Transport
- Habitat Loss
- Noise and Visual Pollution
- Chemical Leaks and Pollution
How are tidal stream devices classified based on their location on the water column?
Tidal stream devices are classified as first or second generation, with first-generation devices usually being bottom-mounted and second-generation devices being either floating or bottom-mounted
What design approaches have been taken to resist the forces on first-generation tidal stream turbines?
Use of heavy ballast blocks (800 to 1200 tonnes) to secure the turbines against strong ocean currents and forces.
Why are first-generation tidal stream support structures considered expensive and limited?
Expensive due to the need for very large vessels for deployment, which can be costly per day, and they are limited to shallow sites
What are the characteristics of first-generation support structures for horizontal-axis tidal turbines?
First-generation structures are designed to resist sliding due to turbine drag force and to resist bending moments due to vertical lever arms
What are the key features of second-generation support structures for tidal stream devices?
- Utilize buoyancy modules to support turbines
- Use mooring systems that operate in tension rather than compression
- Can be installed at an optimal position in the water column
Why is energy storage increasingly critical as the renewables component in an energy system increases?
- To manage the intermittency of renewable sources
- stabilize the grid
- perform load leveling
- regulate frequency
- enhance energy security
What are the different forms in which energy can be stored?
chemical, mechanical, thermal, electrical, and hydrogen forms,
