Marine Energy

Question 1

What is Tidal energy and two examples of it?

Answer 1

Energy from the periodic rising and falling of sea levels. (Lagoons/Barrages)

Question 2

Ocean Energy? Examples?

Answer 2

Energy in ocean currents and waves are converted into mechanical energy, which is converted into electrical energy

Question 3

Out of currents, waves and tidal energy, which has the most utilisable energy?

Answer 3

Currents (~2000TWh) then Tidal (~200TWh) then waves (up to ~10TWh)

Question 4

How much of global primary consumption does marine energy contribute, a lot or a little?

Answer 4

very little. ~2000 TWh of 153,000 TWh..

Question 5

How many tidal periods are there in a day?

Answer 5

2 tidal periods - because the moon orbits the earth in the same direction that the earth rotates

Question 6

How many high and low tides are there in a day?

Answer 6

During each tidal period there is a low and a high tide, so since there are 2 tidal periods during the day there are 2 low and 2 high.

Question 7

What is a spring tide?

Answer 7

A tide during a new and full moon.

Question 8

What is a neap tide?

Answer 8

Seven days after a spring tide, there is a period of moderate tides when the sun and mood are at right angles

Question 9

Main difference between tidal lagoons and tidal barrages?

Answer 9

Lagoons are artificial and do not contain a pre-existing ecosystem. Both capture energy from tidal forces using turbines.

Question 10

What is the tidal range?

Answer 10

The difference between low and high tide. The potential energy in this height change is what is exploited.

Question 11

How does ebb generation work?

Answer 11

1. Sluice gate opens when there is an oncoming tide, filling the basin.
2. At high tide, the gate closes, ocean level begins dropping
3. Once height difference is significant, water directed out of basin through turbines
4. Even when the ocean reaches low tide, water continues flowing, even as the ocean begins to rise again.
5. Turbines blocked, and gates open for basin to fill once again.

Question 12

Advantages of ebb

Answer 12

1. continues to discharge into ocean held at low tide.
2. water basin always above sea level - better recreational resource
3. pumping only works for ebb

Question 13

The capacity factor of lagoons and barrages are ….

Answer 13

low (20-30%)

Question 14

Advantages of tidal stream generators (underwater wind turbine thingys)

Answer 14

• installation easier than lagoon
• can be consolidated into existing structures
• wildlife steer clear due to acoustics
• cheapest to construct of all tidal technology

Question 15

Disadvantages of tidal stream generators (underwater wind turbine things)

Answer 15

• not as much energy as barrages/lagoons

- susceptible to saltwater corrosion

Question 16

What are three groups of wave technologies

Answer 16

Wave-activated devices
Overtopping devices
Oscillating water collumns

Question 17

Marine energy accounts for how much of our global energy use?

Answer 17

(1-2%)