2.14 Hydroelectricity & Tidal Barrages

Question 1

What does HEP mean?

Answer 1

Hydroelectric power

Question 2

How does energy transfer work in both hydroelectric dams and tidal barrages?

Answer 2

• In both cases the water on the higher side of the dam or barrage contains lots of gravitational potential energy. Once the dam or barrage is opened, this energy is transferred to kinetic energy as the water rushes down to the lower side.
• As the water moves past turbines, some of its kinetic energy is transferred to the turbines, causing them to start spinning. Generators can then use this energy to generate electrical power

Question 3

How do hydroelectric dams work?

Answer 3

• As water flows downhill (e.g. from mountains), a hydroelectric dam will trap the water in a man made lake, which is also known as a reservoir.
• Then whenever water is released through the dam, it spins turbines which are connected to generators, and so produce electricity.
• The water can then return to the river on the downstream side of the dam.

Question 4

How do tidal barrages work?

Answer 4

• Tidal barrages are big dams built across river estuaries with turbines in them.
• As the tide comes in it fills up the estuary. The water is then let out through turbines at a set speed.

Question 5

What are the disadvantages of hydroelectric dams? (2)

Answer 5

• There is a big impact on the environment due to the flooding of the valley and possible loss of habitat for some species
• Initial costs are often high

Question 6

What are the advantages of hydroelectric dams? (3)

Answer 6

• A big advantage is immediate response to increased electricity demand - more water can be let out through the turbines to generate more electricity.
• Minimal running costs
• Reliable energy source

Question 7

What are the disadvantages of tidal barrages? (5)

Answer 7

• Tides are pretty reliable (they always happen twice a day). But the height is variable and tidal barrages don’t work when the water level is the same either side.
• They affect boat access.
• They can spoil the view.
• They alter the habitat for wildlife.
• They can only be used in some estuaries.

Question 8

What are the advantages of tidal barrages? (2)

Answer 8

• There is no pollution
• Tides are pretty reliable