Energy from Water (Cambridge (CIE) IGCSE Physics): Revision Note

Wave & tide power

• Energy can be obtained from the kinetic store of the waves and tides

• The motion of the water is used to turn a turbine, which turns a generator, which generates electricity

Wave power

• Wave power uses devices that float on or near the surface 

• The up-and-down motion of the waves drives a generator, either directly or by forcing air through a turbine

Turbines using wave power

Tidal power

• Tidal power uses tidal barrages to store water at a height as the tide comes in and goes out

• When the barrage is opened, water flows through a channel over a turbine

Tidal barrage

Advantages of wave and tidal power

• Wave and tidal power are renewable energy resources

• Wave and tide power produce no carbon dioxide or greenhouse gases as no fuel is needed

• Tides are regular, so tidal power is reliable and predictable

• There are no fuel costs involved in wave and tidal power stations so running costs are low

Disadvantages of wave and tidal power

• Wave power is not available at all times as the waves are not always large enough to turn the turbines

• Tidal barrages are built in estuaries so there are not many suitable locations

  around the world that are suitable for tidal power generation

• Because the equipment is submerged in the sea, underwater maintenance is more difficult

• The underwater turbines and tidal barrages can interfere with shipping routes and cause damage to habitats

• Wave and tidal power stations have a long construction time compared to some other power station types

Hydroelectric dams

• When water is stored above ground level, it has energy in its gravitational potential energy store

• This energy can be transferred to the kinetic energy store if the water is allowed to flow down the slope

• Flowing water turns the turbine to generate electricity

Advantages of hydroelectric power

• Hydroelectric power is renewable because the reservoir is refilled by rainfall

• Hyrdoelectric power does not contribute to global warming and does not produce acid rain

• Hydroelectric dams are reliable since water can be released on demand and dams are well established in most countries

• Hydroelectric power stations are responsive because they can be turned on and off easily to meet changing demand

• Hydroelectric power stations are cheap to run because there is no fuel to buy

• Hydroelectric power stations can produce large amounts of electricity

Disadvantages of hydroelectric power

• Valleys are flooded to create the reservoir used to store the water, which destroys habitats, towns and villages

• There are limited suitable sites available for construction, as hydroelectric dams require both a steady water supply and the necessary vertical height

• Hydroelectric power stations are expensive to build because the land and properties need to be acquired in order to build the reservoir 

• Drought can affect the supply of water

• Pumping systems are sometimes used to return the water to the reservoir

  • Pumped storage uses electricity from the grid to pump water back up to the reservoir, so its environmental impact depends on how that electricity was generated