Physics - 3 Energy Resources - 3.1 Energy Demands & 3.2 Energy From Wind and Water & 3.3 Power From the Sun and the Earth

Energy resource

anything that can be used to generate energy to meet our energy demands

Energy is needed for [5]:

- electrical devices
- heating buildings
- cooking
- water
- transport

How do most power stations work? [4]

1. fuel is burnt
2. burning fuel heats water into steam
3. steam drives a turbine
4. turbine drives an electricity generator

Biofuel

any fuel taken from living or recently living organisms

Examples of biofuel [6]:

- animal waste (methane)
- ethanol (fermented sugar cane)
- straw
- nutshells
- woodchip
- waste vegetable oil & rapeseed (biodeisel)

Advantages of biofuel [4]:

- carbon neutral
- less sulphur pollutant (than fossil fuels)
- good for local economy
- can be used in vehicles

Disadvantages of biofuel [5]:

- lower energy output than other fuels
- uses crops for fuel rather than food
- uses farm land
- could increase food prices
- requires lots of water to grow

Why is biofuel renewable?

its biological source either regrows or is constantly produced, so it is used at the same rate it is replaced

Why is biofuel carbon-neutral?

in theory, the carbon that the living organism takes in balances the amount that is released when the biofuel is burnt

Nuclear fuel

an energy source that results from nuclear fission

Examples of nuclear fuel [2]:

- uranium
- plutonium

Nuclear fission

nuclei of isotopes split apart when struck by neutrons

How does a nuclear power plant generate electricity? [6]

1. nuclear fuel is kept in a sealed can in the reactor core
2. it is struck by a neutron and this begins a chain reaction of fission
3. the core becomes very hot from the energy being released
4. coolant is pumped through the core and then to a heat exchanger (before returning to the core)
5. the heat exchanger uses the energy to turn water into steam
6. the steam turns a turbine which drives an electrical generator

Nuclear vs. Fossil - energy released

nuclear releases about 10000 times as much energy per volume of fuel than fossil

Nuclear vs. Fossil - waste [2]

- nuclear waste is highly radioactive and dangerous; it has to be stored for hundreds of years
- fossil fuel waste is non-radioactive but very harmful to the environment

Nuclear vs. Fossil - greenhouse gases [2]

- nuclear power releases no greenhouse gases as uranium releases energy without burning
- fossil fuels produce greenhouse gases when they burn

Renewable energy

a resource that can be replaced when needed.

Wind power

the use of a windmill to drive an electric generator

Advantages of wind power [4]:

- no pollutants or waste
- cheap to run
- land occupied can be used for farming
- can become tourist attraction

Disadvantages of wind power [4]:

- unreliable
- can 'spoil view'
- constant low-level noise
- can interfere with television reception and radar

Wave power

power obtained by harnessing the energy released by waves at sea

Advantages of wave power [5]:

- running costs are low
- no pollutants or waste
- predictable energy
- no fuel used
- lots of energy

Disadvantages of wave power [6]:

- only effective with large waves
- not many suitable locations
- can be noisy
- in early developmental stage
- expensive to install
- can be hazardous to ships

Hydroelectric power

rainwater is collected in a reservoir flows downhill and drives turbines

Advantages of hydroelectric power [2]:

- no pollutants or waste
- inexpensive to run

Disadvantages of hydroelectric power [3]:

- 'spoils' the landscape
- some environmental impact
- unreliable

Tidal power

traps water behind a barrage before releasing the high tide into the sea through turbines

Solar power

power obtained by harnessing the energy of the sun's rays

Advantages of solar power [2]:

- free to run
- ideal for small amount of energy

Disadvantages of solar power [2]:

- expensive to build/buy
- many are needed to be useful

Solar power tower

1. solar plant that uses thousands of flat mirrors to reflect sunlight onto a water tank at the top of a tower.
2. the water turns to steam
3. piped down to ground level where it turns turbines

Geothermal energy

energy derived from the heat in the interior of the earth

Advantages of geothermal energy [2]:

- no pollutants or waste
- low running costs

Disadvantages of geothermal energy [4]:

- difficult to find locations
- rocks must be suitable
- holes can run out of steam
- dangerous gases and minerals can escape

How do geothermal power stations work? [4]

1. built in volcanic areas or areas with radioactive rocks under the surface
2. drill down to these rocks
3. water is pumped to them and becomes steam
4. steam turns turbines at ground level