Energy Resources & Energy Generation (Cambridge International IGCSE Environmental Management)

Renewable & non-renewable energy

Renewable (non-finite) energy resources

• Renewable resources—energy sources that can be replenished naturally in a relatively short time

  • They are non-finite, meaning they will not run out on a human timescale

• Examples of renewable energy sources:

  • Biofuels—fuels made from living or recently living material, such as crops or waste

    • Includes bioethanol, biogas, biomass, and wood

  • Geothermal power: uses heat from rocks deep underground

  • Hydroelectric power: uses moving water from rivers or dams

  • Tidal power: uses the rise and fall of sea levels

  • Wave power: uses the movement of waves at the ocean surface

  • Solar power: uses energy from sunlight

  • Wind power: uses moving air to turn turbines

Non-renewable (finite) energy resources

• Non-renewable resources—energy sources that exist in limited amounts and cannot be replaced quickly

  • They are finite, meaning once used, they will eventually run out

• Examples of non-renewable energy sources:

  • Fossil fuels—coal, oil, and natural gas formed from ancient organisms
  • Nuclear power—produced by splitting uranium atoms to release heat energy

Types of energy resources

Generation of electricity by renewable energy sources

Biofuels (bioethanol, biomass, biogas, wood)

• Biomass—plant or animal material burned as fuel

  • Burned in a boiler to heat water
  • Water turns into steam, which spins turbines
  • Turbines turn generators to produce electricity

• Biogas—gas (mainly methane) from rotting organic waste

  • Collected and burned in a power station
  • Heat is used to make steam that drives turbines and generators

• Bioethanol—alcohol fuel made by fermenting crops such as sugarcane or maize

  • Burned in power stations or engines to provide heat or movement
  • Can be used to turn generators and make electricity

• Wood—logs or wood pellets burned as fuel

  • Heat from burning wood boils water
  • Steam turns turbines connected to generators

Geothermal power

• Cold water is pumped down into hot rocks underground
• Rocks heat the water so it turns into steam
• Steam rises and turns turbines at the surface
• Turbines drive generators to produce electricity

Cold water is heated by the rocks and returned as hot water or steam, which can be used to generate electricity

Hydro-electric power

• A dam is built across a river to form a reservoir
• Water is released from the reservoir and flows through pipes
• Fast-moving water turns turbines at the base of the dam
• Turbines spin generators to produce electricity

A hydroelectric dam transfers kinetic energy to mechanical energy through moving turbines which turns the generator to produce electricity

Tidal power

• A barrage is built across an estuary or bay
• As the tide rises and falls, water flows through turbines
• Moving water spins the turbines
• Turbines turn generators to produce electricity

Tidal barrages can generate electricity from the movement of water, both as the tide comes in and as it goes out again

Wave power

• Floating devices or wave machines are placed on the sea surface
• Waves move the devices up and down
• This motion drives pistons or turbines inside the device
• Turbines turn generators to produce electricity

Solar power

• Solar panels (photovoltaic cells) are placed on roofs or in solar farms

  • Photovoltaic (PV) cells—panels that change light energy directly into electrical energy
  • Sunlight hits the cells and electrons move, creating an electric current

Solar PV panels use energy from sunlight to produce electricity

• Solar thermal systems can also be used

  • Mirrors focus sunlight onto water-filled pipes or a central water tank
  • Water is heated to make steam
  • Steam turns turbines and generators

Wind power

• Wind turbines have large blades mounted on a tall tower
• Wind pushes the blades, making them spin
• The blades turn a shaft connected to a generator
• The generator produces electricity as the shaft spins
• Wind turbines can be located on-shore (on land) or off-shore (in the sea)

On-shore wind turbines

Generation of electricity by non-renewable energy sources

Fossil fuels (coal, oil, natural gas)

• Fossil fuels are burned in a furnace in the power station
• Heat from burning fuel boils water in pipes or a boiler
• Water turns into high-pressure steam
• Steam is directed onto turbine blades, making the turbines spin
• Turbines drive generators, which produce electricity
• Steam is cooled back into water and reused in a closed loop

The production of electricity from fossil fuels

Nuclear power (uranium)

• Uranium fuel rods are placed in a nuclear reactor

  • Nuclear fission occurs
  • Uranium atoms split, releasing large amounts of heat

• Heat from the reactor core is used to heat water

• Water turns into steam in a separate loop

• Steam spins turbines, which then turn generators

• Electricity is carried away by power lines to homes and industries

Nuclear power

Exam Hint When describing how electricity is generated, always follow the chain: fuel → heat → steam → turbine → generator → electricity wherever it applies. Examiners love this clear sequence because it shows you understand the whole process, not just one part.

But remember—photovoltaic panels change light directly into electricity, with no turbines or steam involved.