(d) Energy resources and electricity generation
- Syllabus
- 2024
- Topic
- —
- Level
- —
Learning objectives
418P Electricity generation transfersDescribe the energy transfers involved in generating electricity using:• wind• water• geothermal resources• solar heating systems• solar cells• fossil fuels• nuclear power419P Large-scale electricity productionDescribe the advantages and disadvantages of methods of large-scale electricity production from various renewable and non-renewable resources
Trace energy transfers in electricity generation
Electricity generation starts with an energy store or incoming radiation and ends with energy transferred electrically. Most methods first create rotation: a moving fluid turns a turbine, and the turbine mechanically drives a generator.
| Resource or method | Energy-transfer chain |
|---|---|
| wind | kinetic store of moving air → mechanical transfer to turbine → kinetic store of turbine and generator → energy transferred electrically |
| water | gravitational store of raised water and/or kinetic store of moving water → mechanical transfer to turbine → generator → energy transferred electrically |
| geothermal | thermal store of hot rocks → heating of water or working fluid → moving vapour turns turbine → generator → energy transferred electrically |
| solar heating system | radiation from the Sun heats a fluid → moving vapour turns turbine → generator → energy transferred electrically |
| solar cells | radiation from the Sun → energy transferred electrically directly by photovoltaic cells; no turbine is required |
| fossil fuels | chemical store of fuel → heating of water → moving steam turns turbine → generator → energy transferred electrically |
| nuclear power | nuclear store of fuel → heating of water → moving steam turns turbine → generator → energy transferred electrically |
In turbine systems, some energy is also transferred to thermal stores of the machinery and surroundings and by sound radiation. The resource changes the starting store or heating step; the turbine-generator stages are often shared.
Do not describe a solar heating system as a solar cell. Solar heating uses radiation to produce thermal energy and usually turbine motion; photovoltaic cells transfer incoming radiation electrically without first making steam.
Compare large-scale electricity resources
A renewable resource is replenished as it is used on a human timescale; a non-renewable resource is finite and will run out. Choosing a large-scale method requires several linked criteria, not a single label such as 'renewable'.
| Method | Resource | Advantages | Disadvantages |
|---|---|---|---|
| wind | renewable | no fuel and no carbon dioxide from operation | intermittent output; visual/noise effects; large or exposed sites; possible wildlife impacts |
| hydroelectric reservoirs | renewable | can provide large output and respond quickly to demand; stored water makes output controllable | suitable valleys are limited; dams flood land and alter habitats |
| tidal water | renewable | tides are predictable; no fuel or operational carbon dioxide | output varies with the tidal cycle; few suitable sites; affects habitats and navigation |
| geothermal | renewable | reliable output, small land area and not weather-dependent | restricted to suitable geology; gases or hot fluids can affect the environment |
| solar | renewable | no fuel, moving turbine unnecessary for photovoltaic cells, no operational carbon dioxide | no output at night and variable sunlight; large land area for high output |
| fossil fuels | non-renewable | reliable, controllable output that can respond to demand | carbon dioxide contributes to climate change; other pollutants can cause acid rain or poor air quality |
| nuclear fission | non-renewable fuel | reliable large output with very low carbon dioxide from operation | radioactive waste needs secure long-term storage; accident risk and decommissioning requirements |
A valid comparison matches the method to the need. Intermittent sources may require storage or support from controllable generation; reservoir hydro can release stored water when demand is high. Site suitability and environmental effects can rule out an otherwise useful resource.
Renewable does not mean continuous, harmless or available everywhere. Non-renewable does not mean unreliable: fossil-fuel and nuclear stations can provide controllable or steady output, but they carry finite-fuel and environmental or waste costs.