Energy resourcesIB MYP Sciences: Revision notes

A renewable resource is replaced as fast as we use it, so it will not run out: solar, wind, hydroelectric, tidal, geothermal and biomass.

A non-renewable resource will run out because it takes millions of years to form, or exists in limited amounts: coal, oil, gas (the fossil fuels) and nuclear fuel (uranium).

Most of our electricity still comes from non-renewable resources, but renewable use is growing to cut carbon dioxide emissions.

Most power stations follow the same steps:

1. A fuel (coal, gas, oil, uranium or biomass) is used to heat water
2. The water becomes steam
3. The steam pushes a turbine, which spins
4. The turbine turns a generator, which produces electricity

The energy changes are: chemical (or nuclear) to thermal, to kinetic, to electrical. Wind, hydroelectric and tidal power skip the steam: moving air or water spins the turbine directly. Solar cells make electricity directly from light, with no turbine.

• Solar: light on solar cells gives electricity directly. No fuel or emissions, but only works in daylight
• Wind: moving air spins turbine blades. No emissions, but output varies with wind speed and turbines can spoil views
• Hydroelectric: water falls from a dam through turbines. Reliable, can be started quickly, but flooding valleys harms habitats and homes
• Tidal: the rising and falling tide spins turbines. Predictable, but expensive and can harm estuary wildlife
• Geothermal: hot rocks underground heat water into steam. Reliable, but only possible in certain places
• Biomass: burning plant material releases energy. Can replace fossil fuels, but releases carbon dioxide and needs land

• Coal, oil and gas: burned to release thermal energy. Reliable and cheap, but they release carbon dioxide, which causes global warming. Coal also releases sulfur dioxide, which causes acid rain
• Nuclear: uranium releases energy in a reactor. A small amount of fuel gives a lot of energy and no carbon dioxide is released while generating, but it produces radioactive waste that must be stored safely for thousands of years, it is expensive to build and an accident would be very serious

To compare resources, judge them on:

• Reliability: can it generate whenever needed? (gas and nuclear: yes; solar and wind: no)
• Cost: building costs and running costs
• Environment: emissions, habitats, waste, land use
• Social and economic effects: jobs, bills, safety, who is affected

A good answer gives advantages and disadvantages, and then a justified conclusion, for example: 'Wind power is a good choice here, because the site is windy and there are no emissions, but a backup supply is needed for calm days.'