Energy resourcesIB MYP Physics: Revision notes

An energy resource is a source we use to generate electricity or provide heat.

Non-renewable resources will run out because they cannot be replaced in a human lifetime:

• fossil fuels: coal, oil and natural gas
• nuclear fuels such as uranium

Renewable resources are continually replaced and will not run out:

• solar, wind, hydroelectric, geothermal, tidal, wave and biomass

Coal, oil and gas power stations: the fuel is burned, releasing thermal energy. This boils water to make steam, which turns a turbine. The turbine turns a generator, which produces electricity.

Energy chain: chemical (fuel), thermal, kinetic, electrical.

Nuclear power stations work in the same way, but the thermal energy comes from nuclear fission of uranium instead of burning.

Burning fossil fuels releases carbon dioxide, which adds to global warming. Nuclear stations release none when running, but they produce radioactive waste.

• Wind: moving air turns the blades of a turbine, which drives a generator.
• Hydroelectric: water from a high reservoir flows down and turns a turbine.
• Tidal: the rising and falling tide turns turbines, often in a barrage across an estuary.
• Wave: the up and down movement of waves drives a generator.
• Geothermal: hot rocks underground heat water to make steam, which turns a turbine.
• Solar: solar cells transfer light directly to electricity; solar panels can also heat water.
• Biomass: plant material or biofuel is burned to heat water to make steam. Carbon dioxide is released, but new plants absorb it as they grow.

To compare resources, think about four things:

• Reliability: fossil fuel, nuclear, geothermal and biomass can run on demand. Wind, solar, wave and tidal depend on the weather or tides.
• Cost: renewables have no fuel costs but are often expensive to build; fossil fuel stations cost less to build but need fuel all the time.
• Location: hydroelectric needs hills and rivers, geothermal needs hot rocks near the surface, tidal and wave need a coast and wind turbines need open, windy places.
• Environmental impact: fossil fuels release carbon dioxide; nuclear leaves radioactive waste; renewables release little carbon dioxide but can affect landscapes, wildlife and noise.

Electricity cannot easily be stored in large amounts, but pumped storage helps. When demand is low, surplus electricity pumps water from a low reservoir to a high reservoir, storing energy as gravitational potential energy. When demand is high, the water is released and flows down through turbines to generate electricity.

This helps to balance supply and demand, and works well with unreliable resources such as wind and solar. Energy is not created: some is lost in pumping, so it is a way of storing energy for later, not producing extra.