1.3.1 Main energy resources, renewable and non-renewable

Energy resources: the stores and flows we draw on for useful work

1. There are ten main energy resources available for use on Earth:
   1. the fossil fuels: coal, oil and gas
   2. nuclear fuel
   3. bio-fuel
   4. wind
   5. hydro-electricity
   6. geothermal
   7. the tides
   8. the Sun
   9. water waves
2. Each one is called a resource because it lets us transfer energy to where it is useful.
3. For example, the chemical store of coal is transferred by heating when the coal is burned, and a wind turbine takes energy from the kinetic store of moving air.
4. Fossil fuels are formed from the remains of living organisms over millions of years; coal, oil and gas are all fossil fuels, and they are burned to release energy when it is needed.
5. Nuclear fuel is not burned: energy is released from changes in the nuclei of its atoms, and this energy is used to heat water and generate electricity.
6. Bio-fuel is made from recently living material, such as crops, wood or plant waste, so it can be grown again.
7. Wind, hydro-electricity, the tides and water waves all rely on movement, so moving air or moving water can turn a generator; the Sun can heat directly or drive solar cells, and geothermal energy comes from hot rocks inside the Earth.

Renewable or non-renewable: is it replenished as fast as we use it?

1. The renewable resources are bio-fuel, wind, hydro-electricity, geothermal, the tides, the Sun and water waves.
2. These are renewable because they are naturally replaced or keep arriving: the wind keeps blowing, the tides keep turning, and more plants can be grown for bio-fuel.

1. The non-renewable resources are the fossil fuels (coal, oil and gas) and nuclear fuel.
2. These are non-renewable because their reserves are finite: fossil fuels take millions of years to form, so they are used far faster than they are replaced, and there is only a limited supply of suitable nuclear fuel.

Matching the resource to the job: transport, electricity and heating

1. The three uses you compare are transport, electricity generation and heating.
2. Transport: oil is the key resource because petrol and diesel are made from it and power cars, lorries, ships and aircraft; bio-fuels run some vehicles, and electric trains and cars use electricity that must first be generated.
3. Electricity generation: fossil fuels and nuclear fuel heat water to make steam that turns generators, while wind, hydro-electricity, the tides and water waves turn generators directly, and solar cells generate electricity from sunlight.
4. Heating: gas is common for heating homes and water, oil, coal and bio-fuels can be burned for heat, and the Sun and geothermal energy provide heating in suitable places.
5. A strong comparison does not just list resources: it links each resource to a use, and notes that some resources, such as gas, have more than one common use.

1.3.2 Reliability, environmental impact and trends in energy use

Reliability: can the resource deliver energy when it is needed?

1. Some resources are more reliable than others because their availability does not depend on changing weather.
2. Fossil fuels, nuclear fuel and bio-fuels can be stored and burned on demand, so their output can be raised when demand rises.
3. Geothermal energy gives a steady supply wherever suitable hot rocks are found.
4. Hydro-electricity responds quickly if a reservoir is full, but a long dry spell lowers the stored water.
5. Wind is unreliable because the wind speed varies: there may be too little wind, or so much that turbines must shut down.
6. Solar energy produces nothing at night and less under cloud or in short winter days.
7. Wave energy rises and falls with the weather.
8. Tidal energy is predictable, because tides can be forecast, but it is not continuous, because the tide turns through the day.
9. A renewable resource is not automatically reliable, and a reliable resource can still cause serious environmental harm, so keep the two ideas separate.

Every resource carries an environmental cost, renewables included

1. Burning coal, oil and gas releases carbon dioxide, a greenhouse gas, so it adds to climate change.
2. Burning some fossil fuels also releases sulfur dioxide, which causes acid rain, and particulates, which harm health and cause global dimming.
3. Extracting and transporting fossil fuels can destroy habitats and cause pollution such as oil spills.
4. Nuclear power makes radioactive waste that must be stored safely for a long time and carries a risk of accidents, though it releases very little carbon dioxide in normal use.
5. Bio-fuels need land to grow, which can mean deforestation, habitat loss or competition with food crops, and burning them still releases carbon dioxide.
6. Wind turbines can create noise, change views and disturb some wildlife.
7. Hydro-electric schemes can flood large areas, destroying habitats and displacing communities.
8. Tidal schemes can alter coastal habitats and affect marine life.
9. Large solar farms use land and can affect habitats and the look of an area.
10. Geothermal energy has a low impact in use, but suitable sites are limited and building the plant disturbs the local area.
11. Renewables usually cause little or no air pollution while running, but construction, land use and effects on habitats mean they are not impact-free.

Why energy use is shifting towards renewables

1. In many countries the use of renewable resources is rising, for several reasons:
   1. governments and the public are worried about climate change and air pollution
   2. fossil fuels are finite
   3. renewable technology is becoming more widely available and may become cheaper
   4. governments may set laws, targets or financial support for low-carbon resources
   5. countries may want energy security by depending less on imported fuels
2. Even so, fossil fuels may stay in wide use because they are reliable, can meet changes in demand and are supported by existing infrastructure, and replacing that equipment is expensive.
3. Patterns differ between countries: the choice depends on the resources available, wealth, geography, population, demand and government decisions, so a sunny country may use more solar energy and a country with rivers and valleys may use more hydro-electricity.
4. When you describe a graph, state the overall trend, support it with data where values are given, and do not claim the trend continues beyond the period shown.

Science can flag the problem but not settle the response

1. Science can identify environmental issues by collecting evidence: measuring emissions, monitoring habitats and modelling possible future effects.
2. Scientific evidence on its own cannot decide what should be done, because a decision also weighs other factors:
   1. political factors, such as government policy and energy security
   2. social factors, such as public opposition, local jobs or displaced communities
   3. ethical factors, such as duties to future generations and whether damage is acceptable
   4. economic factors, such as construction costs, energy prices and the cost of replacing existing systems