Energy Resources (Oxford AQA IGCSE Physics)

Energy Resources

• There are a range of energy sources available for use on a national and global scale

• The use of each one has implications for society in terms of:

  • Extraction methods

  • Pollution & global warming

  • Safety & efficiency

Fossil fuels

• Fossil fuels are formed underground and under sea beds from the remains of plants and animals over millions of years

• There are three fossil fuels

  • Coal

  • Oil

  • Natural gas (methane)

The three fossil fuels

Extraction methods

• Fossil fuels are extracted from underground which usually results in damage to the environment

  • Oil is drilled for under the sea

  • Coal is mined by digging into the ground

  • Natural gas is extracted through a process known as 'fracking' where rocks are fractured by drilling, and then water is pumped into the fissure forcing out the gas which can then be collected

Pollution and global warming

• Burning fossil fuels releases carbon dioxide into the atmosphere

  • Carbon dioxide is a greenhouse gas (along with methane and water vapour) that contributes to global warming

• Sulphur dioxide is also released from burning oil (and products made from oil like petrol and diesel) and coal

  • Sulphur dioxide is acidic when dissolved in water in the atmosphere producing acid rain

• Of the three fossil fuels, natural gas is the cleanest and coal is the most polluting

• There is a global push to move away from fossil fuels due to their impact on global warming

Safety and efficiency

• Fossil fuel power stations use the energy released in the combustion of fuel to heat water to produce steam to turn turbines which generate electricity

• Fossil fuel power stations:

  • are extremely reliable and are already well-established in most countries

  • are responsive (can be turned on and off easily) to meet the changing demands of a nation

  • are expensive to build and decommission

  • are relatively safe

  • produce an average output power of 500 MW

Nuclear fuels

• The nuclear fuels are uranium-235 and plutonium-239

Extraction methods

• These isotopes are found in rocks called ores which are mined from the ground

• Uranium and plutonium are then extracted from the rock

Pollution and global warming

• Nuclear fission releases no pollutants into the atmosphere

• Nuclear reactors do produce radioactive waste that can remain radioactive for thousands of years

  • Radioactive waste is packaged and buried underground

  • Burial sites must remain undisturbed and uninhabited

Safety and efficiency

• Nuclear power stations use the energy released in fission reactions to heat water to produce steam to turn turbines to generate electricity

• Nuclear power stations:

  • are extremely reliable and well-established in some countries

  • are very responsive as the output can be easily controlled

  • are very expensive to build to decommission later

  • are potentially dangerous in the event of an accident

  • produce an average output power of 1 GW

    • This is twice the output power of a fossil fuel power station

Bio-fuels

• Bio-fuels are made from plant matter

Extraction methods

• Crops are grown to produce bio-fuels which uses farmland that could otherwise be used to grow food

• Ethanol or methane can be produced and used in place of fossil fuels

  • However, they have only half the energy density of fossil fuels

Pollution and global warming

• Burning biofuels releases carbon dioxide into the atmosphere

  • However, growing the crops removes carbon dioxide from the atmosphere in the process of photosynthesis

  • Therefore, bio-fuels are considered to be carbon neutral but this opinion is controversial

    • If the land had been used to grow crops for food, the same amount of carbon would have been taken out of the atmosphere and much less carbon would have been returned

Cycle of carbon in biofuel use

Safety and efficiency

• Not many vehicles can run on biofuel alone

• However, all petrol and diesel sold in the UK have a percentage of biofuel mixed in to reduce the volume of pollutants released in combustion

• Biofuels have only half the energy density of fossil fuels

  • So twice the mass would be needed to produce the same power output

Hydroelectric dams

• When water is stored above ground level it has energy in its gravitational potential store

  • This energy can be transferred to kinetic energy if the water is allowed to flow down the slope

  • Flowing water turns the turbine to generate electricity

A hydroelectric dam

• Valleys are flooded to build hydroelectric dams which destroys habitats, towns and villages

• Pumping systems are sometimes used to return the water to the dam

  • The pumping systems use fossil fuels and therefore release large amounts of greenhouse gases into the atmosphere

• Hydroelectric dams:

  • are reliable and established in most countries

  • are responsive because they can be turned on and off easily

  • are expensive to build but cheap to run

  • produce an average output power of 200 MW

• The rise and fall of waves or the tide can be used to turn a turbine and generate electricity

Tide and wave power

• Wave power uses underwater turbines to generate electricity

  • The waves move the water which causes the turbines to turn

Turbines using wave power

• Tidal power uses underwater turbines placed between a river and the sea to generate electricity

  • Water is stored at a height on the ocean side of the barrage at high tide

    • The gate is opened and water flows from the ocean side to the riverside

    • The flowing water turns a turbine

  • Water is stored at a height on the river side of the barrage at low tide

    • The gate is opened and water flows from the riverside to the oceanside

    • The flowing water turns a turbine

Turbines using tidal power

• Tidal barrages are built in estuaries so there are not many suitable locations

• The presence of turbines in the water can interfere with shipping routes and cause damage to habitats

• The technology for wave and tidal power is not advanced enough for large-scale electricity generation

• No fuels are used so there is no pollution

• Smaller systems are useful for small islands

• Wave and tidal power stations:

  • are inexpensive to build and very cheap to run

  • have a long construction time compared to other power station types

  • are very efficient (around 80%)

  • produce an average output power of 16 kW

Geothermal energy

• Tectonic activity causes areas where the rocks below ground become heated

• Water can be poured into shafts below the Earth's surface which is heated by the rocks and returned via another shaft as steam or hot water

• Steam can be used to turn a turbine and generate electricity, and hot water can be used to heat homes

Power station using geothermal energy

• Geothermal energy depends on tectonic activity so there are few suitable locations on Earth

• Methane (natural gas) is found within spaces between rocks so this can be forced out when water is injected into the rocks

  • Methane is a greenhouse gas which contributes to global warming

• Geothermal power:

  • plants are expensive to build and small compared to other power station types

  • is reliable

  • are not very efficient (around 12%)

  • produces an average output power of 300 MW

Wind power

• Wind turbines are regularly placed in coastal, or hilly, areas with windy conditions

  • A group of wind turbines creates a wind farm

  • These are used to power nearby towns and cities

• Wind is used to turn the turbine which generates electricity

Wind turbines

• Wind power is not reliable because the wind does not blow constantly

  • Turbines are built facing a specific direction so they only work when the wind is blowing in that specific direction

• Some people think that wind farms spoil the landscape so there may be local resistance to the construction of wind farms in some towns and cities

• Wind farms:

  • are inexpensive to build and cheap to run

  • have a relatively high efficiency of 50%

  • produce an average power output of 500 MW

Solar cells

• Solar cells transfer energy from sunlight electrically producing a current, and therefore generating electricity 

  • Solar cells, sometimes called photovoltaic cells, are made of semiconducting materials

  • Several cells connected can supply electricity to homes, small-scale businesses, communication devices and satellites

  • Energy generated from solar cells can be stored in batteries for later use

Solar farm

• In many places on Earth sunlight is a reliable energy resource where the sun shines most of the time

  • However, in the UK sunlight is not reliable

• Solar farms produce no greenhouse gases or pollution

• Solar energy can be generated in remote places where they don't have electricity

  • For example to power solar street signs in rural areas

• Solar farms need to be large-scale to produce large amounts of electricity

  • People often don't like the appearance of large solar farms, this is known as visual pollution

• Solar farms:

  • are relatively cheap to set up and run

  • are relatively quick to construct compared to other types of power stations

  • are the least efficient of all the electricity generation methods (20% efficiency)

  • produce an average power output of 5 MW

Renewable & Non-Renewable Energy Resources

Renewable energy resources

• There are two types of energy resources:

  • Renewable

  • Non-renewable

• Renewable energy resources are defined as:

An energy source that is replenished at a faster rate than it is being used 

• This means that renewable energy resources will not run out

• Examples of renewable energy technologies are:

  • Hydroelectric

  • Wind power

  • Wave power

  • Tidal power

  • Solar power

  • Biofuels (including animal waste, wood, and fast-growing crops)

  • Geothermal

Non-renewable energy resources

• Non-renewable energy resources are defined as

An energy source that is not replenished at a faster rate than it is being used 

• This means that non-renewable energy resources are finite and will eventually run out

• Examples of non-renewable energy technologies are:

  • Fossil fuels

    • Coal

    • Oil

    • Natural gas (methane)

  • Nuclear

• As the availability of non-renewables decreases and the demand remains the same, this drives up the prices

  • There are many global initiatives in place to reduce our dependence on non-renewable resources, particularly fossil fuels

    • This is partly to do with lowering demand as availability decreases

    • But is mostly to do with the more urgent need to reduce carbon emissions which contribute to global warming