Topic 8: Energy, power and climate change

8.2 World energy sources

Where does the energy of the world Where does the energy of the world comes from?comes from?

World energy sourcesWorld energy sources

Sources of energy includeSources of energy include CoalCoal OilOil Natural gasNatural gas UraniumUranium SolarSolar WindWind WaveWave TidalTidal BiofuelBiofuel HydroelectricHydroelectric GeothermalGeothermal

Fossil FuelsFossil Fuels

Coal, Oil and Natural Gas are fossil fuels.Coal, Oil and Natural Gas are fossil fuels. These are formed from the fossilized These are formed from the fossilized

remains of plants and tiny organisms remains of plants and tiny organisms buried 600 million years ago.buried 600 million years ago.

The Sun is the source of the energy for The Sun is the source of the energy for these fossil fuels.these fossil fuels.

The burning of fossil fuels releases COThe burning of fossil fuels releases CO22 into the atmosphere.into the atmosphere.

NonNon-renewable energy sources-renewable energy sources

Fossil fuels are non-renewable energy Fossil fuels are non-renewable energy sources.sources.

Once the fuel has been used it is Once the fuel has been used it is exhausted and cannot be replaced.exhausted and cannot be replaced.

Renewable energy sourcesRenewable energy sources

These are sources of energy that cannot be These are sources of energy that cannot be exhausted.exhausted.

Examples are:Examples are: SolarSolar WindWind WaveWave TidalTidal BiofuelBiofuel HydroelectricHydroelectric GeothermalGeothermal

The Nesjavellir Geothermal Power Plant in Iceland

The front of the Pelamis machine bursting through a wave at the Agucadoura Wave Park

Renewable energyRenewable energy is energy generated is energy generated from natural resources—such as sunlight, from natural resources—such as sunlight, wind, rain, tides and geothermal heat—wind, rain, tides and geothermal heat—which are renewable (naturally which are renewable (naturally replenished). replenished).

Energy Density of a fuelEnergy Density of a fuel

The energy density of a fuel is the amount The energy density of a fuel is the amount of chemical energy stored per unit mass of of chemical energy stored per unit mass of a fuel.a fuel.

Energy density= Energy density= amount of energyamount of energy

mass of fuelmass of fuel

The units for energy density are JkgThe units for energy density are Jkg-1-1

The use of energy densityThe use of energy density

A fuel with a higher energy density will be A fuel with a higher energy density will be able to provide more energy per unit able to provide more energy per unit mass.mass.

The higher the energy density for a fuel, The higher the energy density for a fuel, the more energy that can be transported the more energy that can be transported for the same amount of mass of fuel.for the same amount of mass of fuel.

Some approximate energy density valuesSome approximate energy density values

Choice of fuel Choice of fuel

It seems that Uranium-235 would make It seems that Uranium-235 would make the best fuel per kilogram because the the best fuel per kilogram because the energy density is very high.energy density is very high.

Is high energy density the only concern Is high energy density the only concern when choosing a fuel?when choosing a fuel?

Choice of fuelChoice of fuel

Nuclear power stations are very expensive Nuclear power stations are very expensive to build and the cost for the production of to build and the cost for the production of electricity per kilowatt-hr is more electricity per kilowatt-hr is more expensive than using fossil fuels.expensive than using fossil fuels.

There are also political, social and There are also political, social and environmental factors to consider.environmental factors to consider.

Depending on use and storage of the fuel, Depending on use and storage of the fuel, the energy density is an important the energy density is an important considerationconsideration

Chemical composition and heating ability Chemical composition and heating ability are other factors.are other factors.

Chemical composition of coal is in terms of Chemical composition of coal is in terms of its rank, moisture content, volatile content its rank, moisture content, volatile content (% of coal lost as vapours), ash and fixed (% of coal lost as vapours), ash and fixed carbon. carbon.

Coal is divided into different ranks depending Coal is divided into different ranks depending on the carbon and energy content per unit on the carbon and energy content per unit mass. mass.

Different ranks of coal will produce different Different ranks of coal will produce different amounts of heat.amounts of heat.

Rank of Rank of coalcoal PeatPeat LigniteLignite Bituminous Bituminous

coalcoal AnthraciteAnthracite

CarbonCarbon 60%60% 70%70% 80%80% 95%95%

EnergyEnergy 5,500,0005,500,000 6,500,0006,500,000 7,800,0007,800,000 8,600,0008,600,000

Because of the high content of volatile matter in Because of the high content of volatile matter in peat and lignite, they cannot be transported for peat and lignite, they cannot be transported for long distances because of safety risks. Usually, long distances because of safety risks. Usually, a power station is located where the mines are.a power station is located where the mines are.

Coal in some countries have a high sulfur Coal in some countries have a high sulfur content and this greatly affects the air quality in content and this greatly affects the air quality in some areas.some areas.

Australian bituminous coal and anthracite is low Australian bituminous coal and anthracite is low in sulfur and is a top export fuel in Asia. in sulfur and is a top export fuel in Asia.

Rate of world energy usage in Rate of world energy usage in terawatts (TW), 1965-2005 (TW), 1965-2005

World use of energy sourcesWorld use of energy sources

Energy factsEnergy facts http://www.solarenergy.org/resources/energ

yfacts.html

Advantages and disadvantages of Advantages and disadvantages of energy sourcesenergy sources

When considering which energy sources When considering which energy sources to use the following factors have to be to use the following factors have to be considered:considered:

Cost of fuelCost of fuel Availability of fuelAvailability of fuel Transportation of fuelTransportation of fuel Environmental concerns (waste)Environmental concerns (waste) Health concernsHealth concerns