The sun is the ultimate source of all the sources of energy and fuel we use today. We have developed many ways of accessing this energy either directly or indirectly. 

Each different source of energy has implications for climate change. These will be examined in a later section.

Solar energy

Sources of energy on Earth 4
Solar panels

Solar (photovoltaic) panels convert light energy (photons) into electrical energy using the photovoltaic effect. 

Wind energy

Sources of energy on Earth 5
Wind turbines

Wind turbines convert the kinetic energy of the wind into mechanical energy. A generator then converts the mechanical energy into electricity.

Geothermal energy

Sources of energy on Earth 6
Geothermal power

High temperatures are produced continuously inside the Earth’s crust. The high temperatures can be used to heat water with the generation of steam. The steam is used to rotate turbines that power generators to produce electricity. 

Hydrogen energy

Sources of energy on Earth 7
Fuel cell

A fuel cell can combine hydrogen and oxygen to produce electricity, heat and water. 

Tidal energy

Sources of energy on Earth 8
SeaGen tidal energy generator

Tidal power is a form of hydropower, whereby the kinetic energy in rising and falling tides is converted into electricity.

Wave energy

Sources of energy on Earth 9
Wave energy converter

Wave energy works by converting the kinetic energy in ocean waves into electricity. 

Hydroelectric energy

Sources of energy on Earth 10
Hydroelectric dam

This is a form of hydropower that uses a dam on a iver to store water in a reservoir. Water is then released from the reservoir to flow through a turbine which activates a generator to produce electricity.

Biomass energy

Sources of energy on Earth 11
Biomass energy plant

Plants capture solar energy and convert it into chemical energy through the process of photosynthesis.  When plants are burned in a biomass plant the chemical energy is converted into electricity. 

Anaerobic digestion

Sources of energy on Earth 12
Anaerobic digestion plant

Organic wastes (plants, agricultural residue, abattoir waste, sewage sludge) are processed by particular strains of bacteria in the absence of oxygen to produce methane gas. The methane gas is then burned in a gas engine to produce electricity. 

Nuclear power

Sources of energy on Earth 13
Nuclear power station

Uranium is used to fuel a chain reaction that heats a coolant material (water, gas or liquid metal). The heated coolant generates steam that passes through a steam turbine to generate electricity. 

Fossil fuels

Fossil fuels are buried organic deposits formed over eons from plant and animal remains. There are three main types.

Petroleum (crude oil)

Sources of energy on Earth 14
Petroleum refinery

Petroleum is a naturally occurring substance – formed from zooplankton (microscopic marine and freshwater organisms) and algae. Petroleum is made up of organic compounds existing in gaseous, liquid or semisolid forms. The organic compounds are hydrocarbons – combinations of carbon atoms and hydrogen atoms – and combinations of carbon atoms with sulphur, oxygen or nitrogen.

The organic compounds vary greatly in complexity, ranging from methane (one carbon atom bound to 4 hydrogen atoms) to asphaltenes (more than 136 carbon atoms bound to more that 167 hydrogen atoms, 3 nitrogen atoms, 2 oxygen atoms, and 2 sulphur atoms.

Liquid petroleum (crude oil) consists of a range of more complex hydrocarbons and small amounts of asphaltenes. 

Petroleum is refined into gasoline, diesel, aviation fuel and other fuel oils that provide much of the world’s energy.

Natural gas

Sources of energy on Earth 15
Natural gas storage tanks

Natural gas is a naturally occurring material that consists mainly of simple hydrocarbons with 1 – 5 carbon atoms (methane, ethane, propane, butane, pentane). About a third of the natural gas is used to produce electricity.


Sources of energy on Earth 16
Coal-fired power plant

Cola is the third naturally occurring fossil fuel. It is formed from plant matter over geological time and is primarily burned to produce electricity and heat. Coal is currently the largest source of energy world-wide. 

So, the current main sources of energy are the fossil fuels.  These produce  greenhouse gases. Let’s take a more detailed look at what we mean by greenhouse gases.