Energy comes from many sources. To describe these sources, we use two terms: renewable and non-renewable.
Non-renewable energy resources cannot be replaced. Once they are used up, they will not be restored (or not for millions of years). Non-renewable energy resources include fossil fuels such as coal, oil, natural gas and nuclear power.
Fossil fuels (coal, oil and natural gas) were formed from animals and plants that lived hundreds of millions of years ago: even before the time of the dinosaurs. The plants that lived millions of years ago converted the sun's light energy into chemical energy through the process of photosynthesis.
This solar energy was, and still is, transferred down the food chain in animals and, when living organisms died, the chemical energy within them was trapped.
For a fossil fuel to form, there are three important steps necessary: accumulation of organic matter (animal or plant remains), preservation of organic matter to prevent it from oxidising (exclusion of air, for example, by being in the sea or a swamp) and conversion of organic matter into a fossil fuel such as oil or natural gas.
Fossil fuels are described as non-renewable because it takes millions of years for this process to occur.
Natural gas is found under the oceans and near oil deposits. New Zealand's Taranaki region is renowned for its oil and gas reserves. Natural gas was first discovered in Taranaki at the Kapuni field in 1959.
Once a natural gas field is found, the drilling process can begin. Gas is piped from the source and stored for later use. Natural gas is used for cooking and heating as well as for making a number of products such as plastics, fertilisers and medicines.
Coal is a solid form of fossil fuel. New Zealand has a number of coal reserves including in the West Coast area of the South Island and in the Coromandel area.
Oil is a liquid fossil fuel that can be dark brown, yellow or even green. It is easier to mine once it is found because, as it is a liquid, it will flow through pipes, which makes it easier to transport. It can be difficult to locate. Oil forms in reservoirs and, to find these reservoirs, scientists must study rocks and landforms to find potential drilling sites.
A hole is drilled and, if oil is found, it is then piped to the surface. In this form, it is called ‘crude oil'. Crude oil is transported to a refinery that heats up the oil to different temperatures and seperates different types of fuel (such as petrol, jet fuel and diesel) through a process called fractional distillation. Oil is used not just for transport but also in many different products such as plastics, tyres and synthetic materials such as polyester.
Renewable energy comes from sources that can be replaced. Examples include energy from the sun (solar), wind, moving water (hydro) and plants such as pine forests, which supply firewood. This energy is harnessed to drive generators that produce electric power.
Wind, solar, water and geothermal energy are sustainable, clean sources of energy. New Zealand is rich in renewable energy resources and already meets much of its energy needs by harnessing the power stored in rivers, lakes, geothermal fields and woody plants (known as biomass).
Nearly one-third of the total energy consumed in New Zealand – including electricity, heat and transport fuels – comes from renewable sources. About 77% of all electricity produced in New Zealand is generated by renewable energy.