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Renewable energy resources can be replenished in a short period of time, so they will never be all used up. Energy companies throughout the world are using renewable resources more and more to generate electricity.
Hydropower
Hydroelectric plants use the power of falling water to turn the turbines that help generate electricity. Water stored behind a dam is released and directed through special tubes to flow against the blades of turbines and make them turn. Hydropower provides about 60-70 percent of the electricity generated in New Zealand.
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Geothermal Energy
The word "geothermal" comes from the Greek words geo, for earth, and therme, for heat. So geothermal means "earth heat." Geothermal energy is steam (or hot water that has been converted to steam) from deep inside the earth.
Our planet's interior is very hot—at its core, 6,437 kilometres deep, temperatures may reach over
There are some places around the earth where magma (hot molten earth from the mantle) pushes up through cracks into the crust near the earth's surface. Magma can heat nearby rock and water as hot as 370°C. Some of this hot water reaches the earth's surface as hot springs or geysers, and some stays trapped deep underground in cracks and porous rocks. This hot water can be used directly or converted into steam to turn turbines that generate electricity.
The most well known geothermal power station in New Zealand is at Wairakei, near Taupo.
Biomass
Biomass is organic matter, such as agricultural wastes, and wood chips and bark left over when timber is produced. Biomass can be burned to heat water to make steam, which turns a turbine to make electricity. It can also be converted into a gas, which can be burned to do the same thing.
Biomass includes energy crops like wood, straw, and other crops grown primarily for use as a fuel. Energy crops are renewable, but some, like trees, take a long time to grow. Farmers can grow trees on some of their land instead of wheat or other kinds of food. The wood is harvested regularly, cut into small chips and burned to provide heat or run small electric power stations.
Another type of biomass is methane gas, a by–product of decay in landfills. As rubbish rots in the ground, it gives off gases that can be collected and burned to produce heat or electricity
Hydrogen
Hydrogen is a colourless, odourless gas. Hydrogen can be converted into electricity through a chemical reaction in a device called a fuel cell. Converting hydrogen into electricity produces no pollution—only water and heat.
If the hydrogen comes from a renewable resource like landfill gas, fuel cells are considered renewable. However, if it comes from a nonrenewable resource like fossil fuels, fuel cells are considered nonrenewable.
Today, there are already some cars that run on hydrogen. In the future, hydrogen could be used to fuel vehicles and aeroplanes and to provide electricity to buildings.
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Ocean Energy
Ocean energy is a form of hydropower. Oceans cover more than 70 percent of the earth's surface, making them the world's largest solar collectors. The ocean stores thermal (heat) energy, which can be used to generate electricity using special turbine generators.
The energy of the ocean's waves and tides can also be used to generate electricity with dams that force ocean water through turbines. This is called tidal energy, or wave power. The world's first wave power station is on the Scottish island of Islay. It generates enough electricity for about 400 homes.
Scientists and engineers around the world are working on systems to use the ocean's energy on a large scale.
Solar Energy
Solar energy is generated without a turbine or electromagnet. Special panels of solar cells, or modules, can capture sunlight and convert it directly into electricity. These panels are known as photovoltaic, or PV. ("Photo" is Greek for light, and "voltaic" pertains to electricity.) The electricity they produce can be used right away, fed into the power grid for others to use, or stored in a battery so it is also available on cloudy days.
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Wind Power
Wind power is renewable energy that uses the force of the wind to spin turbines. These spinning turbines generate electricity.
Most wind power is produced at wind farms, which are large groups of turbines in consistently windy locations. A very large wind farm can generate enough electricity for all the homes in a city of about one million people. Small wind turbines can be used for individual homes, businesses, and boats. They can be used to pump water, or the electricity can be stored in large batteries for use at another time.
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Nonrenewable resources cannot be replenished. We can make these supplies last longer by using them wisely, but when they are gone we will not have any more.
Some non-renewable resources used are called fossil fuels. Three forms of fossil fuels are coal, oil, and natural gas. They are known as fossil fuels because they were formed from the fossilised remains of animals or plants that lived long ago.
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Coal is a hard, black, rock-like substance made up of carbon, hydrogen, oxygen, nitrogen, and sulfur. The precursor to coal, called "peat," is used as an energy source in many countries. Coal is found in many parts of New Zealand and throughout the rest of the world. Coal is extracted from the ground at large mines.
Oil is a liquid fossil fuel, sometimes also called petroleum. It is found underground within porous rocks. Oil rigs must drill down to deposits deep below the earth's surface to obtain oil. All of the the oil we use in New Zealand comes from outside our country.
Natural gas is made up primarily of a gas called methane. Methane gas is highly flammable and burns very cleanly. Natural gas is usually found underground along with oil. Natural gas is produced in New Zealand around the Taranaki region. The largest site is Maui, offshore from New Plymouth.
Nuclear Power stations use the heat from splitting atoms to convert water into the steam that turns turbines. These stations rely on uranium, a type of metal that must be mined from the ground and specially processed. Fuel rods containing uranium are placed next to each other in a machine called a nuclear reactor. The reactor causes the uranium atoms to split and in so doing, they release a tremendous amount of heat. There are no nuclear power plants in New Zealand.
