Types of energy
Energy exists in many forms, this are the main forms:
- Chemical energy. Chemical energy is stored in chemicals, which are made from atoms that are linked together to make molecules. The energy is released when the links between some of the atoms are broken down into smaller molecules.
- Gravitational energy. This is the force of gravity between an object and the Earth, pulling the object down towards the planet. If an object is in a position, above the surface of the Earth, it possesses stored energy called; gravitational energy.
- Strain energy. Elastic materials can change shape (by squashing, stretching or bending). As they do so, they store strain energy. This energy allows them to return to their original form.
- Nuclear energy. Every substance made from atoms, has a nucleus, made from protons and neutrons. In most elements these are strongly bound together, but in some they aren’t. Than the unstable nuclei may split up to form stable ones. This releases (nuclear) energy.
2 other forms of stored energy. Magnetic potential energy and electrostatic energy.
- Kinetic energy; is the movement of energy.
- Internal energy. Molecules move inside a solid by kinetic energy. This movement is made by the internal energy of the substance. The internal energy is increased by heating the substance.
- Thermal energy. Thermal energy is the energy supplied to a substance which increases its internal kinetic energy. Mostly it’s called heat energy. Another (scientific) name is Thermal energy.
- Sound energy. Sound energy is formed by the vibration of an object. The energy passes through the air by the movement of the atoms and molecules. Sound energy spread in all directions from the point of vibration.
- Electrical energy. Electrical energy is the movement of electrons though an electrical conductor.
- Radiation energy. This kind of energy travels in waves which contain some electricity and some magnetism. They are called electromagnetic waves. There are a lot of different wave sizes and wavelengths. They are divided into 7 groups. These groups are: radio waves, microwaves, infrared, visible light, ultra violet, x-rays and gamma rays. This are 3 examples:
- Light energy. The light energy escaping from the sun we see as a rainbow. Because our eyes see different wavelengths as different colours.
- Infrared radiation. Infrared radiation carries heat (thermal energy) in the form of electromagnetic waves which we feel as the warmth on our skin.
- Ultraviolet light. UV light gives our skin a tan. That’s caused by the chemical changes in our skin. UV light comes on earth as great amounts because of the destruction of the ozone layer.
Energy can be transferred from one form to another. The object or material in which the energy changes form is called the energy converter or energy transducer. The flow of energy through one or more energy converters is called an energy chain.
Sources of energy
We use many different sources of energy to provide everything we use in our everyday lives.
Nuclear fusion in the sun
At the centre of a star it’s so hot that hydrogen nuclei move fast enough to fuse together, to form helium. Than energy is released which is radiated from the sun’s surface as electromagnetic waves.
Energy from the Sun’s light
Biomass; the amount of matter in a living thing.
- Food. Food stored in plants may be eaten by herbivores (e.g. sheep) or omnivores (such as ourselves). Crops we eat provides us with energy. Food provides animals with chemical potential energy. They use this energy to alive and build up their bodies. We take in stored energy, from animals when we eat their meat.
- Fuel wood. In many countries were there isn’t any coal, wood is used as fuel for cooking and heating.
- Ethanol. Countries with a shortage of material to make petrol, ferment plants such as sugar, cane and grain to make ethanol (a type of alcohol). This is mixed with petrol and reduces the demand for oil.
Energy from food wastes
- Biogas. Wastes of eaten food can be used as a source of energy. The wastes from vegetables, humans and animals can be stored in biogas digesters, where microorganisms feed. As they do methane gas is produced. This gas can be used for cooking or lighting and as a fuel to generate electricity.
- Dung. In some countries dung of domestic animals is collected, dried and made into fuel cakes for burning.
Coal is formed from large plants which grew in swamps ± 275 million years ago. They died > fell into swamps, there was a lack of oxygen in the swamp which prevented bacteria growing and decomposing the dead plants. The plants formed peat > the peat became buried and was squashed by the rocks formed above. The increase in pressure squeezed the water out of the peat and warmed it. These processes slowly changed the peat into coal.
Solar cells are made from materials which converts some of the energy in sunlight into electrical energy.
Energy from the Sun’s heat
Most of the energy from the sun is in the form of infrared radiation. This warms the earth and the atmosphere.
Movement of the atmosphere
The air nearest the Earth’s surface warms the fastest and then rises. It’s replaced by cooler air. The cycle repeats itself every time.
Movement of water
- Flowing water. The Sun’s heating effect causes the evaporation of water from the surfaces of the oceans and lakes. The water vapour rises and forms clouds as the air cools.
- Waves. Waves are produced by wind blowing on the oceans. Kinetic energy from the wind in changed into kinetic energy of the water. There are machines who can change that kinetic energy into electrical energy.
- Solar Panels. Solar panels heat water in a house on a sunny day; In the panel are pipes which carry water. They run over a black surface which absorbs infrared radiation from the sun. The water is warmed in a hot water tank.
Energy from nuclear reactions on Earth
The unstable elements (in the Earth) are called radioactive elements. As the become stable they release particles and energy. We use energy from radioactive materials (found in and below the Earth’s crust).
The atoms of some heavy elements such as uranium can split into two smaller, more stable atoms. This process, called nuclear fission, releases large amounts of energy.
Heat energy in the Earth
There are radioactive materials beneath the Earth’s crust which releases energy that heats the core and mantle. Under the crust water heats and forms geysers. The heat in the rocks under the crust can be used as a source of energy. Than cold water is pumped down to the hot rocks where it is turned to steam. Through pipes it is returned to the surface. Then it’s used to generate electricity in a power station.
Energy form gravitational forces
The Moon, the Sun and the tides
Water in oceans is pulled down by the Earth’s gravity and by the gravitational pull of the moon and to a smaller extent by the gravitational pull of the Sun. Difference in force causes the water beneath the moon and on the opposite side of the Earth to rise up slightly, causing high tide. The level of water in other parts of the ocean falls, causing a low tide at those places.
Twice a month the Sun and the Moon are in line as the Moon orbits the Earth. At these times the difference in the sea level at high and low tide is greatest as the (small) gravitational pull of the Sun reinforces the effect of the stronger pull of the Moon. The tides are than called spring tides.
Energy stored in the water at high tide is used by to generate electricity. A dam built across an estuary and the rising water of the tide passes through the pipes in which turbines turn. This movement is passed to a generator and electricity is produced. When the tide falls the water passes through the pipes in the opposite direction and turns the turbine again, so even more electricity is generated.
Non-renewable and renewable energy sources
The sources of energy are divided into 2 groups.
- Now renewable energy sources. These sources cannot be replaced once they’ve been used up (e.g. fossil fuels and radioactive materials)
- Renewable energy sources. These sources can be replaced. (e.g. light and heat from the Sun, biomass, geothermal energy and kinetic energy of the wind, water, waves and the tides)