Energy

Energy - Energy is the ability to do work and it comes in various forms of heat and light. There are two main types of energy, being working energy and stored, or latent, energy. Stored energy becomes working energy when it is used.

We use energy every day. It is used to grow food, warm and cool homes, make electricity, run cars, make products like clothes and toys and any other items. It is a very important part of our lives.

Most countries use stored energy for fuel. By burning fuel, the stored energy is set free in the form of heat. Fossil fuels, such as oil, gas and coal, are mostly burnt.

Fossil fuels form over time from the remains of dead animals and plants. Dead plants and animals are buried under dirt and rock, where the heat from the earth and the pressure from the soil and rocks change them into fossils and then into oil, natural gas and coal. Because it can take thousands of years to make or renew fossil fuels, they are referred to as non-renewable resources.

More than 75% of South Africa’s energy comes from coal. One half of this is used to generate electricity, a quarter is used to produce liquid fuels, and the other quarter is used as fuel to heat homes. South Africa is the country in the world that is the most dependent on coal, and therefore we need to look at generating energy from alternative sources.

Alternative Energy Sources

The alternative energy sources that are used mostly are:

• Solar energy
• Wind energy
• Water energy
• Nuclear energy
• Biodiesel

Solar Energy

The sun is a great source of energy, which is referred to as solar energy, which can be turned into electricity or heat. Solar energy is used in many ways, for example by simply keeping the curtains open during the day, sunlight can light and warm a room.

Example: Solar Energy - Cars with dark seats are good examples of how the absorbers in a solar collector work. Have you ever sat on a dark seat after the sun’s solar energy passed through the windows of a car? The seats absorb heat and feel hot. If the seats were white, the light would be reflected away from the seats and they would absorb less heat.

Technology has been developed to harness the energy of the sun so that it can be stored and used by humans for heating or electricity generation. Solar energy systems, or solar collectors, produce energy without releasing pollution particles or chemicals into the air. Most solar collectors are boxes that have the following components:

• Clear covers to let the solar energy in.
• Dark surfaces, called absorber plates, on the inside to soak up the heat.
• Insulation material to prevent heat from escaping.
• Vents or pipes carry the heated air or liquid from inside the collector to where it can be used.

Simple Solar Water-Heating Device

Solar energy systems fall into three main categories, being:

Photovoltaic Cells, also known as PVs, absorb sunlight and a chemical reaction occurs, turning sunlight into electricity.

Passive solar systems use the sun for lighting and heat by absorbing sunlight and slowly releasing it even after the sunsets.

Solar Thermal Systems heat water or air by using a mechanical device to move it across surfaces that have absorbed sunlight.

Wind Energy

When the power of wind is used to generate electricity, it is referred to as wind energy. The wind turns large fans that power a generator to make electricity. The power of the wind to generate electricity is proportional to the wind speed. Much more electricity can therefore be generated in places with high average winds speeds, and “wind farms” are often established in such places. The windier the location, the more kilowatt-hours can be generated.

Fan Used to Generate Electricity through Wind Energy

Water Energy

Water is another renewable source of energy. A watermill or a hydroelectric scheme uses the force of water to generate electricity. Water moves across impellers, rotating them and generating electricity.

Nuclear Energy

Nuclear energy is generated by using special radioactive materials. Harmful substances are not released when nuclear energy is generated. However, once the radioactive material has been used to generate energy, the waste remains radioactive and hazardous to all living organisms. The waste material must be stored safely for thousands of years to avoid contamination.

Bio Diesel

Biodiesel is a liquid fuel that can replace regular diesel. It is made from used vegetable oil from deep fryers or freshly grown grains, such as maize. The particles released from burning regular diesel can cause cancer, but by using biodiesel this hazard can be reduced. Biodiesel is a renewable energy source.