Solar energy can be defined in many ways but some of these definitions are highlighted below:
i. It can be defined as the power produce from the radiations of Sun;
ii. Heat and light radiated from the sun;
iii. Energy produced by the action of the sun's light or heat;
iv. The radiant energy of the sun that can be converted into other forms of energy, such as heat
or electricity; and
v. Energy produced by photovoltaic solar cells, which are made of semiconducting materials, to
directly convert sunlight into electricity and lot more.
Solar energy has been looked upon as a serious source of energy for many years because of the vast amounts of energy that are made freely available, if harnessed by modern technology.
A simple example of the power of the sun can be seen by using a magnifying glass to focus the suns rays on a piece of paper. Before long the paper ignites into flames.
This is one way of using the suns energy, but flames are dangerous and difficult to control. A much safer and practical way of harnessing the suns energy is to use the suns power to heat up water.
A magnifying glass can be used to heat up a small amount of water. A short piece of copper tube is sealed at one end and filled with water. A magnifying glass is then used to warm up the pipe. Using more than one magnifying glass will increase the temperature more rapidly. After a relatively short time the temperature of the water increases. Continuing to heat the water will cause water vapour to appear at the top of the tube. In theory, with enough patience, several magnifying glasses and very strong sun light enough heat should be generated to boil the water, producing steam. This is one way of harnessing solar power.
The principle of heating water to boiling point was used by the French in 1888. They developed a solar powered printing press. It used the energy of the sun to boil water, producing steam. The steam was used to drive a steam engine which provided the power to drive the mechanical printing press. The machine was unreliable and very expensive to manufacture.
Modern solar panels are a combination of magnifying glasses and fluid filled pipes. The solar panel seen opposite has a glass front which is specially made to focus the power of the sun on pipes behind it. The pipes carry a special fluid that heats up rapidly. They are painted black to absorb the heat from the sun. The silver reflective surface behind the pipes reflects sun light back, further heating the pipes and the fluid they contain. The reflective surface also protects anything behind the solar panel (such as a roof).
The heat produced in the pipes is then used to heat a tank of water. This saves using electricity or gas to heat up the water tank.
Significance of Solar Energy
1. Solar energy is free although there is a cost in the building of ‘collectors’ and other equipment required to convert solar energy into electricity or hot water.
2. Solar energy does not cause pollution. However, solar collectors and other associated equipment / machines are manufactured in factories that in turn cause some pollution.
3. Solar energy can be used in remote areas where it is too expensive to extend the electricity power grid.
4. Many everyday items such as calculators and other low power consuming devices can be powered by solar energy effectively.
5. It is estimated that the worlds oil reserves will last for 30 to 40 years. On the other hand, solar energy is infinite (forever).
Disadvantages of Solar Energy
1. Solar energy can only be harnessed when it is daytime and sunny.
2. Solar collectors, panels and cells are relatively expensive to manufacture although prices are falling rapidly.
3. Solar power stations can be built but they do not match the power output of similar sized conventional power stations. They are also very expensive.
4. In countries such as the UK, the unreliable climate means that solar energy is also unreliable as a source of energy. Cloudy skies reduce its effectiveness.
5. Large areas of land are required to capture the suns energy. Collectors are usually arranged together especially when electricity is to be produced and used in the same location.
6. Solar power is used to charge batteries so that solar powered devices can be used at night. However, the batteries are large and heavy and need storage space. They also need replacing from time to time.