Sources of Energy

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Non-conventional source of energy is those which are not used as extensively as the conventional ones and meet our energy the requirement only on a limited scale.Solar energy, ocean energy (tidal energy, wave energy, ocean thermal energy, OTE), Geothermal energy and nuclear energy belong to this category.

Demand for energy increases day by day. Our lifestyles are also changing, we use machines to do more and more of our tasks.

The sources of energy which have been tapped with the aid of advances in technology to meet our growing energy needs are also called alternative sources of energy.

The oceans acquire almost 71% of the surface of the earth and the enormous amount of water present in them not only act as a big collector of solar heat energy, but also store a large amount of it due to its high specific heat. Thus ocean water can be used as a renewable resource of energy.

The main forms of ocean energy are described as under;

1. Ocean Thermal energy
2. Ocean Tidal energy
3. Sea wave energy, and etc.

Geothermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations. Geothermal energy is one of those few sources of energy that do not come directly or indirectly from the solar energy.

The underground hot water in contact with hot spots changes into steam. As the steam is trapped between the rocks, it gets compressed to high pressure. At some places, hot
water and steam gush out from the Earth’s surface after making their way through large cracks between the rocks and form natural geysers. The geothermal energy carried by natural geysers is utilized for generating electricity.

Advantages :

1. Economical to use geothermal energy.
2. Does not cause any pollution.

Limitations :

1. Geothermal energy is not available everywhere.
2. Deep drilling in the earth to obtain geothermal energy is very difficult and expensive.
3. In New Zealand and the USA, there are no. of power plants based on geothermal energy are operational.

A reaction in which the nucleus of an atom undergoes a change to form a new atom and releases an enormous amount of energy is called as nuclear energy.
There are two distinct ways of obtaining nuclear energy. a) Nuclear fission b) Nuclear fusion.

Nuclear Fission reaction:

This type of nuclear reaction was first of all reported by Otto Hahn in 1938. He stated that when an unstable heavy nucleus is bombarded with slow speed thermal neutrons, it splits into two small stable nuclei liberates an enormous amount of heat and light energy.

Nuclear Fusion reaction:

This type of nuclear reaction was first of all reported by Hans Bethe in 1939. The word ‘fusion’ means ‘to combine together’. So, nuclear fusion means combining together of two or more nuclei to form a single nucleus. Thus, a process in which two lighter nuclei fuse (combine) together to form a stable heavier nucleus with a simultaneous release of a very large amount of energy is called nuclear fusion. The energy produced in a fusion reaction is much higher than that produced in a nuclear fission reaction.

Advantages of Nuclear Energy:

1. It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).
2. Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.
3. It does not produce gases like carbon dioxide which contributes to greenhouse effect or sulphur dioxide which causes acid rain.

Sun is the ultimate source of energy.Energy obtained from the sun is called solar energy.

Solar constant = 1.4 KJ/s/m²

Outer edge of the earth receives solar energy equal to 1.4 KJ/s/m2 or 1.4 KW/ m² [... 1 KJ/s = 1 KW]

Principles of utilisation of Solar Energy:

1. In the appliances requiring a moderate temperature, the incident sun rays are reflected by a plane mirror on a black container which absorbs the solar energy and gets heated.
2. In the appliances requiring a high temperature, the incident sun rays are reflected and concentrated by using a large concave reflector which focuses all the sun rays at a single point called focus and any object kept at the focus gets strongly heated.

Solar energy devices: Devices using solar energy are :

1. Solar cooker
2. Solar water heater
3. Solar cells