The Sun’s energy can be captured in a variety of ways, through either passive or active means. Passive solar heating is the simplest method by utilizing building materials and appropriate sitting.

Active solar systems, while currently only providing a small percentage of the world’s energy needs, collect the Sun’s energy with panels through which air or water is circulated to transfer the heat to a storage or utilization device.

A variety of technologies utilizing solar energy have been developed, and are in use, including solar lighting and heating, concentrated solar power, and photovoltaic’s.

Solar energy is electromagnetic radiation from the sun, particularly important for photosynthesis, which is the basis of all life on earth. Solar energy is a powerful alternative to fossils and nuclear fuels.


The sun offers an ideal energy source, unlimited in supply, inexpensive and which does not produce air and water pollutants. Solar energy originates from the thermonuclear fusion reactions taking place in the sun.

The sun is a huge nuclear reactor where hydrogen gas is continuously burning at high temperature, pressure and generating energy. The earth continuously receives energy from the sun. This energy is received in three main spectral regions, namely: (i) Ultraviolet (ii) Visible light and (iii) infra-red or heat radiation, the energy content being distributed as about two per cent, 47 per cent and 51 per cent respectively.

From the energy content point of view, the ultraviolet radiation has no significance since most of the energy is concentrated in the other two regions. The earth absorbs radiations mainly in the visible region (400 nm to 700 nm) and emits radiation in the infrared region (2 to 40, with maximum at 10). The value of the solar flux reaching the earth’s upper atmosphere is estimated to be about 1400-wattsm2 min the heat equivalent of the solar radiation reaching the earth is estimated to be about 2.68×1024 joules per year.

Limitations of Solar Energy


Solar energy has some inherent limitations:

1. The density of solar energy is low as compared to coal, oil, gas etc.

2. Problem of economically collecting solar energy over large areas and converting it to other forms that can be conveniently transported, stored and used in existing equipments.

3. Its intensity is not constant; it changes from early in the morning to evening with a maximum around 1-2 p.m., the maximum amount being in the range of 1 to 1.1 KW/ m2. This amount does not remain the same during the whole day. It also changes with different seasons of the year and depends upon the sky conditions.


4. Problems of designing facilities that can utilize diffused sunlight.

5. It’s major applications are photo thermal conversion, solar water heating, space conditioning, solar air heating, solar desalination, solar cooker, solar refrigeration, power generation, water pumping, green house technology, generation of fuels, photo voltaic conversion etc.

Advantages of Solar Energy

The nature has never been cruel to mankind. In fact it is fetching him different types of materials and resources to fulfil the different needs of mankind. Solar energy belongs to the same category. The sun is a huge nuclear reactor where hydrogen gas is continuously burning at high temperature and generating energy.


They are mentioned below:

1. Solar energy is a powerful alternative to fossils and nuclear fuels.

2. The sun offers an ideal energy source, unlimited in supply and inexpensive, which does not produce air and water pollutants.

3. Solar energy-is abundant that, with collection efficiency of only 10 per cent, less than five per cent of the United States, surface area could provide the country its energy needs projected for the year 2000 A.D. With the rising fuel charges and end of petroleum deposits in sight, the economic balance is bound to tilt in favour of the solar energy.


4. Light through photosynthesis is the energy source for all major ecosystems.

5. The most important routes of solar energy utilisation are through the conversion of solar energy into heat energy and directly converting the solar radiant energy into electrical energy utilising the process of photo-voltaic conversion.