With the progress of human civilization, we are using energy at a rate unprecedented in the history of mankind. Use of electricity and other sources of energy at every step of our lives are putting an extreme stress on the conventional sources of energy on this planet. Since most of the conventional sources of energy are non-renewable as well, their reserves are expected to be exhausted in only a few years. While sources of petroleum are expected to last for only thirty years, coal is expected to be exhausted in only a hundred years, thus leaving us in a state of energy crisis. The use of renewable sources of energy promises to bail us out of our problem. One of the most popular and well-known sources of renewable energy is definitely solar energy.
Solar energy refers to the energy extracted from the heat and light energy of the Sun. This source of energy is harnessed by human beings from ancient times using a range of technologies. Sun is the ultimate source of energy on this planet. All other sources of energy owe their origin to the Sun. However, when we say solar energy, we refer to harnessing the heat and light energy of the Sun directly. Electricity is generated from the solar energy using heat engines and photo-voltaic cells.
Solar energy can be classified into active solar energy and passive solar energy, depending upon the method by which it is harnessed, converted and distributed. The use of photo-voltaic cells and solar thermal collectors come under the definition of active solar energy. On the other hand, passive solar energy refers to techniques such as orienting a building to the Sun, selecting those materials which have favorable thermal mass, light dispersing properties, etc.
Every day, the Earth receives a large volume of solar energy in the form of radiations from the sun. However, most of this energy is reflected by our upper atmosphere. Another large fraction of the energy received by the sun is absorbed by the clouds, oceans and land masses. However, using only about 1% of the total energy that reaches the surface of the earth can provide a solution to our energy crisis.
Among the several uses of solar energy, one of the most ancient techniques is the use of passive solar energy by influencing the architectural designs of buildings. Orientation of a building relative to the sun can help in saving a good amount of energy due to lighting and heating of the building. Planning the planting cycles and tailored row orientation are techniques that use solar energy in agriculture. Solar energy is also used in heating, ventilation and air conditioning systems. Sunlight is used to heat water in solar heating systems. Solar energy can also be used in water treatment plants by using the heat energy of the sun in solar distillation process to make salty water suitable for drinking. The solar cookers use energy of the sun to cook food.
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