Translations of Encyclopedia about Physics

Alternative Sources of Energy

According to how they can be used, all energy sources are categorised into three groups:

- limited sources of energy (fossil fuels, nuclear fuel), which can be mined but not produced;

- renewable sources of energy (wind, water sources, biomass), which can be partially or entirely damaged by construction (wind, water sources) or by destroying fauna (biomass);

- practically unlimited sources of energy (the sun, the earth’s heat, the rising and dropping of tides), whose intensity cannot be influenced.

Mostly fossil fuels have been used from the start of the industrial era. Based on various studies, which differ based on the assumption of a stagnating, declining or increasing world consumption of energy, fossil fuels should run out within 40 to 200 years. With this in mind and while considering that the use of such conventional or atomic fuels poses a risk for both mankind and nature, these sources of energy should be gradually replaced with alternative sources which, contrary to conventional sources of energy, should not harm nature. If so, then only minimally.

Alternative power plants presently generate around 3% of energy produced on the planet. According to realistic estimations though, its share should increase to as high as 50%.

In the future, the sun should become the most important provider of energy because it is an inexhaustible and ecological source which can be used both directly and indirectly.

Solar collectors enable the direct use of solar energy. These collectors absorb energy from the sun’s rays and apply it through heating processes. The sun’s energy can also warm glass or liquids which, in turn, either accumulate or divide the obtained energy. For example, water may be heated in this manner.

Sunlight can also be converted into electrical energy without the need to use mechanical or intermediary parts. Solar cells, which are made of two closely connected layers of semiconductors, of which one is magnetically positively rectified and the other negatively, can be used for this purpose. When sunlight falls on these cells, electrons between both of these layers (surfaces) are influenced by and accumulate with the help of metal electrodes. Electrical current then results due to the movement of electrons.

The sun’s energy, as it falls onto the earth, is also absorbed by the earth’s surface and converted into heat, which is then used by mankind (this is an indirect use of the sun’s energy). With indirect heating using the sun’s energy, the position of a building, its type of construction, the arrangement of the space within it and the construction material used play an important role. Structures made out of glass, like glass winter gardens, have proven very effective and capable of being heated very quickly, with heat gained by this method diverted to adjoining rooms.

One of the other affects of the sun is the creation of winds, which have been used for several centuries to drive windmills and propel ships. Modern machinery generating wind energy use the wind’s force to generate electrical current. The sun’s energy also maintains the earth’s water currents, which is important if we want to take advantage of the forces of water. Through photosynthesis, plants can use the sun’s energy to be converted into biomass, which, in turn, can be used as fuel.

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