The sun, as is known, is the primary and primary source of energy for our planet. It warms the whole Earth, sets in motion the rivers and imparts strength to the wind. Under its rays, one quadrillion tons of plants grow, which, in turn, feed 10 trillion tons of animals and bacteria. Thanks to the same Sun on the ground, there are accumulated hydrocarbon reserves, that is, oil, coal, peat, etc., which we are now actively burning. To ensure that today, humankind can meet its energy needs, it takes about 10 billion tons of standard fuel per year. (The calorific value of conventional fuel is 7,000 kcal/kg).
What is usually called solar energy? This is the energy produced by the sun in the form of light and heat. Also, there are secondary types of solar energy, such as wind and wave energy. All of these kinds of power constitute a large part of the renewable energy of the Earth.
The Earth receives 174 petawatts (PW) of solar radiation in the upper atmosphere. 30% is reflected back into space, and the rest is absorbed by clouds, oceans and land. The surface of the earth, the oceans and the atmosphere absorb solar radiation, which increases their temperature. Warm air containing water from the oceans rises, causing convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds and causes rain. The latent heat of water condensation increases convection, producing wind. Energy is absorbed by the oceans and land, keeping the surface at an average temperature of about 14C.
Green plants convert solar energy into chemical energy through photosynthesis. The production of our food products is entirely dependent on solar energy. After their life, plants die and disintegrate in the Earth, so solar energy provides biomass that has created fossil fuels that we know.
Ways to use solar energy
People use solar energy in a variety of ways: for heating and cooling premises, producing distilled drinking water, disinfecting, lighting, producing hot water and cooking food. The techniques of using solar energy are limited only by human ingenuity.
There are many ways to convert the energy of the Sun into electrical energy. The use of solar cells (i.e. photoelectric converters) is only one of them. This method is useful, first, its mobility, and secondly, its longevity. A solar battery can be installed on the roof of the car and the wings of the aircraft. It can be embedded in a clock, calculator, laptop and even, paradoxically, into a flashlight. The solar cell lacks any moving parts, and its service life is approximately 30 years. For these 30 years, the element, for the manufacture of which only 1 kg of solar silicon has gone off, can produce as much electricity as is produced from 100 tons of oil at TPPs or from 1 kg of enriched uranium at nuclear power plants.
Solar technologies are passive or active, depending on the way the energy is captured, which is then converted and distributed.
Active solar technology
To active solar technologies include photovoltaic panels and solar thermal collectors.
A solar installation with a capacity of 1 kW today in the US costs about $ 3,000. However, it pays for itself only in the 14-15th year of work, and this, in comparison with the same thermal power stations, is unacceptably long. Therefore, for the conversion of solar energy into electrical energy on an industrial scale, now, the method proposed, according to legend, as early as the third century BC, is mainly used. e. famous scientist Archimedes of Syracuse. True, he did not use sunlight at all to obtain cheap energy but to defend his relatives Syracuse, who were attacked from the sea by the galleys of the Roman commander Marcellus. This is what the Byzantine chronicler Ceci wrote about in his “History”: “When the Roman ships were at the distance of the arrow, Archimedes began to operate a hexagonal mirror composed of small quadrangular mirrors, which could be moved with hinges and metal bars. He installed this mirror so that it intersected in the middle of the winter and summer solar lines, and therefore the sun’s rays received by this mirror, reflecting, created a heat that turned the ships of the Romans into ashes, although they were at the distance of the arrow’s flight.”
It is on this principle that the work of modern solar power plants is based. Mounted on a significant, up to several thousand square meters of territory, heliostats, which turn after the Sun, direct the rays of sunlight onto a container with a heat receiver, which usually is water. Then everything happens in the same way as conventional thermal power plants: water heats up, boils, turns into steam, steam turns the turbine, the turbine transfers rotation to the rotor of the generator, and the latter produces electricity. In the US, several hybrid solar-thermal power plants with a total capacity of more than 600 MW are currently operating. During the day they work from the Sun, and at night, so that the water does not cool down and the electricity does not end – from the gas. The temperature of steam in the plants reaches 370 degrees Celsius, and the pressure is 100 atmospheres.
Passive solar technology
Passive methods include the orientation of the building to the Sun to obtain the maximum amount of daylight and heat, as well as the choice of materials with the desired thermal properties.
If the energy supplied to our planet by the Sun for a year is converted into the same conventional fuel, then this figure will be about 100 trillion tons. This is ten thousand times more than we need. It is believed that 6 trillion tons of various hydrocarbons are stored on the earth. If this is so, then the sun contained in them is given to the planet in just three weeks. And its reserves are so great that it will be able to shine as brightly for about 5 billion years. Green plants and seaweed consume about 34% of the energy coming from the sun. The rest is lost almost in vain, being spent on maintaining a comfortable microclimate in the depths of the ocean and on the surface of the Earth. And if a person could take at least one percent (that is, one trillion tons of that very conventional fuel per year) for his domestic consumption, then this would solve many problems for ages to come. And theoretically, it is quite clear how to take this percentage.
Alternative sources of energy slowly replace our current dependence on fossil fuels. Some fuels can eventually become useless, but solar energy will never become obsolete, will not be controlled by foreign powers, and will not end. The sun uses its hydrogen reserves; it will produce useful energy until it explodes. The task facing people is to seize this power, while the easiest way to do this is to use fossil fuels.