Solar energy or solar power is the most abundant form of energy available on the earth. The net solar radiation which is incident on the surface of the earth is much more than what the world currently needs to meet its energy requirement. If this energy is optimally harnessed, sunlight as a renewable source of energy has the potential of sustaining the energy needs of the future generations. It is inexhaustible, at least for the next 4 billion years to come. Contrarily, increased dependence on the conventional sources of energy is sure to cause an energy crisis, due to their limited availability. Our reservoirs of fossil fuels such as coal and petroleum are expected to last for a few more decades before running out. On the other hand, solar energy is clean and causes no pollution. Investment and research in solar energy can avert the impending energy crisis, and help in achieving sustainable development goals.
The drawback of solar energy is its low intensity, because the radiation is spread over the entire geographical area of the earth. The atmosphere, along with the clouds absorb/scatter almost 54% of the incoming radiation. The light that is incident on the surface is composed of visible light (50%), infrared rays (45%) and traces of ultraviolet rays, along with some other forms of rays.
However, the countries that are situated between the Tropic of Cancer and the Tropic of Capricorn, in the tropical zone receive plenty of sunshine throughout the year. These countries (India being one of them) have enormous potential to channelize solar energy.
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Photovoltaic effect is a process in which a photovoltaic cell, when exposed to sunlight, is capable of producing voltage or electricity.
A photovoltaic cell is a technology to harness solar energy and convert it to electric energy. It is made up of two types of semiconductors- a p-junction and an n-junction. Together, they create a p-n junction. When these two semiconductors are joined, an electric field develops at the junction, causing the electrons to move towards the p-side, and the holes to move towards the n-sides. Under the effect of the electric field, the negatively charged and the positively charged particles move in opposite directions.
Light is a form of electromagnetic radiation, which is made up of small packets or bundles of energy called photons. When a radiation of the required wavelength falls on these cells, the energy of the photon is transferred to an electron of the semiconductor. As the electron gains this energy, it becomes excited and jumps to a higher energy level. It is this motion of the electron through the material in an excited state that induces a current in the cell.
They produce clean energy. The source of energy is the radiation from the sun, which is totally non-polluting. Hence, no pollutants are released in the process and there is no danger of environmental degradation. Using solar energy, we can immensely cut down our carbon emissions.
They are reliable and are based on green technology. They can last for long periods of time with minimum loss of efficiency.
They do not produce any noise and have no moving/mechanical parts. So, there is no disturbance produced.
The operating and maintenance costs involved are minimal. Just cleaning the surface of solar panels is sufficient to maintain their efficiency.
Photovoltaic cells can be of great help in rural and remote areas, which are yet not electrified. Solar resources are already abundantly present. The power loss that occurs due to the long-distance transmission of electricity can be drastically reduced.
They are less efficient as compared to other renewable sources of energy.
They can operate only in the presence of sunlight, which implies that they will not be of any use against the unpredictable weather. On a cloudy or a rainy day, an alternative may be needed.
Solar energy cannot be transmitted over long distances. As photovoltaic cells produce direct current, its conversion to alternating current will involve more equipment and make the process quite arduous.
They are quite susceptible to damage and have to be maintained with care.
Though the maintenance charges are quite nominal, the entire setting up of a solar panel may be expensive.
After the energy crisis of 1970, the interest in solar energy began rising. Research, technological developments and industrial progress have made the use of photovoltaic cells and solar energy viable. As the production and demand increased, the costs began decreasing. However, we still have a long way to go and tap the solar potential.
1. What is the Principle of a Photovoltaic Cell?
A photovoltaic cell is based on the principle of the photovoltaic effect, which involves the conversion of solar energy into electrical energy. When a semiconducting material is exposed to light, it absorbs the photons of the incident light. The energy of the photons results in free electrons within the semiconductor. As these electrons move, the electric current is produced. In a photovoltaic cell, the solar radiation is absorbed, and then converted to electricity. Many photovoltaic cells are put together to form a solar panel. Silicon is one of the most widely used semiconducting materials. As it has a valency of four, the four valence electrons enter into covalent bonding with the surrounding silicon atoms. When the falling light is sufficiently intense, a large number of photons are absorbed, which excite the electrons involved in this covalent bonding.
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2. What is a Photovoltaic Cell Used For?
Photovoltaic cells can be used to supply power to various things, ranging from small devices such as calculators and wristwatches to the signs on roads, commercial hoardings etc. They can be used to provide and improve street lighting.
They are also used to provide power to space vehicles such as satellites and telescopes. These cells are an economical way of supplying power to space facilities which would otherwise require very expensive sources of fuel. The International Space Station is a great example of how photovoltaic cells in the form of solar panels are being used to meet the energy needs in space.