What is Solar Power?
The term solar power is used to describe the methods of harnessing energy from the sun. The sun is 91 million miles (146 million kilometers) distance from the earth and is an extremely powerful energy source. To place a scale on solar energy, the earth receives 1.6 billion kilowatts from the sun annually. However, only 40% actually hits the earth directly, while the rest is reflected by the upper layers of the atmosphere. This tiny fraction that humans can capture and transform into useable energy is several hundred times greater than the world’s annual energy consumption.
Solar power can be used in two different ways: as a heat source and as an electrical source. The process of converting the sun’s rays into electricity is called Photovoltaics (PV).
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In many parts of the world, PV solar is cost competitive with fossil fuels and other energy solutions. More and more people are choosing PV solar as one of their energy sources due to the uncertainty of global supply of fossil fuels and increased awareness of environmental deterioration. With widespread solar adoption in Japan, German, Spanish, Italian and Greek markets, PV solar is set to play a major role in the world’s energy mix.
What are Photovoltaics?
Photovoltaics (PV) is a term used to describe the process of converting sunlight into electricity without any moving parts, noise, pollution or fuel. If you ever used a solar calculator, passed a solar powered road sign or placed money into a solar parking meter, you have seen PV solar in action. V conversion was discovered by French physicist, A. Becquerel in 1839. It is the only means known for converting light directly into electricity.
Photo stems from the Greek ‘phos’, signifying light. ‘Volt’ is named from Alessandro Volta (1745 – 1827), a contributor in the study of electricity. Photovolatics literally means light-electricity. Also known as solar cells, PV cells are the basic component of the conversion and act as semiconductor devices which convert light energy into electricity energy from an inexhaustible energy source, the sun. It makes use of properties found in semiconductor materials used in the electronics industry: diodes, transistors, integrated circuits.
How the Photovoltaic Cells Work
The Solar Cell
PV cells are thin, flat wafers made of materials called semiconductors that are able to conduct, or carry, electricity. Over 90% of the solar cells manufactured today are made from silicon, a semi-conductor, or a semi- metal, that has properties of both a metal and an insulator. One side of the cell is treated with a substance that carries a negative charge (e.g. phosphorous). The other side is treated with a substance that carries a positive charge (e.g. boron). Another layer, this one non-energy conducting, separates the two charges layers. A wire runs from the negatively charged side of the cell to the positively charged side.
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 A solar cell. |
Sunlight – Energy Source
Sunlight drives the PV process and provides the energy that is converted into electric power. Sunlight is composed of tiny bundles of energy (photons), which act like individual bullets.
When photons strike a PV cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material’s atoms in the form of electrical current Photons from the sun, in the form of energy, knock electrons loose, allowing them to flow freely.
This flow of electrons creates a current and by placing metal contacts on the top and bottom of the PV cell, current can be drawn off to be used externally. This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.
Power (watt peak) = Current (ampere) x Voltage (volts)
The cell is the essential component of a PV system, but cannot offer enough energy at one time. The electrical properties of a single cell (unit voltage of about 0.5 volts and power of about 1.5 watt peak) cannot generally supply power to electrical equipment operating at standard voltages (12, 24, or 48 volts). For this reason, solar cells are interconnected with other cells to make a module or panel that creates a specific electrical output.
A typical solar module consists of many cells, a glass cover for protection, an anti-reflective layer to increase the sunlight, a front and back contact or electrode and the semiconductor layers where the electrons begin and complete their voyages. The electric current stimulated by sunlight is collected on the front electrode and travels through a circuit back to the solar cell via the back electrode.
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In turn, a specific number of modules are connected together to form an array or system creating a specific electrical output to suit the application or total demand.
When the sun shines on the PV array /system, DC electricity is generated and can be used to power a variety of applications. From grid connected applications to off grid remote area installations, PV can be used in any case.