Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar energy technologies include solar heating, solar photovoltaic, solar thermal electricity and solar architecture, which can make considerable contributions to solving some of the most urgent problems the world now faces.
Solar Energy is the energy received from the sun that sustains life on earth. For many decades solar energy has been considered as a huge source of energy and also an economical source of energy because it is freely available. However, it is only now after years of research that technology has made it possible to harness solar energy.
Some of the modern Solar Energy systems consist of magnifying glasses along with pipes filled with fluid. These systems consist of frontal glass that focuses the sun’s light onto the pipes. The fluid present in the pipes heats up instantly. In addition they pipes are painted black on the outside so as to absorb maximum amount of heat. The pipes have reflective silver surface on the back that reflects the sunlight back, thus heating the pipes further. This reflective silver surface also helps in protecting everything that is on the back of the solar panel.
The heat thus produced can be used for heating up water in a tank, thus saving the large amount of gas or electricity required to heat the water.
Photovoltaic energy is produced when sunlight is converted into energy with the use of solar cells or semiconductors. These semi conducting cells are usually made of silicon and do not contain any corrosive materials or moving parts. As long as the solar cells are exposed to light, they will produce photovoltaic energy with a minimum of maintenance. This energy is also environmentally clean, quiet, and safe.
The term “photovoltaic” has two parts: photo, a Greek word meaning light, and voltaic, a reference to electrical energy innovator Alessandro Volta. In 1839, French physicist Edmond Becquerel discovered the photovoltaic effect, the production of a volt by use of a semiconductor. This discovery prompted further experimentation with light sources and semiconductors, which led to the invention of solar cells that produce photovoltaic energy.
Individual solar cells, also called photovoltaic cells, are manufactured in different shapes and sizes. Sometimes just one cell is needed to power a device, but most often many cells are connected to one another to form solar panels or modules. These modules can then be connected to create photovoltaic arrays that can be used to power small buildings or large complexes. The resulting output of photovoltaic energy is dependent upon the size of the array. The size may vary, depending on the amount of available sunlight and the amount of power needed.
Even though the power output of a photovoltaic energy system depends on the overall amount of light exposure, it will still generate energy on cloudy or overcast days. To store this energy for later transmission, a variety of storage systems are available to consumers. Most reliable storage systems use a combination of rechargeable batteries and energy-storing capacitors, some of which can be designed for AC or DC power.
The amount of power available on cloudy days and at night in a photovoltaic energy system depends on the energy output of the photovoltaic modules and the battery arrangement. Adding additional modules and batteries will increase the available power, but will also increase the cost of the system. For best results, a thorough analysis of needs vs. cost must be conducted in order to create a system design that will balance cost and need with convenience of use. Systems that are well-designed offer the opportunity for expansion or reduction as energy needs increase or decrease.
Photovoltaic energy is emerging as a viable solution to energy problems worldwide. Its current uses include power stations, transportation, rural electricity supplies, and solar roadways. While still a long way from becoming the world’s major energy source, ongoing research into photovoltaic energy may bring the promise of hope to the future.
The common solar cell that many of us have seen is called a photovoltaic solar cell. These are the type of cells found in solar-powered calculator and on satellites to generate electrical energy. These cells convert light energy directly into electrical energy.
These cells are made up of silicon and are made up of semiconductors. An atom of silicon has 14 electrons arranged in three general electron shells. The first two shells closest to the nucleus are full. The outer shell has four electrons and is only half-full. However, silicon will and can share electrons with its neighbors. In the case of crystalline silicon, there are other silicon atoms that will provide electrons for sharing.
However, pure crystalline silicon is a poor conductor as there are no extra electrons free to move about. Because of this a solar cell is constructed with silicon mixed with impurities; this is called doping the silicon. For example, phosphorus atoms could be mixed with the silicon. Phosphorus has five electrons in its outer shell. It still bonds with the silicon atoms but now there is an extra electron.
When energy is added to the crystal, this extra electron can break free of bond and this leaves a hole. Throughout the lattice, we have a series of extra electrons moving freely of their bonds; these electrons are called free carriers.
When silicon is doped with phosphorus, it is called an N-type crystal as it has extra electrons (N for negative). Part of a common photovoltaic cell is created as an N-type crystal.
However, it is also possible to make P-type (positive) silicon but doping it with a substance having three electrons instead of five. Instead of using phosphorus, born can be used. Boron has three valence or outer electrons. It, consequently, has more holes available for the free electrons created when the N-type silicon is energized. A hole can be thought of as an absence of an electron or a positive charge. The holes can appear to move just like free electrons. Both electrons and holes can be called charge carriers.
Monocrystalline cells are cut from a single crystal of silicon- they are effectively a slice from a crystal.
In appearance, it will have a smooth texture and you will be able to see the thickness of the slice.
These are the most efficient and the most expensive to produce. Polycrystalline (or Multicrystalline) cells are effectively a slice cut from a block of silicon, consisting of a large number of crystals.
They have a speckled reflective appearance and again you can you see the thickness of the slice.
These cells are slightly less efficient and slightly less expensive than monocrystalline cells.
Amorphous cells are manufactured by placing a thin film of amorphous (non crystalline) silicon onto a wide choice of surfaces. These are the least effient and least expensive to produce of the three types. Due to the amorphous nature of the thin layer, it is flexible, and if manufactured on a flexible surface, the whole solar panel can be flexible.
One characteristic of amorphous solar cell is that their power output reduces over time, particularly during the first few months, after which time they are basically stable. The quoted output of an amorphous panel should be that produced after this stabalisation.
A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications.
Most PV panels contain a top protective layer, two specially treated layers of silicon with collecting circuitry attached to the top layer, and a polymer backing layer.
The top layer of silicon is treated to make it electrically negative; the back layer is treated it make it electrically positive. When sunlight knocks electrons loose from the silicon, electrons move up from the bottom layer of silicon and crowd the electrons in the top layer. The electrons freed from the top layer are collected by electrical contacts on the surface of the top layer and routed through an external circuit, thus providing power to the electrical system attached to the panels.
Solar street lights are raised light sources which are powered by photovoltaic panels generally mounted on the lighting structure. The photovoltaic panels charge a rechargeable battery, which powers a CFL or LED lamp during the night.
Most solar panels turn on and turn off automatically by sensing outdoor light using a light source. Solar streetlights are designed to work throughout the night. Many can stay lit for more than just one night not if sun in not available for a couple of days.
The system operates on power generated using solar PV (photovoltaic) system. The photovoltaic array converts the solar energy into electricity, which is used for running the motor pump set. The pumping system draws water from the open well, bore well, stream, pond, canal etc. The system requires a shadow-free area for installation of the Solar Panel.
These systems are most suitable for customer in remote areas, who would like to make use of electricity but are unable to do so because of non-availability of utility supply. In this case the systems are designed keeping in mind the power requirements and autonomy (days of battery back-up) required.
Grid power system consists of solar panels, a system controller and inverter. Solar panel will produce DC (Direct Current) electricity, and this electricity will be run though the converter and inverter to produce AC (Alternating Current) electricity. Then this energy is run into AC power panel back to the utility companies power grid. As on-grid solar power system enjoys the advantages of battery-free and low cost, this can make the system operation life longer. It also can remote monitoring during the operating. It has been become the main stream in solar power generation. The system brings benefits of pollution reduction, energy conservation and environment protection, all of which make remarkable social values.
