SOLAR CELLLS-THE FOUNDTION OF SOLAR ENERGY full report
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03-04-2010, 10:47 PM
A solar cell is a semiconductor device that converts solar energy into electricity by the photovoltaic effect, representing the fundamental power conversion unit of a photovoltaic system ,works under the principle of a P-N junction that absorbs light , releases electrons and holes , creating a voltage in the cell , which is then applied to load; being environmentally aware, and with the price of living rising at an alarming rate, solar power, generating energy from the natural resources of the sun, has in recent times become quite a viable alternative to the normal resources for generating electricity, with a great advantage that solar energy is free; it needs no fuel and produces no waste or pollution, environmentally friendly, so particularly useful in situations where electrical power from the grid is unavailable such as in remote area power systems, Earth-orbiting satellites and space probes, remote radiotelephones and water pumping applications, where its applications stands alone, and exploit with their special advantages ,giving rebirth to the mankind.
Solar cells represent the fundamental power conversion unit of a photovoltaic system. They are made from semiconductors, and have much in common with other solid-state electronic devices, such as diodes, transistors and integrated circuits. For practical operation, solar cells are usually assembled into modules.
Many different solar cells are now available on the market, and yet more are under development. The range of solar cells spans different materials and different structures in the quest to extract maximum the device while keeping the cost to a minimum.
Cheaper (but also less efficient) types of silicon cells, made in the form of amorphous thin films, are used to power a variety of consumer products. We were familiar with the solar-powered watches and calculators, but larger amorphous silicon solar modules are also available.
A particular class of high-efficiency solar cells from single crystal silicon or compound semiconductors (for example, gallium arsenide or indium phosphide) are used in specialized applications, for example, to power satellites or in systems which operate under high-intensity concentrated sunlight.
WHAT IS A SOLAR CELL
A solar cell or photovoltaic cell is a semiconductor device that converts solar energy into electricity by the photovoltaic effect.. Photovoltaicâ„¢s is the field of technology and research related to the application of solar cells as energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the source is unspecified.
WHAT IS THE PRINCIPLE OF A SOLAR CELL
It is based on the ability of a semiconductor to directly convert sunlight into electricity. Basically, a solar cell is a P-N junction that absorbs light, releases electrons and holes, reating a voltage in the cell, which is then applied to the load.
HOW A SOLAR CELL DOES WORKS
In order to produce energy to work a load, e.g., light a light bulb, the solar cell needs an outside source (the Sun) to produce electricity to power it. When light strikes a photovoltaic (solar) cell, atoms are bombarded with photons, and produce electrons. When the atom loses the electron, it leaves behind a Ëœholeâ„¢, which has an equal and opposite charge. Both the electron, with its negative charge, and the hole, with its positive charge, begin are carried down the gradient. A proportion of carriers which cross this junction can be harvested by completing a circuit from a grid on the cell's surface to a collector on the backplane. In the cell, the light "pumps" electrons out one side of the cell, through the circuit, and back to the other side, energizing any electrical devices.
In the conversion process, the incident energy of light creates mobile charged particles in the semiconductor which are then separated by the device structure and produce electrical current.
WHAT ARE THE ADVANTAGES OF SOLAR -CELLS
Recently, more people are becoming environmentally aware, and, with the price of living rising at an alarming rate, we are all looking for ways to save some money. So why not try to save the environment at the same time Solar power, generating energy from the natural resources of the sun, has in recent times become quite a viable alternative to the normal resources for generating electricity.
1. SOLAR ENERGY IS A RENEWABLE RESOURCE
You will never run out of solar energy. Sure, the sun sets at night, and on those dark and gloomy days it may not always be visible, but you can be sure that it will return. Oil, on the other hand, is limited, and once you run out, it is gone forever. Although the amount of power the sun can generate is limited to the amount of sunlight you get, it is possible to generate electricity even on cloudy days.
2. SOLAR POWER IS NON-POLLUTING
Unlike oil, solar power does not emit any sort of toxic gases into the environment. It is a completely environmentally friendly approach to generating electricity. There is even work being done to make the recycling of solar panels more effective.
3. LIGHT FROM THE SUN IS FREE
After the initial costs involved in setting up the solar panels and solar lights etc, you will never have to pay to run them.
4. SOLAR POWER IS QUITE FLEXIBLE
You can have an array of solar panels on your roof to generate power from your home. You can also have smaller solar cells on garden lights or anything else outside that only needs a small amount of electricity. Not having to run a wire can be a huge time saver.
5. SOLAR CELLS REQUIRE MINIMAL MAINTENANCE
Once the solar cells are set up, they require very little maintenance, mainly because there are no moving parts that have to be maintained. Solar cells can last a lifetime and is very easy to install.
6. SOLAR POWER IS SILENT
The methods that are used to find and extract oil are very noisy. Even wind power can create a lot of noise. Solar power is completely silent.
7. SOLAR ENERGY CAN SAVE MONEY IN THE LONG RUN
Solar energy has many advantages, some of them not as common as others. The main reason for this perhaps is that the initial cost is quite high. However, you can save a significant amount of money using solar power, which compares favorably to paying an electricity bill at the end of the month. There is a lot of work that has been done to make solar power more accessible to the common man, with researchers finding ways and means to make this resource a common practice. Solar power is indeed an amazing, natural energy resource with so much potential to be tapped into. It is just a matter of time before solar power becomes a global hit.
WHAT ARE THE APPLICATIONS OF SOLAR CELL
Along side a variety of consumer products - electronic watches, calculators, power for leisure equipment and tourism - there is an extensive range of applications where solar cells are already viewed as the best option for electricity supply. These applications are usually stand-alone, and exploit the following advantages of photovoltaic electricity:
Â¢ There are no fuel costs or fuel supply problems
Â¢ The equipment can usually operate unattended
Â¢ Solar cells are very reliable and require little maintenance
THE APPLICATIONS ARE AS FOLLOWS
The provision of electricity to rural areas derives important social and economic benefits to remote communities throughout the world. Power supply to remote houses or villages, electrification of the health care facilities, irrigation and water supply and treatment are just few examples of such applications.
1. WATER PUMPING: Solar pumps are used principally for two applications: village water supply (including livestock watering), and irrigation. Since villages need a steady supply of water, provision has to be made for water storage for periods of low insolation. In contrast, crops have variable water requirements during the year which can often be met by supplying water directly to produce without the need for a storage tank.
2. LIGHTENING: In terms of the number of installations, lighting is presently the biggest application of photo-voltaic, with tens of thousands of units installed world-wide. They are mainly used to provide lighting for domestic or community buildings, such as schools or health centers. PV is also being increasingly used for lighting streets and tunnels, and for security lighting.
For some time, photovoltaic modules have proved to be a good source of power for high-reliability remote industrial use in inaccessible locations, or where the small amount of power required is more economically met from a stand-alone PV system than from mains electricity. Examples of these applications include:
1. OCEAN NAVIGATION AIDS: Many lighthouses and most buoys are now powered by solar cells.
2. TELECOMMUNICATION SYSTEMS: radio transceivers on mountain tops or telephone boxes in the country can often be solar powered.
3. REMOTE MONITORING AND CONTROL: scientific research stations, seismic recording, weather stations, etc. use very little power which, in combination with a dependable battery, is provided reliably by a small PV module.
4. CATHODIC PROTECTION: this is a method for shielding metalwork from corrosion, for example, pipelines and other metal structures. A PV system is well suited to this application since a DC source of power is required in remote locations along the path of a pipeline.
GRID CONNECTED SYSTEMS
Two types of grid-connected installations are usually distinguished, centralized PV power stations, and distributed generation in units located directly at the customer's premises(PV in buildings).
1. PV POWER Stations: A PV power station feeds the generated power instantaneously into the utility distribution network (the 'grid') by means of one or more inverters and transformers. PV power stations may be approaching economic viability in locations where they assist the local grid during periods of peak demand, and obviate the need to construct a new power station. This is known as peak shaving. It can also be cheaper to place small PV plants within the transmission system rather than to upgrade it ('embedded' generation).
2. PV In Buildings: PV arrays mounted on roof tops or facades offer the possibility of large-scale power generation in decentralized medium-sized grid-connected units.
The main advantages of these distributed systems over large PV plants are as follows:
Â¢ There are no costs in buying the land and preparing the site.
Â¢ The transmission losses are much lower because the load is on the same site as the supply.
Â¢ The value of the PV electricity is also higher because it is equal to the selling price of the grid electricity which has been replaced, rather that to the cost of generating it.
ELECTRIC POWER GENERATION IN SPACE
Photovoltaic solar generators have been and will remain the best choice for providing electrical power to satellites in an orbit around the Earth. Indeed, the use of solar cells on the U.S. satellite Vanguard I in 1958 demonstrated beyond doubt the first practical application of photovoltaics. Since then, the satellite power requirements have evolved from few Watts to several kilowatts, with arrays approaching 100 kW being planned for a future space station.
A space solar array must be extremely reliable in the adverse conditions of space environment. Since it is very expensive to lift every kilogram of weight into the orbit, the space array should also have a high power-to-weight ratio.
1. We can have pollutionâ€œless world.
2. Avoid the scarcity of fossil fuels.
3. Abundant electricity for all purposes.
4. Supply power in deserts, oceans, and to remote areas.
5. Supply of sufficient power to earth orbiting satellites and space probes.
Solar cells are long lasting sources of energy which can be used almost anywhere particularly useful where there is no national grid and also where there are no people such as remote site water pumping or in space, provide cost effective solutions to energy problems in places where there is no mains electricity. Moreover they are totally silent and non-polluting. They have no moving parts they require little maintenance and have a long lifetime when compared to other renewable sources they also possess many advantages; wind and water power rely on turbines which are noisy, expensive and liable to breaking down. We are living in a society where there is a tremendous pollution ,with the scarcity of fossil fuels and resources .To overcome those problems we need to change our life styles. Since the solar energy is abundant and is free of cost, we can utilize the solar power to give a rebirth to mankind.
3. Principles of electronics by Sze
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15-10-2010, 05:36 PM
SOLAR PHOTOVOLTAIC CELLS.ppt (Size: 954.5 KB / Downloads: 346)
SOLAR PHOTOVOLTAIC CELLS
About the company
Milestones of SPV division
Solar Photovoltaic cells
Working of a solar cell
Types of solar cells
Advantages and limitations of silicon wafer
Processes involved in manufacture of solar cells
Polishing and texturisation
Junction isolation or plasma etching
Phosphorus glass cleaning
Post diffusion cleaning
Front metal print
Back metal print
Back metal Al contact
Firing or sintering
Making a solar module
Advantages of SPV
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17-01-2012, 09:32 AM
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