31-05-2012, 05:13 PM
SOLAR POWER SYSTEM
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INTRODUCTION
Sun is the primary source of Energy. The earth receives 16 x 1018 units of energy from the sun annually, which is 20,000 times the requirement of mankind on the Earth. Solar energy can be used for a number of different things. It can be used to provide electricity to your home, your car, and can even be used to heat the water in your home or the water in your swimming pool. Solar energy is a form of energy produced by transforming solar power or power from the sun into electricity. By using photovoltaics, we can transform sunlight into electricity. Solar cells, also known as photovoltaic cells, are capable of transforming solar energy into electricity by using the photovoltaic effect. Such cells have been used for many years especially those used in small electronic calculators.
One of the main reasons people prefer using solar energy is because photovoltaic arrays are capable of generating a form of renewable electricity. Photovoltaic arrays are very common and useful in specific situations such as when electricity from the grid isn’t available. This is common with remote area power systems, satellites, space probes, remote radiotelephones, and water pumping applications. Unlike coal, solar energy is a renewable resource meaning we will never run out of it. So basically, solar energy offers an infinite supply of electricity. A group of cells are assembled together to form solar modules. Solar modules are sometimes linked to photovoltaic arrays.It is no secret that a solar energy system can cost a lot of money. Of course, once is all said and done you will end up saving more money in the long run. There are a number of cheap solar cells that you can install yourself. Dye sensitized solar cells are considered the cheapest solar cells currently available.
These cells are made of cheap materials and do not need elaborate apparatus to manufacture which makes these cells perfect for someone willing to do the work themselves. It is a good idea to buy in bulk as this often results in a bulk package being less expensive than older solid state cells.
These types of cells often come in flexible sheets. While these cells have a lower conversion efficiency than the best thin film cells their price and performance make them a strong competitor to fossil fuel electrical generation.
So what are the benefits of using solar energy instead of fossil fuels? Well, unlike fossil fuels solar energy is a renewable resource. Solar energy will always be around. While it might be difficult to produce energy at night we will always have it. Another major benefit associated with solar energy is the fact that solar energy does not pollute the area with harmful greenhouse gases and carbon dioxide.Solar energy is just as universal as fossil fuels. You can use solar energy for pretty much everything you can use fossil fuels for including heating your water, drying your clothes, heating your swimming pool, power fans and other small appliances.
The major disadvantage of solar energy is the initial cost. You will have to purchase all the equipment, solar cells, and possibly hire someone to install them for you. While this is often a huge price, in the long run you will end up saving money since you will be cutting the cost of you electric bill significantly. Certain locations are not suitable for solar energy.
The area where you live will need to receive enough sunlight during the day to produce enough solar energy to be able to keep your appliances working throughout the night. It is possible to create more energy than you actually use by installing a very expensive solar energy system. Sometimes your utility company might be interested in buying that extra energy from you
PHOTOVOLTAIC CELL
A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver selenide in place of copper oxide. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.
A photovoltaic system (or PV system) is a system which uses one or more solar panels to convert sunlight into electricity. It consists of multiple components, including the photovoltaic modules, mechanical and electrical connections and mountings and means of regulating or modifying the electrical output.
PHOTOVOLTAIC MODULES
Due to the low voltage of an individual solar cell (typically ca. 0.5V), several cells are wired in series in the manufacture of a "laminate". The laminate is assembled into a protective weatherproof enclosure, thus making a photovoltaic module or solar panel. Modules may then be strung together into a photovoltaic array. The electricity generated can be either stored, used directly (island/standalone plant)or fed into a large electricity grid powered by central generation plants (grid-connected/grid-tied plant) or combined with one or many domestic electricity generators to feed into a small grid (hybrid plant).[1] Depending on the type of application, the rest of the system ("balance of system" or "BOS") consists of different components. The BOS depends on the load profile and the system type. Systems are generally designed in order to ensure the highest energy yield for a given investment
PRINCIPLES OF OPERATION SOLAR PHOTOVOLTAICS
The solar energy can be directly converted into electrical energy by means of photovoltaic effect, i.e. conversion of light into electricity. Generation of an electromotive force due to absorption of ionizing radiation is known as photovoltaic effect.
The energy conversion devices which are used to convert sunlight to electricity by use of the photovoltaic effect are called solar cells.
Photo voltaic energy conversion is one of the most popular nonconventional energy source. The photovoltaic cell offers an existing potential for capturing solar energy in a way that will provide clean, versatile, renewable energy. This simple device has no moving parts, negligible maintenance costs, produces no pollution and has a lifetime equal to that of a conventional fossil fuel.
Photovoltaic cells capture solar energy and convert it directly to electrical current by separating electrons from their parent atoms and accelerating them across a one way electrostatic barrier formed by the function between two different types of semiconductor material.
PHOTO VOLTAIC EFFECT ON SEMICONDUCTORS
Semi conductors are materials which are neither conductors nor insulators. The photo voltaic effect can be observed in nature in a variety of materials but semiconductors has shown best performance.
When photons from the sun are absorbed in a semiconductor they create for electrons with higher energies than the electrons which provide the boarding in the base crystal.
Once these electrons are created, there must be an electric field to induce these higher energy electrons to flow out of the semiconductor to do useful work. The electric field in most solar cells is provided by a junction of materials which have different electrical properties.
To understand more about the functioning and properties of semiconductors, let us briefly discuss. Semi conductors are classified into
1) Extrinsic semiconductor
2) Intrinsic semiconductor.
Semiconductors in its purest form are called intrinsic and when impurities are added it is called extrinsic. Further extrinsic semiconductors are divided into p type and N type semiconductor.
P-TYPE SEMICONDUCTOR
When a small amount of pentavalent impurities (e.g. Gallium, Indium, Aluminum, and Boron) are added to intrinsic semiconductor, it is called as p type semiconductor.
In p type semiconductor, when an electric potential is applied externally, the holes are directed towards the negative electrode. Hence current is produced.
N- TYPE SEMICONDUCTORS
When a small amount of pentavalent impurities (e.g. Antimony, Arsenic, Bismuth, Phosphorus) are added to intrinsic semiconductors it is called N type semiconductor.
When an external electrical field is applied the free electrons are directed towards positive electrode. Hence current is produced.