28-07-2014, 10:36 AM
IDEAS ON RENEWABLE ENERGY
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1. INTRODUCTION:
Harnessing of non polluting renewable energy resources to control green house gases is receiving impetus from the government of India. The solar mission, which is part of the National Action Plan on Climate Change has been set up to promote the development and use of solar energy in for power generation and other uses with the ultimate objective of making solar energy competitive with fossil-based energy options. The solar photovoltaic device systems for power generation had been deployed in the various parts in the country for electrification where the grid connectivity is either not feasible or not cost effective as also some times in conjunction with diesel based generating stations in isolated places and communication transmitters at remote locations. With the downward trend in the cost of solar energy and appreciation for the need for development of solar power, solar power projects have recently been implemented. A significant part of the large potential of solar energy in the country could be developed by promoting grid connected solar photovoltaic power systems of varying sizes as per the need and affordability coupled with ensuring adequate return on investment.
IDEAS ON RENEWABLE ENERGY:
Renewable energy is energy which comes from natural resource such as sunlight, wind, tides & geothermal heats.In other words Renewable is natural energy which doesn't have a limited supply, which can be used again & again, and will never run out.
About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from hydroelectricity.
New renewables (small hydro, modern biomass, wind, solar, geothermal, and bio fuels) accounted for another 3% and are growing very rapidly.The share of renewables in electricity generation is around 19%, with 16% of global electricity coming from hydroelectricity and 3% from new renewables.
Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services.
In other word renewable energy is also known as nonconventional energy source
3 IDEAS ON SOLAR ENERGY:
Solar energy is energy that is present in sunlight. Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity and solar architecture, which can make considerable contributions to solving some of the most urgent problems the world now faces. Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favourable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.
INTRODUCTION
Photovoltaic power generation is a method of producing electricity using solar cells. A solar cell converts solar optical energy directly into electrical energy. A solar cell is essentially a semiconductor device fabricated in a manner which generates a voltage when solar radiation falls on it.
In semiconductor, atoms carry four electrons in the outer valence shell, some of which can be dislodged to move freely in the materials if extra energy is supplied. Then, a semiconductor attains the property to conduct the current. This is the basic principle on which the solar cell works and generates power
2.2SOLAR CELLS:
Solar cells are the building block of PV system. . It is a form of photoelectric cell which, when exposed to light, can generate and support an electric current without being attached to any external voltage source.
Solar cells produce direct current electricity from sun light, which can be used to power equipment or to recharge a battery.
The first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC.
Cells require protection from the environment and are usually packaged tightly behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels.
Solar cells are often electrically connected and encapsulated as a module.
Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from abrasion and impact due to wind-driven debris, rain, hail, etc. Solar cells are also usually connected in series in modules, creating an additive voltage.
Connecting cells in parallel will yield a higher current; however, very significant problems exist with parallel connections.
For example, shadow effects can shut down the weaker (less illuminated) parallel string (a number of series connected cells) causing substantial power loss and even damaging the weaker string because of the excessive reverse bias applied to the shadowed cells by their illuminated partners.
Strings of series cells are usually handled independently and not connected in parallel, special paralleling circuits are the exceptions.
The efficiency of a solar cell may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies.
The cost of a solar cell is given per unit of peak electrical power.
High-efficiency solar cells are of interest to decrease the cost of solar energy. Many of the costs of a solar power plant are proportional to the panel area or land area of the plant.
A higher efficiency cell may reduce the required areas and so reduce the total plant cost, even if the cells themselves are more costly.
Materials presently used for photovoltaic solar cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide.
Many currently available solar cells are made from bulk materials that are cut into wafers between 180 to 240 micrometers thick that are then processed like other semiconductors.
SOLAR PANEL:
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. Each panel is rated by its DC output power under standard test conditions, and typically ranges from 100 to 320 watts.
The efficiency of a panel determines the area of a panel given the same rated output - an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel. Because a single solar panel can produce only a limited amount of power, most installations contain multiple panels.
photovoltaic system typically includes an array of solar panels, an inverter, and sometimes a battery and or solar tracker and interconnection wiring.
Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The structural (load carrying) member of a module can either be the top layer or the back layer.
The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The conducting wires that take the current off the panels may contain silver, copper or other non-magnetic conductive transition metals.
2.4.1 Crystalline silicon modules:
Most solar modules are currently produced from silicon photovoltaic cells. These are
typically categorized as monocrystalline or polycrystalline modules.
2.4.2 Rigid thin-film modules:-
In rigid thin film modules, the cell and the module are manufactured in the same production line.
2.4.3 Flexible thin-film modules:-
Flexible thin film cells and modules are created on the same production line by depositing the photoactive layer and other necessary layers on a flexible substrate.
2.5 SOLAR ARRAYS:
A photovoltaic array (or solar array) is a linked collection of solar panels.
The power that one module can produce is seldom enough to meet requirements of a home or a business, so the modules are linked together t
Basic concept on Solar tracking system:-
Sunlight has two components, the "direct beam" that carries about 90% of the solar energy, and the "diffuse sunlight" that carries the remainder - the diffuse portion is the blue sky on a clear day and increases as a proportion on cloudy days.
As the majority of the energy is in the direct beam, maximizing collection requires the sun to be visible to the panels as long as possible.
The energy contributed by the direct beam drops off with the cosine of the angle between the incoming light and the panel. In addition, the reflectance (averaged across all polarizations) is approximately constant for angles of incidence up to around 50°, beyond which reflectance degrades rapidly.
3.1.2 Concentrated photovoltaic (CPV) trackers:-
In concentrated photovoltaic (CPV) and concentrated solar thermal (CSP) applications trackers are used to enable the optical components in the CPV and CSP systems.
The optics in concentrated solar applications accept the direct component of sunlight light and therefore must be oriented appropriately to collect energy.
Tracking systems are found in all concentrator applications because such systems do not produce energy unless oriented closely toward the sun.
The optics in CPV modules accept the direct component of the incoming light and therefore must be oriented appropriately to maximize the energy collected. In low concentration applications a portion of the diffuse light from the sky can also be captured.
The tracking functionality in CPV modules is used to orient the optics such that the incoming light is focused to a photovoltaic collector.
CPV modules that concentrate in one dimension must be tracked normal to the sun in one axis. CPV modules that concentrate in two dimensions must be tracked normal to the sun in two axes.
CONCLUSION:
1. Power generation & efficient distribution is the prime need of the day.
2. To explore the new avenues to sustain the ever increasing demands is the present challenge.
3. This is a provoking seminar topic. To make this type of topic is really feasible for us. I wish this topic motivate you all and made us think for our future generation