solar cell

Solar cell also known as  photovoltaic.

Solar Cell is an electrical device which converts the light energy into electrical energy. ... This voltage increase whit increase in the light intensity. The cell is so designed that a large area is exposed to light which enhances the voltage generation across the two terminals of the cell.

Introduction  : -

                            Photovoltaic systems behave in an extra ordinary and useful way . They react to light by transforming part of it into electricity . More over this conversion is novel and unique ,since photovoltaics.

• It have no any moving part.
• There is no any container for fluids and gases. 
• It don't need any fuel for operate it.
• It have a rapid response, achieveing all full output instantly.
• It can operate on moderate temperature.
• It didn't produce any pollution when it generate electricity.
• It require a little maintenance if it proper manufacturer and installed .
• It Can be made from silicon. The second most abundant element the earth's crust .
• It Have wide power-handling capabilities, from micro-watts to megawatts.

Clearly, photovoltaics have an appealing range

Of charactorstics.

There is some truth to both of these views. The sun's energy, for all is certainly in-exhaustible. However, even thoughs the Sim light stricking the earth is aboundant, it come in a rather delute form.

Solar cell technology :-

                                Photovoltaics is  the field of  technology  and research related to  the devices which directly convert sunlight into  electricity.  The solar cell  is  the elementary building block of  the photovoltaic technology. Solar cells are  made  of  semiconductor  materials,  such  as  silicon.  One of  the properties of  semiconductors  that makes them most  useful is that their conductivity  may easily be  modified by  introducing impurities into  their crystal lattice.

For instance, in  the fabrication of  a  photovoltaic solar cell, silicon,  which has four  valence electrons, is  treated to  increase  its conductivity. On  one side  of  the cell, the impurities, which are phosphorus  atoms with five  valence electrons (n-donor),  donate  weakly bound valence electrons to  the silicon material, creating excess  negative  charge  carriers. On  the other side, atoms of  boron with three valence electrons (p-donor) create  a  greater affinity  than silicon to  attract electrons. Because the p-type  silicon is in  intimate  contact with the n-type  silicon a  p-n junction is  established and a  diffusion of  electrons occurs from the region of  high electron concentration (the n-type  side) into  the region of  low electron concentration (p-type side).  When the electrons diffuse across  the p-n  junction, they recombine with holes on the p-type  side. However, the diffusion of  carriers does not occur  indefinitely, because the imbalance of charge  immediately on either sides of  the junction originates an electric field.  This electric field forms a  diode that  promotes  current  to  flow  in  only  one  direction. Ohmic metal-semiconductor contacts  are made  to  both the n-type  and p-type  sides of  the solar cell, and the electrodes are ready to  be  connected to  an external load.

When photons of  light fall on the cell, they transfer their energy  to  the charge  carriers. The electric field across  the junction separates photo-generated positive charge  carriers  (holes) from their negative  counterpart (electrons).  In this  way an  electrical  current  is  extracted once  the circuit is  closed on an external load.

Application of solar energy or photovoltaics :-

(1)  Rural electrification

• Temporary housing
• Permanent housing
• Centralised electrification with individual consumption control per house, in rural areas
• Refuge and mountain lodge electrification
• Aid stations. (lighting, medication and vaccine preservation with refrigerators)
• Schools and community centres
• Police stations and borders
• Religious facilities (chapels, missions, etc.)

Rural electrification currently has all of the commodities that a conventional electrification system can have since the incorporation of new sine wave inverters, allowing for the use of any appliance.

One of the most important applications is currently the electrification of small rural areas with centralised systems. The advantages with respect to one installation per house are the following:

• Lower installation cost
• Lower maintenance costs
• Higher level of user friendliness
• Higher security of the facility
• Greater total return

(2) Agricultural applications

• Water pumps both in DC and AC (with battery)
• Direct drive water pumps (without battery)
• Warehouse electrification
• Risk controls
• Greenhouses (automation of windows and lighting)

(3)Lighting:

• Billboards
• Public streetlights
• Bus stops
• Tunnel, cave, etc. lighting

Public lighting, through photovoltaic systems, is presented as one of the most economic solutions to light the entrances of the towns, road junctions, rest areas, etc.
A new type of street light is currently being installed, which does not require any maintenance, by integrating long life stationary batteries with gelled electrolytes (over 300 streetlights in the Canary Islands).
Signage:

• Lighthouses and marine buoys
• Air beacons and radio beacons
• Road signs to indicate curves, obstacles, roundabouts, etc. in cities and on roadways using LEDs
• Time and temperature indicators on public roads
• Railway crossings
• Oil rigs

Advantages

• Electricity produced by solar cells is clean and silent. Because they do not use fuel other than sunshine, PV systems do not release any harmful air or water pollution into the environment, deplete natural resources, or endanger animal or human health.
• Photovoltaic systems are quiet and visually unobtrusive.
• Small-scale solar plants can take advantage of unused space on rooftops of existing buildings.
• PV cells were originally developed for use in space, where repair is extremely expensive, if not impossible. PV still powers nearly every satellite circling the earth because it operates reliably for long periods of time with virtually no maintenance.
• Solar energy is a locally available renewable resource. It does not need to be imported from other regions of the country or across the world. This reduces environmental impacts associated with transportation and also reduces our dependence on imported oil. And, unlike fuels that are mined and harvested, when we use solar energy to produce electricity we do not deplete or alter the resource.
• A PV system can be constructed to any size based on energy requirements. Furthermore, the owner of a PV system can enlarge or move it if his or her energy needs change. For instance, homeowners can add modules every few years as their energy usage and financial resources grow. Ranchers can use mobile trailer-mounted pumping systems to water cattle as the cattle are rotated to different fields.

SOLAR CELL SYMBOL

Why should we go solar?

(1)Save Money

Often times the initial solar power cost of installation seems to eclipse the benefits of a clean, renewable energy source and deters people from pursuing the switch. But what many people don’t realize is that installing solar panels for homes on your roof doesn’t just earn you a badge of environmentalism. It saves money and creates a passive income for the future. Figure out the cost of your monthly electricity bills, and depending on how many panels you plan to install, cut that number in half or even eliminate that responsibility from your budget entirely. Solar panels will immediately lower your electric billand shield you from fluctuating rates and the monotony of dealing with local utility companies. And let’s face it, no one enjoys paying those guys..

(2) Earn Money

While the idea of saving money on your electricity bill may already be enough to entice you to jump aboard the solar power bandwagon, many people forget the possibilities of actually profiting from the switch. Renewable energy incentives such as rebates, tax credits, and other various incentives are often offered through your state. If you find you are eligible for these incentives after solar panel installation, the local utility company may be required to pay YOU (through cash or credit) for energy produced and supplied by your panels. Which is pretty great.

(3)Increase Your Property Value

Increasing your property value is always a plus. Not only does solar power save you money and can create added income, purchasing solar panels can actually raise your property value. If you are considering a home remodel to sell in the future, the incentives and credits will help to ease the cost while the panels themselves retain its value, fetching approximately five percent more when your home is finally placed on the market. All aspects considered, solar panels are a remarkable investment for your future as well as the environment.

(4) Help Our Planet

By switching to residential solar energy you are helping the transition to from an over-consumption of fossil fuels to a clean, renewable energy source that will neither deplete nor damage our water, soil, and air. Sustainable energy is the future of power and attainable in the present. To effectively reduce greenhouse gas emissions and begin to neutralize cataclysmic climate change, personal steps must first be taken by individuals such as yourself.