Contents:
Photovoltaic Cells
Solar Heating Panels
In a Nutshell
Sources Used


Photovoltaic Cells

Photovoltaic energy is the conversion of sunlight into electricity. A photovoltaic cell is used to convert solar energy directly into electrical power. A photovoltaic cell is a non mechanical device usually made from semiconductor materials, for example silicon.

Sunlight is composed of particles of solar energy called photons. When these photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed, but only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.

When the electrons leave their position, holes are formed. When many electrons, each carrying a negative charge, travel toward the front surface of the cell, the resulting imbalance of charge between the cell's front and back surfaces creates a voltage potential like the negative and positive terminals of a battery. When the two surfaces are connected through an external load, electricity flows.

This diagram shows the parts of a photovoltaic cell and how they work together.

Examining a Photovoltaic cell
Examining a Photovoltaic cell




















This diagram shows how the negative and positive layers of a photovoltaic cells interact, and the steps which they undergo in order to convert sunlight into electricity
Steps that a Photovoltaic Cell undergoes to convert sunlight into electric energy
Steps that a Photovoltaic Cell undergoes to convert sunlight into electric energy






















Some advantages of using systems of photovoltaic cells are:
1. Sunlight is converted directly into electricity, so bulky mechanical generator systems are unnecessary.
2. Photovoltaic systems (arrays) can be installed quickly and their sizes are easily modifiable
3.
They have minimal environmental impact, since they require no water for system cooling and generates no by-products.
Photovoltaic cells, like batteries, generate direct current (DC) which is generally used for small loads (electronic equipment).





Solar Heating Panels

A solar heating panel is basically a group of solar collectors usually positioned on a roof or where it will be able to collect a maximum amount of sunlight. It is connected to pipes containing a heating fluid mixture of water and antifreeze. Solar heating panels are usually used to heat water in households.

When the sun heats up the solar collectors, the heated fluid mixture is pumped through pipes to a heat exchange coil in a twin coil hot water cylinder. Here the captured solar energy is transferred from the hot fluid in the coil to the household's hot water supply. The hot water in the cylinder can then be used in the taps, shower, washing machine, and other appliances.



This diagram illustrates the process that sunlight goes through in order to heat a household's water.

A typical Active Solar Heating system layout
A typical Active Solar Heating system layout




In a nutshell.............
Photovoltaic cells change sunlight directly into electricity. PV systems are often used in remote locations that are not connected to electric grids. They are also used to power watches, calculators, and lighted road signs.
Solar Power Plants generate electricity indirectly when the heat from solar thermal collectors is used to heat a heating fluid mixture, which produces steam that is used to power a generator.




Sources Used: