Solar power is the transformation of the energy provided by sunlight into electricity.  The resulting electricity is known as Photovoltaic Energy.  Photovoltaic Energy is created through the conversion of sunlight via a photovoltaic (PV) cell, often referred to as a solar cell.  You have probably seen one on a calculator you've used in the past.

Sunlight is composed of photons, or particles of energy. The amount of energy in a photon corresponds to the different wavelengths of the solar spectrum.  Available solar energy is often expressed in units of energy per time per unit area, such as watts per square metre  (W/m²). The amount of energy available from the sun outside the Earth’s atmosphere is approximately 1367 W/m²; that’s nearly the same as a high power hair drier for every square meter of sunlight!  Some of the solar energy is absorbed as it passes through the Earth’s atmosphere.  As a result, on a clear day the amount of solar energy available at the Earth’s surface in the direction of the sun is typically 1000 W/m².  At any particular time, the available solar energy is primarily dependent upon how high the sun is in the sky and current cloud conditions.  On a monthly or annual basis, the amount of solar energy available also depends upon the location.  Furthermore, usable solar energy is depends upon available solar energy, other weather conditions, the technology used, and the application.  When photons strike a photovoltaic cell, they are either reflected, absorbed or pass right through the cell. Photons that are absorbed by the cell are able to provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are excited and "freed" from the material's atoms.  The exciting of electrons, resulting in a bouncing back and forth, creates friction and therefore heat. The solar cell takes a percentage of these electrons and directs them to flow in a path. This flow of electrons is, by definition, electricity.

The newly created electricity is either used directly or stored in batteries until it is needed.  The power provided by the photovoltaic cell is known as "DC", or "direct current". To run most appliances found in your home the DC power needs to be converted to "alternating current" or "AC", which is the type of electricity which is found in your home in a wall socket. By using an inverter the DC power can be converted into AC power if needed.

The performance of a PV cell is measured in terms of its efficiency at turning sunlight into electricity. Only sunlight of certain energies will work efficiently to create electricity, and much of it is reflected or absorbed by the material that make up the cell. Because of this, a typical commercial PV cell has an efficiency of 15% – about one-sixth of the sunlight striking the cell generates electricity. Low efficiencies mean that larger arrays are needed, and that means higher cost. Improving PV cell efficiencies while holding down the cost per cell is an important goal of the PV industry. The first PV cells, built in the 1950s, had efficiencies of less than 4%.

The concept of using solar technology to power a small calculator is no different than using it for larger scale applications.  OK, a calculator is small, and doesn't require much power, but it also has a very small solar cell (take a look for yourself) and is typically used indoors, therefore, not taking advantage of direct sunlight.  Using larger solar cells, positioning them to take advantage of direct sunlight, and storing the resulting energy can allow you to make use of solar power for much larger applications and even when the sun is no longer in the sky. 

Advantages of Solar Energy

Solar energy has the following advantages over conventional energy:

• The energy from the sun is virtually free after the initial cost has been recovered.         
• Depending on the utilization of energy, paybacks can be very short when compared to the cost of common energy sources used.         
• Solar and other renewable energy systems can be stand-alone; thereby not requiring connection to a power or natural gas grid.         
• The sun provides a virtually unlimited supply of solar energy.         
• The use of solar energy displaces conventional energy; which usually results in a proportional decrease in green house gas emissions.
• The use of solar energy is relatively untapped market. 

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