Developed in the mid 20th century in space exploration programs, photovoltaic technology (FV) is rapidly expanding for applications on Earth, such as powering isolated users or systems installed on buildings and connected to an electric grid.

The operation of photovoltaic devices is based on the ability of certain semiconductor materials, when properly treated, to convert solar radiation energy into electric energy in a continuous current flow without the need for moving mechanical parts. The semi-conductor material that is almost universally used for the purpose is silicon.

The base component of a FV system is the photovoltaic cell, which can produce about 1.5 W of power under standard conditions. Several cells assembled and connected to each other in a single structure form a photovoltaic module, which has a power of between 50 and 100 watts. Several modules can be connected in a series of a “string”, which then in turn can be connected in parallel to form a photovoltaic generator of the desired power. The transfer of energy from the photovoltaic system to the user is accomplished through additional devices needed to transform the continuous current produced by the modules and adapt it to the needs of the final user.

Given their modularity, the photovoltaic systems are highly flexible in their usage. Based on their electric configuration, the photovoltaic systems are generally separated into:

• stand alones
  
• grid connected
  
• photovoltaic plants
  
• systems integrated in buildings

The worldwide photovoltaic market has developed considerably in recent years, with an exponential growth in installed power. The highest increases have been seen in Japan, the United States and Germany, primarily because of incentivization programs by the governments, which subsidized the installation of FV systems, and, in some cases, bought excess electricity produced by these plants and put it back into the grid at a price much higher than that of selling traditional electricity. In Italy, after a period of major activity in the early 1990s, the market experienced severe slowing, primarily due to the lack of adequate incentivization mechanisms.

Starting in September 2005, photovoltaic energy got new life from a decree that provides highly advantageous incentivized rates, as well as the option to trade on site an annually adjusted sale of solar energy to the electric distributor. Plants can be chosen in the three categories of 20 kW, from 20 and 50 kW, and up to 1 MW with incentives that last for 20 years. For details, visit GRTN's web site

Advantages of solar energy

• The energy source is unlimited and well distributed
  
• There are no moving components and therefore it has an operational life span of over 25 years
  
• Minimal maintenance is required to keep the system functioning
  
• The systems are modular and can be easily installed in different sizes, from kilowatts to many megawatts.
  
• Photovoltaic systems can be integrated on structures and buildings and therefore no additional land area is required
  
• It produces no noise, toxic emissions or polluting gase