The Italian expertise
The Italian companies offer top expertise in the production of solar cells and modules, inverters and ultra-thin photovoltaic films, which enable solar energy systems to be integrated into glass and other components of a building’s exterior without detracting from its aesthetic qualities.
The Italian companies are also manufacturers of vacuum solar collectors, offering solutions dedicated to the production of sanitary hot water and complete systems for radiant heating backup. Italy is active in the concentrating solar power (CSP) and photovoltaic concentrating systems (CPV) production, manufacturing mirrors, molten salts tubes and other components.
Solar power plants
Solar energy is the energy produced through the direct exploitation of the energy radiated by the sun on the Earth, collected and accumulated through the various technologies available. Solar radiation constitutes the most abundant renewable resource in terms of available potential.
Solar energy is used to generate electricity (photovoltaic, thermodynamic ) or to generate heat (solar thermal).
The main technologies used to transform energy from the sun into usable energy are:
- Photovoltaic energy, which takes advantage of the properties of special semiconductor elements to produce electricity when stimulated by light;
- Solar thermal energy, which takes advantage of solar rays to heat a liquid with special characteristics, contained in the interior, which transfers heat, through a heat exchanger, to water contained in a storage tank;
- Thermodynamic solar systems, which take advantage of a series of parabolic mirrors linearly constructed to direct the sun's rays onto a receiver tube, that holds a thermal carrier fluid or a series of flat mirrors concentrating the sun's rays at the top of a tower filled with molten salt.
The photoltaic technology allows to transform directly solar energy into electric energy, through the photovoltaic effect, that is to say, exploiting the properties of certain semiconductor materials conventiently "drugged" of generating electricity, when exposed to solar radiation.
The device used for the generation of electric energy is the PV module, composed by some cells of semiconductorn material, linked together electrically; some modules connected in series and in parallel constitute the PV generator.
PV generator and the inverter constiute the main elements of a PV plant, which can be realized with fixed module or tracking.
Electric energy production of a PV plant dipends on some factors:
- available solar radiation;
- modules' orientation, grade and positioning;
- efficiency of the plant's main electric components.
In Italy, for example, fixed modules' optimal exposure is towards south, with a grade of almost 30-35 degrees; considering the plant's overall efficiency 75%, it can be obtained on average with a variariation of the operation equivalent hours included between 1.000 and 1.600 kWh/kWp.
It's possible to collect the PV plants in three cathegories:
1. conventional PV plants;
2. PV plants integrated with innovative features (BIPV);
3. concentration PV plants (CPV).
The first includes the use of conventional PV plants, the second uses non conventional modules and special components, specifically developed to replace architectonic elements, the third is constituted by the set of modules wherein solar light is concentrated though optical systems, on PV cells, allowing a better performance, compared to other technologies.
Number and capacity of photovoltaic plants in Italy
In 2011, Italy was the first country to have new installed capabilities for photovoltaic energy. At the end of 2011, there were 330,200 plants installed, for a total of 12.8 GW of installed capacity and a production of 11 TWh. Over the year, there were 174,220 new units for an additional power of 9,300 MW, almost three times that of the power existing on December 31st, 2010.
The rapid spread of technology testifies the high degree of acceptance. There is at least one production plant for 95% of Italian municipalities (7,730 out of 8,094 in 2011; 876 in 2006) and 95% of existing plants are connected to a low voltage with an average size of 11 kW.
Italy was ranked as second in the world for total photovoltaic capacity in world in 2011 after Germany, and first in terms of new capacity installed in the same year (ahead of Germany).
This is the result of a race which has seen the number of existing plants double each previous year's total since 2007 and more than triple the capacity in operation.
Photovoltaic parks are now relevant. Seasonality, diurnality, intermittency, ubiquity, and concentration on lower voltage levels lead to reconsideration of the management of the national electric system in terms of distributed generation.
|Capacity class (kW)
As of 31 Dec. 2012, Italy had 478.331 PV plants, with a gross maximum capacity of 16.420 MW.
The stock of PV plants mostly included those supported under the Conto Energia scheme, except for those receiving Green Certificates or other incentives.
In 2012 the number of the installed plants has grown up. Thy were up by 148.135 units, + 44,9% of plants existing in Italy at the end of 2011, and the triple of the italian plants at the end of 2010.
Installed capacity has reached 16.420 MW. The stronger increase, in percentage, has involved the plants in the range of 3 to 20 kW (+47,2 %).
|Average Size (kW)
||2012/2011 % change|
The average size of the plants reduced from 38,7 kW of 2011 to 34,3 kW of 2012.
This event is dued to the reduction of the big plants’ installation, determined by the Decree Law 1/2012, that has limitated the PV ground installed.
At the end of 2013, there were more than 550,000 plants installed, for a total of more than 17.5 GW of installed capacity.
The value of world installed capacity in the year 2013 , has allowed Italy to occupy the first places of the world's market, before China, Germany, United States and Japan.
Thermodynamic solar systems
The operating principle of a solar thermodynamic plant, that is the indirect invertion of solar energy into electric energy, can be divided in two subsequent phases: solar energy is transformed in thermal energy through the heating of a heat transfer fluid: this thermal energy is later inverted in electric energy by means of a conventional thermodynamic cycle.
During the first phase, reflecting elements channel solar rays to heat, at high temperature, the heat transfer fluid, feeding a power grid which, as a traditional station, exploits the heat to produce electricity.
Thermodynamic plants differ from the type of system used to capture direct solar energy:
- plants with solar mirror field and central tower (Solar Tower);
- plants with linear parabolic collectors (Parabolic Trough);
- plants with circular parabolic collectors (Dish Stirling);
- plants with linear collectors of Fresnel (Linear Fresnel Reflector).
In the first case there are plane mirrors channeling solar rays towards a collector standing on top of a very high tower, in the other cases there are parabolic or linear collectors that concentrate the heat towars a tube collector that can be crossed by a fluid or a gas.
The equivalent hours of an annual operation, related to the solar quote, of a thermodynamic plant, vary according to the presence or not of a thermal stockpile system of the capted energy, for example with a stockpile system they vary between 3.500 and the 5.000.
The solar thermodynamic plants, unlike the PV plants, exploit the direct solar radiation, so that the electric energy production is directly linked to the available solar radiation; for this reason, their application is efficient only in the areas where the climate is sunny most part of the year.
Solar thermal energy
Thermal solar plants are constituted by panels producing hot water, exploiting solar energy.
Solar radiation heats up a liquid circulating inside a receiver (collector or panel), conveniently isolated to limit heat dispersion towards the external surrounding. This liquid, so, transfers the absorbed heat to a water stockpile tank.
Use of hot water collected in the tank, instead of the water produced by a bolier or by an electric water heater, allows to save on gas consumption or on electric energy.
Thermal solar plants are usually used to produce sanitary hot water, to heat up buildings and also to heat production in the industrial and agricultural sector.
Thermal solar panels can also be used for the summer refreshment through the use of solar cooling plants.
Technology used in the thermal solar plants is simple and reliable and allows, in general, to obtain relevant energy savings against low costs of investment.