Concentrated and solar photovoltaic
Solar energy is a renewable energy source that can produce electricity, avoiding gas emissions into the atmosphere (ex. CO2) or waste production. The production of electricity can occur directly via photovoltaic technology, which is based on the properties of some suitably treated semiconductor materials, to generate electricity when they are hit by solar radiation. Generation can occur with flat photovoltaic cells or concentration photovoltaic cells.
The most common material used to make flat photovoltaic cells is Silicon, mono multi-crystalline (85% of world production of modules). Other materials used for cells without concentration are the so-called "thin films", which include:
• Amorphous silicon (a-Si), already present on the market for several years
• Copper indium selenide (CIS) and copper indium gallium selenide (CIGS), extremely promising with module efficiencies of around 11%
• Cadmium telluride (CdTe), which constitutes an excellent choice for module efficiency (approximately 12%) and for the price (the lowest per unit of power generated)
Collectively, PV power installed in the world at the end of 2010 was estimated at 40 GW and the installed PV power in Italy was approximately 10 GW at the end of July 2011.
In order to evaluate the energy performance of photovoltaic systems installed, RSE is carrying out the analysis of the functioning of a sample of photovoltaic plants throughout the country, different from each other by size, type of cells and installation method.
The concentration PV technology is one of the most promising technologies in the renewable energy sector.
Light is concentrated 500-1000 times by a lens system for illuminating high efficiency and small photovoltaic cells (a surface of a few mm2), in this way the expensive photovoltaic material is replaced by the less expensive material used for the lenses (glass, silicone or plastic). The conversion efficiencies achieved by photovoltaic devices based on III-V materials of the periodic table of elements (GaAs, InGaP etc.) now exceed 40%, at concentration factor values only of around 400. The conversion efficiency of concentration photovoltaic modules that use multi-junction cells therefore reach values of around 28%, thanks also to the use of efficient optics. Being able to use only the direct component of solar radiation, the concentration systems require the use of solar trackers.
RSE has created new laboratories in Piacenza for the development and characterization of new materials, cells, modules and concentration photovoltaic systems. The laboratories host a new generation MOCVD reactor for epitaxial growth of III-V materials and equipment for the production process of the devices. There are also test facilities for measuring performance of solar cells and modules in-door and out-door. The activities also include the modeling of innovative semiconductor structures and development of new concept prototypes.