1. ENEL GREEN POWER Enel solar laboratory Catania 03/03/015

2. ENEL GREEN POWER The Enel Green Power is one of the most important solar industries of Sicily, it is located in Catania. It has a good concentration and a good exposure to the sun, it reaches the maximum value of GHR (Global Horizontal Radiation) in June with 900 W/m^2

3. Solar Energy The potential of solar energy in the world, with particular reference to photovoltaics are very large: according to the EPIA (European Photovoltaic Industry Association) in the last ten years, the photovoltaic industry has grown in the world at an average rate of 35%

4. The photovoltaic process The direct conversion of solar energy into electrical energy is produced with the photovoltaic cell, and uses the physical phenomenon of the interaction of light radiation with valence electrons in semiconductor materials, called the photovoltaic effect. Whatever the material used, the mechanism by which the cell transforms sunlight into electrical energy is essentially the same.

5. ENERGY OF SOLAR RADIATION E= h x c/λ = hvλ h= 6,625 x 10^-34 J*s (plank constant) materials and electrical conduction CONDUCTOR 10 ^23 10^-6 SEMICONDUCTORS 1,45 x 10^10 2,3 x 10^5 INSULATIONNo concentration electric 10^14 MaterialCarriers concentration (cm^-3) resistivity

6. Energy gap is the phisical work necessary to move an electron from valence band to conduction band. PV Cell: 1)Photon, small particel like balls, creates a HOLE/ELECTRON pairs 2)P-n junction creates an electric fiel E which separates electrons and holes created by photons 3)In an external circuit a current occurs

7. STC (Standard test conditions) Gsun= 1000 W/m^2 1,5 atm T=25°C I-V curve: electrical parameters of a PV cell

8. Cell energy losses: Reflection of sun light on the cell front surface Hv > Eg Heat dissipation of photon energy Responses of semicondoctor material is spectral dependent Electron-hole recombination

9. In the Enel Green Power located in Catania, engineers study and test PV cell put in different ways for one month, one year, ten year to find the best solution for every place with other conditions and compares them. We know that in each country, nation or part of the world there are different climate conditions that influence the choose of PV technologies. 1) The inclination of the roof; 2) Temperature: too hot or too cold temperature reduce the energy production; 3) shadow: just on cell in a shadow zone can influence all the system of production. The best inclination of the system is given by the latitude of the zone

11. PV cells of fotovoltaic system are ensured for 25 years. The energy production has a reduction of 15% and every seven years it necessary changes the inverter INVERTER: it converts the DC corrent (continuos corrent) in AC corrent (alternate corrent).