To quantify the performance of an installation, the annual energy produced using a photovoltaic system depends upon 3 parameters: the irradiation collected, the peak power and the yield of the installed panels.
The performance ratio is a criteria used for the evaluation of the quality on a photovoltaic system, because of all the components characteristics are taken into account within the calculations.
This ratio is defined by the comparison between the real yield of the photovoltaic system and the theoretical data achievable. The calculation enables to obtain values which are independent from the peak power, the geographical inputs, the global solar radiation and the orientation of the panels.
The general value got on a reasonably efficient installation reaches 75 %.
The performance ratio depends on converters possibilities, losses within the cables, shadows effects, modules temperatures and temperature correction factor, good connections of the modules in series etc...
The peak power of a photovoltaic cell summarized Wp (Watt peak), represents the maximum electrical power delivered within standard conditions: solar irradiation of 1000 Watts by m², temperature of 25° Celsius and atmospheric pressure of 1,5 bar. These conditions are rare in reality, so the practical power reached by the panels differs from lab standards values. The main interest of this parameter is the possibility available to compare between them the different kind of possible equipments.
Quantity of energy collected by the photovoltaic captors (in Wh/m2). The irradiation depends upon the kind of panels used (that is to say fix, uniaxial, biaxial or azimutal) its orientation (azimutal ?) and the angle of the surface vs the verticality, the latitude of the place and its pollution level, the period of the year and the moment within the daylight time, the nature of the clouds etc... The European Union issued maps for the solar radiation average values, which give all the necessary data (in kWh/m2/an). More
The « Energy Pay Back Time » corresponds to the ratio between the total energy consumed by the PV installation among its production, transportation, installation, recycling and the corresponding energy produced during a normal year. The EPBT reaches 2 years for mono-crystalline Silicon cells and about 1 year for the amorphous silicon panels. The duration life time of panels is nowadays of 20 to 30 years. After 20 years, the cells still produce 80 % of their original yield.
The yield of a photovoltaic cell with multi-crystalline silicon varies from 13 to 16 % on average. Consequently, 1 m2 of cell will produce about 150 Watts - peak (Wp) and will produce practically in France, according to the regions, on average between 140 to 190 kWh/year of electrical energy to the network.
The quantity of CO2 rejected into the atmosphere avoided in France is about 40g eq. CO2 by kWh. The equivalent European value is 372g eq. CO2 by kWh produced, because of some European countries still use massively coal as electricity production source.
The energy consumption necessary for the production of the photovoltaic systems is comparable with the equivalent data coming from the other industries (coal, gas, oil , nuclear...) the main difference being that there are no unrecyclable materials at the end of the life time process (no wastes).