The power provided by a photovoltaic system is not constant, it varies according to where it is located and when it is measured; the intensity of solar radiation on the ground is influenced by its angle of inclination, which varies throughout the day. It also varies according to the equipment chosen (high-efficiency modules, shadefix, optimisers, micronverters, etc.).
The Sun releases huge amounts of energy in the form of electromagnetic radiation, the radiation that reaches the earth is:
- direct, impacting the panel surface at a single, well-defined angle
- diffuse, in every direction of the atmosphere and affects it at various angles
- reflected (albedo contribution), if the photovoltaic module is not horizontal.
On a clear, dry day, the direct component prevails, whereas on an overcast or foggy day, the diffuse constituent is much more intense.
In both cases it is essential to choose the most suitable panel
- analysing the first case, a clear day in a dry climate: conventional modules provide sub-optimal photovoltaic performance in hot conditions; compared to these, our flagship product maintains its power 2 or 3 times better and produces up to 34% more energy at high temperatures.
- analysing the second case, a day with an overcast sky: the spectral composition is closer to the ultraviolet, to which the cells of which the modules we use are particularly sensitive, thus presenting a good yield even in winter or on days with little sunshine. What’s more, these cells are also immune to the LID effect, which is a loss of performance observed in crystalline silicon modules that occurs in the very first hours of exposure to the sun.
Thus, the electricity that can be produced by a photovoltaic system depends mainly on:
- availability of solar radiation
- orientation and inclination of the modules
- system efficiency
The average annual yield of a photovoltaic system is around 1000-1100 kWh in northern regions, 1200-1300 kWh in central Italy and 1400-1500 kWh in southern regions; lower latitudes enjoy greater exposure to solar radiation because the rays arrive more perpendicular to the surface. The lower latitudes enjoy greater exposure to solar radiation because the rays arrive more perpendicular to the surface. With the same technology, the efficiency of the photovoltaic system will be higher, but thanks to new technologies, it is possible to narrow this margin, just think that even further north, in Austria and Germany, solar panels are much more widespread than in Italy.
The annual energy that is expected to be produced for each kWp can be calculated by multiplying the average annual radiation on the horizontal plane by the efficiency, which takes into account the losses on each component of the system (resistance/loss of the cells at high temperatures, sensitivity of the cells to the ultraviolet spectrum, any shading, presence of shadefix, optimisers or microinverters, dirty module surface, any losses due to reflection, presence or absence of the LID effect…). …), it goes without saying that a well-designed system, with quality materials and professionally installed, will have a higher overall yield.