A photovoltaic power plant directly transforms solar energy into electrical energy. It is essentially composed of: a series of photovoltaic panels (or modules), various electrical panels and connecting cables, one or more inverters, one or more voltage transformers, accessories (electrical cabinets) where necessary, and metal supporting structures.
A typical medium-size plant (1.0 MWp, for example,) is composed of a series of silicon panels arranged in a regular pattern: roughly 4,500 modules covering a net surface area of approximately 7,000 m2, corresponding to a gross surface area of 20,000 m2.
Each panel generates its own flow of current that, combined with the others, is collected and sent to the inverter. The current leaving the panels is direct current, while the mains network supplies alternating current. The inverter transforms direct current into alternating current.
Alternating current up to 1,000 amperes, with roughly 230 V, leaves the inverter. Before it leaves the plant and is introduced into the grid, the current must pass through the final stage consisting of the transformer, which raises the 230 V low-voltage current to medium voltage (normally 20,000 V) suitable for long-range transmission.
The quantity of energy produced and introduced into the grid is measured by appropriate ‘fiscal’ energy meters which are regularly checked and calibrated.
Polycrystalline photovoltaic modules have now reached an average conversion efficiency of roughly 15%: this means that merely 15% of the energy harnessed from the sun can be converted into energy, while the remaining part ‘escapes’ the energy conversion process. Scientific research continues to progress and industry performance grows year after year, for the benefit of future generation modules and power plants.