D7 Electrical and Photovoltaic Installations

Topic

Sizing an electrical installation involves meeting two independent criteria simultaneously: the conductor must be capable of carrying the expected current without overheating, and the voltage drop along the cable run must not exceed regulatory limits—a requirement that, in practice, necessitates using cables with larger cross-sections as the distance increases for a given power load.

In solar photovoltaic generation, the energy produced by a system depends on the solar radiation striking the panel array—the same radiation addressed in the passive solar design and integrative project modules—as well as the installed area and the panels' conversion efficiency; however, it also depends on an overall performance factor that accounts for all actual system losses—such as wiring, panel heating, accumulated dirt, and inverter conversion—and which remains relatively high in well-designed installations. The inverter, responsible for converting the direct current (DC) produced by the panels into the alternating current (AC) used by the building, also has its own conversion efficiency—very high in modern equipment—which determines how much of the energy captured by the panels actually becomes usable.

To assess the profitability of a photovoltaic installation, the initial investment plus operation and maintenance costs over its entire service life are compared against the total energy expected to be produced during that same period; this yields a cost per unit of generated energy, allowing the installation to be compared with any other electricity source.

Thus, this module—which begins by outlining two simultaneous criteria for electrical conductors—concludes by demonstrating that the energy ultimately delivered by a photovoltaic installation is the result of a chain of successive efficiencies (panels, system, and inverter), where a single weak link diminishes the performance of all the others.

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