Optimizing the panel area of a photovoltaic system in relation to the static inverter—Practical results

Abstract Due to poor sizing, grid-connected photovoltaic systems often underexploit the capacity of the static inverter resulting in reduced efficiency and an increase in the cost of energy. The objectives of the present project are: • — to show the effects of an oversized solar module area on the efficiency and profitability of a system • — to define the conditions required for oversizing. The simulations performed in a previous phase of the project showed that higher profitability was attained with the power of the photovoltaic field area sized between 40 and 80% (depending on the conditions) above the nominal power of the static inverter. The validation of these results was obtained from two sites: • — Herdern (near Zurich/Switzerland/lat 47.5°N/long 8.4°E/410 m above sea level) with three installations of 4.4, 3.8 and 3.4 kW S.T.C. for an inverter of nominal 3.3 kW a.c. • — Lausanne (Switzerland/lat 46.6°N/long 6.6°E/410 m above sea level) with three installations of 5.6, 4.0 and 2.4 kW S.T.C. for a static inverter of nominal 3.4 kW a.c. Detailed results are available for tests performed on both installations. The results clearly demonstrate the difference between optimal energy production and optimal energy cost. Finally, recommendations are given for optimization calculations of the photovoltaic module area and new construction directives for static inverters with a view to oversizing are issued.