Optimization of building integrated photovoltaic systems

The low irradiance efficiency of photovoltaic modules is important to the optimization of building integrated photovoltaic (BIPV) systems. BIPV arrays are often not facing south and are frequently mounted vertically. Under these conditions, a greater portion of the total sunlight striking the array is diffuse, which is of lower intensity than direct sunlight. A 1 kWp, grid connected array of PV modules was used for assessing the accuracy of an energy performance model developed for BIPV systems. The algorithm for calculating power output of the photovoltaic array is derived from the ideal diode equation. An empirically derived parameter modifies the equation and the resulting model can be used to predict the performance of a variety of PV cell technologies at all irradiance levels.