Concentrating PV technologies

Abstract

The current state of solar cell development is illustrated in Figure 46.1. While single-junction silicon solar cells dominate today’s solar industry, the rapid rise in efficiency versus time (experience curve) of the multijunction cells makes this a particularly attractive technology path. The high efficiency, in comparison with single junction cells, such as silicon, is obtained by stacking several junctions in series, electrically isolated by tunnel diodes, as explained in Chapter 44. These can be qualitatively viewed by adding the voltages of three junctions in series, while maintaining the current of a single junction (Figure 46.1). Under concentrated sunlight, multijunction (GaInP/GaAs/GaInNAs) solar cells have demonstrated an efficiency of 44.4% within the lab, as compared to silicon cells’ best efficiency of 25%. This means that, in sunny areas, a multijunction concentrator system can generate almost twice as much electricity as a silicon panel with the same area.