Between 2004 and 2008, silicon supply constraints caused more than a doubling of raw material cost [14]. In an effort to further reduce production costs, PV manufacturers have tried to reduce the amount of costly semiconductor material used in the module. These initiatives have generated interest in concentrated photovoltaics (CPVs).
CPVs use polymeric lenses and packaging components to focus incident light on encapsulated cells, thereby increasing collection efficiency over a smaller cell area. Concentrated photovoltaic modules constituted 125 peak kilowatts, 0.06% of U. S. PV exports, in 2005, and 27,527 peak kilowatts, 2.8% of U. S. PV exports, in 2008 [15]. This explosive growth is the outcome of increased competitiveness due to improvements in cell efficiency. CPV has the highest cell efficiency, ~28% relative to other technologies, such as
PV
FIGURE 6.5
Depiction of a lens, parabolic mirrors, and reflectors with corresponding tracking requirements.
single crystalline silicon (~25%) and thin-film technologies (~13% to 20%) (Figure 5.4).
PV concentrators use either lenses, mirrors, or a combination to magnify incident irradiance (Figure 6.5). The concentrator type is categorized based on geometric configuration, concentration factor, and tracking requirements.
