Close up of a 35 kW concentrating solar unit
AMONIX
Concentrating light on a solar cell greatly increases its output. With improvements in technology now starting to offer efficiencies of 38%, the concentrating PV sector says that US$3/W systems are just a couple of years away.
CENTRATING PV - THE BASIC PRINCIPLE The principle of concentrating PV (CPV) is quite straightforward. In the familiar 'flat-plate' PV modules, a large area of photovoltaic material (usually crystalline silicon) is exposed to the maximum naturally occurring sunlight. Normally, that maximum is achieved by installing the modules at an incline optimized for the latitude, but sometimes they are installed on moving frames that can follow, or track, the sun as it passes across the sky. The PV cells perform under direct (sunny) or diffuse (cloudy) radiation conditions, but output is at its highest when the maximum amount of light falls on the cells (assuming there are no detrimental effects from overheating). The amount of light that falls on a cloudless day (this varies according to location and season) is regarded as one 'sun', which is defined as 1000 W/m2.
BENEFITS OF CPV - First among the main benefits of concentrating PV is its efficient use of solar cell material.For a given electrical output, concentrator systems use a far smaller amount of (expensive) semi-conductor or solar cell material than flat-plate systems. The large areas of mirrors or lenses used to provide optical concentration are inexpensive compared with large areas of solar material, so this can keep system costs low.
The manufacturing process is lower-tech than for flat-plate modules it can be scaled up relatively easily and economically, giving concentrating technology a further advantage, says sector insiders.Table 1 shows an estimation of manufacturing investment costs.
TABLE 1. Investment required for a 100 MW/year manufacturing plant1 Technology Cost (US$ million) Crystalline silicon PV 150-300 Thin-film PV 150-300 Concentrating PV 30-50
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