William P. Mulligan

Generation 3: Improved performance at lower cost

This paper reports recent progress by SunPower Corporation to commercialize the Generation 3 product. The Generation 3 product has been designed to deliver both increased performance and lower manufacturing cost. Improved performance was achieved through optimization of the diffusion recombination losses. A conversion efficiency of 24.2% was achieved on a champion cell made on production equipment using a production wafer, 155.1cm2 n-type CZ. This result was verified by the National Renewable Energy testing Laboratory. Modules made with Generation 3 cells were measured by NREL to have > 20.4% total area efficiency (>332W with 1.63m2 modules). This paper presents the design changes before detailing the resulting performance.

A mirror-less design for micro-concentrator modules

The authors present a novel nonimaging optics design for a flat-plate concentrator PV power system. The design consists of a conventional primary/secondary lens combination, but uses aspheric and TIR (total internal reflection) lens components in the primary to reduce the focal length and, hence, the thickness of the whole module. Ray tracing simulations indicate that an acceptance angle in excess of /spl plusmn/2.6/spl deg/ can be achieved, which makes this design suitable for light-weight, low-cost tracking systems. The design also has the advantage of being mirror-less, avoiding all manufacturability and reliability issues associated with metallization processes as faced by previous low-profile designs.

Simulation and characterization of high efficiency back contact cells for low-concentration photovoltaics

Herein, the performance of low-cost crystalline silicon solar cells under low to medium levels of concentration is explored. Simulations and experimental results are shown for concentrations up to 20 suns. An efficiency of 23% at 9 suns is achieved on a 34.5 mm x 125 mm solar cell using SunPowers standard production process. Low sensitivity of cell performance to illumination profile and position is also demonstrated.