The Boeing Company Phantom Works has developed three different prototype photovoltaic concentrator arrays since March 2007. Identified as Prototype A, B and C, the experimentally proven technical characteristics of each design are presented.The concentrator designs utilize a 1 cm 2 multi-junction solar cell assembly in conjunction with SMS non-imaging optical designs [1, 2] manufactured with low-cost mass-producible technologies. Prototype A is an on-axis XR optical concentrator with a 733x geometrical concentration demonstrating a ± 1.73° acceptance angle and 23.7% conversion efficiency. Prototype B is an off-axis free-form XR optical concentrator with a 810x geometrical concentration demonstrating a ± 1.32° acceptance angle and 25.3% conversion efficiency. Prototype C is the most recent off-axis free-form XR optical concentrator with a 801x geometrical concentration and a theoretical ±1.80° acceptance angle demonstrating a conversion efficiency greater than 27.0%. Prototype C is also the basis for the Boeing Proof of Design (POD) module, demonstrating an acceptance angle of ±1.48° and a conversion efficiency of 29.4% (as of May 8, 2009). Manufacturability has been paramount during the design process, resulting in high performance concentrating photovoltaic modules using production quality components.
A novel photovoltaic concentrator is presented. The goal is to achieve high concentration design with high efficiency and high acceptance angle that in the same time is compact and convenient for thermal and mechanical management [1].This photovoltaic system is based on 1 cm 2 multi-junction tandem solar cells and an XR concentrator. The XR concentrator in this system is an SMS 3D design formed by one reflective (X) and one refractive (R) free-form surfaces (i.e., without rotational or linear symmetry) and has been chosen for its excellent aspect ratio and for its ability to perform near the thermodynamic limit. It is a mirror-lens device that has no shadowing elements and has square entry aperture (the whole system aperture area is used for collecting light). This large acceptance angle relaxes the manufacturing tolerances of all the optical and mechanical components of the system included the concentrator itself and is one of the keys to get a cost competitive photovoltaic generator.For the geometrical concentration of 1000x the simulation results show the acceptance angle of ±1.8 deg. The irradiance distribution on the cell is achieved with ultra-short homogenizing prism, whose size is optimised to keep the maximum values under the ones that the cell can accept.
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