Semprius' two-stage pupil imaging concentrated photovoltaic (CPV) module design incorporates extremely costeffective
glass ball secondary lenses in addition to plano-convex primary lens arrays. Optimization of the optical
concentrator design involves modeling the illumination uniformity of the primary aperture (the 'pupil') on the multijunction
solar cell in response to the secondary lens index, diameter, surface quality, location, and tolerance offsets. We
reconcile our theoretical model with experimental results from a single fully adjustable 'concentrating unit cell', and we
thereby create a robust model for design updates, for tolerance and sensitivity modeling, and for prediction of full
module and on-sun tracker performance based on receiver placement relative to our primary lens array. In this paper, we
discuss the rationale behind our optics approach, our criteria for optimizing our optics, and our tolerancing approach.
Then we discuss our experimental approach, including our universally adjustable 'concentrating unit' fixture, our light
source, and our primary and secondary optics. We show sensitivity curves of our 'concentrating unit' performance to
receiver placement, and ball lens size. We reconcile these with our ray-traced model, and, finally, we show predicted
module performance based on receiver tolerance data and receiver wiring in the module using a parameter driven high
level circuit model.