Sensitivity of concentrating photovoltaics to solar tracking error

An asymmetric, three-parameter field-of-view (FOV) is defined and proposed as a more comprehensive alternative to the symmetric acceptance angle currently used to characterize concentrating photovoltaic device sensitivity to non-zero angles of incidence of solar irradiance. Normalized contour maps of module response against two-axis solar tracker errors in degrees were generated from module short-circuit current, maximum power, and current at maximum power measurements over a range of solar incidence angles. For each of these performance parameters, a quadric surface was fit using linear least squares to the upper 10% of the module response data set. The three-parameter FOV is defined as the elliptical area enclosed by the largest level curve of the fit surface that can be inscribed within a convex hull representation of the upper 10% data set. Applying this FOV as a tracking-error data filter for efficiency measurements from NREL´s Prototype Concentrator Evaluation Test Bed (OCIV) resulted in an 8% increase in measured efficiency on one of the tested modules.