Analysis of the performance of prism daylight redirecting systems with bi-directional scattering distribution functions

Abstract

Simulation with two types of bi-directional scattering distribution function (BSDF) was used to model the prism daylight redirecting fenestration (PDRF) in the indoor luminous environment. A goniophotometer was used to develop two different BSDF data sets: Klems data and Tensor tree data. Coefficient of determination and linear regression of the illuminance values with Klems and Tensor tree BSDF data were analyzed at low, medium, and high solar altitudes under Perez sky models with various sky conditions. The comparisons indicate that the Klems and Tensor tree angular data of PDRF materials show strong correlations and good linear regression relationships in general with PDRF daylighting clerestories. The study results demonstrated that using measured Klems data for combined daylighting and energy simulation of PDRF system is feasible as the simulated illuminance levels with Klems and Tensor tree data are similar under Perez sky conditions. The simulation results also showed that the PDRF daylighting windows above vision windows increase the work plane illuminance (WPI) opposite the window wall under clear sky conditions.