In this work, we present a method of simulating the reflectance spectra of black silicon surfaces using the finite element method. Outlined is the design and verification of a new set of algorithm-controlled geometries, rendering a vast array of different structural permutations, whilst measuring the spectral response of each individually. Our model is focussed on the variation of these geometries within the limits of certain ranged parameters for quantities such as nanowire height, radius, pitch, bend and bunching. Also explored is the variation of nanowire positioning within the simulation domain, leading to the more accurate depiction of non-uniform spacing between any given pair. Reflectance data was collated and averaged from all the random models to reliably determine the reflectance of an entire b-Si surface. The comparison between simulated results and their real equivalents offers the possibility of a simulation model versatile enough to predict the spectra of new and unorthodox designs.