A model for predicting the solar reflectivity of the ground that considers the effects of accumulating and melting snow

Simulation tools for predicting building thermal performance and solar system performance must accurately calculate solar irradiance to surfaces of arbitrary orientation. This is imperative to correctly predict passive solar gains to buildings and to accurately estimate thermal and electrical production of solar collectors. In cold climates, where snow covers the ground for long periods of time, ground reflected radiation can represent a substantial fraction of the total incident irradiance to highly tilted and vertical surfaces (e.g. windows). A new model has been developed to improve the calculation of ground-reflected radiation in simulation tools. The model is based upon empirical observations taken at a measurement site in Ottawa (Canada), and has been validated using disjunct data from the measurement site, and with published data from two other sites in the USA. The model was found to increase the accuracy of ground reflectivity predictions for cold and humid climates.