Comparative Thermal Simulation of Conventional and Daylight-deflecting Systems with BSDF-based Models in TRNSYS and EnergyPlus
Abstract
Upcoming trends in implementing complex façade systems in the modern architecture of office buildings requires the development of improved methods and validation tools for planning and engineering purposes. For a detailed modeling of complex fenestration systems (CFS) within dynamic thermal simulation tools like TRNSYS17 and EnergyPlus8.0, models based on bi-directional scattering distribution functions (BSDF) are available. Thus, in combination with the well-established software tool WINDOW7 from LBNL, a flexible implementation of different glazing systems including blinds and other shading layers is possible. This paper shows the theoretical concept of CFS modeling including BSDF-data by a new model, which is implemented as beta-version in the multizone building model (Type 56) of TRNSYS17. In cooperation, static validations of the new model with WINDOW7 by comparative simulations under varying system parameters were worked out. Ongoing improvements on the CFS modeling algorithms during the validation process are described in this work. In addition, the TRNSYS model was compared to the validated BSDF model of Energy Plus8.0 under varying boundary conditions. The results of the TRNSYS model show excellent accordance with WINDOW7 under static conditions after optimization. The comparison to Energy Plus 8.0 show slight deviations which result from non-steady boundary conditions. The actual models based on BSDF data allow a complete modeling of daylight deflecting systems for the optical properties, but show still limitations in flexible thermal algorithms especially for complex blind geometries.