Differential time scale solutions for dynamic boundary conditions within whole-building energy simulation

This paper presents a set of solutions to enable  differential time scales for dynamic boundary conditions within whole-building energy simulation, specifically occupant behavioral adaptations in response to short-term changes in solar and daylighting conditions. The concept is to allow specialized libraries to determine in tandem the state of critical variables, such as window blinds and lighting systems, at higher frequencies than the building domain time step (e.g. 5 versus 60 minutes), and in turn set critical building domain boundary conditions, aggregated over the time step period (e.g. aggregated lighting loads over 60 minutes). The hypothesis is that the strategy would provide substantial savings in simulation time, in principle without penalizing simulation accuracy. Experiments were carried out on single-occupancy and open plan offices, and classrooms, with building domain simulation time steps ranging from 5 to 60 minutes, while allowing specialized libraries to set in conjunction solar and daylighting values and component states at 5 minute intervals. Relative discrepancies were more strongly found for heating loads in single-occupancy offices, yet remained under 5% in all cases. Relative discrepancies in peak cooling demand in open-plan office environments approached 2%. Relative discrepancies for cooling loads and peak heating loads were all under 1% in all cases. Results clearly support the premise that substantial gains in simulation time are possible this way without penalizing simulation accuracy.