Utilization of irradiance ratios for calculating the effect of reflections from obstructions in building energy simulati
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Utilization of irradiance ratios for calculating the effect of reflections from obstructions in building energy simulation
Politecnico di Milano, Department of Architecture and Urban Studies (DAStU), via Bonardi 3, 20133 Milano, Italy
Abstract
Keywords
The ability to take into account reflections from obstructions is of fundamental importance in
irradiance ratios,
building energy simulation (BES), because reflections can have a substantial influence on solar
shading factors,
gains. In BES tools, this ability is often implemented duplicating functionalities that have already
analogue models,
been solved efficiently in lighting simulation tools. This happens because importing those
solar reflections,
functionalities from a lighting simulation tool (source) into a BES tool (target) is usually a complex operation producing non-portable results. This article demonstrates that this ability can be imported modularly and portably without intervening in the internals of the two tools. This can be obtained by: (1) creating, in the source tool, pairs of models which are analogue—on the one hand—to the original model in the target tool, and—on the other hand—to the model in the
Research Article
Gian Luca Brunetti ()
insolation factors
Article History Received: 15 October 2019 Revised: 22 June 2020 Accepted: 31 August 2020
target tool hypothetically enriched with some predictive ability only available in the source tool; (2) measuring, at each time step, the ratio between the performances predicted by the source tool
© Tsinghua University Press and
as regards the two analogue models; (3) re-scaling, at each time-step, the performance predicted
Springer-Verlag GmbH Germany,
by the target tool on the basis of that ratio. When appropriate analogue models are utilized, this
part of Springer Nature 2017
strategy enables distinct simulation tools to work like an integrated computing unit.
1
Introduction
E-mail: [email protected]
Building Thermal, Lighting, and Acoustics Modeling
In building energy simulation (BES) tools, the ability to take into account solar reflections from obstructions is of fundamental importance to simulate the thermal behaviour of buildings. Indeed, the influence of reflections is pervasive, because interreflections operate at various scales in the built environment, as an effect of both shading devices and buildings (Figure 1). But also, the effects of reflections are complex, and can influence thermal gains substantially. In some situations, the reflective action of obstructions can influence solar gains even more than their obstructive action, depending on the geometries at play and on the type of reflections (Figure 2). The types of reflections, the size and distance of reflectors, and, therefore, the view angles involved, can have a substantial influence on the amount and timedependence of solar gains. In particular, the time-dependence of the effects of specular reflections is greater than that of diffuse reflections (Figure 3); and as a result, specular reflections
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