A New Methodology for Quantifying the Impact of Direct and Diffuse Solar Radiation on Energy Savings in Commercial Office Spaces

Abstract

In this paper, we describe a new methodology for quantifying how direct and diffuse solar radiation impact total energy consumption in a standard perimeter office room by optimizing the allowed daylight penetration for achieving overall energy reduction. Our methodology is different from standard studies that focus on modification of window glazing geometrical, optical and/or thermal parameters and their impact on energy consumption. In our study, we consistently use the same window glazing geometry, and modify the weather file by varying the direct and/or diffuse components of solar radiation. This combination emulates the effect of an advanced dynamic glazing on the incoming solar radiation and is independent of the technology used. Such a glazing would regulate the proportions of direct and diffuse solar radiation to achieve overall energy reduction. In other words, our approach does not try to qualify or evaluate a particular glazing technology, but rather to generate specifications for advanced dynamic glazings that can manage the incoming radiation and hence help drive the development of such advanced dynamic glazing technology.To achieve our goal, we use EnergyPlus to simulate a 6m×3m×3m (length×width×height) office space with a 40% WWR, at all four cardinal orientations. To eliminate any effects that could arise from heat transfer from adjacent rooms — e.g., through walls — we treat those surfaces as adiabatic. In addition, since the front façade wall is the host surface of the window and thus cannot be defined as adiabatic, we intentionally set the façade wall at very high R-value, thus minimizing any thermal impact from that surface too. As a result, the only element responsible for daylight and thermal impact in the office space is the glazing. We present the results by comparing the energy requirements under various solar radiation penetrations into the office, as they are managed by the glazing. We compare the results under non-dynamic and dynamic glazing operation and offer recommendations on the optimum glazing operation for achieving year around energy savings. By investigating the interplay between managed solar radiation, via the emulated advanced dynamic glazing, and energy consumption in the room, we identify and quantify opportunities for energy savings.