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Title: Examination of the technical potential of near-infrared switching thermochromic windows for commercial building applications

Current thermochromic windows modulate solar transmission primarily within the visible range, resulting in reduced space-conditioning energy use but also reduced daylight, thereby increasing lighting energy use compared to conventional static, near-infrared selective, low-emittance windows. To better understand the energy savings potential of improved thermochromic devices, a hypothetical near-infrared switching thermochromic glazing was defined based on guidelines provided by the material science community. In this paper, EnergyPlus simulations were conducted on a prototypical large office building and a detailed analysis was performed showing the progression from switching characteristics to net window heat flow and perimeter zone loads and then to perimeter zone heating, ventilation, and air-conditioning (HVAC) and lighting energy use for a mixed hot/cold climate and a hot, humid climate in the US. When a relatively high daylight transmission is maintained when switched (Tsol=0.10–0.50 and Tvis=0.30–0.60) and if coupled with a low-e inboard glazing layer (e=0.04), the hypothetical thermochromic window with a low critical switching temperature range (14–20 °C) achieved reductions in total site annual energy use of 14.0–21.1 kW h/m2-floor-yr or 12–14% for moderate- to large-area windows (WWR≥0.30) in Chicago and 9.8–18.6 kW h/m 2-floor-yr or 10–17% for WWR≥0.45 in Houston compared to an unshaded spectrally-selective, low-e window (windowmore » E1) in south-, east-, and west-facing perimeter zones. Finally, if this hypothetical thermochromic window can be offered at costs that are competitive to conventional low-e windows and meet esthetic requirements defined by the building industry and end users, then the technology is likely to be a viable energy-efficiency option for internal load dominated commercial buildings.« less
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  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Building Technology and Urban Systems Dept.. Environmental Energy Technologies Division
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0927-0248; ir:187530
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Solar Energy Materials and Solar Cells; Journal Volume: 123
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B); California Energy Commission (United States)
Country of Publication:
United States
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 14 SOLAR ENERGY; thermochromic; windows; solar control; daylighting; building energy efficiency