02354nas a2200229 4500008003900000245013200039210006900171260001200240300001000252490000800262520159100270653003201861653001801893653001801911653001201929100002101941700001801962700002101980700001802001700002902019856007602048 2013 d00aAn empirical study of a full-scale polymer thermochromic window and its implications on material science development objectives0 aempirical study of a fullscale polymer thermochromic window and c09/2013 a14-260 v1163 a
Large-area polymer thermochromic (TC) laminated windows were evaluated in a full-scale testbed office. The TC interlayer film exhibited thermochromism through a ligand exchange process, producing a change in solar absorption primarily in the visible range while maintaining transparent, undistorted views through the material. The film had a broad switching temperature range and when combined to make an insulating window unit had center-of-glass properties of Tsol=0.12-0.03, Tvis=0.28-0.03 for a glass temperature range of 24-75°C. Field test measurements enabled characterization of switching as a function of incident solar irradiance and outdoor air temperature, illustrating how radiation influences glass temperature and thus effectively lowers the critical switching temperature of TC devices. This was further supported by EnergyPlus building energy simulations. Both empirical and simulation data were used to illustrate how the ideal critical switching temperature or temperature range for TC devices should be based on zone heat balance, not ambient air temperature. Annual energy use data are given to illustrate the energy savings potential of this type of thermochromic. Based on observations in the field,a broad switching temperature range was found to be useful in ensuring a uniform appearance when incident irradiance is non-uniform across the facade. As indicated in prior research, a high visible transmittance in both the switched and unswitched state is also desirable to enable reduction of lighting energy use and enhance indoor environmental quality.
10abuildings energy efficiency10aSolar control10aThermochromic10awindows1 aLee, Eleanor, S.1 aPang, Xiufeng1 aHoffmann, Sabine1 aGoudey, Howdy1 aThanachareonkit, Anothai uhttps://facades.lbl.gov/publications/empirical-study-full-scale-polymer02423nas a2200301 4500008003900000245013000039210006900169260001200238520147600250653002201726653001601748653002701764653001901791653002201810653001801832653002301850653001801873653001101891100002101902700002401923700001801947700002301965700002401988700001802012700002902030700002102059856004102080 2013 d00aA Pilot Demonstration of Electrochromic and Thermochromic Windows in the Denver Federal Center, Building 41, Denver, Colorado0 aPilot Demonstration of Electrochromic and Thermochromic Windows c07/20133 aChromogenic glazing materials are emerging technologies that tint reversibly from a clear to dark tinted state either passively in response to environmental conditions or actively in response to a command from a switch or building automation system. Switchable coatings on glass manage solar radiation and visible light while enabling unobstructed views to the outdoors. Building energy simulations estimate that actively controlled, near-term chromogenic glazings can reduce perimeter zone heating, ventilation, and air- conditioning (HVAC) and lighting energy use by 10-20% and reduce peak electricity demand by 20-30%, achieving energy use levels that are lower than an opaque, insulated wall.
This project demonstrates the use of two types of chromogenic windows: thermochromic and electrochromic windows. By 2013, these windows will begin production in the U.S. by multiple vendors at high-volume manufacturing plants, enabling lower cost and larger area window products to be specified. Both technologies are in the late R&D stage of development, where cost reductions and performance improvements are underway. Electrochromic windows have been installed in numerous buildings over the past four years, but monitored energy-efficiency performance has been independently evaluated in very limited applications. Thermochromic windows have been installed in one other building with an independent evaluation, but results have not yet been made public.
10abuilding controls10adaylighting10aDemand Side Management10aelectrochromic10aenergy-efficiency10aSmart windows10aswitchable windows10aThermochromic10aWindow1 aLee, Eleanor, S.1 aFernandes, Luis, L.1 aGoudey, Howdy1 aJonsson, Jacob, C.1 aCurcija, Dragan, C.1 aPang, Xiufeng1 aDiBartolomeo, Dennis, L.1 aHoffmann, Sabine uhttp://gsa.gov/portal/content/187967