9 research outputs found
Electrochromic windows for commercial buildings: Monitored results from a full-scale testbed
ABSTRACT Electrochromic glazings promise to be the next major advance in energy-efficient window technology, helping to transform windows and skylights from an energy liability to an energy source for the nation's building stock. Monitored results from a full-scale demonstration of large-area electrochromic windows are given. The test consisted of two side-by-side, 3.7x4.6-m, office-like rooms. In each room, five 62x173-cm lower electrochromic windows and five 62x43-cm upper electrochromic windows formed a large window wall. The window-to-exterior-wall ratio (WWR) was 0.40. The southeast-facing electrochromic windows had an overall visible transmittance (T v ) range of T v =0.11-0.38 and were integrated with a dimmable electric lighting system to provide constant work plane illuminance and to control direct sun. Daily lighting use from the automated electrochromic window system decreased by 6 to 24% compared to energy use with static, low-transmission (T v =0.11), unshaded windows in overcast to clear sky winter conditions in Oakland, California. Daily lighting energy use increased as much as 13% compared to lighting energy use with static windows that had T v =0.38. Even when lighting energy savings were not obtainable, the visual environment produced by the electrochromic windows, indicated by well-controlled window and room luminance levels, was significantly improved for computer-type tasks throughout the day compared to the visual environment with unshaded 38%-glazing. Cooling loads were not measured, but previous building energy simulations indicate that additional savings could be achieved. To ensure visual and thermal comfort, electrochromics require occasional use of interior or exterior shading systems when direct sun is present. Other recommendations to improve electrochromic materials and controls are noted along with some architectural constraints
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Electrochromic windows for commercial buildings: Monitored results from a full-scale testbed
Electrochromic glazings promise to be the next major advance in energy-efficient window technology, helping to transform windows and skylights from an energy liability to an energy source for the nation's building stock. Monitored results from a full-scale demonstration of large-area electrochromic windows are given. The test consisted of two side-by-side, 3.7x4.6-m, office-like rooms. In each room, five 62x173-cm lower electrochromic windows and five 62x43-cm upper electrochromic windows formed a large window wall. The window-to-exterior-wall ratio (WWR) was 0.40. The southeast-facing electrochromic windows had an overall visible transmittance (Tv) range of Tv=0.11-0.38 and were integrated with a dimmable electric lighting system to provide constant work plane illuminance and to control direct sun. Daily lighting use from the automated electrochromic window system decreased by 6 to 24 percent compared to energy use with static, low-transmission (Tv =0.11), unshaded windows in overcast to clear sky winter conditions in Oakland, California. Daily lighting energy use increased as much as 13 percent compared to lighting energy use with static windows that had Tv=0.38. Even when lighting energy savings were not obtainable, the visual environment produced by the electrochromic windows, indicated by well-controlled window and room luminance levels, was significantly improved for computer-type tasks throughout the day compared to the visual environment with unshaded 38 percent-glazing. Cooling loads were not measured, but previous building energy simulations indicate that additional savings could be achieved. To ensure visual and thermal comfort, electrochromics require occasional use of interior or exterior shading systems when direct sun is present. Other recommendations to improve electrochromic materials and controls are noted along with some architectural constraints
Recommended from our members
Electrochromic windows for commercial buildings: Monitored results from a full-scale testbed
Electrochromic glazings promise to be the next major advance in energy-efficient window technology, helping to transform windows and skylights from an energy liability to an energy source for the nation's building stock. Monitored results from a full-scale demonstration of large-area electrochromic windows are given. The test consisted of two side-by-side, 3.7x4.6-m, office-like rooms. In each room, five 62x173-cm lower electrochromic windows and five 62x43-cm upper electrochromic windows formed a large window wall. The window-to-exterior-wall ratio (WWR) was 0.40. The southeast-facing electrochromic windows had an overall visible transmittance (Tv) range of Tv=0.11-0.38 and were integrated with a dimmable electric lighting system to provide constant work plane illuminance and to control direct sun. Daily lighting use from the automated electrochromic window system decreased by 6 to 24 percent compared to energy use with static, low-transmission (Tv =0.11), unshaded windows in overcast to clear sky winter conditions in Oakland, California. Daily lighting energy use increased as much as 13 percent compared to lighting energy use with static windows that had Tv=0.38. Even when lighting energy savings were not obtainable, the visual environment produced by the electrochromic windows, indicated by well-controlled window and room luminance levels, was significantly improved for computer-type tasks throughout the day compared to the visual environment with unshaded 38 percent-glazing. Cooling loads were not measured, but previous building energy simulations indicate that additional savings could be achieved. To ensure visual and thermal comfort, electrochromics require occasional use of interior or exterior shading systems when direct sun is present. Other recommendations to improve electrochromic materials and controls are noted along with some architectural constraints
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Monitored Energy Performance of Electrochromic Windows Controlled for Daylight and Visual Comfort
A 20-month field study was conducted to measure the energy performance of south-facing large-area tungsten-oxide absorptive electrochromic (EC) windows with a broad switching range in a private office setting. The EC windows were controlled by a variety of means to bring in daylight while minimizing window glare. For some cases, a Venetian blind was coupled with the EC window to block direct sun. Some tests also involved dividing the EC window wall into zones where the upper EC zone was controlled to admit daylight while the lower zone was controlled to prevent glare yet permit view. If visual comfort requirements are addressed by EC control and Venetian blinds, a 2-zone EC window configuration provided average daily lighting energy savings of 10 {+-} 15% compared to the reference case with fully lowered Venetian blinds. Cooling load reductions were 0 {+-} 3%. If the reference case assumes no daylighting controls, lighting energy savings would be 44 {+-} 11%. Peak demand reductions due to window cooling load, given a critical demand-response mode, were 19-26% maximum on clear sunny days. Peak demand reductions in lighting energy use were 0% or 72-100% compared to a reference case with and without daylighting controls, respectively. Lighting energy use was found to be very sensitive to how glare and sun is controlled. Additional research should be conducted to fine-tune EC control for visual comfort based on solar conditions so as to increase lighting energy savings
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Effect of outside air ventilation rate on volatile organic compound concentrations in a call center
No abstract prepared
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A Pilot Demonstration of Electrochromic and Thermochromic Windows in the Denver Federal Center, Building 41, Denver, Colorado:
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A Design Guide for Early-Market Electrochromic Windows
Switchable variable-tint electrochromic (EC) windows preserve view out while modulating transmitted light, glare, and solar heat gains. Consumers will require objective information on the risks and benefits of this emerging technology as it enters the market in 2006. This guide provides such information and data derived from a wide variety of simulations, laboratory tests, and a 2.5-year field test of prototype large-area EC windows evaluated under outdoor sun and sky conditions. This design guide is provided to architects, engineers, building owners, and others interested in electrochromic windows. The design guide provides basic information about what is an electrochromic window, what it looks like, how fast does it switch, and what current product offerings are. The guide also provides information on performance benefits if more mature product offerings were available