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Exclusive Window onto Higgs Yukawa Couplings
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Temperature-dependent growth window of CaTiO 3 films grown by hybrid molecular beam epitaxy
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Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery
Purpose: The authors propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. Methods: In this model, a 360° arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multileaf collimator constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. Results: The authors demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. The authors first obtain a reference plan for intensity modulated radiotherapy (IMRT) using fluence map optimization and 20 intensity-modulated fields in equally spaced beam directions, which is beyond the standard of care. Modeling the typical clinical setup for the treatment sites considered, IMRT plans using seven or nine beams are also computed. Subsequently, VMAT plans are optimized by dividing the 360° arc into 20 corresponding arc segments. Assuming typical machine parameters (a dose rate of 600 MU/min, and a maximum leaf speed of 3 cm/s), it is demonstrated that the optimized VMAT plans with 2–3 min delivery time are of noticeably better quality than the 7–9 beam IMRT plans. The VMAT plan quality approaches the quality of the 20-beam IMRT benchmark plan for delivery times between 3 and 4 min. Conclusions: The results indicate that high quality treatments can be delivered in a single arc with 20 arc segments if sufficient time is allowed for modulation in each segment.
Extension of water-window harmonic cutoff by laser defocusing-assisted phase matching
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Super-insulating aerogel windows: Quadruple-pane thermal performance in a double-pane window
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Performance of Windows in Walls With Continuous Insulation
Window openings in walls are a significant contributor to poor thermal performance because of thermal bridging through the framing members (e.g., studs, joists, plates, bracing) and because windows lack the thermal properties of insulation. Window installation guidance for walls with continuous insulation (CI) is critical for continued market growth of this energy efficiency technology. This research project offers window manufacturers a starting point and a potential path toward developing installation instructions for windows over CI. The objectives of the research include evaluating the common method for installing windows in walls with CI, as well as establishing acceptance criteria for evaluating the performance of windows installed in walls with and without CI. The research measures: 1. The performance characteristics (e.g., water management, structural integrity) of windows in walls without CI. 2. The performance of different thicknesses and types of CI used in walls. 3. The performance of different types of window assemblies (e.g., double-hung windows, mulled double-hung windows, mulled casement windows, and slider windows) installed over CI. 4. The performance of window flange types (e.g., rigid mounting and less robust flanges) installed over CI. 5. Installing windows over CI using baseline installation instructions versus window manufacturer installation instructions. The project’s sequential testing protocol consists of the following: • A water penetration resistance testing adapted from two ASTM standards: E331 (uniform static air pressure in four steps) and E547 (cyclic static air pressure) • A temperature cycling adapted from ASTM E2264 Method B (convective hot air) • A service condition wind loading test adapted from ASTM E330 • A six-month vertical displacement observation phase prior to the structural performance testing • A final water penetration resistance test after vertical displacement observation • A structural performance test adapted from ASTM E330. Key research findings include: • The criterion for passing a water penetration resistance test is that there is no water overflowing at the interior face of the studs. If there is any bubbling or slight pooling of water at the sill, then it must recede after the pressure is removed. Excessive leakage and/or water leaking to the interior face of the framing around the window constitutes a failure. • All single double-hung windows installed directly to lumber or over oriented strand board passed all test protocols. • For most wall specimens, the test results showed that the use of foam sheathing did not affect the performance of the window for water leakage. • All wall specimens underwent temperature cycling. The results indicated that temperature cycling had little to no effect on windows installed over foam sheathing. • For wall specimens that underwent six-month vertical displacement monitoring, the results showed that windows installed over foam sheathing do not sag over time. • The single-hung and double-hung windows installed using window manufacturer installation instructions passed the structural performance test, compared to failures observed in windows that were installed using generic installation instructions. The generic and manufacturer installation methods differed on the following construction details: type of fasteners, fastening patterns on the flanges, and window shimming details. • Additional testing is required to determine methods to improve structural pressure performance of slider windows. Potential solutions that would require additional testing may include fastener spacing, different types of fasteners, masonry window clips, construction adhesive, foam sealant, stronger window flange material, and/or straps.
Evaluation of Energy Efficiency Performance of Heated Windows
Fenestration systems are widely used across the world. There is expansive research on window configurations, frames, and glazing technology, but not enough research has been published on reducing window heat loss through heat application to a pane. The presented study attempted to evaluate the performance of heated windows by developing an experimental setup to test a window at various temperatures by varying the power input to the window. Heated double pane window was installed in an insulated box. A temperature gradient was developed across the window by cooling one side of the window using gel-based ice packs. The other face of the window was heated by enabling power at different wattages through the window. The temperature of the inside and outside panes, current and voltage input, and temperature of the room and box were recorded. The data was used to calculate the apparent effective resistance of the window when not being heated vs. when being heated. The study concluded that, when window temperature was maintained close to the room temperature, the heated double pane window is effective in reducing heat loss by as much as 50% as compared to a non-heated double pane window. When temperature of the window was much higher than the room temperature, the heat loss through the window increased beyond that of a non-heated window. The issues encountered during the current stages of experiments are noted, and recommendations are provided for future studies.
Window Cooling Studies and Disk Vibration Testing on a Subset of Mo-100 Disks
Production of metastable Technetium-99 (Tc-99m), a radioactive tracer that emits gamma rays, is vital to the medical imaging community. Tc-99m is extracted from the decay of Molybdenum-99 (Mo-99) which has a half-life of about 2-3 days. The work presented in this report is part of the NNSA’s mission to produce Mo-99 commercially, within the US, without the use of highly enriched uranium (HEU) in support of nonproliferation and global security. Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 through the irradiation of Mo-100 targets using an electron beam. The NMR target comprises a stack of approximately 60-70 Mo-100 disks with diameter 24 mm and thickness 0.74 mm held in stainless steel laminations, each separated using 0.25 mm thick stainless-steel spacers. The symmetric target stack is housed in an Inconel vessel with two Inconel windows on either side. Two electron accelerators are used to produce 40 MeV, 3.16 µA electron beams each that penetrate the Inconel windows and irradiate the Mo-100 disks. Approximately 90% of the total 250 kW beam power is deposited in the NMR target during the irradiation process, with a smaller percentage adding up to 2.2 kW of heat deposited on the Inconel window. During irradiation, pressurized helium gas flows through thin gaps between the disks cooling the beam window, target disks, disk laminations and spacers. Both NMR and LANL have found during cold testing of the target system (no heat deposition) that the Mo 100 disks undergo significant mass loss and disk breakage due to vibrations induced by the flowing helium gas. The mass loss is not only undesirable due to monetary loss from reduced final quantities of Mo-99, but also due to the hazards associated with radioactive material trapped in the cooling lines and particle filters. The effect of flow rate and target geometry on the flow induced vibrations need to be quantified, and recommendations provided to minimize this mass loss. LANL has previously also tested NMR’s Inconel beam window by heating the window, while flowing pressurized helium, using the average heat deposited on the window. However, the NMR beam is pulsed with a duty cycle of 12.5%, which introduces oscillation in temperature around the nominal 600 °C steady state value with each pulse. Available fatigue curves for Inconel are few, established for room temperature, and they are based on mechanical strain cycles not thermally induced strain as in the NMR target. The effect of pulsed beam heating on the Inconel window therefore needs to be quantified. This report details the experiments conducted to assess the factors that lead to mass loss in the NMR target disks as well as to understand the effect of a pulsed beam on NMR’s Inconel window. This work describes LANL’s experimental characterization of the flow induced vibrations and disk mass loss in a reduced scale set-up containing 5 to 10 Mo-100 disks. We use high speed imaging, displacement measurements and microphone measurements combined with signal processing to estimate the vibration frequency of each disk. The effect of disk thickness, target fit and duration of testing on the mass loss is described. We find that in the current configuration of NMR targets, the vibrations and mass loss on the first disk are minimized, while those in the adjacent disks are highest. The microphone and high-speed image data show that increased flow rates and increased duration of testing increases vibration frequency and mass loss. The mass loss is due to both disk rotation and back and forth motion. There are visible wear marks on the disks with the highest mass loss. We also note that the current NMR window gap reduces flow induced vibrations compared to the previous smaller gaps. Improved target holders significantly reduce disk mass loss to almost negligible quantities. This work finds that the larger window to first disk gap and improved target holder geometry should allow NMR to successfully conduct irradiations with minimal mass loss. The window tests were conducted to understand the effect of a pulsed beam on both the window longevity and to estimate the window temperature and displacement during pulsing. The experiments presented here were performed at significantly low power, due to the limitations of the induction heating system. The window temperature rose to approximately 73 °C with a significantly reduced power of 45 W without beam pulsing. With a 5 Hz pulse rate, 12.5% duty cycle, the window temperature remained constant at 26 °C. These experiments will be repeated with improved coil geometry and reported in upcoming journal papers.
Low-e Storm Windows: Market Assessment and Pathways to Market Transformation
Laboratory and field studies sponsored by the U.S. Department of Energy (DOE) demonstrate that the use of low-emissivity (low-e) storm windows can lead to significant heating and cooling energy savings in homes. This report examines the market for low-e storm windows based on market data, case studies, and recent experience with weatherization deployment programs. It uses information from interviews conducted with DOE researchers and industry partners involved in case studies and early deployment efforts related to low-e storm windows. In addition, this study examines potential barriers to market acceptance, assesses the market and energy savings potential, and identifies opportunities to transform the market for low-e storm windows and overcome market adoption barriers. Based on laboratory testing, case studies, and climate-based modeled energy savings, the installation of low-e storm windows is estimated to reduce heating and cooling consumption by 12 to 33% in residential homes. Individual home savings would depend on the overall condition of existing windows and home as well as climate conditions. Based on these heating and cooling saving ranges, low-e storm windows have a technical potential energy savings – that is, the energy savings that would result if all low-performing windows were covered with low-e storm windows – ranging from 0.7 to 1.96 quadrillion Btus primary (source) energy. Of this technical potential, this study estimates that market adoption of low-e storm windows could reasonably achieve savings of 140 trillion Btus of primary energy annually by 2025, assuming DOE implements a number of market transformation activities directed toward low-e storm window market adoption. To assess the marketability and market adoption potential of low-e storm windows, this study examines and characterizes the benefits and costs of the technology, the size and characteristics of likely target markets, the potential pathways to reach these markets, possible market barriers, and the likelihood of overcoming these barriers. A number of promising market transformation pathways are identified including existing weatherization assistance programs, utility energy-efficiency incentive programs, federally sponsored energy efficiency retrofit programs, standards and rating organizations, and federal building energy-efficiency mandates and programs. By working with storm window manufacturers, installers, energy-efficiency consortiums, and the Federal Energy Management Program, the U.S. Department of Energy’s Building America program could implement a number of targeted outreach, education, and technical assistance programs to help effectively transform the market for low-e storm windows and have a measurable impact on reducing residential energy consumption over time.
Evaluation of Thin Triple-Pane Windows in the PNNL Lab Homes
In recent years, improvements in glass manufacturing have allowed the production of thin triple-pane windows, which are manufactured with a thickness similar to standard double-pane windows. Because this highly insulating “thin triple” glass product can be incorporated into almost any existing window frame and can be fabricated at a modest added cost, the U.S. Department of Energy is sponsoring laboratory and field demonstration testing of thin triple-pane windows to validate thermal performance and installation requirements in real-life field settings. To examine the performance of thin triple-pane windows, the Pacific Northwest National Laboratory (PNNL) evaluated the windows at the PNNL Lab Homes, a matched pair of homes located on PNNL’s campus in Richland, Washington. In this study, one Lab Home contained a complete set of nine thin triple-pane windows, while the other Lab Home contained baseline double-pane windows. The Lab Homes experiments demonstrated significant that replacing clear glass double-pane windows with thin triple-pane windows provided year-round energy savings and reduced peak demand both in the heating and cooling seasons. The Lab Homes experiments also validated other performance benefits of the thin triple-pane windows including reduced condensation potential, more even temperatures throughout the home and near the windows, and reduced sound attenuation through the windows, leaving the home quieter and more comfortable for the occupants.
Results from Laboratory and Field Study of Thin Triple Pane Windows
Heat transfer through windows accounts for a significant percentage of a building’s energy use and adds substantially to the peak cooling load of a home. In recent years, improvements in glass manufacturing have enabled the use of a very thin central pane of glass similar to a cell phone screen to produce a thin triple-pane window, for finished insulated glass units (IGUs) with an overall thickness similar to standard double-pane windows. Because this highly insulating “thin triple” glass product can be incorporated into almost any existing window frame and can be fabricated at a modest added cost, the U.S. Department of Energy sponsored laboratory and field demonstration testing of thin triple-pane windows to validate thermal performance and installation requirements in real-life field settings. Thin triple pane windows were evaluated at the PNNL Lab Homes, a matched pair of manufactured houses located on PNNL’s campus in Richland, Washington and also at 16 different field study sites around the country. The experimental results include a comparison of heating, ventilation, and air-conditioning (HVAC) energy usage, condensation potential, occupant comfort, sound infiltration, and thermal performance. Field study data will be gathered through June of 2022; preliminary results are being shared in this paper. The lab houses are identical except that the reference house had standard double pane windows with assembly U-0.66 and the test house had thin triple pane windows with assembly U-0.19. Across the experimental test days, the daily HVAC savings ranged from 0.2 to 18.7 kWh (3%–18%) for the heating season and from 2.5 to 8.0 kWh (23%–41%) for the cooling season. The higher thermal performance of the thin triple-pane windows also reduced the condensation potential on the interior surface during winter months and provided more even distribution of temperatures throughout the home in comparison to the baseline. In addition to the added thermal performance, the thin triple-pane windows demonstrated significant acoustic benefits, reducing sound infiltration by 8 dB to 10 dB. For the field test portion of the project thin triple pane insulated glass units were produced by two different manufacturers, and then installed without modification into the ½” IGU pockets of the standard double pane frames of four other manufacturers. Field tests performed on existing homes in Washington, Montana, Colorado, and New York compared thin triple pane retrofits to original window conditions (before and after). Field tests at new construction sites in Minnesota, Michigan, and New York compared thin triple pane windows to commercially available solutions such as double pane or traditional triple pane (with a standard-thickness center pane). Field test work is ongoing, but preliminary results appear to follow the sound, surface temperature, and energy improvement results from the Lab Homes comparison. Additionally, reports from builders and installers indicate that thin triples require almost no added time or effort to install and look nearly identical to other windows, indicating the possibility of offering next-level performance with a product that requires very little modification to current production or installation practices, long considered a major barrier to technology uptake in the construction market.
Energy impacts of nationwide window upgrades in commercial buildings
This report presents comprehensive estimates of the energy impacts of nationwide commercial building window upgrades in the United States, using a conservative approach. Windows play a substantial role in determining building energy use and occupant experience. Estimates point to commercial building windows impacting loads that represent more than 6 quads (approximately 6%) of annual primary energy use in the U.S. (Harris, 2022). Beyond heating and cooling loads, windows also have effects on lighting and occupant comfort. The fastest route to improving the energy efficiency of windows in U.S. buildings is upgrading or replacing windows in existing buildings. This is due to poor performance of windows in older existing buildings compared to most new construction, low levels of window replacement, and long window service life compared to energy-using building components. Nationwide window upgrades were considered using the following technologies: • Secondary glazing systems • Double pane (clear and tinted) • Triple pane (clear and tinted) • Electrochromic glazing Nationwide upgrades provide on the order of 4%–6% site energy savings in typical buildings, or up to 26% in buildings with the highest savings potential. Electrochromic windows, with their ability to adapt dynamically to environmental conditions, can provide additional benefits, ranging from median savings of 7.2% in buildings with window to wall ratio (WWR) greater than 10% and up to 28% for some buildings. Savings increase substantially for buildings with higher WWR. This study’s approach focused on isolating the direct energy benefits from improvement in window performance, and does not take into account the following additional benefits from window retrofits, which are likely to be substantial: • Managing peak demand and enabling HVAC equipment downsizing. • Energy savings from customizing upgrades to building type and climate. • Energy savings and comfort improvements resulting from post-retrofit reductions in air leakage. • Non-energy benefits, such as occupant comfort and resilience during extreme weather.
Low-E Storm Windows Gain Acceptance as a Home Weatherization Measure
This article for Home Energy Magazine describes work by the U.S. Department of Energy to develop low-emissivity storm windows as an energy efficiency-retrofit option for existing homes. The article describes the low-emissivity invisible silver metal coatings on the glass, which reflect heat back into the home in winter or back outside in summer and the benefits of low-e storm windows including insulation, air sealing, noise blocking, protection of antique windows, etc. The article also describes Pacific Northwest National Laboratory's efforts on behalf of DOE to overcome market barriers to adoption of the technology, including performance validation studies in the PNNL Lab Homes, cost effectiveness analysis, production of reports, brochures, how-to guides on low-e storm window installation for the Building America Solution Center, and a video posted on YouTube. PNNL's efforts were reviewed by the Pacific Northwest Regional Technical Forum (RTF), which serves as the advisory board to the Pacific Northwest Electric Power Planning Council and Bonneville Power Administration. In late July 2015, the RTF approved the low-e storm window measure’s savings and specifications, a critical step in integrating low-e storm windows into energy-efficiency planning and utility weatherization and incentive programs. PNNL estimates that more than 90 million homes in the United States with single-pane or low-performing double-pane windows would benefit from the technology. Low-e storm windows are suitable not only for private residences but also for small commercial buildings, historic properties, and facilities that house residents, such as nursing homes, dormitories, and in-patient facilities. To further assist in the market transformation of low-e storm windows and other high-efficiency window attachments, DOE helped found the window Attachment Energy Rating Council (AERC) in 2015. AERC is an independent, public interest, non-profit organization whose mission is to rate, label, and certify the performance of window attachments.
End-Use Savings Shapes Measure Documentation: Window Film
This documentation focuses on a single end-use savings shape measure - window film. The window film studied in this analysis, called solar control film, is a passive retrofit solution for windows that does not involve window replacement. This type of film is composed of transparent, tinted, or metalized laminated polyester layers and can be attached to an existing window surface (either on the exterior or interior side of the window). The properties of the window film are designed to shift the thermal and optical performances of the overall glazing system in order to serve various needs the customer would have (e.g., heat, glare). While the practical goal of purchasing and installing a window film varies widely in the real market, this study only focuses on the goal of energy savings, and highlighting the corresponding emissions. Other important aspects that customers typically consider include visual comfort, privacy, aesthetics, ultraviolet protection, etc. Thus, in practice, customers often choose a window film product not only to save energy (or cost) but also to mitigate issues around glare, excessive light, daytime privacy, or inconsistent appearance of the building. Window film products that were modeled in this analysis significantly reduced the solar heat gain coefficient of the overall glazing system, resulting in better energy savings for buildings in hot climate regions. However, significantly reducing the solar heat gain coefficient that can block unfavorable heat during the summer can actually harm blocking favorable heat during the winter. By applying window films on a stock of buildings covering various load and weather conditions, this analysis highlights when (e.g., time of day) and where (e.g., geospacial location) we can save energy with window films.
Empirical assessment of a prismatic daylight-redirecting window film in a full-scale office testbed
Daylight redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. Microstructured prismatic window films can be manufactured using low-cost, roll-to-roll fabrication methods and adhered to the inside surface of existing windows as a retrofit measure or installed as a replacement insulating glass unit in the clerestory portion of the window wall. A clear film patterned with linear, 50-250 micrometer high, four-sided asymmetrical prisms was fabricated and installed in the south-facing, clerestory low-e, clear glazed windows of a full-scale testbed facility. Views through the film were distorted. The film was evaluated in a sunny climate over a two-year period to gauge daylighting and visual comfort performance. The daylighting aperture was small (window-towall ratio of 0.18) and the lower windows were blocked off to isolate the evaluation to the window film. Workplane illuminance measurements were made in the 4.6 m (15 ft) deep room furnished as a private office. Analysis of discomfort glare was conducted using high dynamic range imaging coupled with the evalglare software tool, which computes the daylight glare probability and other metrics used to evaluate visual discomfort. The window film was found to result in perceptible levels of discomfort glare on clear sunny days from the most conservative view point in the rear of the room looking toward the window. Daylight illuminance levels at the rear of the room were significantly increased above the reference window condition, which was defined as the same glazed clerestory window but with an interior Venetian blind (slat angle set to the cut-off angle), for the equinox to winter solstice period on clear sunny days. For partly cloudy and overcast sky conditions, daylight levels were improved slightly. To reduce glare, the daylighting film was coupled with a diffusing film in an insulating glazing unit. The diffusing film retained the directionality of the redirected light spreading it within a small range of outgoing angles. This solution was found to reduce glare to imperceptible levels while retaining for the most part the illuminance levels achieved solely by the daylighting film.
Window Attachments: The Next Big Energy-Savings Measure?
Windows in residential buildings are estimated to generate 29% of all HVAC heating and cooling load, approximately 2.67 quadrillion Btu (Apte and Arasteh 2006). Although more than a third of residential windows are single pane, very few utility programs offer incentives for installation of energy-efficient windows (Bickel et al. 2013). The reason is simple: unless someone is already planning to replace their windows, the payback can often take a decade, if not longer. Preliminary data indicates that some energy-efficient window attachments, such as low- emissivity (low-e) storm windows and interior panels, cellular shades, interior and exterior roller shades and shutters, window films, solar screens, window quilts, and awnings, can deliver cost-effective energy savings. Additionally, the means to reliably identify and compare energy-efficient window attachment products will soon be available through the Attachment Energy Rating Council (AERC), a public interest energy performance rating and certification organization co-funded by the U.S. Department of Energy (DOE) and the window attachment industry. This paper presents, for the first time, national and regional energy savings estimates for cellular shades and low-emissivity storm windows and panels using existing data on household energy savings potential. This paper is an early step in the process of determining the cost-effectiveness of window attachments for utility programs. The next step is for utilities to develop pilot programs to conduct field tests of these products, which will generate the energy savings data to determine if full-scale programs are cost-effective.
Double or Triple? Factors Influencing the Window Purchasing Decisions of High-Performance Home Builders
To better understand why triple-pane windows are so slow to catch on and to inform the development and adoption of a new approach to insulated windows, thin triple-pane windows (or thin triples), Pacific Northwest National Laboratory (PNNL) conducted a market assessment of the window purchasing practices of new home builders in 2018-19. While there are several players who can impact the adoption of new residential window technologies, this report focuses strictly on home builders and the key part they play in new window technology adoption. A better understanding of the motivations, experiences, and concerns expressed by new home builders regarding window purchases could inform efforts to develop and deliver thin triple-pane windows and lead to their widespread acceptance in the marketplace. For the past several years, the DOE has supported the development of a thin triple-pane window that uses a center pane of thin glass and krypton gas fill to produce an insulated glass unit (IGU) with nearly the same weight and the same thickness as a double-pane IGU but with the performance of the heavier, thicker, standard triple-pane windows available today. To conduct this study, PNNL interviewed 29 home builders who have participated in the DOE Zero Energy Ready Home (ZERH) program. These builders include many of the most active builders in the DOE ZERH program. Together, they have constructed 2,534 of the 3,417 homes certified through the DOE program as of April 1, 2019. In 2018, they constructed an estimated 1,040 homes and purchased an estimated 17,800 windows. This report summarizes the key findings from these interviews.