An official website of the United States government
Windows are one of the main contributors to building energy consumption, and emerging dynamic window technologies offer improved performance. Specifically, NIRfocused window technologies are desirable in climates that consume both heating and cooling energy. However, the whole building energy effects of changeable NIR response of building windows have not been captured, largely due to the lack of an appropriate energy simulation method and NIR-focused window modeling. This study focuses on developing a simulation method that enables the comprehensive evaluation of the whole building energy effects of dynamic NIR modulations. Using an EnergyPlus EMS-based parametric framework, annual energy savings were estimated for a switchable between glass built-in system across three representative cities in ASHRAE climate zones 3, 4, and 5. This NIR-focused technology yielded energy savings of up to 19%. The results demonstrate the effects of NIR-focused window technologies on heating and cooling loads in different climates.
more »
« less
Parametric Energy Simulation Methods for Solar-NIR Selective Glazing Systems
Abstract Solar near-infrared (NIR) selective glazing systems have been proposed by incorporating photothermal effects (PTE) of a nanoparticle film into building windows. From an energy efficiency perspective, the nanoscale PTE forms unique inward-flowing heat by heating up the window interior surface temperature under solar near-infrared, significantly improving the window thermal performance. Also, the PTE-driven solar heat gains are dynamic upon solar radiation and weather conditions. However, the PTE on annual building energy use has not been investigated thoroughly, due to the lack of an accurate and appropriate energy simulation method. In this study, we used the EnergyPlus energy management system to develop a parametric energy model and simulation approach in which a solar-temperature-dependent thermal model was embedded into the parametric energy simulation workflow. Applying this method, we examined the solar near-infrared-dependent PTE-induced thermal performances of glazing systems and their effects on annual heating energy use in representative cold climates (i.e., Zones 4, 5, and 6). The results show that the dynamic model considering the PTE demonstrated more heating energy savings, up to 11.64% in cold climates, as opposed to the baseline model that ignored the PTE. This work presents a method to model and simulate the dynamic thermal performance of windows with PTE.
more »
« less
- Award ID(s):
- 2001207
- PAR ID:
- 10335122
- Date Published:
- Journal Name:
- Journal of Physics: Conference Series
- Volume:
- 2069
- Issue:
- 1
- ISSN:
- 1742-6588
- Page Range / eLocation ID:
- 012129
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Shortwave solar irradiance through building windows may have significant impacts on indoor thermal comfort, especially in near-window zones. Such effects change with intensity and spectral variations of the solar irradiance incident on building windows, which is related to the day of the year, time of day, orientation and dimension of the window, and atmospheric conditions. To assess the effects on thermal comfort, we derived a variable - mean radiant temperature delta based on a proposed spectrally-resolved method to represent the quantity of shortwave solar irradiance incident on occupants and be incorporated into PMV (predicted mean votes)-based thermal comfort models. By characterizing the variations of the calculated PMV values under different solar conditions, the influencing factors to indoor thermal comfort by shortwave solar irradiance were obtained and analyzed. Last, upon a series of parametric settings and numerical analysis, simplified statistical regression models were also established to directly predict spectrally-resolved mean radiant temperature delta and PMV values. This could be convenient and extensively to estimate the solar effects on indoor thermal comfort within the near-window zones.more » « less
-
The effects of solar radiation play an important role in human thermal comfort, especially within the near-window zones. In the incorporation of the solar effect into the thermal comfort model, the comprehensive solar-optical characteristics of windows have to be taken into account, especially when it came to a largely variant or unbalanced spectral distribution of a building window. In this work, we examined the thermal effects varying with different spectral characteristics of glazing systems and also preliminarily proposed a new indicator “thermal effect index (TEI)” that can be used to estimate the impact levels of window systems on indoor users’ thermal comfort in near-window zones. TEI could be used as a benchmark for assessing a window system’s potential impacts on indoor users’ thermal comfort, especially when direct sunlight is enabled in a space.more » « less
-
null (Ed.)Single-pane windows still account for a large percentage of US building energy consumption. In this paper, we introduced a new solution incorporating the photothermal effect of metallic nanoparticles(Fe3O4@Cu2−xS) into glazing structures to utilize solar infrared and then enhance the window’s thermal performance in winter. Such spectrally selective characteristics of the designed photothermal films were obtained from lab measurements and then integrated into a thermodynamic analytical model. Subsequently, we examined the thermal and optical behaviors of the photothermal single-pane window and compared its overall energy performance with the conventional low-e coated single-pane window, in which typical window properties, dimensions, winter boundary conditions, and solar irradiance were adopted. The numerical analysis results demonstrated that the photothermal window systems could yield 20.4% energy savings relative to the conventional low-e coated windows. This research paves an underlying thermodynamic mechanism for understanding such a nanoscale phenomenon at the architectural scale. From the implementation perspective, the designed photothermal film can be added into the existing single-pane windows for energy-efficient retrofitting purposes.more » « less
-
ABSTRACT To understand the potential impacts on both thermal performance and condensation risks of using low-e coatings in buildings, especially in the single-pane sector, in this work, parametric numerical analysis in winter is conducted. Three building glazing models, including the single-pane without low-e coatings (SNL), single-pane with exterior low-e coatings (SEL), and single-pane with interior low-e coatings (SIL), are selected and simulated through COMSOL over a range of outdoor temperature and indoor humidity. The temperature of the interior surface of windows, heat flux through windows, winter U-factor of center-of-glass will be obtained and compared. Additionally, a numerical code is developed in R to compute and plot the condensation temperatures of these three models upon the given indoor humidity levels and simulated surface temperatures. The comprehensive analysis of condensation risks on the glazing inner surface of the three models will be conducted. This parametric simulation effort indicates an interesting feature for a single-pane window: while the SIL gives a substantially lower U than the SNL, it also corresponds to an increased condensation risk under certain limits of external temperature and indoor humidity levels. Upon the resultant condensation temperatures and thermal performance analysis, we can conclude the parameters of the windowpane property, coating emissivity and placement, local climate, and building interior thermal settings must be taken into account collectively when it comes to adding low-e coatings to single-pane windows.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1742-6596/2069/1/012129
