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Optimizing building performance through the integration of electrochromic glass technology in building facades: a simulation-based study of an office building in Cairo, Egypt
Abstract
Purpose
The built environment enhances quality of life, prompting architects and engineers to explore innovative technologies for improving building performance. Electrochromic (EC) glass technology is one such solution that offers real-time control of building facade glazing properties. Conventional building materials often struggle to adapt to changing external conditions, increasing reliance on mechanical systems. EC glass technology addresses this by adjusting its tint in response to these conditions, potentially reducing energy consumption and improving comfort.
Design/methodology/approach
This study investigates the advantages of integrating EC glass technology into building facades by evaluating its efficacy in enhancing thermal performance, energy efficiency, and operational expenses. The study uses building performance simulation software to model a proposed office building in Cairo, Egypt, comparing two scenarios: one with conventional glazing and the other with EC glass technology. The aim is to highlight the benefits of EC glass technology in building facades for improving thermal comfort, daylighting and energy efficiency. The analysis will compare cooling and heating designs and energy consumption, ultimately concluding the technology’s impact on enhancing energy efficiency.
Findings
Integrating EC glass technology significantly reduces solar heat gains and heating, ventilating and air conditioning (HVAC) energy consumption. Solar heat gains dropped by 77.47%, resulting in a 50.95% decrease in HVAC energy use compared to conventional glazing. This technology also enhances thermal comfort and daylighting, improving the indoor environment.
Originality/value
Then, integrating EC glass technology improves building performance, resulting in energy savings, enhanced comfort and efficient daylight use. This technology is essential for sustainable building design, contributing to resilient and enjoyable environments.
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This study investigated the thermal, visual environments of real-life climate chambers installed with a full-scale dark gray electrochromic glass window (ECW) under tropical climate in Singapore. Two large-scale climate chambers were built and installed with electrochromic windows or 6 mm single clear glass for comparison, and their thermal and visual performances and effects on the efficiency of air-conditioning were real-time measured and analyzed in detail. Compared to the chamber installed with 6 mm glass, the coefficient of performance (COP) of the air conditioner can be enhanced by 29.64 % and 45.40 % if replaced by bleached and tinted ECWs, respectively. Our study shows that ECW can efficiently reduce around 80 % of the heat flux passing through the indoor under both states, and provide a cooler and more comfortable thermal environment. In contrast, the bleached ECW showed the best performance with 39 % of the daytime spent with a comfortable visual environment without glare. With a 4 % solar heat gain coefficient and a 0.1 % visible light transmission, the fully tinted ECW could reduce the mean radiant temperature and operative temperature by up to 4.7 °C and 11.6 °C, respectively, when compared to the 6 mm glass. The operative temperature of the chamber with fully tinted ECW was even 0.6 °C lower than that of the bleached state. In conclusion, the fully gray tinted ECW showed superior thermal performance with high energy efficiency, and the bleached state gave better visual environment comfortably and economically.
This study comprehensively evaluates the energy-saving potential and visual comfort aspects of electrochromic (EC) smart windows in a hot-humid climate office building. Using an advanced building simulation tool, EC windows are compared to conventional low-E glazed windows, considering two control triggers: daylighting level and glare control. The primary objective is to determine energy savings achievable with EC windows while addressing visual comfort. Detailed analysis of the building’s energy performance and indoor environment is conducted. Results show significant energy savings of 23% with EC windows using daylighting control but limited visual comfort in some zones. Conversely, EC windows with glare control achieve 17% energy savings while maintaining visual comfort throughout the building. These findings highlight the potential of EC windows with glare control in saving energy and maintaining visual comfort in hot-humid office buildings. Further research is needed to optimize performance for different building types and climates. In conclusion, this study provides insights into energy-saving capabilities and visual comfort considerations with EC smart windows, emphasizing the importance of appropriate control triggers for maximizing energy savings and occupant comfort. Future investigations should explore EC window performance across diverse building typologies and climates to enhance the benefits of this innovative technology.
One method in terms of architectural technology used to minimize the negative impact of overheating is to design a building with double skin façade and integrating it with electrochromic glass. The purpose of this research is to reveal whether the use of a double skin façade and the application of electrochromic glass would be preferable for buildings in tropical climates, in terms of obtaining aesthetic points while not having to sacrifice thermal comfort nor committing energy waste at the same time. The data in this research is obtained with qualitative – descriptive comparative method, which is applied for room temperature measurement with a computer simulation software, based on pre-existing theories, reference standards and material specifications from existing manufacturers. The results of this study conclude that the application of double skin façade in a building does make a significant contribution to achieving thermal and lighting comfort. Both profiles of space reduction with the use of electrochromic glass in buildings in tropical climates are able to reach ideal temperatures in comparison to when ordinary glass material is applied. And third, it is proven that the double skin façade technology and applying electrochromic glass on a building can provide significant energy efficiency for long-term projects.
https://books.google.co.in/books?id=bytQEAAAQBAJ&pg=PA40&lpg=PA40&dq=sharma,Applications+of+nickel-titanium+alloy,+Journal+of+Engineering+and+Technology&source=bl&ots=1MuNkSIfoy&sig=ACfU3U0_zd86Tvex8niN6gpzJXcfue2qgg&hl=en&sa=X&ved=2ahUKEwj93YWv5LP0AhXYSGwGHdUjCzwQ6AF6BAgSEAM#v=onepage&q=sharma%2CApplications%20of%20nickel-titanium%20alloy%2C%20Journal%20of%20Engineering%20and%20Technology&f=false
Adaptive facades, like electrochromic (EC) smart windows, represent the next generation of glazing with dynamic modulation of transparency, to suitably modulate the daylight and solar energy entering buildings. A study is reported, dealing with the manifold effects of building integration of an innovative solid-state EC device, assessing effects on the building energy balance and daylighting performance, in terms of Useful Daylight Illuminance (UDI) and Discomfort Glare Index (DGI). All the analyses were carried out using the experimental results, reporting the main figures of merit of EC devices as an input for building simulations, in the EnergyPlus software.
Electrochromic windows can play an important role for energy saving as well as for controlling the visual and thermal conditions inside a room. This paper starts with a critical review and the state-of-art regarding the products today commercially available as well as the studies conducted on full scale electrochromic windows. The analysis allows to define the main parameters characterizing the electrochromic windows with particular regard to their optical, thermal and electrical characteristics, while assuming that the physical quantities, generally used to evaluate the behaviour of standard glasses, are not sufficient to evaluate the performances of the smart windows. In addition the experimental studies conducted on full scale electrochromic windows are analysed highlighting the measured physical quantities and the applied measurement methodologies considering both field and laboratory tests. Taking into account the need to accurately predict the operating characteristics and optimum design of electrochromic windows, a review of the theoretical studies available in the scientific literature as well as the developed theoretical models are presented. Finally, an experimental station for evaluating the on-site performances of different types of full scale smart windows and the layout of sensors used for the acquisition of internal and external physical quantities was described.
The next generation of advanced fenestration products includes dynamic electrochromic (EC) windows which can modulate the solar energy entering a building by application of an applied voltage. The windows can be switched from 62% visible transmittance (Tvis), 0.47 solar heat gain coefficient (SHGC) to a fully tinted state with ⩽2% Tvis, 0.09 SHGC. EC windows save energy in buildings – the total energy use for an eight story ASHRAE 90.1 2007 commercial office building with EC windows was modeled using the eQuest building simulation program and compared with the energy use of the same building with a variety of static glazings. The simulations were carried out in three US climate zones, encompassing a broad range of environmental exposure conditions from hot and dry (Arizona) to very cold (Minnesota). For all climate zones, building energy savings with EC glass were ⩾45% when compared to single pane static glazings common in existing building stock. When EC glass was compared to ASHRAE 90.1 2007 code compliant glazings, energy savings greater than 20% were calculated for the same building configuration. Optimum EC window control and performance strategies were derived from the modeling results. The EC glass and dimmable electric lights were synergistically controlled to maximize the use of natural daylighting and minimize electricity for lighting. Since EC glass can tint to ⩽2%, shades and/or blinds are not required for glare reduction, and building occupants always have a comfortable working environment and an unobstructed view and connection to the outdoors. All static glazing systems were assumed to have manual shading devices that are pulled by building occupants when glare becomes uncomfortable. For integrated building control systems, the peak load is significantly reduced when dynamic glazings are part of the building envelope. Consequently, chiller costs are lower, and the upfront capital costs for new building construction are reduced. Another key benefit of EC glass, elucidated by the simulations is reduction of CO2 emissions. EC glass reduces peak load carbon emissions by as much as 35% in new construction and 50% in renovation projects.
Traditional windows cannot adapt to external and internal environmental conditions. Smart windows are the next generation of windows, which can change their thermal and optical properties to control indoor environmental conditions. Electrochromic (EC) windows can control solar energy and provide visual comfort. These windows can be used with other tools such as various glazing types, building integrated photovoltaic (BIPV) and building energy management system (BEMS). This paper aims to evaluate the effect of EC windows, various glazing types, BIPVs and BEMS on energy consumption of high-rise office buildings. A model was created and several inputs were entered into the model. Then, annual simulations evaluated the effect of EC windows and other parameters on energy consumption of the building in four climate conditions of Iran. First, the effect of EC windows and various glazing types on energy consumption of the building were identified separately. Afterward, 12 different scenarios were defined to evaluate the effect of using both EC windows and optimal glazing type on energy consumption of the building. Then, BIPVs were combined with EC windows and photovoltachromic (PVC) windows were modeled using inputs of EC windows and BIPVs. In the end, BEMS was combined with PVC windows and had a positive effect on energy consumption of the building in all climate conditions. Finally, simulation results indicated that energy consumption of the building reduced up to 35.57% using EC windows and other tools. The difference between simulation and actual results is predicted to be at least 1.60% and maximum 6.22%.
Reducing building energy consumption while ensuring indoor comfort conditions is driving the building envelope transition from static to responsive. In this context, electrochromic windows represent a promising solution to manage optical and thermal requirements in response to changing boundary conditions or user requirements, and control strategies play a central role in the exploitation of this technology.
The present paper proposes a Hybrid Model Predictive Control strategy for the online operation optimization of an electrochromic-based active façade. The controller was implemented and tested on a simulated case study. This was achieved by co-simulating the optimal controller which used reduced data-driven grey-box model, with a high accuracy white-box physical model. This setup enabled to close the control loop and to perform an accurate performance benchmarking. Results showed that the proposed Hybrid Model Predictive Control strategy outperformed two baseline Rule Based Controllers, reducing simultaneously energy consumption, peak power and percentage of discomfort hours by up to 82%, 71% and 51% respectively. In comparison with the two baseline controllers and considering all the scenarios, the overall energy consumption could be reduced by approximately 40%–60% on average. In addition the work demonstrates how tuning the Hybrid Model Predictive Control weights adds flexibility to the controller, significantly changing its behaviour to meet the requirements of the designer.
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