German scientists invented “smart glass” that detects the presence of the user and reduces energy consumption

    13 May 2021

    German scientists have developed glass that reduces energy consumption and regulates the temperature in the room.

    This was announced by the University of Kassel in an article “MOEMS micromirror arrays in smart windows for daylight steering”, published recently in the first issue of the journal of optical microsystems, techxplore.com reports.

    “Our smart glazing is based on millions of micromirrors, invisible to the bare eye, and reflects incoming sunlight according to user actions, sun positions, daytime, and seasons, providing a personalized light steering inside the building”, Harmut Hillmer says.

    The micromirror array is invulnerable to the wind, window washing or any weather conditions. It’s located in the space between the window glass filled with noble gas such as argon or krypton. Glazing provides free solar heat in winter and prevents overheating in summer. Also it transmits natural daylight, saves energy up to 35%, significantly reduces CO2 emissions by up to 30% and reduces the use of 10% of steel and concrete in high-rise buildings.

    In addition to the energy problem, artificial lighting also has consequences for health and well-being. Various studies have linked artificial lighting to a lack of concentration, high susceptibility to illness, disturbed biorhythms and insomnia. Smart glass can reduce dependence on artificial lighting by optimizing the natural daylight in the room.

    If there is no user indoors in the summer, all the mirrors switch vertically, keeping the sun’s heat outside, which saves energy by minimizing heat transfer. When the sensors detect the presence of the user, the upper mirrors open and reflect daylight on the ceiling. The room stays cool, saving energy on air conditioning. Parts of the room far from the window can be effectively illuminated by daylight, saving energy on artificial lighting.

    If no user is present in winter, all the mirrors open and collect energy, reflecting solar radiation on the wall, acting as a solar heater. This saves energy for heating. As soon as the sensors detect the user’s presence, in winter, all mirrors redirect all solar energy to the ceiling to minimize glare. Now the ceiling acts as a solar heater, saving thermal energy.

    Modern intelligent glazing is optimized for both winter and summer and can provide energy savings all year round. There’s a need for intelligent and automatic technology that can respond to the local climate (daytime, season), use available sunlight, regulate light and temperature and save a lot of energy.

    MEMS micro-mirrors are integrated into insulating glazing and are controlled by an electronic system. The orientation of the mirrors is regulated by the voltage between the respective electrodes. Room motion sensors determine the number, position and movement of users in the room.

    The results include much higher actuation speed in the sub-ms range, 40-times lower power consumption than electrochromic or liquid crystal concepts, reflection instead of absorption, and color neutrality. Rapid aging tests of the micromirror structure were performed to study reliability and revealed sustainability, robustness, and long lifetimes of the micromirror arrays.

    And with positive results like that, the benefits of this smart glass are crystal clear.

    Let’s recall that buildings are responsible for 40 % of primary energy consumption and 36 % of total CO2 emissions. And, as we know, CO2 emissions trigger global warming, sea level rise, and profound changes in ocean ecosystems. Substituting the inefficient glazing areas of buildings with energy efficient smart glazing windows has great potential to decrease energy consumption for lighting and temperature control.

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