Controlling radiative heat flows in interior spaces to improve heating and cooling efficiency

Abstract

Summary Heating and cooling in buildings account for nearly 20% of energy use globally. The goal of heating and cooling systems is to maintain the thermal comfort of a building's human occupants, typically by keeping the interior air temperature at a setpoint. However, if one could maintain the occupant's thermal comfort while changing the setpoint, large energy savings are possible. Here we propose a mechanism to achieve these savings by dynamically tuning the thermal emissivity of interior building surfaces, thereby decoupling the mean radiant temperature from actual temperatures of interior surfaces. We show that, in cold weather, setting the emissivity of interior surfaces to a low value (0.1) can decrease the setpoint as much as 6.5°C from a baseline of 23°C. Conversely, in warm weather, low-emissivity interior surfaces result in a 4.5°C cooling setpoint decrease relative to high emissivity (0.9) surfaces, highlighting the need for tunable emissivity for maximal year-round efficiency.

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

“…In hot weather, to prohibit the transfer of heat from outdoors to indoors, both minimal IR transmission and low emissivity are required. [130,450] In cold weather, high solar transmittance to allow heat entering the building and low MIR emissivity to prevent the heat escaping from indoors to outdoors are desired. [130,450] Several research groups are working on multifunctional TPV which are specifically designed to simultaneously control the electricity generation, visible light transmission and heat insulation.…”

“…[130,450] In cold weather, high solar transmittance to allow heat entering the building and low MIR emissivity to prevent the heat escaping from indoors to outdoors are desired. [130,450] Several research groups are working on multifunctional TPV which are specifically designed to simultaneously control the electricity generation, visible light transmission and heat insulation. Sun et al studied a transparent SC based on a polymer absorber coupled with Bragg reflector layers for high IR reflection (Figure 12h).…”

A Shish-Kebab Superstructure Film for Personal Radiative Cooling

“…With the aggravation of global warming, heat stress becomes an increasingly serious problem, which could cause physical discomfort to people, increase the risk of disease, and seriously threaten human health. , Rather than cooling the human body directly, buildings around people are cooled first in the traditional cooling process, which will inevitably generate energy waste. − Therefore, the concept of personal thermal management (PTM) has been proposed. − It focuses only on heating and cooling the human body and the local environment, thus reducing unnecessary energy consumption to the surrounding building. − In a normal environment, the body skin, which is approximately 34 °C, emits mid-infrared (MIR) radiation with a wavelength of 7 to 14 μm to the outside. This accounts for nearly 60% of the human body’s heat loss (Figure a) .…”

Artificial neural network-based smart aerogel glazing in low-energy buildings: A state-of-the-art review

“…The investigated solutions can be summarized as passive and active solutions ( Jung et al., 2019 ). The passive solutions mainly include high emissivity surface ( Xu and Raman, 2021 ), low-e glazing system, double-glazing system, air-vacuum layered triple glazed windows ( Fang et al., 2020 ), reflective venetian blind ( Wang and Chen, 2016 ), and naturally ventilated double skin façade ( Wang et al., 2016 ). The active solutions mainly include the mechanically ventilated glazing systems ( Cuce and Riffat, 2015 ).…”