Photonic Structure Textile Design for Localized Thermal Cooling Based on a Fiber Blending Scheme

There is great potential for energy savings in buildings if temperature set points of cooling systems can be extended by 1–2 °C (2–4 °F) provided that the thermal comfort of building occupants is maintained. Since most body heat is dissipated through thermal radiation, the photonic properties of textiles can play an essential role in localized thermal cooling. Current textiles are very opaque at infrared wavelengths and prevent the efficient transmission of thermal radiation from the human body when temperature set points are increased. In this work, we show a design approach for photonic structure textiles based on fiber materials that are both comfortable to wear and allow localized thermal cooling at increased set points. Our design principle is based on the blending of fibers that are largely infrared transparent to achieve efficient cooling and natural, infrared-opaque fibers for comfort of wearing. We use a full-vector electromagnetic field method to calculate our designs' spectral, directional properties and we apply a detailed radiative heat transfer model based on a full spectral, directional net radiation method that we developed. We demonstrate that our designs, containing up to one-third cotton and two-thirds nylon, allow net heat transfer at an extended set point of 26.1 °C (79 °F) that exceeds the cooling abilities of a cotton-only design at the current thermal comfort set point of 23.9 °C (75 °F), which can result in more than 30% energy savings. We also find that the combined (radiative, convective and conductive) heat transfer for our designs at 26.1 °C (79 °F) exceeds the metabolic power rate of 58.2 W/m2 for an adult in a sedentary state.