The need for energy-efficient thermoregulation solutions is mounting, especially as the use of air conditioners alone accounts for 10% of all global electricity consumption in buildings (IEA, 2018).
Stanford’s paint – which is suitable for indoor and outdoor use and can be applied to various surfaces, materials and forms – could help keep buildings and spaces cooler in the summer and warmer in the winter, subsequently cutting energy usage, costs and greenhouse gas emissions.
It consists of two layers (which need to be applied separately). The bottom layer contains aluminium flakes and is infrared-reflective, while the ultra-thin infrared-transparent top layer includes inorganic nanoparticles that come in a wide range of hues. This feature allows the paints to be produced in colour, expanding on the limited palettes of metallic silver, grey or white that low-emissivity coatings currently tend to be available in. The various colours tested by the team (including blue, red, yellow, green, orange and purple) were found to reflect 10 times more high mid-infrared light than conventional paints in the same colour.
The paint can be applied to exterior walls and roofs to keep heat out, or interior walls to keep heat in. When tested in artificial cold environments, the energy used for heating reduced by around 36%, while in warm conditions, the energy needed for cooling was cut by almost 21%.
The team is now refining the formulation for practical applications, such as water-based solutions for conventional commercial paints.