Biocool

Cities consume about 75% of the world's primary energy and are responsible for almost 60% of global greenhouse gas emissions. The planning and use of urban areas have a significant impact on energy performance in terms of consumption and production, microclimate and especially heat waves which are amplified by climate change, but also by pollution. Urban surfaces have a huge role in this heat island effect. The project aims to find solutions that contribute to limiting these effects by playing on two aspects: radiation and water recovery that can also contribute through evaporative cooling depending of the climate. Living organisms have been submitted to selection and natural evolution under constraints that enabled them to develop a variety of materials depending on different environments (humid, dry, sunny, …). They present solutions for thermoregulation with complex nanostructures of hierarchical morphologies across scales to control the reflection, absorption and emission of the electromagnetic spectrum. The surface micro/nano texturing combined with optical properties can allow the combination of antireflection and enhanced anti- wetting properties or, on the contrary, favour selective protection from solar radiation and collect humidity and store water at the interface (cuticle). The project BioCool seeks to investigate and adopt the underlying multiscale micro/nano-structure of various species of insects and plants interfaces for their unique self-thermo-regulation properties. Through bioinspiration of their structures, high solar reflectance can be obtained with concurrent thermal emission in the atmospheric window that enables cooling performances to be enhanced, with additional multi-functionalities such as water harvesting, self-cleaning and climate impact mitigation. The success of the project will enable radiative cooling materials to surpass the performances of existing high albedo (reflective dominant) materials. In addition, the cross-collaboration enables accurate numerical approach and experimental characterization to understand and master the radiative cooling performances across different climates (tropical vs temperate), with potential to be scaled up for applications across buildings, windows and electronic devices. The impact analyses will be carried out at the city scale using numerical simulations taking into account surface metaproperties. An experiment in real climatic conditions will also be carried out in addition to the tests conducted on samples