Poster: What the white orchid can teach us about radiative cooling

POSTER

Abstract

Sub-ambient radiative cooling has great promise for non-electric heat mitigation. Passive, direct-sunlight, sub-ambient cooling requires ultra-high reflectivity in the solar spectrum and high emissivity in the long wave infrared between 8 and 13 microns. Here, we explored the remarkable properties of white Phalaenopsis Orchid petal whose average reflectivity exceeds even Barium Sulfate and Zinc Oxide when tested in an integrating sphere and exceeded the whiteness of the whitest commercial paint. Using 3D optical profilometry, we found a rich 3D multi-scale substructure which included epidermal cells, walls, grating-like features and transparent sub-micron spheres. We will discuss both the full-spectrum properties of the Orchid and its potential for biomimicry in radiative cooling.

*We are grateful to the various supporting institutions including, the University of South Africa, iThemba LABS (ITLABS), the National Research Foundation of South Africa (NRF), the African Laser Centre (ALC), the international Organization of Women in Science (OWSD), the Abdus Salam International Centre for Theoretical Physics (The Abdus Salam-ICTP), the Royal Society-London and naturally the United Nations Education, Sciences & Culture Organization (UNESCO) as well as the French Foreign Ministry and the ADESFA program. Likewise, the Centre for High Performance Computation (CHPC) is acknowledged.

Publication: N. Botha, N. Numan1, J.K.Cloete, B. Machabakacha, M. Akbari, R. Morad, I. Madiba, Z. Nuru, A. Gibaud, M. Henini, S. Berthier, P. Ho, C. Hunt, N. Taormina, J. Howell, M. Maaza. On the remarkable optical properties of the white Phalaenopsis Orchid & their potential biomimicry-radiative cooling applications. In manuscript.

Presenters

  • Clara Hunt

    • Chapman University

Authors

  • Paige P Ho

    • Chapman University

  • Clara Hunt

    • Chapman University

  • John Howell

    • Chapman University

  • Nathan Taormina

    • Chapman University

  • Malek Maaza

    • University of South Africa