This newsletter is created for you, to keep you informed of Nature-inspired innovations and research for our tropical context. With the support of DesignSingapore Council's Good Design Research (GDR) initiative, bioSEA and collaborators are developing a toolkit to advance the application of biomimicry in the built environment, to value-add to our sustainability ambitions, and initiate new thinking and ideas.
Welcome to the 3rd issue of The Biomimicry Design Toolkit Newsletter!
All three champions of Nature's solutions for cooling have their own biological processes of Form and Function to manage heat. For this issue, we would like to shine the spotlight onElephant Skin!
Incidentally, Pantone’s dominating paint colours of 2022, include 17-0205 TCX: Elephant Skin!
Image credit: Pantone
Whatever challenge you are looking to address, one can ask Nature. After all, Nature can serve as a model, measure and mentor!
Elephants live in challenging environments, requiring a number of special adaptations for survival. To keep their body temperature stable in hot climates, they have to find ways to stay cool: one such adaptation is the wrinkled skin that helps them hold onto water for longer than other animals.
Elephants have a unique way of staying cool. Unlike humans, they do not sweat or shed their dead skin as we do. Instead, their dead skin accumulates as thick layers on the surface of the skin with age. Eventually, the skin develops cracks due to the layers of dead skin cells accumulating. Water seeps through these cracks using capillary action, which allows the skin to hold more water. The textured surface increases the surface area to volume ratio and creates self-shaded areas that facilitate convective heat loss.
How elephants textured and cracked skin help them keep cool?
Image credit: National Geographic.
Natural systems follow special morphological rules to generate interfaces (that rather shields) allowing the optimal flow of heat with the organism's body. Special morphological adaption can be found in skin surfaces to facilitate heat dissipation, such as in elephants. Our study (Peeks & Badarnah 2021, link here) presents a textured facade panel that mimics the skin morphology of elephants. It proved that morphological variables (such as hexagonal packing) and depth of texture impact heat loss, which could contribute to reducing energy consumption generally used for conventional mechanical systems' operations.
By learning from nature, especially from complex skin structures and assemblies, meaningful exploitation of functional morphologies in buildings could lead to a new class of energy-efficient solutions. We hope to expand this approach from lab settings into real applications to buildings and develop adaptive solutions that respond to change and minimize the impact on the environment.
Building on past research by Lidia Badarnah, and inspired by the skin of elephants, the bioSEA team is creating 3D-printed façade tiles that combine two mechanisms for passive cooling: self-shading and evaporative cooling. Elephant skin has a unique, fractal-like pattern of wrinkles and cracks. These crevices create shadows that keep water on the elephant's body longer, preventing it from evaporating. We are working with computer programs to create similar irregular surfaces.
These programs contain specific values that can vary, and the values can be combined in different ways. The values act like ‘genes’ and make up a kind of blueprint for the tiles’ shapes. Even though the tiles are extremely simple relative to anything in nature, finding optimal values and combinations of tens or hundreds of genes would be a prohibitively tedious task without the help of evolutionary algorithms. Using a genetic algorithm, we have created a tile pattern that reduces the amount of radiation absorbed, and certain combinations of ‘genes’ reveal themselves as particularly good solutions. Using this method, we have created a set of elephant skin-inspired tiles ready for thermal analysis.
Incident radiation on textured façade tiles. Image credit: Nathan Hays/bioSEA
Computational Fluid Dynamics (CFD) simulations are being performed to measure radiation-driven heat flow through the tiles, to see if the self-shading aspect of evolved surfaces provides any thermal benefit and whether evolved surfaces outperform randomly generated patterns. Next, we will examine how rain and drizzle affect the thermal performance of façade tiles (i.e., the tiles' ability to hold water and the associated evaporative cooling effects).
In the future, we plan to study the side effects associated with holding water on façade surfaces along with the strengths and weaknesses of different tile materials.
- Dr. Lidia Badarnah, Senior Lecturer in Architecture, UWE Bristol, UK.
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