Biomimetics design tool used to develop new components for lower-energy buildings

Abstract

The contributions to knowledge documented in this doctoral thesis are two-fold. The first contribution is in the application of a new biomimetic design tool called BioTRIZ. Its creators claim it can be used to facilitate the transfer of biological principles to solve engineering problems. The core case-study of this thesis documents how this tool was used to frame and systematically explore low-energy solutions to a key technical problem in the underdeveloped field of radiative cooling. Radiative cooling is a passive mechanism through which heat from a building can be rejected to the sky – an abundant but underused natural heat sink. Published in the Journal of Bionic Engineering, the study was the first independent application of BioTRIZ in the academic literature. The second contribution to knowledge is in the design, development and testing of the most promising biomimetic concept to come out of the BioTRIZ radiative cooling study. ‘Heat-selective’ insulation gives a roof mass a cool view of the sky because integrated pathways focus and channel longwave thermal radiation through it. It is biomimetic because it achieves infrared transparency by adding structural hierarchy to the component, rather than manipulating the properties of the material itself. Test panels on a rooftop in central London cooled to between 6 and 13 degrees below ambient temperature on May and April nights. Radiative cooling powers of between 25 and 70 W/m2 were measured when plates were at ambient temperature. Daytime radiative cooling below ambient temperature occurred when clouds blocked direct sunlight. Radiative cooling power was increased by 37% using reflective ‘funnels’. Two additional BioTRIZ analyses are presented as minor case studies. They each attend to a key technical problem in the field of passive thermal energy storage in buildings. They serve to illustrate the type of results that can be expected from using BioTRIZ during low-energy building design.