Biomimetics for passive air conditioned design for buildings in the hot arid regions

Abstract

The high energy consumption for air conditioning in buildings is a serious concern due to its consequences on the earth's ecological life. In nature, animals regulate their body temperature in extreme environments without prejudice to the environmental system. Therefore, this study aims to design a passive cooling unit for buildings in the hot arid regions by emulating biological cooling strategies in nature. It adopted a biomimetic exploratory method to determine three of the efficient biological cooling strategies in nature based on the morphological attributes. These are; cooling through animals’ respiratory passages, thermal radiators and airflow cooling in termite mound. A comparative study was conducted on four case studies under each of the three cooling strategies to come up with the working principles that can be used as a guide to design a biomimetic cooling system. One of these strategies, the camel nasal respiratory cooling was simulated to design a cooling unit installed in wind towers for buildings. To validate the applicability of the camel nasal-inspired cooling design, experimental tests have been conducted in both wind tower and wind tunnel in a desert city, Seiyun in Yemen. The study main parameter was the design cooling efficiency for (i) three materials: clay, clay with jute fiber, and clay with wood wool pads, (ii) design height, and (iii) climatic environmental variables. The results showed that the best cooling efficiency among the three materials was the design of clay with jute fiber 85.2 %, followed by clay with wood wool pads 76.6 %, and clay 66.3 %. The former two designs have effectively dropped the temperature in hot arid climate up to 18.9 °C for jute design and 16.5 °C for wood wool design. This indicates that the bio-inspired design can replace the mechanical air conditioning system. Additionally, the cooling efficiency of the design increases by the increment of its height and the ambient temperature. However, it decreases with the increment of the inlet air wet-bulb temperature, air humidity, and air velocity. Thus, it can be concluded that emulating biological thermo-regulatory strategies is useful for the design of energy-efficient cooling systems. This study contributes to possible passive cooling design for buildings in the hot arid regions.