Sahra Sphere - technical excerpt Team report: Alazar Wake Kore, Hadi Saif Ali, Hundaol Benti Bekele. 11 Biological Solutions Closed loop Cooling Using the concept of burrowing, we devised a mechanism to enhance greenhouse cooling. The closed-loop cooling system works by biomimicking the concept of burrowing in animals. Water compartments are buried deep underground (2 to 3 meters deep), and hot water from the building travels through tubes to the underground compartments. When the hot water flows to the loop underground, the heat is dissipated out of the tubes, cooling the water, which then flows back into the house. The now cool water loops around the greenhouse absorbing the heat and, in the process, cools down the greenhouse. The process then repeats. Existing systems that resemble our proposed ideas include geothermal cooling and heating that small scale houses use in cold regions of the world. The system used the same concept of burrowing. However, the borrowing is done a few meters away from the house but in our structure, we placed it directly below it. In addition, our system is made solely to keep the greenhouse at a cool stable temperature. Fig ) Hand Drawn concept of a closed loop cooling system 12 Honeycomb Pod The efficient space and material usage of the honeycomb can be introduced to the working of hydroponics. This can be achieved by creating a hexagonal cylinder, arranging them from top to bottom in a triangular pyramid for water and nutrient movement, and leaving the middle empty for a water tank. There are lots of structures that are made to mimic the honeycomb but unlike our design, these structures do not utilize a pyramidal shape for maximum horizontal and vertical space. (Below is a hand sketch of the pods) Atmospheric water generation To generate water from air, we can use cooling condensation of vapor that is in the air and by mimicking the Namib desert beetle. We can achieve this by creating a temperature difference, setting a high surface area for absorption, and supplying and circulating humid air through our device. Usually, these devices are used to collect humidity from the outside surrounding and form water from thin air, but the amount of energy they use, the installation is too expensive and requires huge land which is scarce in arid areas. Hence, our design proposes to convert the humidity released from the plants inside the greenhouse and recycle it.(Below is a hand sketch of the concept) 15 Final Design (Prototypes) In the final prototype model for the greenhouse, we used: • Cardboard base • 3D printed hexagonal pods • Plastic Dome • Water pipes • ESP 32 controller • Humidity sensor • Temperature sensor • Arduino uno • LED • Water pump • Batteries • Small Solar panels Building Procedure of the Prototype ✓ The base o Cylinder is made of Cardboard with radius of 48 cm o Height of 10cm ✓ Upper dome – plastic dome of radius 43 cm ✓ Closed loop system –tubes, pumps, and batteries ✓ Hydroponic pods - Cardboard with 6 sides of dimensions (Side x Height): • Smaller pod (19 pcs) - 3.5 x 5 cm • bigger pod - (18 pcs) - 3.5 x 7.5 cm - • The combined structure has dimensions – 45 cm width and 20 cm height ✓ Solar panels that are mounted to the top side of the dome Below you will find the images of the components. 18 Final Design (Actual architecture) • The final design is a large geodesic dome made of preferably 8mm thick Poly carbonate Panels due to their high R and low L values (measures of energy performance of a window) but these materials can be substituted by any other sustainable material. Spraying this with a coating made of bicarbonate material will help block 70% of the sunlight from getting in. The outer design utilizes geodesic dome architecture, which has several real-world proven advantages: high structural to weight ratio, aerodynamic resilience to high winds, lightweight, uses less material to build, and can provide passive ventilation due to its shape promoting natural airflow. • The inside is covered with water tubes made of copper looping the dome. The tubes are part of the closed loop cooling system that ensures the internal of the dome is always at optimal temperature for the crops to grow. The closed-loop cooling system is buried at a depth of at least 2 to 3 meters. This system provides the primary cooling system for the greenhouse. This system can last decades without facing any significant issues. To make it even more sustainable, the system can run purely on solar energy. • Inspired by the honeycomb structure, inside the massive dome resides a unique architectural structure (referred to as “Hydroponic pods”) made from ferrocement or other sustainable materials. The structure is built in a pyramidal shape with a single comb structure at the top and stairs to allow access to the pods. This design has several advantages: the comb (hexagonal structure) alone has huge space optimization benefits but combining it with a pyramidal design can produce maximal vertical space with a minimal footprint on the ground, help produce more plants in less space, material usage efficiency, high strength to weight ratio, and constructional efficiency. • At the bottom of the dome structure, there are open slots where humid air escapes into and then captured by a thermoelectric dehumidification system. This system takes the humid air, cools it down, and collects the moisture which acts as a secondary water source for the plants.