Are Underwater Cities Possible?

Continued global population growth may necessitate underwater living in coming centuries. Beyond this, underwater cities, though appearing highly futuristic at present, could play a key role in enabling humans to establish colonies on different planets in the future. Relatively recently, a planet containing water vapor and likely liquid water in its composition was discovered. Technology for underwater living developed on Earth could serve as a precursor to creating habitats on such planets in the future. The ocean spiral design proposed by Japanese Shimizu Corporation is not only sustainable but also possesses the characteristic of being a completely self-sufficient concept. This concept reaching depths of 500 metres underwater plans a complete living space filled with residences, offices, hotels, shops and research facilities. According to the created concept, the entrance section of Ocean Spiral city will be located 200 metres below sea level, a distance sufficient for sunlight to reach. However, through a lower spiral, it will also be possible to descend to greater ocean depths. For energy, thermal power will be obtained by utilizing the temperature difference between surface water and deep sea temperature. Shimizu Corporation claims that the technology required to construct the structure and sustain life beneath the ocean surface could be ready within 15 years. According to the company, Ocean Spiral City could be constructed with a budget of USD 26 billion.

What Are the Barriers to Underwater Living?

With current technology, engineers can rapidly construct an underwater colony capable of supporting up to 100 people. However, for a more extensive facility, technological advances in specific areas will be necessary. In addition to effective emergency evacuation systems, further research and development is required to provide air supply and environmental control of humidity. Current underwater habitats use compressors to pump air from the surface down through tubes. To remove carbon dioxide, they are forced to add a chemical product called Sodasorb. This method certainly will not suffice for an underwater city where thousands of people would live. For this reason, researchers must create a fresh oxygen source. Generating sustainable energy for submarine housing is also among the most challenging topics. There are many options ranging from using ocean waste to utilizing thermal power from temperature differences. However, other possible solutions include placing solar panels on the surface or utilizing wave motion in the ocean. Creating multiple modules rather than one giant balloon for the underwater city would be more rational. Modules can be made of steel, glass or a special resin. Smaller structures offer flexibility advantages. In this way, modular living spaces can be created, added or removed. [gallery columns="2" size="medium" ids="eyJ1cmwiOiJodHRwczpcL1wvd3d3LnR1cmtjaGVtLm5ldFwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAxOVwvMTBcL2R1bnlhXy5qcGciLCJ0aXRsZSI6IlN1IEFsdFx1MDEzMSBcdTAxNWVlaHJpIiwiY2FwdGlvbiI6IiIsImFsdCI6IlN1IEFsdFx1MDEzMSBcdTAxNWVlaHJpIiwiZGVzY3JpcHRpb24iOiIifQ==,eyJ1cmwiOiJodHRwczpcL1wvd3d3LnR1cmtjaGVtLm5ldFwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAxOVwvMTBcL29jZWFuXy5qcGciLCJ0aXRsZSI6Im9jZWFuXyIsImNhcHRpb24iOiIiLCJhbHQiOiIiLCJkZXNjcmlwdGlvbiI6IiJ9"] Shimizu Corporation states that the concept's foundation stems from the enormous potential of cycles connected with the deep sea, air, sea surface and seabed. The company outlines five main reasons for developing the project in the deep sea as follows: Potential to supply seafood, produce desalted water, generate energy, process carbon dioxide, and extract resources from the ocean and seabed. Ocean Spiral is designed as a massive sphere known as the "Blue Garden". Measuring 500 m (1,640 ft) in diameter, a volume mostly floating just below the surface, though the top of this sphere is planned to be positioned to cut through sea level.

According to the concept, this sphere will contain 75 floors with areas designated for residential, commercial and research purposes. It is expected to accommodate a population of 5,000 people with 4,000 permanent residents and 1,000 visitors.

Access to the Blue Garden and Ocean Spiral will be via the "main entrance" at the water surface. The Blue Garden itself contains a massive atrium, hotel suites, observation gondolas, marine park, entertainment and retail plaza. Temperature, humidity and oxygen levels are controlled inside. Below the Blue Garden lies a 3-4 km (1.9-2.5 mile) long spiral connected to the 'Earth Factory' positioned on the seabed. The spiral houses the functions required for the Ocean Spiral complex to operate in the deep sea. Energy is generated through ocean thermal energy conversion, food is produced through deep-sea fishing and water is desalted. A monitoring facility is also located here and therefore a harbour where submarines can dock is included. The Earth Factory is anchored to the seabed and connected to similar satellite facilities through transportation tunnels. These "factories" are used to store, process and reuse carbon dioxide, as well as to develop and produce deep-sea resources. The foundation of Ocean Spiral construction is the spherical shape of the Blue Garden. The spherical shape was chosen to provide strength against external water pressure. The sphere is further reinforced with a central internal tower. A frame for the sphere and tower will be constructed using resin concrete. The frame will be clad using triangular acrylic panels measuring 50 m (164 ft) along the edge and reinforced using semi-transparent fiberglass cross-bracing rods. All construction is planned to take place at the ocean surface. Shimizu notes that it is likely that the materials used and construction processes will be refined as the project progresses and technology continues to develop.

Key Features of the Ocean Spiral Concept

Structural plan: A concrete underwater city spanning 500 metres in diameter. Power: Water pressure is neutralized through the spherical shape. Concrete: Strong, resin concrete. Reinforcement placement: Stainless resin rods. Environmental sensitivity: Material derived from recycled PET bottles is used in resin concrete. External wall plan: Creating a transparent sphere with 360° panoramic views in the deep sea forms the basic concept of the project. This sphere is intended to have the following characteristics. Durability: Achieved with acrylic panels arranged in triangular shapes 50 metres in length per leg. Reinforced with semi-transparent FRP ribs. Cleaning: Use of micro-bubbles is envisioned to prevent biofouling. Connections: Water-tight, corrosion-resistant and other such properties. Equipment plans: The difficulty here is providing comfort specific to the deep-sea environment. Air conditioning: After dehumidification, comfortable radiant cooling through cold water use for occupants. Heat insulation: A comfortable environment achieved through the heat insulation properties of acrylic panels (3 metres thick). Shimizu envisions an environmentally friendly underwater city sustained by energy derived from an "earth factory" at the ocean floor. The factory will use microorganisms to convert carbon dioxide into methane; electric generators located in the ocean spiral will use a process known as ocean thermal energy conversion to harness energy from temperature differences in seawater to generate additional power. Desalted water produced using hydraulic pressure will be pumped to the residential module. Although the "underwater city" is currently only a concept, it could become reality in coming centuries. Prepared by: B. Serhat Cengiz

Sources: • https://www.shimz.co.jp/en/topics/dream/content01/ • https://edgy.app/underwater-city-challenges • https://newatlas.com/ocean-spiral-underwater-city/34947/ • https://www.dezeen.com/2017/11/06/video-ocean-spiral-shimizu-corporation-spiralling-underwater-city-movie/