GREEN FLOAT: The Ocean Future City

by Masaki Takeuchi (Inhouse Architect of SHIMIZU Corporation)

Introduction

The world is currently facing the sea level rise due to climate change and there is an urgent need to create a sustainable society. We are facing many sorts of problems of energy, water, food, garbage, air pollution and so on. Fortunately, however, 70% of the earth’s surface is covered with the ocean. The ocean has a tremendous capacity and a big influence on the global environment and the sustainability of human beings. We are heading new challenges for a better future utilizing the potential of the ocean. "Green Float" is a 1000m high skyscraper proposed on a 2000m diameter floating structure. It is assumed to be located mainly in the equatorial ocean, with blessed marine weather conditions. In order to obtain technical experiments and certification, we assumed GREEN FLOAT II (1/10 scale model, a 100m tall skyscraper built on a 200m diameter floating structure).

Green Float II (Designed by SHIMIZU CORPORATION)

Outline of Mega Floating City “Green Float”

The man-made island is 3000 m in diameter and actually floats on the ocean. There is a 500m-wide lagoon around the periphery, so the net land area has a diameter of 2000 m. The skyscraper city is 1000 m tall, and the city in the sky begins 700 m above sea level. The middle levels comprise a plant factory that makes the island city self-sufficient in food. The ground level supports such facilities as a natural farm, a playground, and a beach resort. The peripheral area of the city in the sky is a residential zone that is inhabited by 30000–50000 people. The central area is a business zone with offices and research centers. The business zone is intended mainly for the research, development, and branch offices of companies engaged in biotechnology, renewable energy, and marine enterprises. The lagoon waterside on the ground level will afford residents the opportunity to enjoy the lagoon and green forests.

Project summary

“Green Float” is a new model for environment-friendly Mega Floating City, under development by Shimizu Corporation, Japan. The concept of “Green Float” embodies two areas of innovation. One is “Green innovation”, achieving self-efficient zero carbon and zero-emission cities by utilizing the potential of the ocean, and the other is “Float innovation”, unaffected by sea-level rise and ensure high flexibility for city growth. By integrating “Green Innovation” and “Float Innovation”, a super high value-added Mega Floating city can be realized.

Figure 1. Section image.

Figure 2. GREEN & FLOAT innovations.

Float innovation

Locating the city at a low latitude near the Equator would minimize the floating risk posed mainly by wave heights and strong winds. Because typhoons, hurricanes, and cyclones rarely occur there (Figure 2), the equatorial region is considered the most advantageous for a super high-rise mega floating city that reaches beyond a certain height.

a) New location

For an existing large harbor city that faces difficulties in securing vacant land, it would be possible to extend the city functions offshore far beyond the limit of landfills. For an island country that is short of land area, new areas for development could be secured. Compared with landfill, the development would be possible that is environmentally and ecologically friendly.

b) Unaffected by rising sea levels due to climate change.

There are many island nations that are facing being submerged because of rising sea levels due to climate change. A mega floating city is one way to save such countries.

c) Avoiding the influence of earthquakes and tsunamis.

When a tsunami reaches a shallow shore, the wave heigt increases. However, a megacity floating offshore is completely immune from the impact of earthquakes and tsunamis.

d) Transferable and flexible city

Because of durability issues, many cities and buildings on land cease to be functional within their lifetimes. By contrast, a mega floating city is easily moved once its role ends, allowing the location to be redeveloped. By relocating and continuing to use the lifetime of matter, the life cycle cost can be reduced. Also, to meet the needs of the expansion of urban areas, it is possible for the city to grow naturally as cells, modules, and units, much like a water lily grows on water.

Figure 3. Lagoon resort beach.

GREEN innovation

In the future global environmental age, most energy that will be used will be renewable energy with no CO 2 emissions. Because the equatorial regions are rich in sunlight, the green potential, centered on renewable energy, would be maximized.

a) Pleasant and comfortable temperature

The Pacific equatorial islands experience a constant temperature of around 28°C. Because the temperature drops by 0.6°C for every 100 m of height, it will be 6°C lower at 1000 m. With the sky city rising 700–1000 m above the Equator, the temperature there would be a refreshing 26°C all year round.

b) Zero carbon and renewable energy

Solar power can provide electricity efficiently in regions with favorable sunshine hours and solar radiation angle. In addition, because the sea surface is at a much different temperature than the sea bed, the efficiency of power generation based on the ocean temperature difference also improves. Taking the CO 2 emissions data for Japan as a benchmark, Figure 3 shows how Green Float could reduce such emissions.

c) Fresh water

The annual precipitation is high in the equatorial Pacific,but precipitation levels differ considerably between the rainy and dry seasons. By storing water in the high-rise mega floating city and controlling water use throughout the city, it would be possible to supply as almost same as the amount of water required for living.

d) Food self-sufficiency

By harnessing the power of the sun as much as possible, providing a vertical vegetable factory would contribute positively to food self-sufficiency, food mileage, and food traceability.

e) Zero emissions and recycling

Human waste in the form of water, garbage, and CO 2 can be nutritious for plants. By harnessing the height of the sky city to redistribute human waste to lower levels, plants and other living things would be supplied with nutrition. This raises the possibility of complete resource recycling from waste to food.

Figure 4. CO 2 reduction of GREEN FLOAT.

Figure 5. Vertical vegetable factory

Validation of Float technology

Green Float II (200 m in diameter; Figure 5), which is roughly one tenth the scale of Green Float (2000m in diameter) is taken as the latest technology-embodied model. Assuming a bay location, which is the extension of the urban area, authors have conducted experiments and analyses of the response to tsunami and strong winds.

Figure 6. Section.

(1) Earthquakes and tsunamis

Authors assume the meteorological and oceanic conditions of a large Japanese city. Buildings and structures with floating isolation are extremely safe because they experience very little seismic force in the event of an earthquake. In addition, the authors found experimentally that the tsunami does not exceed the breakwater of 1 m even with the tsunami of 10 m or more, which far exceeds the tsunami assumption in the assumed location. This is because the water level gradually increases due to the tsunami inside the bay. Of course, the structure itself is extremely safe

(2) Typhoon (waves and winds)

Again, the authors assume the meteorological and oceanic conditions of a large Japanese city. Even assuming the direct hit of a typhoon bigger than the Ise Bay Typhoon, structural safety was secured sufficiently for the floating structure (lower part), the skyscraper (upper part), and the mooring facilities. The acceleration also caused no furniture to fall over.

(3) Certification from official third party

Green Float II has received AIP from Nippon Kaijikyokai as certification by a third-party organization that is concerned with the structural safety of floating structures.

Figure 7. Tsunami experiment.

Figure 8. Typhoon experiment.

Future

(1) GREEN FLOAT construction method

A mega floating city requires advances in aspects such as unitization and robot construction more so than a city on land. Although the future construction plans of Green Float remain at the idea stage at present, authors will try to improve the technology through future model projects.

(2) Realizing GREEN FLOAT

After the technology has been established, the project is realized using different variations of architectural applications and shapes. We are working with the government agencies and private projects in several countries at the schematic design and technical demonstration level. In the future, I believe that new cities and architectural solutions can be realized by floating.

Figure 9. City in the Sky.

Figure 10. Mega floating city, GREEN FLOAT.

About Author

Masaki Takeuchi (Inhouse Architect of SHIMIZU Corporation)

In March 1980 , Masaki Takeuchi graduated from Waseda University. In April 1980,he joined “Shimizu Corporation”. The projects below are some of his works:

• Urban-scale project competition at Osaka branch about City

• Developing the new value technologies; LCV (Life Cycle Valuation), eco-BCP(Business Continuity Plan)

• Ocean City Project: November 2008: The Maritime Future City named “GREEN FLOAT” (Project Leader), November 2014: The Deep Sea Future City named “OCEAN SPIRAL” (Project Leader), October 2015: Improving technical feasibility; experiment & analysis (Project Leader), December 2017: GREEN FLOAT II acquired the certification ; Class NK's AIP (Approval in Principal), in structural safety of the floating structure of super high rise buildings.