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Green Float concept: a carbon negative city on the ocean


November 9, 2010

Green Float cities would grow just like a lily floating on the water

Green Float cities would grow just like a lily floating on the water

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The idea of going offshore to satisfy our renewable energy needs isn't new, but the grand vision of Japan’s Shimizu Corporation goes way beyond harnessing green energy at sea for use in cities on Terra firma – it takes the whole city along for the ride. The company, along with the Super Collaborative Graduate School and Nomura Securities, is researching the technical issues involved in constructing its Green Float concept – a self-sufficient, carbon-negative floating city that would reside in the Equatorial Pacific Ocean.

The concept would comprise individual floating cells or districts resembling water lilies with a radius of 1km (0.62 miles) that would form a compact village that could house 10,000 to 50,000 people. Joining these districts together would form a city or module that would be home to 100,000 people, while a group of modules would form a country (though we assume there is some red tape involved before you get a seat at the U.N.).

Floating cities in the sky

The majority of the inhabitants would live in 1km high “City in the Sky” towers located at the center of the circular cells, while additional “Waterside” residential zones comprising low-rise townhouses would be located on the outer edge of the structure’s outer circumference. To take advantage of the cooler temperatures, the tower residences and services would be located at the top of the tower at an elevation of 700 m (2,296 ft), providing year-round temperatures of 26-28 °C (79-82 °F). As the population of the cities grow, additional cells could be added, spreading out like the water lilies they resemble.

The central tower would be surrounded by grassland and forests, while the outer circumference would adjoin marine forests, lagoons and beach resorts. The cells are designed to be completely self-sufficient in terms of food with the 1 km high towers containing a plant factory, while livestock and other farming would take place in “plains” also surrounding the tower. Seafood lovers would obviously also be well catered for through fishing the surrounding ocean and the marine forests.

Carbon negative

The cities would use a number of technologies to make a carbon negative system. The designers say the compact form of the city alone would allow a 40 percent reduction of CO2 through more efficient transport and distribution, while energy conservation through increased thermal insulation, facility efficiency and next-generation technologies would provide a further 30 percent reduction. The use of solar power provided by space satellites, ocean thermal energy conversion and wind and wave technologies would provide an additional 30 percent reduction. The ocean would also be used for carbon sequestration.

The Green Float concept would also produce zero waste by recycling resources and converting waste into energy. It would even help clean up the oceans by collecting any passing “garbage islands” for use as an energy resource.

Location, location, location

The islands would be located at the equator as it isn’t prone to typhoons and the climate is stable. However, in the event of large waves, strong elastic membranes would be attached to the lagoons around the outer circumference of the cells, with the shallows above the membranes standing 10m (32.8 ft) above sea level. The water pressure difference between the lagoons and the ocean would limit the movement of the membranes and buffer the force of the open sea waves. Additionally, 20-30m (66-98 ft) high seawalls would be constructed to handle a worst-case scenario.

The Green Float concept was on display at the recent Innovation Japan University Exhibition 2010 where DigInfo TV was told that the Green Float cities wouldn’t be fixed in place but would literally float slowly on the ocean currents. Given much of the technology included in the concept doesn’t exist yet, Shimizu, as part of a three-way agreement with the Super Collaborative Graduate School, and Nomura Securities, will initially concentrate on nurturing R&D; projects on the technologies required for such a project. However, the company’s hopes of turning it into a reality by 2025 may be a little ambitious.

But ambition isn’t something that seems to be lacking at Shimizu. The company also proposes encircling the moon in a belt of solar collectors that would collect solar energy and transmit it to Earth using microwave and laser transmission technologies. You definitely couldn't accuse this organization of thinking small.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

The floating island concept is really exciting, but this design is totally outlandish. The world\'s coastal areas are getting crowded, so floating islands are a good idea. However, they must be affordable and suitable.

Affordability means being much cheaper than oil platforms for the same series of water depths. Suitability means being stable in heavy seas and high winds. The floating island must not pitch and roll like a ship.

A diameter of 500 meters might be manageable. Anything larger and the superstructure would be impossible to engineer, except in fairly shallow water. Anything smaller would not stable amidst the wind and waves.

Innovative underwater breakwaters would be required. Huge ocean waves cannot be stopped simply by putting up a wall. And building a platform on spars like a semi-submersible oil platform is outrageously expensive. The waves must be dissipated starting hundreds of meters out from the floating island.

The superstructure could not be expected to support the vertical forces of housing and other structures on the island, so these would necessarily float independently. Reduction of vertical integration in the manufacture of a floating island might necessitate that the superstructure be designed independently to the floating modules. Hollow-bottom pontoons are out the question for safety reasons.

Many of the design issues are reduced in shallower water, though at a certain point the design is less like a floating island and more like a pier.

The construction of the first true open water floating island will be a very exciting thing.

2nd May, 2015 @ 5:23 a.m. (California Time)

Hey penguin696, nice post! RE: waves, might it be possible to adapt this concept:http://www.gizmag.com/physicists-hide-buildings-from-earthquakes/12304/ ?

Alan Belardinelli
2nd May, 2015 @ 5:23 a.m. (California Time)

More fantasy visualizations destined to go no where.

Sorry, websites have show these kinds of dreams for years (and magazines for decades). Much as I would like to, I just can\'t entertain this stuff anymore. They just go no where.

2nd May, 2015 @ 5:23 a.m. (California Time)

There is another organization also working on designs for building sustainable cities on the oceans: The Seasteading Institute, San Francisco USA. http://www.seasteading.org/

It\'s only a matter of time (10 years... 20 years... 50 years) before this becomes feasible; it\'s just solving some hard engineering problems through technology, and then eventually the tech becoming economical. Both organizations are clearly focused on the engineering of it right now -- very cool.

Adam Selene
2nd May, 2015 @ 5:23 a.m. (California Time)

Seems to me that the best solution to waves is to convert them to usable energy. There are over 125 current designs in at least the early testing stage for converting wave energy to electricity. This could both power the city and absorb any potentially destructive energy

2nd May, 2015 @ 5:23 a.m. (California Time)

One tiny Tsunami, this so call structure will flip. Just don\'t make sense. I prefer submersible concept.

2nd May, 2015 @ 5:24 a.m. (California Time)
The idea of an island floating at sea is great and the equatorial location is nearly ideal especially if it can move a little North and South to keep sun directly overhead at noon both Winter and Summer. This is great for solar power. The structure might be floated with large diameter pipes or tanks filled with fresh water. This would provide a hugh mass which any waves would have difficulty moving quickly and so increase stability of the whole platform a great deal. Still you might need a ring a mile or two out to break waves atoll like with your island in the center in nearly calm water. If it is true that ocean levels are going up, where are all the displaced people going to go?

Best way to fund might be to build first as a super luxury resort. Note, in deep water a tidal wave from earthquakes is very broad and will filp nothing not even a row boat.

2nd May, 2015 @ 5:24 a.m. (California Time)

Consider using an OTEC to generate power.

"OTEC is an old, simple, well understood, and well-proven renewable energy technology that has remained largely under developed today owing to the remote nature of the marine locations and large minimum system scales it requires. OTEC functions basically like any solar-dynamic power system employing Rankine cycle systems –such as large solar-dynamic plants based on vast solar mirror collector arrays and a thermal fluid. The difference with OTEC is that the solar collector is the ocean itself, the system running on the difference in temperature between warm surface seawater and cold deep seawater"


Edward Villarreal
2nd May, 2015 @ 5:25 a.m. (California Time)
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