Floating and vertical farming technologies are in use today on a small scale, but some researchers and entrepreneurs say they are promising forms of alternative food production.

“It will be the international breakthrough for urban farming,” says Hans Hassle, founder Plantagon, Stockholm, Sweden, of the company’s 180-ft-tall vertical greenhouse and office building, scheduled to begin construction in Linkoping, Sweden in the summer of 2015.

The impetus to plant farms in towers or on floating platforms, is to cut down on major cities’ reliance on imported food.

Hassle says that by 2050, 80% of the earth’s population will live in urban areas, and Plantagon’s research is aimed to meet the projected geographic shift in food demand.

Sky Greens is a major commercial, vertical farm located on 8.5-acres in Singapore, which imports 90% of its food, according to Jack Ng, founder, Sky Greens, Ltd. Ng’s greenhouses feature a 30-ft-tall planting system with rotating troughs irrigated by gravity-fed water wheels, says Ng. He claims his facility supplies at least 1.5% of the produce for Singapore’s population of 5.3 million.

The idea of commercial floating farms is less proven today; futuristic designs by architects like Shimizu Corp. and groups like the Seasteading Institute keep imaginations and investors involved. The latter released a book and commissioned a concept design reports about floating islands with farms aboard. Simpler floating farms made of water hyacinths and bamboo exist in Bangladesh, where flooding is common.

Giant Solar Energy Farms

North African solar energy will power the United Kingdom and possibly other European countries in a scheme now unfolding in Tunisia to develop a 2,250-MW solar-tower plant. The project has a power-purchase agreement offer for 500 MW and commercial operation is scheduled for 2018.

TuNur Ltd., the plant’s owner, is a joint venture of solar powerplant developer Nur Energie Ltd., renewable-energy investment company Low Carbon, both U.K.-based, and a group of Tunisian investors. The project, now undergoing permitting in Tunisia and in Europe, is designed for a 25,000-acre site in the southwest Tunisian Sahara. It is set to reach financial close and start construction in 2016.

The project will consist of 18 modules generating 125 MW each. Each tower will stand at the center of rings of heliostats totaling up to 2.5 million sq meters reflecting the sun’s heat to the receiver, which is a set of vertical tubes installed on the tower. The heat-transfer medium, a mixture of molten salts, will be heated at the peak and be pumped into a heat exchanger, where it will superheat steam to power a turbine generator.

The generated power will be stepped up to 500 kV, converted to direct current and delivered via 600 km of overhead lines and 600 km of submarine cable to Montalto di Castro, Italy. There it will be stepped down to 400 kV AC for transmission into the European system.

The system has been designed by a leading U.K. engineering firm, which a Low Carbon official declined to name. TuNur will run separate commercial tenders toward the end of 2015 for the power plant and transmission to allow all major EPCs participate, the official says. Total capital required will be $12.5 billion, split between two tranches of 1000 MW. TuNur partners and shareholders have invested about $12.5 million to date.

TuNur will potentially be the largest concentrated solar power plant in the world when it is completed. Currently the largest such power plant is Ivanpah, in California, which produces 392 MW.