One of the finalists for the prize in this year's Buckminster Fuller Challenge is a project that would use known technologies to convert the Sahara desert into a sustainable source of fresh fruit and vegetables.
Every year, the Buckminster Fuller Challenge asks designers, architects, inventors, students, scientists, and just about any one else to submit ideas that could help solve the world's pressing problems using Fuller's idea of "design science." The finalists have just been announced. Most of the entries focus on the developing world, but some propose solutions to problems like getting packages around in New York City (use special routes that go through subways) and broadcasting PSAs about the environment effectively.
The project you see above is called Sahara Forest. Its creators write:
The purpose of our scheme ‘The Sahara Forest Project' is to reverse the trend of desertification, grow food crops and, through the climatic benefits produced by revegetation and carbon sequestration, to address climate change. The project combines two proven and economically viable technologies, the Seawater Greenhouse and Concentrated Solar Power (CSP), for the first time. The Seawater Greenhouse is an ingenious technology that creates a cool growing environment for food crops in hot arid regions and is a net producer of distilled water from seawater. Designed by Charlie Paton with three pilot versions built, the scheme essentially mimics the hydrological cycle in miniature. Seawater is evaporated from cardboard grilles at the front to create cool humid conditions within the greenhouse and is then condensed as distilled water at the back. CSP concentrates the sun's heat to drive steam turbines and produce zero-carbon electricity. A 300km by 300km square of the Sahara desert would be sufficient to generate all the world's electricity needs. The two technologies are powerfully synergistic: They both work best in sunny regions, the Greenhouse produces surplus de-ionised water that CSP plants need to maintain maximum efficiency while CSP produces large amounts of surplus heat that can be used to increase the amount of seawater evaporated and thereby extend the area of land that can be irrigated.
Here is a seawater greenhouse in action in the Oman desert.