Unlimited Solar Energy from the Ocean?

In the late 1800’s, the French physicist Jacques Arsene d’Arsonval proposed a method for generating electricity using the sea as a giant solar-energy collector. It is considered that the technology, termed “Ocean Thermal Energy Conversion” (OTEC), may enable the establishment of an efficient energy storage system across the world, supplying enough energy for our entire planet.
Jacques Arsene d’Arsonval
French physicist
Jacques Arsene d’Arsonval

OTEC is based on the idea of exploiting the differences in temperature between deep waters and surface waters in order to generate electric power. Shallow ocean waters can heat up to a temperature of 29C in the tropics. Only one kilometer below these warm waters, temperatures are significantly lower, often falling below 5C. These extreme temperature differences are used to operate vapor turbines, which drive generators to produce electricity. Experts estimate that on an average day, 60 million square kilometers of tropical seas absorb an amount of solar radiation that is equal in heat content to about 250 billion barrels of oil. To get a better perspective on these numbers, this actually means that less than 0.001% of this energy converted into electric power would be sufficient to supply over 20 times the electricity consumed daily in the United States. 

Throughout the years, a number of attempts were made to refine the technology and construct a practical prototype of an OTEC plant. D’Arsonval’s student, Georges Claude, was the first to succeed in building an OTEC plant in Cuba in 1930, which was capable of generating 22 kW of electricity using a low-pressure turbine. This experiment proved the viability of such a system or, in Claude’s words “Made my virulent opponents hold their tongues.” Five years later, Claude constructed another OTEC plant aboard a cargo vessel. Unfortunately, it was destroyed shortly after the vessel departed due to poor weather conditions. The appearance of large amounts of cheap oil in the mid-twentieth century eventually brought OTEC research to a halt.      

Ocean Thermal Energy Conversion (Credit: National Renewable Energy Laboratory) 
Ocean Thermal
Energy Conversion
(Credit: National Renewable
Energy Laboratory)

A team of British architects, including Dominic Michaelis, Alex Michaelis, and Trevor Cooper-Chadwick, are currently working on a project they hope will bring the century-old idea back to life. They have proposed to construct a network of “floating platforms”, which in addition to being OTEC power generators, will be equipped with wind and wave turbines. In this way, the platforms will simultaneously exploit a number of natural energy sources to provide ‘around the clock’ electricity. The scientists say that a single “island” of this design will be able to produce around 250MW, while 50,000 of these “islands” will be able to meet the daily energy requirements of the entire world’s population. 

The architects say that an OTEC plant will not only be a supplier of green energy, but due to its unique conversion process, will also provide desalinated water as a byproduct. In addition to about 300,000 liters of fresh water each day, the OTEC plant may also be used to produce hydrogen fuel by using electrolysis. Alex Michaelis envisions the islands themselves as home to workers, who will operate and maintain the plants. Michaelis envisions the inhabitants will be able to grow seafood and vegetables, living and working in rotations on the islands.  

 Sea solar power plant concept (Credit: Sea Solar Power International)
Sea solar power plant concept
(Credit: Sea Solar Power International)

Many critics have questioned the viability of the 50,000 artificial islands system, saying it is unlikely that the project can be implemented cost-efficiently. In response to this criticism, Michaelis says that “If we consider that we are at war to find a new form of clean energy, wartime effort in World War II produced vast numbers of planes, tanks, ships and other armaments on both warring sides. 20,300 Spitfires alone were built, making the construction of more than 50,000 of these plants seem a reasonable number.”     

TFOT previously covered a number of unique renewable energy technologies, including “EnviroMission’s” Solar Tower and JAXA’s project to build the world’s first space-based power generation system. You can also check out our article about “nano flakes” – a newly discovered material, capable of converting solar energy into electricity almost twice as efficiently as traditional solar cells.    

More information on the project, as well as the latest news on OTEC, can be found here.