Energy Islands
Tech Level: 12

As the world grows ever more energy-hungry, and the need for alternate power sources become paramount, a new proposal has come along that combines a number of emerging technologies into a single structure.

At the heart of this new system is a process called Ocean Thermal Energy Conversion, or OTEC. The original idea is credited to 19th century architect Jacques-Arsene d’Arsonval, who envisioned using variations in ocean temperatures to create electricity. Today, a modern, expanded version also includes supplementary solar-electric, wind, tide, and wave generators at the same site to produce electricity.

The extreme differences in water temperature between the surface and a kilometer cab reach up to 24 degrees Celsius in tropical waters. Ammonia or other working fluid with a low vapor point is used. The ammonia is gaseous at surface temperatures and used to drive electrical turbines. Cooler water from the depths, typically around 5 degrees, is then used to recondense the ammonia and send it back into the system to be reused. This constant cycling of the ammonia vapor drives an electrical generator.

Even though its energy conversion efficiency is relatively low, about 3% at best, a full-scale OTEC plant could generate about 250 megawatts, or the equivalent of a quarter of an average fossil fuel power plant.

The OTEC generator would only be part of the energy island, however. Solar cells, multi-tiered wind turbines, wave actuators around the rim of the island, and tidal generators below the surface all combined would provide an additional 73 MW to add to the OTEC plant’s 250 MW. Estimates state that it may take between 4 to 8 energy islands to replace one nuclear power plant, or half that to replace a conventional fossil-fuel plant. Some 53,000 would be needed to supply the world’s current energy needs. But as they would have to be widely spread over the tropics of three ocean to be maximally effective, even this number would only have minimal effect on navigation and the environment.

One advantageous side-product of the OTEC process is desalinated water from the evaporation and condensation of the water pumping through the system. The island would produce several tons per day, and can be used for export to agricultural concerns on land, or even be used to cultivate hydroponic farms on the lower levels of the island. Using electrolysis on the steam from the evaporator could also yield a cheap and plentiful supply of hydrogen for various energy and commercial uses.

But the biggest advantage with energy islands, of course, is that all the energy it produces comes from 100% renewable, non-polluting sources. They would utilize deep-ocean artificial island techniques such as those used for oil drilling platforms, but expanded to accommodate a much larger surface area.

The biggest obstacle to creating these energy islands is mostly economic. Most agree that OTEC technology could become commercially viable if given the proper funding and time for research, something that most organizations until recently have been very unwilling to do. However, with oil prices rising alongside environmental concerns, OTEC and energy islands are currently being actively researched by the governments of Japan, Taiwan, India, South Africa, the Philippines and the United States.


Article added 10/20/2008