Floating 'Energy Islands' Could Power the Future
The ocean harbors abundant energy in the form of wind, waves and sun. All of these could be sampled on something called an Energy Island: a floating rig that drills for renewables instead of petroleum.
The concept is the brainchild of inventor Dominic Michaelis. He was originally unsatisfied with the slow progress in developing ocean thermal energy conversion (OTEC), a process in which cold water is pumped up from the deep ocean to generate electricity.
“Nothing new was happening with OTEC, so I thought why not bring other marine energy technologies on board?” Michaelis said.
The Energy Island that he and his son have designed would have an OTEC plant at its center, but spread across the 2,000-foot-wide (600-meter-wide) platform would also be wind turbines and solar collectors. Additionally, wave energy converters and sea current turbines would capture energy from water moving around the structure.
One of these hexagonally-shaped islands could generate 250 megawatts (enough power for a small city), Michaelis said. Even more power is possible by mooring together several Energy Islands into a small archipelago that could include greenhouses for food, a small harbor for ships and a hotel for tourists.
To attract possible investors, the Energy Island team will present their concept this week at the U.S. China GreenTech Summit in Shanghai.
Running hot and cold
The principle reason to build an Energy Island is to harvest OTEC.
“The advantage of OTEC over other marine energy technologies is that it’s constant, 24 hours a day and all year round,” Michaelis told LiveScience.
This is because it is based not on the sun or the wind or the waves, but on the temperature difference between warm water at the sun-heated surface and cold water in the deep, dark ocean.
The biggest temperature differences can be found in tropical seas, where the surface water is around 80 degrees Fahrenheit (25 degrees Celsius).
This warm water is drawn in from around the Energy Island and used to evaporate a working fluid, which might be seawater or ammonia. The resulting vapor pushes a turbine that produces electricity.
To condense the vapor back to fluid, cold water at about 40 degrees Fahrenheit (5 degrees Celsius) is pumped up from a half mile below the surface. This condensation creates a pressure drop that helps suck more vapor through the turbine blades.
The same basic process occurs in a coal-fired or nuclear power plant, but the temperature difference between water boilers and cooling towers is much greater than in an OTEC system.
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