January 29, 2008 While governments and corporations were exploring petroleum as a fuel source in the 19th century, Jacques Arsene d’Arsonval proposed another liquid source for power – the ocean. It may have taken a hundred years, but his ideas are finally starting to come into fruition. Ocean Thermal Energy Conversion uses the temperature difference between surface and deep-sea water to generate electricity – and though it has an efficiency of just 1-3% - researchers believe an OTEC power plant could deliver up to 250MW of clean power, equivalent to one eighth of a large nuclear power plant, or one quarter of an average fossil fuel power plant. Architect and engineer Dominic Michaelis and his son Alex, along with Trevor Cooper-Chadwick of Southampton University are developing the concept with plans of putting the theory to the test on an unprecedented scale by building a floating, hexagonal Energy Island that will harness energy from OTEC, as well as from winds, sea currents, waves, and the sun.
The US National Renewal Energy Laboratory estimates that the world’s tropical seas absorb the solar power equivalent of 250 billion barrels of oil per day. OTEC uses warm surface water to vaporize a fluid with a low boiling point, typically ammonia or propane, and pumps cooler water from depths of up to 1000 meters below the surface to re condense the fluid. The movement of the liquid through the system is enough to continually power a turbo-generator. The simplistic nature of the station, which behaves almost like a gigantic internal combustion engine, allows OTEC power plants to be largely self-sufficient. And unlike wind and solar energy, which have a fluctuating output that changes according to the weather and the time of day, the regularity of ocean temperatures and movements provide a far more stable and consistent source of power.
The Energy Island project is bidding for the US$25 million funding offered by Richard Branson’s Virgin Earth Prize, which is awarded for environmentally responsible research. The OTEC technology is something of a green dream; not only is it clean and renewable, but so are its by-products. By subjecting the steam to electrolysis, large quantities of hydrogen can be produced, paving the way for cheaper hydrogen fuel cells. And by using an Open-cycle OTEC - where low-pressure containers boil seawater and condense the steam elsewhere after passing it through the turbo-generator – large amounts of fresh water can be created. Energy Island is also packed to the brim with other renewable energy collectors, with wind, wave, current and solar sources providing a total of 73.75 MW.
Michaelis estimates it would take a chain of 4-8 Energy Islands to achieve the production levels of a nuclear power plant. To replace nuclear power entirely, Michaelis estimates a chain of 3708 modules would be required, stretched over a total length of 1928 kilometres, and consuming a total square area of roughly 30 by 30 kilometres. To shoulder the entire global energy consumption, based on 2000 figures, 52 971 Energy Islands would be needed, occupying a total area of 111 x 111 kilometres - described on the Energy Island site as “a pin point in the oceans.” Though the Islands have to be spread out to be effective, their location doesn’t infringe on otherwise usable real estate, as is the case with land power stations, and some bioethanol farms. Michaelis claims that in certain areas, chains of Energy Islands may even help maintain the environment, by combating erosion from the predicted rising sea levels, supporting deep-water ecosystems and aquaculture, and cooling greenhouses.
Energy Island isn’t the first project to portray OTEC as the solution to Earth’s power and pollution woes. Previous plans for the technology, most notably John Craven’s, have been positively utopic. Craven saw OTEC not only as a source of cheap power and water, but also as a method for accelerating crop growth, and, (no utopia would be complete without it), a provider of free air conditioning. Project Windfall, meanwhile, was a plan authored by a Florida group that involved installing an OTEC plant in order to reduce the hurricanes that routinely ravage the east coast.
But while OTEC has captured the imagination of scientists, it has not had nearly so much success with governments. The United States established the Natural Energy Laboratory of Hawaii Authority in 1974, viewing the high electricity costs of the state, and the dynamics of the surrounding water, as the ideal testing ground for OTEC technology. The NEL successfully demonstrated a 250 kW closed-cycle plant in 1999, but ultimately the money evaporated faster than the water, and Congress shifted attention to more economical areas of research. OTEC could be commercially viable, said test director Luis Vega, but it needed “patient funding” to reach that stage.
Only now, with rising oil prices and the increasingly cataclysmic predictions of global warming, could OTEC receive the “patient funding” necessary for progress. Plans for OTEC plants are being entertained by the governments of Japan, Taiwan, India, South Africa, the Philippines and the US, which recently passed a bill that gives OTEC, and tidal, wave, and ocean current research, $50 million per year for five years.
However, the next breakthrough in OTEC research may well come from the armed forces. The US government has been directing its various departments into funding and using renewable energy – in an example that must give Democrats migraines of confusion, Guantanamo Bay receives a quarter of its power from wind energy. By 2025, the Pentagon is to increase its renewable energy use to 25% of its total power. The Navy is planning to build an 8MW OTEC facility in 2009, near the island of Diego Garcia in the Indian Ocean, while the Army is planning to build an OTEC facility in the Marshall Islands in the Pacific.
As the Energy Island site states, despite being 100 years old, OTEC is in its infancy. But given the renewed interest, and the multitude of various benefits, it’s possible that the next 100 years of this concept could profoundly change the energy and environmental management of the Earth.