Power from the Gulf Stream

CNN.com recently ran a story about scientists at Florida Atlantic University researching and considering ways to harness energy from Gulf Stream currents off the coast of Florida. We happen to have a Gulf Stream expert in the UNC Press family, so we asked Stan Ulanski, author of The Gulf Stream: Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic, for his take on the matter. Here is his response.

As the world’s supply of fossil fuels diminishes and known oil reserves decrease, many countries are seeking new energy sources. This push to provide energy to satisfy the ever-increasing demand from both the industrial nations and those countries (like China and India) seeking to expand their economic base also has the potential to significantly increase greenhouse gas emissions, which many scientists believe could lead to significant and irreversible climatic changes.

To counter this spiraling fossil-fuel dependence and mitigate carbon dioxide emissions, the public and private sectors have brought forth numerous proposals that have championed the use of renewable, non-polluting energy sources, such as solar, wind, and bio-fuels.

But a group of researchers at Florida Atlantic University have expanded the search for clean energy to the ocean, in particular to the oceanic realm hundreds of feet below the surface. In this dark abyss flows the Gulf Stream, a powerful current off of Florida’s eastern coast. The flow is fast and intense, with speeds of more than four knots–making the Gulf Stream one of the swiftest currents in the world’s oceans.

Studies have shown that the Gulf Stream, as it surges past Florida, maintains its relatively high speed to a depth of over a thousand feet. From its tropical origins, the Gulf Stream moves water poleward at a rate hundreds of times the combined flows of the Amazon and Mississippi Rivers. This large transport off of Florida amounts to more than 1 billion cubic feet of water every second, and it is this prodigious amount of water that the personnel at Florida Atlantic University’s Center of Excellence in Ocean Energy Technology want to tap. They have estimated this narrow, fast, and deep current could power millions of Florida homes, essentially supplying the state with one-third of its electricity. Their goal is to set an array of underwater turbines, similar to wind turbines on land, which as the Gulf Stream flows past a turbine, it turns a rotor blade to generate electricity for energy-strapped southern Florida.

Though the Gulf Stream can move for surprisingly long distances, hugging the eastern seaboard from Florida to North Carolina, southern Florida probably has the greatest potential for success for such a project. Because of Florida’s relatively narrow, shallow continental shelf–an offshore, underwater topographical feature–the Gulf Stream brushes closest to the Florida coast than along any part of its journey northward. The relatively short distance between the turbine array and the coast minimizes the loss of power from the electrical conductivity cables, which will run along the sea floor to the coast.

Though the Gulf Stream has been studied since the colonial period–Benjamin Franklin made systematic measurements of the current’s temperature–and much of its gross anatomy is known, the Florida Atlantic University team will have to perform a resource assessment in order to understand how much energy the Gulf Stream is capable of generating over a prolonged period. The jetlike structure of the current is at present being probed by four acoustic Doppler current profilers. Hopefully from this data will emerge an answer to a fundamental question: how much energy can safely be extracted versus the environmental effects?

Potential obstacles to a full-blown project include the effects the turbines might have on the marine life, recreational activities, and shipping. Migrating animals are of a particular concern to the environmental community. During the spring and summer, right whales travel from their calving grounds off the Georgia and Florida coasts to the plankton-rich northern waters.

The Gulf Stream is part of something much larger than itself–a global “ocean conveyor belt.” Though the details of this conveyor belt still need to be worked out, the Gulf Stream represents the upper, or surface, limb of the conveyor, which also includes deep flows that transport water throughout the world’s oceans. How would the turbines impact the flow of the Gulf Stream, if at all? A decrease in northward transport by the Gulf Stream could potentially impact the whole ocean conveyor belt, disrupt latitudinal heat transport, and trigger a climatic shift. The stuff of science fiction? During the next few months, the university’s ocean engineers and scientists will attempt to answer many of these questions and unlock some of the secrets of this great oceanic river in the Atlantic.

Stan Ulanski
James Madison University