Read the New Column, “Power from Tides”

Tidal currents in Cobscook Bay on the Gulf of Maine. Courtesy University of Maine

My latest “Innovate” column explores the mysteries of gathering electricity from the tides. Tides are in a category by themselves as a source of energy; they exert themselves in every ocean, but only in a few locales do they get moving fast enough to spin a turbine. In the U.S. some of those places are the East River in New York, Puget Sound in Washington State, the Gulf of Alaska, under the Golden Gate Bridge, and the Gulf of Maine. The pulses of the Gulf’s Cobscook Bay are shown at the left in all their beguiling glory.

Cobscook Bay. Image credit: The Nature Conservancy

I got turned on to the Gulf of Maine when I found my interview subject, Dr. Huijie Xue of the University of Maine (and creator of this graphic). A specialist in modeling of tidal currents, Xue is monitoring the very first turbines to be placed in the Gulf by the Ocean Renewable Power Company. Specifically, she’s trying to figure out if a bank of turbines on the bay floor will harm the bay’s extraordinary ocean life.

It is a breathtakingly difficult question to answer, mostly because no one has ever tried to study tides to this level of granularity. In the 20th Century only commercial reasons to measure tides were shipping and boating. Tell a fisherman when to expect the surface tide will turn and how fast, and that’s all science needed to answer. Now Xue is among a new generation of oceanographers attempting to decipher the tidal action from bay floor to the surface at locations like Cobscook Bay, with its torturously complicated shape. Then she needs to determine what effect a turbine might have on, say, the transportation of lobster larvae. Not so easy.

In the column I also look at cool designs for tidal turbines, which I will explore more deeply in my next post.