Is tidal energy just another environmental disaster?

There is a company called Verdant Power that is currently testing underwater turbines designed to convert the kinetic energy from tidal current into electricity.  The project is the Roosevelt Island Tidal Energy (RITE) project, and is located in the channel next to Roosevelt Island in New York City.  This past December, Verdant installed two turbines for initial evaluation, and plans to install four more in April assuming tests go as expected.

The Verdant turbines look and function much like a windmill, except the turbine blades are turned by water rather than wind.  (Verdant even calls their turbine an underwater windmill.)  As with a wind farm, several of these “tidal turbines” can be arranged in an underwater field to take full advantage of the current.  In order for tidal turbines to work, the water must pass through a relatively narrow channel that creates a strong current. Roosevelt Island creates an excellent channel in New York’s East River for tidal currents, which Verdant says has to energy potential to generate 10 megawatts of power.  As with wind, solar or conventional hydro power, tidal power produces no hydrocarbons and no CO2 .  That’s the good part.

But what about fish kill, spawning cycles, and underwater noise?  It could be an issue, according to Friends of the San Juans, an environmental group in Northwest Washington that has formally intervened against a tidal generating facility proposed by Snohomish County Public Utility District.  Indeed, the thought of having a field of 168 underwater windmills occupying a channel does give one pause.  According to an excellent article published in the Everett Herald recently, other groups such as the Orca Network have similar concerns.

That’s what makes the Verdant RITE project so intriguing.  It’s not just a “proof of concept” for the ability to generate power from tidal forces; it is also a detailed study on the effect of these turbines on the marine environment. An overview of the study can be found on Page 2 of the April 2006 Newsletter of the International Energy Agency’s Ocean Energy Systems organization.  Keeping in mind the article was written by a Verdant spokesperson, it does outline Verdant’s objectives to measure fish movement, navigation, recreational impacts, historical consequences, and water quality.  If the environmental impact proves acceptable, this important test could pave the way for future tidal projects.  And, according to a report generated by the Electric Power Research Institute,  tidal power could be one of the most environmentally benign ways to generate electricity.

So how is the RITE project working out?  After 40 days of operation, the system has exceeded expectations.  Tidal action has made it possible to generate electricity 77% of the time, and the turbines work equally well in both directions.  Average power output while the tide is flowing has been about 14.5 kilowatts.  This isn’t a huge amount of electricity, but keep in mind this is a pilot test.  According the the EPRI report, “Existing tidal power plants include a 240 MW plant in France, a 20MW plant in Nova Scotia, and a 0.5 MW plant in Russia.”  Clearly, this is a technology with the potential to substantially reduce our reliance on fossil fuels for generating electricty.

No doubt there will be environmental impact; there always is.  But the question to ask is not whether tidal power generation affects the environment, but how it compares with the way we produce power today.