New York: Leading the way in tidal power

Tidal energy has been, for many decades, coveted as a compelling but mostly unreachable source of sustainable power. As the second-most plentiful renewable energy source on the planet, it is much more abundant and reliable than wind power and has the potential to be useful in many coastal cities. However, up until the present, strategies for obtaining tidal energy, such as dam construction, were generally regarded as unsustainable since they often severely damaged coastal ecosystems and potentially prevented the flow of ocean sediments. Also, such systems were often very costly and were frequently damaged by strong water currents and wave movements during severe storms.

However, in of November 2008, the New York-based company Verdant Power achieved a major green technology milestone by successfully completing a two-year demonstration of its newly developed free-flow tidal turbine system. During the two years, six 5m diameter 35 kW turbines (shown above) installed in New York’s East River supplied a total of 80 megawatt hours of energy, powering a supermarket and parking garage on nearby Roosevelt Island.

After two failed attempts with previous prototypes of the turbine, which were shredded by strong tidal currents, the latest aluminum alloy versions successfully held their shape for the two year period in the face of brutal storms. Furthermore, thanks to a 2 million dollar grant from the New York government, an in-depth study into the environmental effects of the turbines was conducted. Results showed no evidence of increased fish mortality or injury, or any irregular bird activity in the project area. With such a minimal environmental impact, these turbines are likely to become competitive with other renewable energy collecting methods in the immediate future. As silent, out-of-sight energy harvesters that can deliver larger amounts of power in more reliable tidal time cycles, they offer benefits that many other renewable energy collecting methods cannot.

However, while the technological issues seem to have subsided, it seems there are some major obstacles to overcome in terms of finance and government policy. Requiring more durable and presently more expensive materials than wind turbines, tidal energy turbines have been very slowly recognized by investors. According to a recent TIME magazine article, “Tidal projects have high initial construction costs — turbines are practically handmade — and that won't change until the market grows and developers can harness economies of scale.” Additionally, with a lot of government red tape to sift through and political hesitancy to close off potential boating and swimming sites for turbine use, many experts believe it will still be a while before tidal systems become widely used. Nevertheless, the New York City government seems to be showing a lot of support for the project and should be moving ahead shortly with the construction of two large scale energy farms in its East River.

“Supporting innovative projects like Verdant's… will help us meet our goal of reducing New York City's greenhouse gas emissions by 30% by the year 2030.” -New York City Mayor Michael R. Bloomberg, June 11th 2007

The two large-scale energy farms

Verdant Power, as part of its RITE project (Roosevelt Island Tidal Energy), is in the midst of applying for a license to build and market both a 30 turbine 1 MW farm and a 60 to 120 2-4 MW farm in New York’s East River. For comparison, 1 MW is approximately the power output of a single wind turbine operating at full capacity but these water turbines should be able to harvest much more energy than the comparable windmill since the flow of tidal currents is much more continuous than that of wind. So far, the New York government has already completed a pre-filing process to allow for an expedited review of the application to build the farm and it is likely that construction will begin soon. With eventual hopes of mass producing and installing as many as 300 turbines in the East river, the free-flow tidal turbine may end up becoming a hallmark of New York City and a widely-used international technology.

Adaptable turbine use

In addition to the RITE project in New York, the free flow turbine will also hopefully be installed in the St. Lawrence River in Cornwall, Ontario, after initial investigations into the feasibility of installing them are made. The project, entitled CORE (Cornwall Ontario River Energy) will use the constant currents of the river to ultimately generate up to 15 MW of power locally. Unlike the tidal turbines in New York’s East River, the CORE river turbines do not need to pivot to capture the reverse flow of tidal movements and can deliver energy in a much more constant manner as the river continually flows in the same direction. The project illustrates the adaptable nature of the free flow hydroelectric turbine and the huge potential for its application elsewhere in the world.

Through a series of studies prepared for the National Research Council of Canada Hydraulics Laboratory, it is estimated that the attainable capacity of the Canadian free-flow hydropower market is more than 15,000 MW. With such estimates, it seems very possible that a majority of future energy could come from hydroelectric turbines.

How the turbines work

Each turbine has three 2-meter-long aluminum alloy fins extending outward that are designed to withstand strong water currents. In the typical water flow of the East River, the fins move relatively slowly so as not to do any major damage to creatures and objects in the water. However, usually fish and wildlife will avoid the turbines altogether by inhabiting the shallower waters closer to shore where the currents are not as swift. As the tides change, the turbines pivot around to capture the flow of water in the other direction thus allowing for maximal energy harvesting.