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The high and the low tides which make the water level go up and down are very suitable to built tidal power plants, but then it may not be always possible to do so due to huge costs or other limitations. So described in this article is a cheaper alternative to tidal plants namely underwater turbines. Actually the word “alternative" is not technically correct since the underwater turbines do not match the tidal power plants in their generation capacity as of now, but surely they are interesting and useful devices and are similar to tidal plants in that they also use lunar energy for power generation.
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A Typical Underwater Turbine
The current level of technology is not very developed as far as underwater turbines go and a typical set of turbines (take a look at the picture below) are hardly sufficient to power one commercial setup, but then something is better than nothing. As you can see in the pictures, these generators are quite similar in structure and appearance to wind turbines with the only difference that they use water currents instead of air currents for their operation. The turbines shown in the figure have been installed in the East River in New York.
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The turbines used in this particular setup are unducted axial flow rotor turbines with the blades made out of composite light materials. Since it can be imagined that going down to repair these turbines or brining them up for doing so would be a costly and time consuming process, they are designed with characteristics such as self cleaning and long trouble free operation. The power range of these turbines lies in the range of approximately 50 – 100 KW which certainly is not great but still is not meager by any standards.
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Benefits of Underwater Turbines
The biggest benefit of such an arrangement is obviously the freedom from building any sort of dams and similar structures for holding water which makes tidal plants a costly venture. Since they are relatively small sized and cheaper bigger industrial units could have their own of turbines and use for powering their equipment and premises thus relieving the main grid of the load even if partially. They also do not leave any by products or affect water quality in any manner since not fuels or chemicals are involved in the process.
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Potential Threats of Underwater Turbines
The same fears which haunt the tidal power plant opponents also come into play here. Though it is claimed that these are friendly for marine life, it is hard to imagine that they would not chop off the heads of bigger and rarer species of marine life, possibly including whales, sharks, dolphins and so forth. The manufacturers of this particular turbine claim that they rotate at a fish safe rpm (whatever that means) of 35 rpm.
Opponents also fear the increasing number of such turbines could cause interruption in natural current flow of oceans thus affecting the environment in the long run.