Environmental Impact of Technology
The principal area of environmental concern that arises during the operation of a hydrokinetic turbine is the effect on marine or aquatic life and the regional ecosystem.
Clean Current employs several features to mitigate the risk of potential injury to fish and marine mammals due to the rotation of the turbine blades. They include: a duct that ensures that fish and mammals are not accidentally struck by an exposed blade tip; and fixed guide vanes that prevent larger mammals from entering the turbine.
A study performed by the Energy Power Research Institute (EPRI) in Nov 2011 showed no evidence of fish harm or mortality when fish were forced through operating turbines. The following is a quote from the Executive Summary of this report.
“Little, if any, mortality, injury, and scale loss are expected to occur for fish encountering an LST in an open water environment (i.e., riverine or tidal). Similarly, fish entrained through a Welka UPG turbine will suffer little or no injury and mortality over the likely range of operating conditions.” 1
Another potential concern is the impact of the acoustic signature of turbines on fish and cetaceans. The rotation speed of the turbine varies between 20 and 180 rpm depending on current speed and unit size. As a result, a very low frequency noise will be produced. Cetaceans and other marine mammals are not sensitive to low frequency noise (for example, the peak sensitivity for Killer Whales is 20 kHz) and their echo communication is at a much higher frequency (10-80 kHz). The amplitude of the turbine noise is also expected to be low and this combined with the fact that the background noise of energetic tidal and river sites is very high is therefore expected to have minimal effect.
In terms of sediment suspension and deposition caused by tidal farm installations, small scale installations have been modelled and are predicted to have negligible impact. Significant research is continuing in this area with the objective of determining a maximum allowable tidal farm size that produces minimal impacts.
An excellent resource for information on the environmental impact of renewable energy technologies is Tethys. Tethys is a knowledge management system that gathers, organizes, and provides access to information on the environmental effects of marine and hydrokinetic (MHK) and offshore wind development. This information is made available by collaboration at local, national, and international levels. Tethys is named after the mythical Greek titaness of the seas.
1 “Evaluation of Fish Injury and Mortality Associated with Hydrokinetic Turbines”, EPRI, Project Manager – P. Jacobson, 1024569, Final Report, November 2011.