ORIGINALLY PUBLISHED IN 2009.
What do you think about this now?
***************************************************************************************************
Turbines perilous to marine animals
Image via Wikipedia
By MICHAEL DADSWELL
Wed. Sep 23 - 4:46 AM
There are misconceptions concerning the turbines that will be used to extract energy from the Bay of Fundy tides and these need addressing. Tidal power from free-running, propeller driven generators is not a free energy gift. There will be environmental costs extracted from the fisheries and tourism of Nova Scotia, which your readers should know.
I have been studying the effects of tidal power on fish and fisheries since 1980 when it became apparent a tidal power plant would be installed at Annapolis Royal. Yes, I am a biologist, but I have consulted with many physical scientists and engineers over the last 29 years during my studies on hydraulic turbines. These include George Baker, an engineer and the former vice president of the Nova Scotia Tidal Power Corporation, who was primarily responsible for the design and construction of the Annapolis Royal tidal power plant. In fact, Mr. Baker funded our work over a period of 10 years because he also wished to know effects of these turbines on fish. What we found was not pretty!
During our studies at Annapolis Royal, we found there was a dramatic impact on the fishes using the Annapolis River estuary. Impacts, which continue today (see blog of the Annapolis Royal Heritage Society Sept. 8, 2009 concerning dead sturgeon found below the generator), were spread across the entire community of fishes.
Francis Jordan asked for the numbers, so here they are. We found that 40 per cent to 50 per cent of the small, out-migrating juvenile fishes (shad, gaspereau, herring, 10 cm long) were killed by turbine passage. Death was mainly by pressure flux and shear around the turbine blades.
Large fishes were mainly injured or killed by turbine blade strike. Experiments with acoustic-tagged adult shad (50 cm long) found that 20 per cent to 25 per cent were killed from a single pass. Larger fishes such as striped bass and sturgeon (one to two metres long) were often found cut in half and many gaspereau, mackerel, flounders, eels and other species were killed or maimed.
Our findings were published in peer-reviewed, scientific journals. If Mr. Jordan does not believe me, then contact the graduate students who worked on the project, many of whom are now university professors or fisheries scientists with the government.
All turbines proposed for the Bay of Fundy and discussed in the environmental assessment released by tidal power proponents in July are generically similar to the Annapolis Royal turbine. They are hydraulic lift turbines that work by Bernoulli’s Principle (which allows airplanes to fly).
Blade design generates lift from the flow of water over them, making the turbine turn and similar physical effects (pressure flux, shear, strike) will occur in these units and harm marine organisms. The problem is there are many more fishes passing through the Minas Channel. They will encounter the turbines more often because the planned turbines will generate in both directions of the tide (Annapolis only generates on ebbing tide), and the open Bay of Fundy contains many marine mammals, including seals and whales with larger body sizes, (two to 20 metres), making probability of blade strike high.
There is little difference between ship propellers and tidal turbines: both work because of Bernoulli’s Principle. The saving grace of ships’ propellers is that most are much smaller than the turbines. If you do the math, a 15-metre diameter tidal turbine turning at the RPMs outlined in proponent’s environment assessment actually have blade tip velocities of 34 to 62 km/h. Few fish or whales can swim that fast and avoid the blades, especially smaller species.
Having said that, every year fish and whales turn up dead on beaches around the Maritimes having been killed by ships’ propellers. Ships may not leave a trail of fish carcasses behind them, but they do kill some of the marine fauna. Ask whale biologists what they think.
My contention is that the large-scale development of tidal power in the Bay of Fundy will do immense damage to the fisheries and whale-watching businesses in the Maritimes. Please remember fisheries and tourism are two of our larger economic engines. Why replace one renewable resource with another when we can obtain it from other sources (wind, solar)? Hydroelectric turbines have done immense damage already to the fisheries resources and tourism of the Maritimes. Remember all the Atlantic salmon rivers we have lost to hydroelectric power generation.
Michael Dadswell is a biology professor at Acadia University
.
Photo Courtesy Blue Ocean Gear
