Just because they don’t produce noxious emissions, doesn’t mean they don’t have environmental impacts. We’re coming to understand this about many renewable energy sources, but when it comes to tidal power, the knowledge void has been especially large. “There really isn’t that much information, anywhere, about the environmental effects of tidal turbines,” says Brian Polagye, a University of Washington (UW) research assistant professor of mechanical engineering.
Enter the UW tidal-energy monitors. There’s Polagye and his team who, according to the university, are carefully monitoring a demonstration project that will place two 30-foot-wide turbines in Admiralty Inlet, the main entrance to Puget Sound. There’s also Teymour Javaherchi, a UW mechanical engineering doctoral student, who has developed a set of numerical models to gauge how changing water pressure and speed around turbines affects sediment accumulation and fish health.
At the site of the Admiiralty Inlet project, the UW team has been using a tripod about the size of a small refrigerator for the last two years to monitor water quality, ambient noise, currents, temperature and salinity, and to record marine mammal calls and electronic tags on passing fish. “This observational data will help determine precisely where to put the tidal turbines, and establish potential environmental effects once they are in the water,” said researchers.
Javaherchi, meanwhile, is finding that pressure changes caused by spinning tidal turbines could occur very quickly, possibly endangering fish, and also that slower water speeds behind turbines could allow more particles to sink to the bottom rather than being carried along by the current, turning a rocky sea bottom sandy. However, the UW researchers say these impacts are hardly deal killers for tidal power – they just give developers the information they need to adapt their designs. As Alberto Aliseda, Javaherchi’s thesis adviser, put it: “Maybe the best turbine is not the one that extracts the most energy, but the one that extracts a reasonable amount of energy and at the same time minimizes the environmental effects.”
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