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Venturi System Optimizes Water Flow Harnessing
A Patented venturi-turbine system by Aaron Davidson and Craig Hill of Tidal Energy Pty Ltd, increases the turbine efficiency as much as 3.84 times compared to the same turbine in free stream without the venturi, making this a world best if not world leading design.
The venturi not the turbine is the key component of the Davidson-Hill design. The design uses the venturi to create faster flow across the turbine increasing turbine efficency and output power of almost any type of turbine.
The venturi concept could also be integrated into wind turbine scenarios, but the company is focusing first on water free-flow scenarios such as tide, ocean currents, and run-of-the-river.
The technology can also be used to pump water, for desalination, and for hydrogen production using electricity to break the covalent bond between the hydrogen and oxygen atoms via the process of electrolysis.
The DHV Turbine can be mounted on a mono pile on the sea bed where surface events such as large ocean swells and sea chop might buffet the turbune, slung under a pontoon on a swing mooring or flown like a kite under water. In each case power is cabled to shore for use.
Since half of Earth's population lives within 50 miles of a coast  ( http://www.whoi.edu/oceanus/viewArticle.do?id=4498), harnessing the ocean's energy using such devices can move the world profoundly toward clean, sustainable and local energy production.
D&H plan to keep cost down by the use off-the-shelf generators, readily available in the industry, which are robust in ocean environments; such as are used in the submarine industry.
The company is now commencing the commercialization stage, with an expected price that competes with coal in the range of 3.5 to 6 cents per kw-h.