Blue Energy Technology has an innovative adaptation for tidal current power using vertical axis blades. Instead of the horizontal propeller, their Davis Hydro Turbine is vertically oriented.  Through narrowing duct channels the tidal force is directed into the vertical hydrofoil turbine blades that spin the generator.  This system is similar to Hydroelectric Dams that have been used at the opening of estuaries or rivers but the company claims that their system is far less intrusive and their construction process has a much lower impact.  They have a range of sizes from small installations for single homes up to massive systems that are capable of producing thousands of kilowatts. These larger installations can be incorporated into bridges and do not completely block off the water way like a damn would so they do not disrupt migratory paths.  Plus they employ a system of fences and sonar controlled auto-breaking systems to prevent harm to large marine mammals.