![]() ![]() Oscillating devices are the most common form of reciprocating devices. Reciprocating devices do not have rotating components and instead have a hydrofoil that is pushed back and forth transverse to the flow direction by lift or drag.Photo Credit: Ocean Renewable Power Company (ORPC) Concerns about noise, electromagnetic fields, changes in flow, and impacts on water quality are similar to that of axial flow turbines. There is typically less environmental concern for collision between turbine blades and marine organisms because, depending on the design, blades are spinning in the same direction to the flow of water.The electricity production mechanism is similar to axial-flow turbines. Turbines can be open or ducted (shrouded) and placed anywhere in the water column, though bottom-mounted is the most common. They typically have cylindrical cross-sections amenable to placement in confined channels or allowing tight array spacing. When mounted vertically, these devices can operate regardless of the direction of flow. They can be mounted in either vertical or horizontal orientations. These turbines capture kinetic energy of moving water with spinning blades oriented perpendicular to the direction of flow.Large-scale tidal changes in flow (from arrays) may disrupt natural physical systems to cause degradation in water quality or changes in sediment transport, potentially affecting ecosystem processes. Likewise, chemicals such as anti-corrosion paint and small amounts of oil and grease may enter the waterbody during spills, though some turbine designs do not require lubrication, and affect water quality. ![]() As with all electricity generation, there is a slight concern that electromagnetic fields generated by power cables and moving parts of the turbines may affect animals that use Earth's natural magnetic field for orientation, navigation, and hunting. There is also concern that noise from turbines can affect animals that use sound for communication, social interaction, orientation, predation, and evasion. The main environmental concern is collision between turbine blades and marine organisms due to natural animal movements, attraction to the device, or inability to avoid the turbines within strong currents.They can have pitching blades allowing them to change their hydrodynamic performance based on flow conditions or control settings. Turbines may use active or passive measures to yaw or vane in the direction of flow. ![]()
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