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HydroAir

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TM

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Variable Radius Turbine

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Dresser-Rand is developing alter-

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native energy sources, including

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marine renewable (wave) energy.

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Turbine always rotates

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in trie same direction

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owe

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Structure

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Air Flow

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'ft

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Upward pressure

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from wave motion

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Air Flow

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Wave Trough

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* II *

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Downward pressure

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from wave motion

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Sea bed

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Oscillating Water Column Device.

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Oscillating Water Column Technology

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Oscillating Water Column (OWC) technology is the most successful and extensively

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studied technology for extracting energy from ocean waves. OWCs can be

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located on the shoreline, nearshore or offshore. Incoming surface waves induce

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an oscillating flow of air within the chamber which, in turn, flows backwards and

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forwards through an air turbine installed in a duct connecting the chamber to the

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atmosphere. The turbine converts this air movement into electrical energy.

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The challenge of OWC technology is to achieve satisfactory efficiency over

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a wide operating range, considering that the airflow not only varies between

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zero and 100 percent, but also changes direction (shaft rotation must also be

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maintained in the same direction).

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Dresser-Rand has patented a Variable Radius Turbine (VRT) called HydroAir.

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The turbine is constructed to withstand the rigors of a marine environment

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using a combination of stainless steel, aluminium and reinforced composites to

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resist corrosion. In addition, it offers the following benefits when compared to

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other turbines being used for wave energy capture:

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• Above average efficiency

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• One moving part - the rotor

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• Lower rotational speeds than competing turbines

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• Currently designed up to 500 kW

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• Wde operating range

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• Self-starting

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• Reduced noise

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The VRT design comprises two sets of static guide vanes located on either

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side and of a larger diameter than that of the rotor. These vanes are

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connected by a shaped duct to provide a route for the (inlet/outlet) airflow. Air

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enters the duct at a relatively low velocity and acquires a swirl motion as it

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passes through the inlet guide vanes. The air then accelerates as it passes

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down the narrowing duct towards the turbine rotor. The air drives the rotor, and

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then decelerates as it travels back through the expanding duct before passing

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over the outlet guide vanes. The process is repeated (in reverse) for the next

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wave cycle.

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In comparison with both Wells turbines and conventional impulse turbines,

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the HydroAir turbine solution offers a step-change in efficiency and operating

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range. The HydroAir turbine achieves its remarkable performance with fixed

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blade geometry, providing the reliability that is critical to the commercialisation

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of wave power.

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owe

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Structure

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Main Waterline

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DRESSER "RANDi

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