Dresser-Rand is developing alternative energy sources, including wave energy. Oscillating Water Column (OWC) technology is the most successful and extensively studied technology for extracting energy from ocean waves. OWCs can be located on the shoreline, nearshore or offshore.
Dresser-Rand has patented a Variable Radius Turbine (VRT) called HydroAir to be used on OWC power plants. This technology has been developed in conjunction with Cranfield University, UK.
Incoming surface waves induce an oscillating flow of air within the chamber which, in turn, flows backwards and forwards through an air turbine installed in a duct connecting the chamber to the atmosphere. The turbine converts this air movement into electrical energy. The HydroAir impulse turbine is constructed to withstand the rigors of a marine environment using a combination of stainless steel, aluminum and reinforced composites to resist corrosion.
In addition, it offers the following benefits when compared to other turbines being used for wave energy capture:
- Above average efficiency
- One moving part - the rotor
- Lower rotational speeds than competing turbines
- Currenly designed up to 1 MW
- Wide operating range
- Reduced noise
The VRT design comprises two sets of static guide vanes located on either side and at a larger diameter than that of the rotor. These vanes are connected by a shaped duct to provide a route for the airflow. Air enters the duct at a relatively low velocity and acquires a swirl motion as it passes through the inlet guide vanes. The air then accelerates as it passes down the narrowing duct toward the turbine rotor. The air drives the rotor, and then decelerates as it travels back through the expanding duct before passing over the outlet guide vanes. The process is repeated (in reverse) for the next wave cycle.
The HydroAir turbine solution offers a step-change in efficiency and operating range over other OWC turbines. The HydroAir turbine achieves its remarkable performance with fixed guide vanes, providing the reliability that is critical to the commercialization of wave power.