AquaEnergy Group, Energetech and The Manchester Bobber have come to my attention as three additional developers of wave power systems.
AquaEnergy Group is developing a wave energy converter called the AquaBuOY. Clusters of these small, modular buoys would be moored several miles offshore where the wave resource is the greatest. Energy transfer takes place by converting the vertical component of wave kinetic energy into pressurized seawater by means of two-stroke hose pumps. Pressurized seawater is directed into a conversion system consisting of a turbine driving an electrical generator. The power is transmitted to shore by means of an undersea transmission line. The AquaBuOY consists of four elements:
- Buoy - A 30 ft long buoy, 15 feet of which is submerged, is used to support the system and keep it stable.
- Acceleration tube - The acceleration tube is a vertical, hollow cylinder rigidly mounted under the body of the buoy. The tube is open at both ends to allow unimpeded entry and exit of seawater in either direction.
- Piston - Positioned at the midpoint of the acceleration tube is the piston, a broad, neutrally buoyant disk. When the buoy is at rest, the piston is held at the midpoint by the balanced tension of two hose pumps that are attached to opposite sides of the piston and extend to the top and bottom of the acceleration tube, respectively.
- Hose-Pump - The hose-pump is a steel reinforced rubber hose whose internal volume is reduced when the hose is stretched, thereby acting as a pump. The pressurized sea water is subsequently expelled into a high-pressure accumulator, and in turn fed to a Pelton turbine which drives a generator. Generated electricity is brought to shore via a standard submarine cable.
AquaEnergy is currently designing and permitting the Makah Bay (state of Washigton, USA) one megawatt demonstration power plant, with a goal of delivering power to the Clallum County Public Utility's grid by the end of 2006.
Energetech uses a parabolic wall to focus wave energy on to an oscillating water column (OWC) chamber. The rising and falling motion of the waves causes an oscillatory water motion within the chamber, which in turn forces a high-speed airflow past a unique controllable turbine. The air flow past the turbine oscillates in the same manner as the water column requiring a turbine that can operate with this motion. A control system senses the rising and falling of the waves and sends a signal to a 'Dennis-Auld' turbine which is designed to operate with an oscillatory flow. The turbine drives an induction generator to produce electrical power.
Construction of the first 1 MW power plant, the Port Kembla (Australia) project, was begun in early 2004 and was initially installed in June 2005. Initial tests indicated some minor improvements were required and the unit was brought back to shore for modifications. During the time at the site, initial operation indicated that the chamber and design concept worked successfully and power was generated. The modifications have been completed and a September report indicated the unit was back in operation.
Greenwave Rhode Island is a $3.5 million, 500 kw not-for-profit pilot Energetech project. Operation is expected in 2006 and will continue for 3 years. The states of Connecticut, Massachusetts and Rhode Island have contributed $1 million in planning and development funds to the project and it is being conducted in cooperation with the Universty of Rhode Island.
The Manchester Bobber, being developed by the University of Manchester, UK, generates electricity from the up and down motion of the ocean, no matter what the source; waves, tidal or current. The advantages of this device are:
- All vulnerable componets are housed in protected environment located above sea level with easy access and readily available for maintenance, resulting in higher reliability.
- The 'Bobber' responds to waves from any direction with requiring any adjustment
- Each individual element of the 'Bobber' may be maintained independent of others in the group without interruption of the power generated in the group.
Phase one; design, development and testing of a 1/100th scale working model were completed in January 2005 and the phase two construction of a 1/10th scale model has been completed and testing was started in September 2005. Phase three will involve a full scale prototype being constructed and tested in parallel with detailed costings and engineering design for the optimum full scale concept.
AquaEnergy Group Ltd., Mercer Island, WA, USA
Energetech Australia Pty. Ltd., Randwick, Australia
"Manchester develops new wave energy device: The Manchester Bobber", U of Manchester press release, 9/5/05
Manchester Bobber: Technical Description, Manchester Bobber website