The Australian company's WEC is designed to mine near-shore waves with an average wave height of a mere 1.4 meters. The company says this is all part of a strategy “to develop a wave-based technology that was economically competitive with onshore wind power generation, currently the lowest cost renewable energy source.”Now, as we’ve noted before, wave energy is an unformed field, with plenty of tinkerers, inventors, schemers and dreamers. Fun stuff, but if we wrote a story about every one of them, we’d never have time to write about wild new solar or wind concepts.
Bombora earns a bit of a spotlight, though, because it earned an endorsement of its technology, becoming one of five winners of GE’s first ecomagination ANZ Challenge. That earned Bombora a tidy $100,000. GE is also dangling the possibility of a commercial relationship, including a $10 million capital pledge through the program.
The Bombora grabs energy by use of a flexible, air-filled membrane. As the wave passes it, the device “operates much like a series of foot pumps, pressurising air into a common manifold system to a drive a turbine and generator." The company says this system is simpler than other wave devices that need to be finely tuned to the waves to pick up their energy. By capturing more of the wave's energy more consistently, even when the waves aren't immense the Bombora will do well, it's designers say:
Devices like Bombora’s, with improved wave coupling, wide bandwidth of operation, good efficiencies and good light wave operation should demonstrate very attractive capacity factors.… (T)he Bombora device does not have to try to capture all of the high energy storm sea states to meet its expected annual energy production and can be located in areas with relatively modest wave resources.
The choice of air as the energy transfer mechanism is interesting – many WEC designs use a fluid. For instance, we recently wrote about the SurgeWEC, a near-shore device like the Bombora, though further along in development. It consists of a big, flat paddle that moves back and forth as the waves come through, and that motion drives hydraulics that are used to generate power. On the company website, Bombora's designers explained their choice to go with air:
Bombora assessed alternative working mediums such as liquids and found that friction losses became substantial and the inertial phase lag (created from accelerating and decelerating the liquid) made the system slow and not responsive enough to effectively capture the passing wave energy flux over a broad range of operating conditions. The effect can be thought of much like the difference you feel between sucking water or air in and out of a child’s rubber duck. The duck is much harder to fill and empty when held underwater, due to the friction and inertial effects of the water.
The 1.5-megawatt Bombora, about 80 meters wide, would be submerged at the sea floor four to ten meters under the surface of the water, parallel to the waves.
From the Bombora website, it appears the company has done a scale test in a wave simulator, but nothing out in the sea. That might actually happen sooner rather than later after the ecoimagination money and attention.
“The finalist announcement couldn’t come at a better time” Glen Ryan, a company co-director, said in a statement. “We have been self funding the project thus far and have now decided to accelerate our development schedule to complete our next phase. This will require us to raise our first round of external capital.”
If they go outside Australia in doing so, they might have to explain the origin of “Bombora.” From Wikipedia: “Bombora is an indigenous Australian term for an area of large sea waves breaking over a shallow area such as a submerged rock shelf, reef, or sand bank that is located some distance from the shoreline and beach surf break. In slang it is also called a bommie.”