I recently read an interesting article about Oscilla Power, a Seattle-based company that makes wave power generators.

Oscilla’s wave energy harvesters are based on a phenomenon called magnetostriction, a property of some ferromagnetic materials to change their shape slightly in the presence of a magnetic field.

However, Oscilla applies this process in reverse – called reverse magnetostriction – by applying stresses or strains to the materials so their magnetic characteristics change.  When coupled with a generator that has permanent magnets and wire coils, the process generates electricity.

Oscilla owns a number of patents and pending applications covering its technology, including two related U.S. Patent Nos. 7,816,797, and 7,964,977, entitled “Method and device for harvesting energy from ocean waves.”

These patents are directed to a device (100) for harvesting energy from the oscillations of ocean waves (102).  The core modules of the device (100) include at least one buoy (104) attached to magnetorestrictive elements (106) via tethers (110).

The magnetorestrictive elements (106) are anchored to the seafloor or to another rigid body using anchors or weights (108).

According to the Economist piece, the magnetorestrictive elements are bars made from a strongly magnetic alloy of iron and aluminum.  These bars need be compressed only very slightly (one part in 10,000) to generate electricity.

Even such a tiny compression takes a large force when the bar is made of solid metal, but ocean waves have sufficient power to generate the required force and do so by oscillation.  Oscilla’s generators have two large objects connected by cables:

A buoy floating on the surface of the ocean contains the generating apparatus of alloy bars, magnets and coils, as well as sets of hydraulic rams which can squeeze the bars.  The cables connect the buoy to a heave plate maintained in a stationary position.

As the buoy rises and falls with the waves at the surface and the heave plate stays still, the tension on the cables increases and decreases.  The changing tension drives the rams and produces electricity.

Because the generators operate on changing tension, they don’t need to employ lot of moving parts and should therefore be more reliable than conventional wave power generators.

After a successful trial of a four-meter prototype last year, Oscilla hopes to build a full-scale device by 2018.

Carnegie Wave Energy (Carnegie) is an Australian company that develops and commercializes wave energy technology that can not only provide power but also desalinated water.

Carnegie says it will build the world’s first wave-powered desalination plant that will generate energy as well as fresh water (see CleanTechnica article here).

The company’s CETO technology includes a buoyant acuator design rated at 240kW.  The technology is covered by at least one international, or PCT, patent application, Publication No. WO 2009/076712 (‘712 Application).

Entitled “Buoyant actuator,” the ‘712 Application is directed to a wave energy apparatus (11) including a buoyant actuator (19) with an exterior surface and an interior that is substantially hollow except for a buoyant internal support structure. 

A major advantage of the technology, according to the ‘712 Application is that the substantially hollow nature of the buoyant actuator makes it “lightweight compared to prior art floats.”

The exterior surface comprises a plurality of facets (101), which are tessellated to “create the generally spherical shape (somewhat similar to that of a soccer ball)…”  According to the ‘712 Application, one embodiment of the apparatus has 36 facets, of which 12 are pentagonal and 24 are hexagonal. 

The apparatus is installed for operation in a body of seawater (12) having a water surface (13) and a seabed (14), and exterior surface of the apparatus has a plurality of openings for fluid flow between the hollow interior and the surrounding body of water.

Pumps (15) are anchored within the body of water (12), attached to a base (17) anchored to the seabed (14), and operatively connected to the buoyant actuator (19) by a coupling (21) including a tether (23).  Each pump (15) is activated by movement of the buoyant actuator (19) in response to wave motion.

The pumps (15) provide high pressure water, which can be used for power generation and/or desalination.  Indeed, Carnegie’s desalination pilot project at the Garden Island naval base near Perth will use the high pressure water to operate reverse osmosis desalination technology.

This will be a world first, according to the CleanTechnica piece, and an elegant clean tech double bill.

I received an interesting press release about something called Nautical Torque technology, a process for generating energy from the rise and fall of ships and other large vessels with the tide.  It was invented by the late Cahill Maloney; his son, Galen, is now carrying the torch.

The process is described and claimed in U.S. Patent No. 8,143,733, entitled “System and method for providing nautical torque technology” (‘733 Patent). 

The ‘733 Patent is directed to a system for nautical torque tidal movement power generation (100) comprising an arrangement (110) of modular, electrically interconnected power generating devices (120) positioned to receive kinetic energy from the movement of water.

Accelerator gearboxes (130) are mechanically coupled to large masses (113).  A torque conversion unit (160) includes an upper drive arm (161) coupled to one large mass (113), a lower drive arm (162 coupled to a second large mass (113), cotter pins (162), a circular sprocket (163), a guide sprocket (164), a reversible gear unit (165), pylons (166), and a circumference sprocket (167) coupled to the reversible gear unit (165).

According to the ‘733 Patent, this assembly generates energy when the large masses move up and down with a tidal movement of about one foot per hour:

[The system comprises] at least one tidal movement wave 112 wherein said tidal movement wave 112 travels at a rate of substantially 1 foot per hour in a substantially vertical translation such that said large particles of mass 113 floating on a surface of said tidal movement wave 112 would travel a total of one foot per hour . . . wherein said large particles of mass 113 produce movement of 1 foot per hour in a substantially vertical direction and transmit energy output to one or more electrical transmission power generating devices 120.

According to the Nautical Torque web site, Mr. Maloney is working on a prototype to demonstrate the scalability of the technology.  More info about the inventor and the project can be found here.

Ocean Renewable Power Company (ORPC) is Maine company that develops ocean and river power systems. 

According to this NRDC blog post, ORPC’s Cobscook Bay tidal energy project in the Bay of Fundy in Maine is the first in the U.S. to receive a FERC license, include a power purchase agreement, and install and operate a power-producing tidal generator.

ORPC’s tidal generators are modular turbine-generator units that can be stacked in various configurations for bodies of water of different depths.  The company has a RivGen model for small river sites, Ocgen for depths of more than 80 feet, and the TidGen for depths of 50-100 feet.

According to Cleantech PatentEdge™, ORPC owns at least seven U.S. and international patents and pending applications covering its tidal generator technology. 

U.S. Patent No. 7,902,687 is entitled “Submersible turbine-generator unit for ocean and tidal currents” and directed to ORPC’s modular unit (‘687 Patent).  The turbine-generator unit (400) includes a support structure (410) mounting a pair of turbines (420) coupled by a rotatable shaft (430) to a generator (600).

Each turbine (420) has airfoil-shaped blades (500) mounted transversely to the direction of fluid flow for rotation in a plane parallel to the fluid flow.  According to the ‘687 Patent, the turbines are capable of rotation under reverse fluid flow and rotate in the same direction regardless of fluid flow direction.

U.S. Patent Application Publication No. 2009/0129928 (‘928 Application) covers ORPC’s turbine structure.  Entitled “High efficiency turbine and method of generating power,” the ‘928 Application is directed to a turbine (100) having a plurality of blades (105) tracing a spiral wound path about a central shaft (110).

The blades (105) are connected to the central shaft (110) by a plurality of radial spokes (115), which are substantially perpendicular to the central shaft (110).  The blades (105) have an airfoil, or hydrofoil, shaped cross-section (200) with a leading edge (210), a trailing edge (220) and a centerline chord (230).

According to the ‘928 Application, the hydrofoil shaped cross section (200) preferably is asymmetrical, which helps generate maximum torque and thereby boosts efficiency.  In addition, the hydrofoil cross section (200) presents a non-zero angle of attack for generating lift and maximizing generated torque.

The latest ORPC project update here said the company’s TidGen turbine generator is nearly complete and being prepared for deployment.