Green Patent Blog®

Nordic Windpower (Nordic) is a Berkeley, California company that designs, manufactures and sells utility-scale wind turbines. 

Earlier this month Nordic announced that it had received a $16 million loan guarantee offer from the U.S. Department of Energy.  Nordic said it will use the government funds to expand its Idaho assembly plant.

Nordic’s turbines have a two-blade design rather than the more traditional three-blade rotor common in utility-scale wind.

A two-blade design reduces the cost associated with providing blades and simplifies assembly but also requires a different hub design because a two-blade turbine is less balanced and more prone to fatigue from that unbalance than the conventional three-blade turbine.

Teeter hubs, which are hinged to the turbine shaft, were developed for two-blade turbines, but they don’t hold up well in extreme wind conditions.

Nordic has developed flexible teeter hub technology so the rotor blades can flex at the hub to dissipate high winds before they can reach or damage the turbine drive train.  International Pub. No. WO 02/079647 (’647 Application) describes and claims Nordic’s flexible teeter hub assembly. 

The ‘647 Application is directed to a teeter hub (2) that allows some flexing while also better absorbing extreme torque.  Blades (1) are connected to the hub (2), and the hub is connected to the turbine shaft (3). 

The reaction arm (15) extends all they way through the hub (2) from the periphery adjacent the turbine shaft (3) to the opposite side of the hub.  The length of the reaction arm (15) allows the hub assembly to better absorb extreme torque caused by high winds.

The bearing (12), the reaction arm (15) and the spring elements (13) together form a hinge assembly.  When high winds blow, the hinge assembly allows the hub (2) to pivot slightly while the springs (13) counteract the teeter movement. 

The torque is absorbed with an even distribution on the bearing (12) and the springs (13) thus minimizing damage to the turbine.

In a previous post, I wrote about the new Swift wind turbine, developed by Scottish energy products and solutions company Renewable Devices Swift Turbines Ltd. (RDST) for use in densely populated areas.  Last month RDST obtained a patent for its turbine:  U.S. Patent No. 7,550,864 issued June 23, 2009.

RDST’s design overcomes the problem of wind turbine noise by using a circular diffuser (21) that rings the turbine blades.  In operation, when the airflow reaches the ends of the blades, it contacts the diffuser and proceeds in a circumferential path instead of flowing off the ends of blades.

The Swift turbine also has a furling device (50) with tailfins (53, 54).  When the airflow exceeds a certain speed, the furling device rotates the rotor to maintain the direction of the airflow in line with the turbine’s rotational axis.  In excessively high winds, the turbine rotor can be rotated out of the airflow altogether.  These measures reduce the vibrations of the turbine assembly components. 

Finally, the Swift turbine has a mounting structure that includes a rubber core to absorb vibrations before they spread upward to the moving parts of the turbine assembly.

RDST overcame rejections by the U.S. Patent & Trademark Office that its patent claims were obvious over two prior art patents by using a host of arguments, including some of the so-called “secondary considerations” of non-obviousness.

Independent claim 1, as amended during prosecution (and as ultimately issued) recited:

A rotor for a roof-mounted wind turbine comprising a plurality of radial blades and a ring-shaped diffuser connected to the outer tips of the blades, wherein the diffuser is an aerofoil diffuser and is configured such that it inhibits the partly axial and partly radial airflow from the blades, said airflow becoming circumferential when it contacts the aerofoil diffuser, thereby reducing acoustic emissions.

Thus, the claimed turbine rotor contained the following mechanical components:  a rotor, a plurality of blades, and a ring-shaped diffuser, wherein the diffuser is an aerofoil diffuser.

The U.S. Patent & Trademark Office (PTO) viewed this iteration of claim 1 as a combination of known elements and rejected the claim as obvious over two prior art patents, one of which disclosed a rotor, blades and a diffuser and another that taught an aerfoil diffuser.  According to the patent examiner, it would have been obvious to combine the aerofoil diffuser of reference two with the rotor blades and diffuser of reference one to achieve a reduced noise level.

RDST successfully overcame this rejection by pointing out deficiencies in the cited prior art and by using a host of non-obviousness arguments.  For instance, RDST argued that the prior art taught away form attaching a large mass to the ends of rotor blades, that the degree of noise reduction was an unexpected result and that competing designs had failed to achieve comparable noise reduction.

Finally, to tie it all together for the patent examiner, RDST submitted audiovisual evidence of the its quiet turbine in action.

Pax Scientific, Inc. (”Pax”) is a San Rafael, California company that specializes in fluid-handling technology used in applications such as fans, mixers, pumps, turbines, heat exchangers, ducts and propellers.  Pax owns U.S. Patent No. 5,934,877 (’877 patent), entitled “Rotor with logarithmic scaled shape”.

The ‘877 patent is directed to a rotor, the surface of which is configured according to a logarithmic curve known as the Fibonacci Progression, or the Golden Section.  According to the ‘877 patent, this type of surface is commonly found in shells of the phylum Mollusca, particularly in the classes Gastropoda (that’s squid, cuttlefish and octopus to you and me) and Cephalopoda (e.g., snails and slugs).

This is an example of biomimetics, the application of systems found in nature to the study of engineering and the development of technology.  The ‘877 patent states that the invention “enables fluids to move over the surfaces of the rotor in their naturally preferred way, thereby reducing inefficiencies created through turbulence and friction…”

Claim 1 of the ‘877 patent reads:

A rotor for use with a fluid flow generator or reactor, said rotor being intended to rotate about a central axis and having a surface which defines an arcuate fluid pathway for fluid flow about the central axis about which the rotor is able to rotate, wherein the surface has the configuration of a logarithmic curve substantially conforming to the Golden Section.

Last month Pax sued Re:Thought, LLC (Re:Thought), a Colorado product design consulting firm, and Robert Irwin, the company’s co-founder, in federal court in San Jose, alleging that the firm’s Biometric Horizontal Wind Axis Turbine (BioHAWT) infringes the ‘877 patent. 

According to the complaint (pax_complaint.pdf), Irwin repeatedly contacted Pax’s president and CEO, Jay Harman, about developing a wind turbine using the techniques of biomimetics.  Pax alleges that Irwin revealed details about his design, including pictures and sketches, and solicited technical advice from Harman. 

Despite being warned that his design would infringe Pax’s ‘877 patent, the complaint states, Irwin and Re:Thought displayed a prototype of the BioHAWT in Denver in the fall of 2008.  The complaint accuses Re:Thought of direct infringement and and Irwin of contributory infringement and inducing infringement.

WePOWER is a Laguna Niguel, California renewable energy company that provides wind, solar and magnetic energy solutions.  The company’s specialty is vertical axis wind turbines (VAWT) for use in cities and suburban areas.

WePOWER had been partnering with another California VAWT startup called PacWind and announced last month that it has purchased PacWind’s proprietary technologies.  The deal gives WePOWER ownership of U.S. Patent No. 7,109,599 (’599 patent) and U.S. Patent Application Pub. No. 2008/0273978 (’978 application), both relating to omni-directional VAWTs.

The ‘599 patent is directed to a wind rotor having a central vertical axis of rotation (13).  The rotor assembly includes an upper ring (25) and a lower ring (26), with a plurality of vanes (35) connected to the upper and lower rings and extending axially between the rings.  An electric generator (40) is supported by the rotor foundation.

The ‘978 application is directed to a vertically-oriented wind turbine (20) with a central axis of rotation (21).  The turbine assembly has a generator (24) mounted to a base (23).  A bearing (25) supports the rotor (26) and mounts two sets of three arms each (28, 29, 30), with one set above the other.  Vanes (31, 32, 33) are rigidly attached to the ends of respective arms (28, 29, 30).

The PacWind acquisition boosts WePOWER’s position in the small wind market, including its trendy and cleverly named sub-specialty of wind-powered billboard advertising, which the company calls ”windvertising” (see the “windvertising” piece here, the New York Times article here and the Triple Pundit story here).

WePOWER has put a “TM” after WINDVERTISING on its web site, signaling that it is using the term as a trademark (see here), but a search of the U.S. Patent & Trademark Office database indicates no trademark application has been filed yet.

A post on the Green Light blog led me to an interesting Green Inc. story about a new cottage industry - refurbishing and reselling used wind turbines. 

As wind turbines have become larger and more efficient, 1980’s era wind farm owners have discarded their old turbines in favor of the newer models.  A bunch of companies that overhaul and sell used wind turbines have emerged, including Halus Power Systems (Halus), Energy Maintenance Service (EMS), Aeronautica Windpower and Nexion DG.

The first thing I thought of as a patent attorney was the potential infringement liability.  If indeed the turbines at issue are from the 1980’s, to the extent they were patented, the patents have expired by now.

But if these companies are servicing turbines made more recently, infringement could be an issue.  Under U.S. patent law, once a patented article is sold, repair of the article is permissible, but reconstruction (making an essentially new article on the template of the original) constitutes infringement.

The line between repair and reconstruction is not always clear and depends on the facts of each case.  The types of refurbishment that the U.S. Court of Appeals for the Federal Circuit has held to be permissible repair include re-applying a non-stick coating to a cooking device, replacing an inner container for medical waste, and replacing disks in a tomato harvester head.

By contrast, when an entirely new cutting tip was created for a patented drill bit after the existing cutting tip could no longer be sharpened and reused, the Federal Circuit found the overhaul to be reconstruction.

Two key issues run through the case law on repair and reconstruction.  The first is whether the entire patented article as a whole can be viewed as having completed its useful life.  In these cases, refurbishment typically is deemed infringing reconstruction.

The second is whether the whole patented article consists of a combination of unpatented parts.  In those cases, even where refurbishment is extensive and includes disassembly, modification or replacement of many of the unpatented components, the process is likely to be viewed as permissible repair.

So, assuming the possibility of overhauling patented wind turbines, if the used or broken turbines still have useful life in them and consist of unpatented blades, generator, gearbox, etc., these resellers are likely to be in the clear.  On the other hand, if the turbines are spent or have anything like the patent protection of Clipper Windpower’s Liberty wind turbine, an overhaul could rise to the level of patent infringement.

Another factor, of course, is authorization from the patent holder.  Halus’s website says the company specializes in remanufacturing wind turbines originally produced by Vestas, but it’s unclear whether there is some type of partnering arrangment between the two companies.