Thursday, October 4, 2012

Extra Energy for Wind Turbines

A large proportion of the inventions approved by USPTO’s Green Technology Pilot Program are directed toward wind turbines. All aspects of wind energy have been patented under the program – towers, turbines, nacelles, blades, generators, control systems, even construction techniques. Wind turbines convert the kinetic energy of wind to rotational motion of the blades (or rotor), thence to electrical energy via the coupling of the rotor to a generator housed in the turbine nacelle.  In operating wind turbines for generating electricity it is sometimes necessary to reduce the power output of the turbines in a wind farm.  Conditions requiring reduced turbine power output might include maintenance periods, low or high wind conditions outside the operating envelope of the turbine, or periods when electricity generated by the wind turbine is not needed. Reduced wind turbine output (or “wind turbine curtailment” in the technical parlance) means that the aerodynamic energy present in wind is not captured, and from a clean tech standpoint, is wasted.

The New

Figure from US 7,750,490
Method and system for extracting inertial energy from a wind turbine”, US 7,750,490, was issued to Hartmut Scholte-Wassink (Lage, Germany) on July 6, 2010. The patent was assigned to the General Electric Company. GE has been a very significant participant in the Green Tech Program receiving more patents than any other assignee. The patent provides two sets of claims: claims 1–8 are systems claims, and claims 9–15 are methods claims. Claim 9, the independent method claim states:
"A method for operating a wind turbine during curtailment of the wind turbine, the wind turbine comprising a generator and a rotor having at least one rotor blade, the wind turbine also comprising a drive train that includes at least one shaft coupled to the rotor and configured to drive the generator, said method comprising:
operatively coupling a control system to the wind turbine, the control system configured to adjust wind turbine operation to facilitate increasing a speed of rotation of the rotor during curtailment of the wind turbine;
and, operatively coupling an extraction device to the generator, the extraction device configured to extract inertial energy stored in the drive train upon release of the curtailment."
The extraction device in this invention constitutes a frequency converter (shown as 44 in the patent’s Figure 2) that is used to extract the potential energy stored in the increased shaft rotation speed described in claim 9 and other claims.

The Old

Figure from US 452,546 - May 1891

The earliest wind turbine patent related to the ‘490 patent, via the same original classification, was not issued by the Green Tech Pilot Program. It preceded the start of the Program by more than 118 years. J.M. Mitchell of Lawrenceville, GA was awarded patent US 452,546 in May 1891 for a “Wind apparatus for generating electricity and charging secondary batteries.” Mitchell explains:
"My invention relates to that class or type of mechanism whereby the natural powers or forces are sought to be utilized for the generation of one or more electric currents, the object being to supply electric currents having suitable energy for the operation of electric-arc lamps or other devices, or, on the other hand, for incandescent lamps, or doing other work, such as operating motors, and for other purposes. 
"It is the purpose of my invention to provide a simple and efficient apparatus in which the motive power is the wind, and to so construct the parts and organize the same that the wind-wheel shall be at all times presented to the direct action of the air-currents without breaking the electrical connections between the poles of the dynamo turning with said wheel."
Mitchell’s patent describes in detail all aspects of the turbine nacelle, transmission, generator, and includes battery storage (38 in his figure). A clean tech man ahead of his time.

Patents issued in the USPTO Green Technology Pilot Program, many of which are based on technology well over a century old, are described in Way Better Patents Discovery and Analysis Report.