Patent Application
20120093627
This disclosure relates to electric power-generating devices, such as wind turbines and ocean current turbines, and more particularly to a structural support for a wind turbine blade which has a detachable outer aerodynamic blade tip, which can be replaced with a longer blade tip that increases the rotor diameter and captures more wind energy or a shorter blade tip to reduce wind energy exposure.
Modern wind turbines are typically designed to a standard wind classification defining an average wind speed, turbulence intensity, extreme wind, and average air density. Current wind turbine design practice uses the wind classification to define extreme loads and fatigue loads that drive the design of the mechanical structure. However, wind turbines are typically deployed to sites or locations within an array of wind turbines at a particular site, which have lower average wind speeds, air density or turbulence intensities than that defined by the standard wind classification used for the design. This results in excess design margin in the machine design that can be leveraged by incrementally increasing the rotor diameter to the point at which the operational loads experienced by the machine will more fully utilize its structural capacity.
What is needed is a method to optimize the energy capture of an array of wind turbines at a given site, given the site-specific conditions each one will experience.
What is further needed is a method for wind or ocean current turbines which will facilitate an increase or a decrease of rotor blade lengths specific to the site at which the blades are deployed.
What is also needed is a rotor blade structure for wind or ocean current turbines, which is modular and detachable for easy access for servicing and maintenance, and which is lightweight, easily maintainable, and durable.
According to one embodiment of the present disclosure, a fluid flow power generating method is provided. More particularly, the method comprises mounting a turbine on a structure which is held stationary with reference to a fluid flow. The turbine includes a rotor having a main blade connected to a rotor hub at a proximal end and including a distal end with provisions for attaching a modular extender blade tip to the main blade. An optimum energy capture is determined using site specific conditions including one or more of air density, wind speed, extreme wind, wind shear, noise and turbulence intensity. An extender blade tip is chosen from a number of extender blade tips. The chosen blade tip has a length which is the closest to the optimum energy capture determined in the previous step. The chosen extender blade tip is then attached to the main blade.
In accordance with another embodiment of the present disclosure, a method is provided for selecting a turbine blade for fluid flow power generation. According to this method, a blade base portion is formed, as are a plurality of blade tip portions of varying lengths and/or shapes. An optimum energy capture blade length and shape is determined for a site at which the blade will be employed using site specific conditions, including one or more of air density, wind speed, extreme wind, wind shear, noise and turbulence intensity. A blade tip is then selected from the plurality of blade tips formed, which blade tip when mounted to the blade base portion will most closely approach the determined optimum energy capture blade length and shape. The selected blade tip portion is then secured to the blade base portion.
According to a further embodiment of the present disclosure, a method is provided for selecting a turbine blade for a fluid flow power generation. In accordance with the method, a configuration is determined for a blade base portion. Then, an optimum energy capture blade length and shape is determined for a site at which the blade will be employed. This determination uses site specific conditions, including one or more of air density, wind speed, extreme wind, wind shear, noise and turbulence intensity. A configuration of the blade tip portion is then determined and the blade mold is configured based on the previous steps. A blade is then manufactured in a blade mold which is configured in accordance with the last step.
The present disclosure relates to a fluid flow (wind or water) power generating system, which includes a rotor blade with interchangeable blade tips in order to vary the radius of sweep of the rotor blade to increase or decrease a cross-sectional ea of fluid flow swept by the rotor blade.
To optimize the energy capture of an array of wind turbines at a given site, a method is provided to deploy rotor blades of different lengths to fully utilize the structural design capacity of the machine, given the site-specific conditions it will experience.
The method includes the utilization of modular blade tip extensions added to a baseline blade length to achieve the different rotor diameters necessary to maximize the energy capture from each individual machine, while staying within the allowable structural design envelope. This approach to energy capture optimization takes advantage of site specific conditions of air density, wind speed and turbulence intensity that are typically less than what was defined by the standard wind classification used for the machine design.
In accordance with an aspect of the disclosure, a turbine is mounted on a structure (such as a tall wind tower or a tethered underwater nacelle) that is held stationary in the horizontal axis with reference to the fluid flow. The turbine includes a rotor having a main blade connected to a rotor hub and interchangeable modular blade tips. The blade tips vary in length relative to the main blade to expose more or less of the rotor diameter to fluid flow. A generator is connected to the turbine for generating electrical energy.
In accordance with a further aspect of the disclosure, the modular blade tips are detachable from the main blade for easy access for servicing and maintenance.
In accordance with a further aspect of the disclosure, a calculation methodology is used to establish what increase in rotor diameter is possible on a site specific, or pad specific location within a site, while still staying within the design envelope for the wind turbine machine.
In accordance with a further aspect of the disclosure, a joining method is provided for simple connection to and removal of the modular blade tips from a baseline blade during the manufacturing process or the site setup process.
Significant value is provided by the disclosed process through increased energy capture at a given site. For the owner/operator of a wind turbine, increased energy capture equates to increased revenue and profit.
This disclosure has the advantage that it increases energy capture at a given site by utilizing larger rotor diameters across the site, or at individual locations within a site array.
The modular method of the disclosure results in lower tooling costs, and allows for changing the blade lengths should on-site conditions change after on-site installation of the blades. An alternative approach is to capture more energy through longer blades by manufacturing a new blade design for each incremental increase in length for the given on-site conditions. This results in much higher tooling costs.
The invention will be described in detail with reference to the drawings in which:
In these figures, similar numerals refer to similar elements in the drawings. It should be understood that the sizes of the different components in the figures may not be to scale, or in exact proportion, and are shown for visual clarity and for the purpose of explanation.
Referring to
As to
With reference to
With reference now to
The wind power-generating device is held by the tower structure 36 in the path of the wind current such that the power-generating device is held in place horizontally in alignment with the wind current. An electric generator is driven by the turbine to produce electricity and is connected to power carrying cables inter-connecting the generator to other units and/or to a power grid.
Power capture from wind and ocean current turbines is directly proportional to the cross-sectional area swept by the turbine's rotor blades. So, the length of the extender blade (length a, length b or length c) determines a respectively greater power capture. Conventional rotors utilize blades manufacture to a fixed length, joined at a rotating hub. These blades may be of variable pitch (selectively rotatable about their longitudinal axes) in order to alter the angle of attack relative to the incoming fluid flow, principally for power shedding in high-flow velocities. Alternatively, these blades may be fixed pitch or stall-regulated, wherein blade lift and therefore power capture falls off dramatically as wind speeds exceed some nominal value. Both variable pitch and stall regulated rotor blades with fixed diameters are well known in the art. U.S. Pat. No. 6,726,439 B2, describes a wind or water flow energy converter comprising a wind or water flow actuated rotor assembly. The rotor of U.S. Pat. No. 6,726,439 B2 comprises a plurality of blades, wherein the blades are variable in length to provide a variable diameter rotor. The rotor diameter is controlled to fully extend the rotor at low flow velocity and to retract the rotor, as flow velocities increases such that the loads delivered by or exerted upon the rotor do not exceed set limits.
The blade tip portions 22 and 22′ are designed to be attached or detached from the base blade 20 for servicing or replacement with the same blade size or with a different blade size, such as sizes a, b, or c, as shown in
To secure the blade tip 22′ to the main blade 22, fasteners can be threaded through aligned apertures. For servicing, the fasteners are removed. With reference again to
With reference now to
The rotor diameter is selected depending upon the characteristics of the site upon which the wind turbine is to be situated. The wind power-generating device is held by the tower structure in the path of the wind current such that the power-generating device is held in place horizontally in alignment with the wind current. An electric generator is driven by the turbine to produce electricity and is connected to power carrying cables inter-connecting the generator to other units and/or to a power grid.
A calculation methodology is used to establish what increase in rotor diameter is possible on a site specific, or pad specific location within a site, while still staying within the design envelope for the wind turbine machine. If the site characteristics change, perhaps by wind turbines being added or subtracted to an array of turbines in a wind farm, a more appropriate blade tip can be designed and manufactured to replace an existing blade tip. Since the blade tip can be removed and fitted with a different blade tip, the changed site characteristics can be accommodated.
It is entirely conceivable that different blade tips will be necessary for different wind turbine machines located at a wind farm, depending upon the exact location of a given wind turbine in the wind farm. Equipped with different tips, each wind turbine may have different aerodynamic properties in order to customize the wind turbine for that specific site, including a given location in the array of wind turbines at a wind turbine site.
In order to determine what site specific parameters may need to be accommodated at a specific wind turbine site, an anemometer may be positioned at the site in order to obtain, for example, one year's worth of data. That data can be entered into a suitable computer and a suitable software program can be run in order to determine the meteorological characteristics for that specific site. Then, a blade can be tailored for both energy capture and noise reduction with the tip design of the blade giving the wind farm operator different aerodynamic properties. In this way, the wind farm operator can optimize the core structure design for the majority of the blade and have a modular tip with which the length, aerodynamic performance, load and noise characteristics of the wind turbine can be optimized. In this way, manufacturing consistency is enhanced. The following chart illustrates the known maximum lengths of blade lengths and rotor diameters:
In another embodiment, the baseline blade length can be on the order of 42.5 m, 44 m or 47.5 m and a tip can be added thereto to optimize the overall length of the blade for the sites specific conditions.
The site suitability assessment process is well known to those skilled in the art. In the instant disclosure, the output of the site suitability assessment process is employed to modify the blade drawings, as well as the manufacturing process. The conventional state of the art is to use a fixed type of blade for a given wind regime and to curtail the operation of the turbine via controls based on site suitability assessments. The instant disclosure is advantageous in that it optimizes the wind turbine machine for energy capture while maintaining the loads envelope of the specifically tailored blades for the specific site.
With reference to
At step 105, a suitable computer and/or site operator determines load, noise and performance characteristics of the wind turbine site. This may include obtaining meteorological data of the type discussed previously for an extended period of time. The extended period can be one or more months, one season of a year or more than one season. An entire year's worth of data (12 contiguous months or four seasons) can be gathered, if so desired.
At step 110, an optimum energy capture blade design is determined based on the characteristics developed in step 105 above. The design can be determined by a computer, an engineer, or by both acting together.
At step 115, the site operator assesses a need for blade design modifications based at least in part on the determined load, noise and performance characteristics of the blade.
At step 120, an engineer creates and/or updates blade drawings for blade production corresponding to the rotor blade of the wind turbine based at least in part on the assessed need for blade design modifications.
At step 125, an engineer creates and/or modifies blade molds in accordance with the blade drawings of step 120.
At step 130, a blade is manufactured employing the blade mold designed in step 125.
The method ends at step 135. Subsequently, the blade so manufactured is mounted to a rotor held on a tower, such as rotor 38 supported on tower 36 shown in
In one embodiment, a wind turbine blade built on a common base structure is provided with a customizable out board section based on a wind site characteristic assessment. In another embodiment, a wind turbine blade is provided with a modular tip that can be customized based on wind site characteristic assessments and mounted to a common in board section of a wind turbine blade.
For example,
At step 155, a site operator mounts a wind turbine on a structure that is held stationary with respect to a fluid flow. The wind turbine includes a rotor with a main blade portion connected to a rotor hub at a proximal end and includes provisions for attaching a modular extender blade tip to a distal end of the main blade.
At step 160, the site operator, optionally in conjunction with a suitable computer, determines an optimum energy capture using one or more site specific conditions such as air density, wind speed, extreme wind, wind shear, noise and turbulence intensity. These conditions can be evaluated over an extended period of time as discussed previously.
At step 165, the site operator selects from a finite number of extender blade tips an extender blade tip having a length and/or shape that is closest to providing the determined optimum energy capture calculated at step 160.
At step 170, the site operator attaches the selected extender blade tip to the blade main portion. This step creates the overall blade meant for use at that site.
The method ends at step 175.
In one embodiment, the in-board section or root section 20 of the blade can be on the order of 90 to 95 percent of the overall length of the blade while the tip section can be on the order of anywhere from 5 to 10 percent of the overall length of the blade.
The disclosure has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
