|CANADIAN ELECTRICITY FORUM, New Supply Options In Alberta's Changing Electricity Marketplace Forum, EDMONTON, ALBERTA (October 30 - 31, 2000)
WARPTM THE NEXT WIND ENERGY TECHNOLOGY FOR ELECTRICAL POWER GENERATION AND TRANSMISSION|
Alfred L. Weisbrich, PE, President, ENECO
Gunther J. Weisbrich (Speaker), Vice President, ENECO
Each windframe module provides highly amplified wind flow fields at each rotor level. This basic physical phenomenon is known as the Bernoulli Principal (Figure 8). Wind tunnel and CFD (Computational Fluid Dynamics) analysis have verified a wind amplification factor of 1.7 to up to 1.8 times that of the open free wind speed. The impact of such amplification is dramatic because of the cubic effect of wind speed to a rotor in the general power equation (P ~ D2 * V3) (Figure 9) where D is the square of the diameter of the blade and V is the cube of the wind velocity. A slight increase in velocity translates into a significant power increase. The conventional POPs approach is to make the D ever larger (historically from ~50 feet diameter blades to over 300-foot diameter blades) in order to capture more energy. WARP™ concentrates on increasing the velocity (V) because it is a more powerful factor on power. Another critical factor that WARP™ addresses is the ability to capture the high wind speed resource at elevation (Figure 10 and 11). The HDTV/radiobroadcast tower industry has demonstrated that towers as tall as 2000 feet can be built. Clearly the taller one builds a WARP™ system the greater the wind resource it is able to capture and amplify. Unlike POPs that can only capture the near ground (~ 400 feet) wind resource, WARP™ can capture the great wind resource at much greater elevations.
Another breakthrough of the WARP™ design is that the active module with the four turbines has the ability to freely yaw 360 degrees on a track (Figure 3). This affords a particular advantage with the WARP™ system in that the turbines always seek to be square and stable to the wind direction. This eliminates the processional forces of a single big rotor windmill, which misalign with the wind or lag the wind due to yaw drive poor responsiveness. When the wind direction changes, the active modules will automatically realign themselves to be perpendicular to the new wind direction (Figure 12). Large bladed POPs need large motorized assistance to constantly chase alignment with the wind (another cost and maintenance problem). The complications associated with wind shear (Figure 13) and direction with height (Eckman Spiral, Figure 14) is also eliminated by the WARP™ design. Since each active module is independent of the next active module, no variation in either the wind direction or wind shear will be expected to cause problems. Large bladed POPs have to constantly fight the differing force and direction of the wind at the top of its revolution with the direction and force of the wind at the bottom of its revolution. In essence, the active WARP™ modules, will always be aligned perpendicular to the wind direction, at any height, and will do this automatically.
The advantage of having each module independent from another is significant. If a failure of one module does occur, the whole system is not down. All the other turbines on the other active modules will still be generating. Unlike large bladed POPs, a single loose nut and bolt will cause the whole system to be down. If a rotor failure does occur with the WARP™ system, the modules will automatically weathervane the rotors out of the wind direction (due to the creation of a thrust imbalance) and become stationed in a stable and protected position. The damaged rotor will then be in a position to be serviced while all the other turbines on other active modules would still be operating and therefore generating.
WARP™ MAJOR BENEFITS
The fact that WARP™ systems use small diameter rotors, are able to amplify the wind and capable of being built very tall (800+ feet), allows a major problem to be solved. The unsightly view of a large wind farm (Figure 15) is due to the fact that one POP must be spaced 10X (ten times) the diameter of their blades apart (e.g. a 100 ft diameter POP must be 1000 feet away from the next one) to avoid unreasonable performance loss. This spacing is a requirement to help eliminate any aerodynamic eddy effects from one rotor to the next. A comparison of the land requirements for a hypothetical 400-Million kWh/Yr. wind farm is illustrated in Figure 16. In this example, (based on a very conservative early 50% amplification factor) three commercially sized wind systems are compared with 32 WARP™ towers each 780 feet tall with 10 foot diameter turbines. If all wind conditions are equal, it would require 1350 units of a 70 ft diameter blade system to use about 14,000 acres, 324 units of a 128 ft diameter blade system to use about 11,000 acres and 46 units of a 300 ft diameter blade system over 6,000 acres. The WARP™ wind farm would require less than 1000 acres to supply the same electrical power. This significant reduction in acreage will minimize the expense of land costs, allow wind farms to be built closer to populated areas and minimize the unsightly view of large land sprawl.
WARP™ systems also lend themselves to take advantage of mass production economics. The manufacturing industries have long understood the power of mass/volume production. WARP™ systems are comprised of relatively simple, modular and repetitive components (Figure 17). Cost savings will be gained from manufacturing many identical components and/or through the purchasing power gained from buying large quantities of identical components. This mass production economics is not readily available to the large bladed systems and therefore will always be a problem for them. In addition to the costs savings afforded mass production, WARP™ components tend to be small and modular and therefore much more manageable. This allows for less expensive and complicated transportation, construction (Figure 18) and maintenance (Figure 19).
Avian mortality (bird kill) is a major concern, especially to the Audobon Society which has highlighted this problem in the US as a result of hundreds of birds of prey, including dozens of golden eagles, killed by large bladed windmills in California. This environmental problem is judged to be avoided with the WARP™ system because birds can easily discern building-type structures such as a WARP™ plus evade small high speed rotors.
Large bladed wind farms have also been cited for their annoying low frequency noise pollution. The slow speed of revolution produces a low frequency noise that does not easily attenuate (much like the base of a stereo that goes through the wall while the high frequency treble does not), and becomes annoying to the local population. WARP™ rotors, on the other hand, are high speed with a high frequency noise that is more readily attenuated (Figure 20) and therefore less of a problem.
WARP™ towers are significantly more stable and safe than conventional large bladed wind systems. A WARP™ system is designed to distribute all the loads over the tower (versus the POP having all the stress concentrated at single apex focal point, i.e. where the tower and blade are joined). WARP™ towers can be further secured through simple guy wiring application to virtually any point. When comparing a simple lattice tower with a WARP™ tower, the WARP™ tower can be shown to have a 50% lower drag coefficient than the lattice tower (Figure 21). This is due to the aerodynamic fairing of the patented module design. The static modules in addition give the tower additional strength through ring stiffening characteristics.
Yet another advantage that WARP™ has over the conventional large bladed wind systems is the minimization of lightening strikes (Figure 22). The conventional large bladed systems attract electrical strikes due to having a large metallic blade connected to another large metal gearbox (not to mention the associated combustible gearbox fluids). WARP™ towers minimize this risk by being grounded and having their blades and modules constructed from nonmetallic materials.
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