REVOLUTIONARY NEW DESIGN!
VERTICAL AXIS INVOLUTE SPIRAL WIND TURBINE
This design offers many advantages over a traditional Horizontal-Axis Wind Turbine (HAWT) or Vertical Axis airfoil blades:
Vertical axis means it spins like a top, without having to turn into the wind, nor torquing the gyroscope and wearing out bearings.
Gravity creates even blade torque rather than the huge forces of downward acceleration imposed by propeller-blade tip speeds in a spinning HAWT of 5 or more times the wind-speed. There is little force on bearings of a the gyroscopically-stabilized Involute VAWT. I expect the small roller-blade bearings on top of this 4ft-diameter prototype will last 20 years with lubrication.
The three large involute spiral vanes spin the wind inward, rather than spilling it outward as with thin propeller blades (both horizontally and vertically mounted). This means that the wind is pushing evenly on the greatly-enlarged vane-curvature, being continuously redirected, loosing more of its power, all the way throughout the turbine diameter, creating a lower-pressure area behind the turbine to entrain outside air to augment and streamline the lift and drag components.
The curvature of the involute spiral provides superior lift and drag propulsion throughout the turbine area, providing more torque at a fifth the speed of a HAWT, safe for birds, which can easily see the turbine, and probably even sail right through it for a joy-ride!
More torque at lower speeds means we can finally get significant power from more common moderate winds.
The geometry of this tensegrity structure is extremely strong and stable for its weight.
The pictures on the right and below show a 4ft diameter involute spiral VAWT with a 20ft tall revolving tensegrity mast. The turbine weighs 21 lb, with another 6.5 lb lb for the mast, + bearing, cables and tensegrity wires, for a total weight of turbine and tower of only 30 lb!
The heavier generator & gearbox will be down below, where they are easy to work on and don’t stress the tower. An anemometer on top and stiff telltales at vane openings show wind movement as vanes turn into and out of wind.
involute VAWT on 20ft mast
VIEW VIDEO OF STREAMLINED FINNED TURBINE
IWT bike frame-low
The drawing on the left was first built with sailcloth vanes (right), which was very promising, but proved too flexible for optimum performance. The turbine was mounted on the crank shaft of a bicycle frame, as pictured, which has worked well, allowing a generator to be mounted on rollers on the variable-speed rear -wheel. The 3-vaned aluminum model shown below, named “Wendy the Windturbine”, was then built. It is a great improvement, producing significant power for it’s small size in a moderate breeze. To elevate Wendy into less turbulent wind a 12ft revolving extension tube was added, held rigid by another set of 3 guy cables from the base of the turbine (center picture). The entire rig — turbine, mast, extension-tube, bearings, guy-cables weighed about 40lb and worked very well. With a better bottom thrust bearing, this extension technique was duplicated to raise the turbine higher into stronger winds.
Involute wind turbine_3-sails_2-views02
Involute wind turbine-aluminum vanes-1s
wendy on 12ft mast-good
View 2.5 minute Quicktime Video of first sailcloth VAWT in Action!
View 1 minute Realplayer Video of Wendy in Action!
View YouTube video of erecting Wendy on 12ft. revolving mast
Wind power has the potential to supply much of the energy demands of the world, and is the most rapidly expanding sector of current alternative energy technology. Most existing wind turbines are of the familiar horizontal axis configuration, with spinning propellers directed into the wind by a “tail” or, for larger systems, electronically controlled motors. These “lift” propulsion blades are typically of airfoil shape, like airplane wings or propellers, which rely on the low-pressure lift from the momentum of the wind passing over the airfoil shape. The vertical axis Darrius rotor is also a “lift” device, with its airfoil-shaped “eggbeater” blades. The vertical axis wind turbine (VAWT) pictured above is a so-called “drag” propulsion device, along with equally strong “lift” components that allow the rim speed to be several times faster than the wind speed. In this VAWT, the spiral vanes continually diverts the mass of the wind to perform work on the sail. Results from a few tests indicate that we can increase the low-speed power significantly over the horizontal axis rotating blade wind turbine, largely because we are diverting the mass of the wind inward and continuously changing its direction of travel through laminar flow over much greater surface area vanes instead of just “lift” propulsion from thin fat airfoil-shaped blades that spill the wind outward in a thin plane of rotation.
According to a Gruman Aerospace research paper on the subject (Tornado-Type Wind Energy System, James T. Yen, Research Department Grumman Aerospace Corporation, published in IECEC ‘75 Record)*, the increase in power of drag propulsion over lift propulsion can theoretically be thousands of times greater! If this is true, it is a little known but extremely important fact for designing wind energy technology.
* “Thus, in contrast to conventional wind turbines that use only the wind kinetic energy V2/2, we will additionally use the wind pressure energy P/þ which in magnitude is more than 3000 times larger than the wind kinetic energy for a wind of 15 mph (and more than 750 times larger for 30 mph winds).”
For further theoretical discussion, go to “Wind Power Analysis”
This concept could also revolutionize sailing, for which I have designed a unique drag-propulsion mechanism that could get us quickly around Puget Sound, fastest into the wind! This VAWT can also be mounted on the top of a tree, with 3 stays and 3 additional cables holding the triangular stand vertical. Any swaying of the tree in the wind should also increase the velocity of the spinning gyroscopic turbine (as a gyroscope resists being moved out of its plane of rotation), thus amplifying the power imparted to the generator by the movement of the tree as well! This hypothesis of course needs to be tested.
A vertical axis wind turbine has several advantages over the more traditional horizontal wind turbine especially in uneven wind conditions, where a horizontal wind turbine has to change directions, which puts stresses on the bearings and tower and dissipates energy, Gravitational stresses on the vertical axis turbine are even, allowing lighter and larger construction. This vertical-axis wind turbine incorporates 3 involute spiral sails in a configuration that utilizes the mass momentum of the wind to spin the sails around a central mast. Force is applied to the sails by the wind both entering and leaving the turbine, allowing maximum extraction of energy from the wind. The unique nature of the involute spiral is that the wind is increasingly diverted into and out of a central vortex with no constriction in the path, only smoothly-diverting surfaces. Other advantages to this particular design will be covered below.
This project began in the early 70’s with a fascination for the Savonius rotor, a cut-in-half and shifted oil drum wind generator spinning around a vertical axis. I wondered what the optimum offset and if the half-circle curves could be streamlined better, so I built a series of vertical axis wind turbine prototypes, with thin aluminum printing plate vanes glued between 78-rpm phonograph records. I filmed them on Super-8 next to a wind speed anemometer, and counted revolutions. I found the Savonius weak and stalling in it’s worst aerodynamic position, and found several new and faster vane configurations. The clear winner of them all was the 3-vane involute spiral. A 6-vane involute configuration was slightly more responsive in slower winds.
Involute of Circle math02 Involute of Circle_240_48-s
This circle of Radius 1 unwinds its circumference to trace out an involute spiral , which can continue spiraling around in a path exactly 2 pi away from the next inner spiral. (For an animated graphics showing the generation of an involute spiral, click here.) In other words, a non-constricting path is trace out, which is ideal for applying all of the wind mass to push on the vanes. As the 3-vane drawing above right shows, segments of the same involute can be duplicated around the central circle, creating multiple non-constricting wind paths. Dimensions in the drawing on the right are of the prototype pictured here.
Involute wind turbine Wind turbine-single aluminum vane
This 3-sailed prototype was built by participants in a Community School class, “Testing a Vertical-Axis Wind Turbine”
We utilized a bicycle frame for the drive train and as part of the support framework. The mast is connected to a variable-speed bicycle chain-drive mechanism that drives an electrical generator. We experimented first with a Zap bicycle motor being driven as a generator by the bicycle tire on the drive mechanism.
The sails were, first made of Dacron sailcloth (later replaced with aluminum vanes) and held rigidly in position with an involute-curved boom halfway above the 4’ diameter base disc, which is further aligned with tension cables to the base of the mast. Three tension cables keep the top bearing centered over the triangular base support and tension the leading edge.
The 48” diameter base disk, with 53” tall sails, creates a 9.5 sq.ft. cross-sectional area exposed to the wind, or the equivalent in swept propeller area of a 3.5ft. dia circle. Comparing this to the popular “Hornet” horizontal wind turbine (http://www.survivalunlimited.com/eaglewindturbine.htm), which has a (6) blade diameter of 59” to 144”. The smallest 59” dia blade sweeps an area of 19 sq.ft, or twice that of our prototype model. Even when we consider the sum of the curved area of the three sails (10.2 sq.ft x 3 = 30.7 sq.ft.), equivalent to a 9.8′ (117″) dia circle, we are still under the larger Hornet blade-sweep-area. The 59” diameter Hornet will give 300 Watts in a 15 mph wind, 150 Watts in a 10 mph wind, which is closer to what we might expect here on a windy day. Ideally, we would like to take advantage of even a 5 mph wind, which will only give 25-30 Watts with the Hornet specially-designed fat blades on their Ospray ultra-low wind speed model.
We finally got our first prototype built and out in the wind, and what a perfect day for it! We averaged 20 mph winds, which spun the wind turbine at 120 to 130 rpm, which translates to speed of circumference of the 4 ft dia. sail-disk of 17 – 18 mph, which is 85-90% of the wind speed, spinning the bicycle wheel on high gear at 52/14 = 3.7 x 130 = 481 rpm x 27” = 47 mph. There was not enough torque to turn the powerful bicycle motor (with it’s 1.25” roller and much magnetic and frictional resistance at that speed ~ when we geared down it could almost balance the friction of the motor, but we didn’t generate much power. Those of us taking part in the test (Larry, Blaine, Bill & Ebey) nevertheless considered it a successful test and exciting beginning, for the following reasons:
Wind turbine luffing-sSignificant power was generated despite the flapping sails and severe imbalances. The cloth sails were too loose for the high winds, and the leading edge bowed in and out 3 or 4 inches as it spun, adding vibration & slowing it down considerably. The sails luffed badly on the upwind side, caving in and rippling the surface coming into the wind. This seemed to be the most severe dampening to the smooth spinning of the sails and their aerodynamic properties.
The sails/disk/booms were quite imbalanced, especially as we tightened the tension lines, which shook the truck it was mounted on, dissipating considerable power and prevented higher speeds.
We replaced the cloth sails with stiff aluminum sheets that keep their smooth profile throughout their spin and are easier to tune the tension members and balance the rig.
Another observation from our truck-roof mounting platform. While getting the turbine up in position certainly wasn’t a breeze in this 20 mph wind, once it was up and spinning, we were able to unstrap it and stand there talking for a while without having to hold it down. Very little energy was offered in resistance by the turbine vanes, and the gyroscopic stabilization got us talking about how easy it would be to mount it on top of a tree, using the existing framework with 3 cables down to bolts in the tree 6 feet down. How much energy could we capture from the tree swaying?
What about adding more sails? Remember, this turbine achieves much of its power from the impact of air molecules on the continuously-inward-spiraling turbine vanes. If we have 3 more vanes, we have doubled the molecular impacts from the air, and because the geometry of the passageways between the sails is non-constricting, all impacts are moving the vane around the mast. This proposition has been challenged by sailors and wind turbine experts alike…… only testing will tell….. What about making one with a clear lower disk, so we can watch ribbons, photograph meter readouts, meditate on the expanding spirals?
Frequently Asked Questions:
Q: why the “conical” design instead of a “cylindrical” configuration of greater wind shadow and surface area?
I and others have experimented with cylindrical profiles. While the cylindrical cross section has greater surface area, there are several advantages to the conical shape.
Engineering-wise, it is easier to build stiffer and lighter with tension/compression balance.
The lightest, sturdiest support mechanism is with a bearing at the top held in place by guy cables. The conical sail configuration is ideally suited to this support method, whereas an extended support framework must be built on top of the upper disk to allow support cables to be oriented downward at the best support angle without touching the turbine.
When you eliminate the top disk, you can build a larger conical turbine, with greater wind shadow than a cylindrical one of the same amount of material.
Because the wind traveling through the conical design flows through a double involute path of varied length, there should be an optimum region of the cone that is “tuned to the wind”, creating max power from a spectrum of wind speeds, so this configuration may have aerodynamic advantages too.
We have hot been able to accurately determine the relative efficiencies of conical vs cylindrical design. Extensive wind tunnel testing is essential to optimize this technology.
What about combining the slow_speed vawt with an airfoil blade to get it turning in lighter winds?
The large vanes in involute spiral configuration create the most rotational thrust with the least turbulence at 1/3 to 1/6th the tip speed of a thin airfoil blade. I don’t believe the two technologies can be successfully integrated. The balance of high pressure thrust on the concave side of the curved vane with low pressure lift on the other side of the vane is a smoothly transitioning phenomenon, which would be radically altered by any attempt to change the shape to create more lift at any particular location on the vanes.
How many vanes of what size involute in what wind conditions are optimum?
This and other important questions need to be determined in wind-tunnel experiments. Want to help? Although it would be highly interesting to employ flow-analysis software to predict performance and optimization of variables, I don’t trust computer simulations to give an accurate prediction of performance with respect to these variables, especially considering the unknown interactions happening in the center of the turbine (~ I suspect traveling vortex streets connecting intake & outlet ~) and with entrained air around the periphery. Counterweighted flow flaps have been mounted onto the leading edge of the turbine vanes and show a precise moment of switching from air entering to air exiting the channel as the turbine turns.
Large commercial turbines get bigger and bigger, despite the “elephant” syndrome that the mass of a solid object increases 8-fold when doubling the size dimensions. This has been possible through more complex engineering and optimizing materials, but this is all at a price. According to the 2009 Wind Market Report from Lawrence Berkeley National Laboratory, a contemporary wind turbine averages about two megawatts in capacity, or enough power for almost 500 U.S. homes. According to Winds of Change; A Manufacturing Blueprint for the Wind Industry from AWEA, the average turbine weighs 200 to 400 short tons, 90 percent of that in steel and most of the rest in fiberglass, copper, concrete, aluminum and adhesives. It has about 8,000 components. At 300 tons / 2 MW = 300 lb / kW for turbine & tower. At that rate, this 30 lb turbine should give 100W power in rated wind speed (say 24mph). It will give much more. Looking at Enercon’s latest direct-drive generator in a 6 MW turbine. It weighs an astonishing 450 tonnes, which is equivalent to 150 lb / kW for a direct-drive generator. Again, the economics look good for smaller turbines of this light-weight design.
We briefly tested a wind-diverter, which seemed to add more turbulence than power to the sails, and the stiff aluminum vanes obtain considerably higher speeds without the complications of the diverter, although it may help on a cylindrical design, mounted horizontally above an obstruction like a building-roof or bluff.
After we replaced the cloth sails with stiff aluminum vanes, we placed the wind turbine on the garden gate in a location surrounded by trees, which blocked most of the wind and caused turbulence. Still, we were able to generate a small amount of electricity with a bicycle generator.
Then we took it to the beach and with 18-22 mph winds were briefly generating power from a Zap bicycle motor turning an electric trolling motor. The knurled drive roller of the Zap motor creates much frictional resistance which, multiplied by the geared-up chain drive, stops the turbine in low winds. With a bicycle generator, we were able to light a bright headlight and taillight with about 15mph winds. A WindBlue Permanent Magnet Alternator (PMA) was tried, but it is too large for such a small turbine in typical wind conditions here. We are looking for a super-low-speed PMA that will generate power at 30rpm, has no magnetic drag and will generate a trickle-charge from the get-go. This is the holy grail of wind turbines ~ If you know of such, let me know!
At speeds above 150 rpm, the aluminum vanes wanted to flare out at the top and threatened to touch the support cables, so we had to keep a drag on the turbine at wind speeds above 16mph. The turbine is not dynamically balanced and shook the truck at high speeds. Both of these conditions were aggravated by the fact that for this first test we omitted the lower tensioning cables, relying entirely on the stiffness of the vane curves, which was actually quite impressive. The bicycle frame is bent, causing misalignment of chain and sprockets. The bicycle wheel is severely out of round, requiring excessive pressure on the generator rollers, so there is considerable friction in the system. Nevertheless, the turbine rim speed was consistently faster than the wind speed, sometimes by as much as 50% more (not 150% as stated in the video), which indicates that both lift and drag propulsion are involved.
We are excited about the potential of this VAWT design. Theoretically, there are greater efficiencies to be realized from other unique features comparing this design with airfoil blades.
I now have 23 pages of plans, including 20 technical drawings and 21 photographs and 3D rendered illustrations! Details include a 5-vaned model 8ft in diameter and a unique power-to-generator coupling system!
DOWNLOAD FREE PLANS HERE ~ CLICK ~ BUILD ONE!
I am sharing this information freely with the world because I feel strongly that there is great potential for superior wind power from this design. I am only one person with limited resources and time. R&D is costly and time-consuming, and we global citizens need to be experimenting and perfecting the technology.
I would like to see larger units built and tested, configurations with 5 vanes or more, longer involute paths (imparting greater directional changes to the wind, thus extracting more energy), experiments with wind diverters, etc. If cloth sails had two more involute-shaped battens in the middle and more tension elements, perhaps that would be as good as making them with stiff material to resist deformation in high winds, and larger sails could be reefed and transported easier.
We need funding to test the turbine mounted on a boat driving a screw propeller or preferably a drag-propulsion paddle mechanism of my revolutionary design, to do wind tunnel experiments, to build larger units with direct-drive generator, and to test upside down as a tidal-power generator. This will produce much more power and test the hydrodynamics of the shape.
I have lots of ideas and suggestions. All I ask is that you inform me of your development work and let me offer suggestions and coordinate efforts and information so that all will benefit.
I am available as a consultant.
Email or write to:
7118 Fiske Rd
Clinton, WA 98236
or call 360-579-1763
Larry Dobson is an energy consultant and has studied and experimented with new approaches and concepts in Alternative Energy Applications, notably, high temperature biomass combustion, heat-exchanger design, biogas systems, solar collector and heat storage technology, wind turbine design, human-powered vehicles, power linkages and superior articulated stilt designs. He is skilled in realistic 3D Solidmodeling (Computer-Aided-Design), steel and aluminum structural design, fabrication and TIG welding. Dobson has received grants from Alternative Sources of Energy Magazine, Washington State Energy Office, and U.S. Department of Energy – Office of Energy-Related Inventions, for work in alternative energy. He is featured in a book by Adam Woog, “Sexless Oysters and Self-Tipping Hats, 100 Years of Invention in the Pacific Northwest”