I am not quite sure what to make of this design concept. Effectively the majority of incoming air stream is coaxed to give up the majority of its energy content as it is transferred through a tuned disk stack.
I am having no problem in seeing that it will work but am having plenty with the cost of drag. This looks like a drag machine. I would like to see a good energy audit done on the machine to see how it stacks up to present designs which obviously minimize drag and maximize torque.
However, the exit velocity should be very low.
I have seen other novel attempts to convert wind energy into power. I have also seen no reason to be particularly optimistic and it is all about drag. They all seem to be able to operate a prototype in ideal conditions at least and then fade back into obscurity.
It is simply not an easy problem.
Bladeless wind turbine inspired by Tesla
May 7, 2010 by Lisa Zyga
(Left) The bladeless wind turbine, and (right) the stack of disks which rotate and are connected to a shaft. Image credit: Solar Aero.
(PhysOrg.com) -- A bladeless wind turbine whose only rotating component is a turbine/driveshaft could generate power at a cost comparable to coal-fired power plants, according to its developers at Solar Aero. The New Hampshire-based company recently announced its patent on the Fuller wind turbine, which is an improvement on a patent issued to Nikola Tesla in 1913.
The bladeless wind turbine is completely enclosed in a relatively small compact unit. Instead of using wind-powered blades to rotate a shaft and generator, the Tesla-inspired design consists of an array of closely spaced, parallel, thin metal disks separated by spacers. When air flows in the spaces between the disks, the spacers are arranged in such a way as to provide inward momentum to the air, causing the disks to move. The disks are connected to a shaft by spokes, so that the rotating disks cause the shaft to rotate as well. As explained in the patent held by Howard Fuller, the turbine design “provides maximum efficiency in converting wind energy to mechanical power.”
“The turbine of the present invention has the advantage that it is efficient over a wider range of fluid flow rates, as compared with turbines of the prior art, due to the airfoil-shaped spacers,” the patent explains. “This feature makes the present turbine especially useful for generating power from wind, which is inherently random and variable.”
What this efficiency translates to, according to a recent article at EcoGeek, are final costs of about $1.50/watt rated output, which is roughly 2/3 the cost of comparable bladed units. Further, “total operating costs over the lifetime of the unit” are estimated at about $0.12/kWh, which is comparable to current retail electrical rates. The number of disks determines the amount of power that can be produced, and a unit the size of the one pictured should be capable of generating 10kW of power, according to the company.
One major advantage of not having blades is reduced maintenance costs. For instance, the turbines can be mounted on towers or poles, while generator equipment can be located at the tower base, eliminating the need for climbing the tower for routine maintenance. Also, the turbines only need to be mounted high enough to clear nearby obstacles to wind flow. Since there are no external blades that require ground clearance, the tower can likely be shorter than those used for turbines with blades.
Further, the screen-enclosed turbine prevents injuries to birds and bats, avoids the visual pollution of spinning blades, and proper construction can make the turbine nearly transparent to radar microwave emissions, such as those from nearby defense facilities. Due to its reduced maintenance costs and limited infrastructure requirements, the turbine could even be located on urban rooftops.
Besides wind, the turbine’s design also makes it adaptable for geothermal applications, in which a heated fluid is used to drive the turbine. Since the turbine works even with relatively cool fluid, the invention could be particularly useful for situations where the geothermal source does not provide enough heat to produce the “superheated” steam needed to drive a conventional steam engine.
Virtually silent, fully enclosed, bladeless wind turbines on the way
By Karen Sprey
17:30 May 6, 2010
Virtually silent, fully enclosed, bladeless wind turbines on the way
A wind turbine that uses boundary layers instead of blades to generate power has been patented by Solar Aero, a New Hampshire
Solar Aero's Howard Fuller says the principal of operation is roughly the same as for the Tesla steam turbine.
"Closely-spaced discs trap the motive fluid molecules (in this case air) in a laminar flow adjacent to the disc surface. This provides aerodynamic drag, which imparts force to the disc surface. By using multiple discs, the turbine then provides considerable torque to accelerate the rotation of the central driveshaft, which is directly coupled to an alternator, typically located at the base of a tower, or alternatively co-located on a rooftop."
The turbine is likely to have a cut-in speed of about 3.5 knots and optimum speed is about 20 knots and near transparency to radar microwave transmissions can be achieved with proper construction materials and techniques.
Although currently only in pre-prototype stage, it is anticipated that units would be available in different sizes. The smallest unit would be likely to produce about 5kW at 15 knots.
Solar Aero expects costs to be comparable to coal-fired power generation - around $0.05/kWh. When used in conjunction with a suitable storage device, this should provide reliable, inexpensive power in either residential or commercial applications.
Maintenance costs should be less than for bladed turbines. As the up-tower turbine is supported solely on zero maintenance magnetic bearings, there will be no friction to impede acceleration and no routine lubrication required.
Solar Aero is currently completing a full scale prototype. The design will be available for worldwide production licensing following testing.
Contact Solar Aero for further information.
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