The company has developed an electric wind generator characterized by its lack of blades. The system, also known as Vortex Bladeless, leverages aerodynamic instabilities to capture energy.
Vortex Bladeless engineers created prototypes of this innovative wind turbine a couple of years ago. To reduce development time and cost, they turned to finite-elementanalysis (FEA) and computational fluiddynamics (CFD) solutions to hone their designs and product development process.
Traditional wind turbines – those with blades that rotate around a horizontal axis – typically consist of a tower, control system and the blades. When the wind turns the blades, they spin a shaft that connects to a generator. The generator produces the electricity.
Wind turbines come in a range of sizes. Those rated below 100 kW can be employed for small applications such as water pumping while wind turbines rated from 100 kWto several MW can be used in larger applications such as wind farms.
Costs associated with wind turbines include construction, infrastructure, maintenance and transportation, among others. For a small home-based wind turbine, the installation cost is approximately $7,000 per kW capacity. A large commercial wind turbine rated at 1 MW costs in the neighborhood of $1 million.
Overall, the wind power industry is growing, according to the Global Wind Energy Council, an international trade association. Trends driving its growth include the climate, lower costs for wind and solar technology, U.S. market stability and industry growth in other regions, including Asia. The Council forecasts that by 2030, windpower could reach 2,110 GW and supply upto 20% of global electricity. This could translate into creating 2.4 million new jobs and reducing CO2 emissions by more than 3.3 billion tons.
Vortex Bladeless engineers collaborated with Altair in the design of the novel turbine. This included usingAcuSolve CFD technology to simulate vortex shedding, an aerodynamic phenomena resulting from windpassing around a blunt object. The lateral forces generated from vortex shedding cause the cylindrical turbine to oscillate in resonance, “powering” a lineal alternator to produce electricity.
An Alternative Approach
The Vortex Bladeless electric wind generator offers an alternative to traditional wind turbines. It has a cylindrical shape that oscillates in the wind, and electricity is generated through a lineal alternator system. The device is configured with a fixed mast, a power generator and a hollow, lightweight and semi-rigid fiberglass cylinder on top.
The outer conical cylinder is designed to be substantially rigid and has the ability to vibrate, remaining anchored to the bottom rod. The top of the cylinder is unconstrained and oscillates in the wind. An inner cylindrical rod, which may penetrate into themast for up to 20% of its length, is anchored to it at its top and secured to the ground atits bottom part.
The device capitalizes on an aerodynamic effect known as “vortex shedding.” As the wind passes around a blunt body, the flow is modified and generates a cyclical pattern of vortices (swirling air). Once these forces are strong enough, the body might start to oscillate and enter into resonance with the lateral forces of the wind. This aerodynamic instability is known as Vortex Induced Vibration.
Instead of avoiding Vortex Induced Vibration, the bladeless wind generator takes advantage of the oscillation, capturing the energy.
Understanding the Vibration
The “Vortex Street” effect was first described in 1911 by Theodore von Kármán, a pioneer in theoretical aerodynamics. This effect is produced by lateral forces of the wind on any fixed object immersed in a laminar flow.
The wind flow bypasses the object, generating a cyclical pattern of whirling air that can become an engineering challenge for vertical cylindrical structures such as towers, masts and chimneys. These objects may start vibrating, enter into resonance with the lateral forces of the wind and ultimately collapse. Examples of this effect on structures are the collapse of three cooling towers that occurred in 1965 at the Ferry bridge powerstation near Pontefract, England, and the 1940 collapse of the Tacoma Narrows Bridge in Washington State, USA.
However, Vortex Bladeless engineers have figured out a way to use the same aerodynamic forces to produce energy: The Vortex wind generator successfully adapts its natural frequency to resonate with the frequencies of wind vortex generation within a varying speed range.
The natural frequency of vibration dependson the body mass (an increase in mass reducesthe natural frequency) and rigidity (morerigidity creates higher frequency). The Vortex generator — including the diameter of the structure, height and total mass – is designed to achieve maximum performance from the average observed wind speeds.
The company further maximizes the output from a given wind speed by modifying the rigidity of its structure. The top of therod has a magnetic confinement system with permanent magnets that increase the apparent stiffness of the system according to the degree of flexion.
When wind intensifies, the magnetic force of repulsion goes up. This reduces the distance between the rod and the magnet. As a result, the oscillation and the potential of generated energy increase to the maximum. As such, Vortex can automatically vary rigidity and “synchronize” with the incoming wind speed in order to stay in resonance without any mechanical or manual interference.
Vortex Bladeless generates electricity through an alternator system made of coils and magnets adapted to the vortex dynamics. There are no gears or moving parts in contact, so there is no friction. The company reports that testing shows electrical conversion yields of about 70% to 85% of those obtained by a conventional rotary alternator.
To help develop an efficient device, Vortex engineers worked with Altair to create computational models. Altair supported and trained the Vortex engineers through the development process.
The collaboration started with a technical project to simulate the aerodynamic behavior of the device. Altair engineers performed a fluid-structure interaction study with AcuSolve®, the company’s computational fluid dynamics (CFD) solver, and OptiStruct®, its linear and non-linearstructural optimization software. The computer-aided engineering (CA E) modelsenabled engineers to predict the movementof Vortex Bladeless with different wind intensities. In addition, Vortex Bladeless engineers have used HyperWorks VirtualWind Tunnel™ to perform external aerodynamic analysis on the structure.
Recent development efforts include optimizing the alternator design as well as the geometry of the system. With the new geometry, the system can capture almost 40% of the wind’s kinetic energy (similar to conventional wind turbines). According to Betz’s Law, the maximum power that can be extracted from the wind, independent of the design of a wind turbine, is 59.3% of its kinetic energy.
Vortex Bladeless co-CEO of Technology David Yanez says, “Without simulation, our product would have been developed at a much slower rate. It would have cost a lot more because we would have needed many more prototypes. We feel very confident that Altair’s solutions suit our needs. This applies not only to the software capabilities but also to the highly valued support Altair brings to this partnership. Since the virtual demonstration of the product is one of our milestones, we truly believe that Altair’s contribution has hada great impact on our day-to-day work.”
The Case for Innovation
The team at Vortex Bladeless cites several advantages to its innovative wind energy system. Chief among them is cost. With the final Vortex Bladeless product, engineers expect to reduce manufacturing costs by 53% and operating costs by 51% compared to traditional wind turbines.
In addition, the design completely eliminates mechanical elements that can suffer wear and tear from friction. The company estimates an 80% reduction in maintenance costs compared to traditional wind turbines.
The Vortex operating principle also enables the system to:
Eliminate the need to adjust the installation for the best angle of the wind.
Improve on limitations associated with the “shadow effect,” the disturbance of the downstream wind current, which is why traditional wind turbines need to be installed at a certain distance from each other.
Minimize the threat to bird populations.
Operate silently. With the oscillation frequency of the equipment below 20 Hz, the sound level impact is nonexistent.
The initial Vortex Bladeless products are being designed to produce 100 watts of powerfor use in Africa and India. The company also plans versions that will deliver 4 kW for use in conjunction with solar panels and 1 MW for larger applications.
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Beverly A. Beckert is Editorial Director of ConceptTo Reality.