Bladeless Wind Turbines

Innovations focus on a lightweight, noisless alternative

Wind energy has become an essential part of the global renewable energy landscape and dependence on it is anticipated to increase in the foreseeable future. At present, wind turbines are the most commonly used machines for converting wind energy into electrical energy, with the movement of the blades fuelling an electricity generator. The wind turbines in use at present have blades that rotate due to the force exerted by wind and convert the rotational mechanical energy into electricity.

Wind turbines with blades have their own advantages and disadvantages. Instead of deliberating on the advantages, it is more important to highlight the disadvantages associated with the use of blade technology. The issues associated with bladed wind turbines include transportation problems, the need for a strong foundation, mechanical wear and tear, lower rotational efficiency and noise pollution caused by the rotation. These problems are compelling innovators and engineers to look at bladeless wind turbines.

Fundamentals of the technology

The general perception at present is that bladeless wind turbines are less efficient in the conversion of captured wind power to electrical energy as compared to their bladed counterparts. Bladeless wind turbines with centripetal flow were patented by Nikola Tesla in 1913. Bladeless turbine technology basically consists of a cylinder fixed vertically to an elastic rod. The outer cylinder is designed to be largely rigid, and it oscillates while remaining anchored to the bottom rod, generating electricity through an alternator system. The top of the cylinder is unconstrained and has the maximum amplitude of oscillation.

Bladeless turbines are built using resins reinforced with carbon and/or glass fibres, which are also used in conventional bladed wind turbines. The top of the rod supports the mast, while the bottom is firmly anchored to the ground. It is made of carbon fibre-reinforced polymer, which provides great fatigue resistance, and it has minimal energy leak when oscillating.

Bladeless wind turbines are designed such that they stand erect and oscillate in response to the vortices. At present, the global bladeless wind turbine market is being propelled by the single-handed efforts of a Spanish company, Vortex Bladeless, which has innovated the current design of bladeless turbines. Vortex Bladeless WTG is a vortex-induced vibration resonant wind generator that harnesses wind energy from a phenomenon of vorticity called vortex shedding. In fluid mechanics, as wind passes through a blunt body, its flow is modified and it generates a cyclical pattern of vortices. Once the frequency of these forces is close enough to the body’s structural frequency, the body starts to oscillate and enters into resonance with the wind, a phenomenon known as Vortex Induced Vibration (VIV). The Vortex-turbine’s pole geometry is specially designed to achieve maximum performance vis-à-vis the average observed wind velocities. It is able to adapt very quickly to the wind direction changes and turbulent air flows commonly observed in urban environments.

The idea behind the Vortex wind turbine is the possibility that same forces can be exploited to produce energy. Currently, the Vortex wind turbine generates electricity through an alternator system, made by coils and magnets, adapted to vortex dynamics, and without gears, shafts or any rotating parts. This design enables lower maintenance and eliminates the need for greasing. The frequency of shedding in the Vortex turbine is proportional to the velocity of the wind stream. However, each structure has its own natural vibration frequency. To match a device’s natural frequency with the local wind frequencies, one should modify the body mass (the higher the mass, the lower the natural frequency) and the rigidity (the greater the rigidity, the higher the frequency), among other parameters. When the natural frequency of the device matches the wind vortices, the structure begins resonating, hence oscillating, so the bladeless wind turbine can harness energy from the movement like a regular generator.

The main materials used for the manufacturing of Vortex turbines are carbon fibre polymers, plastics, steel, neodymium and copper. The working limits of these materials are far from Vortex’s operational standards. Bladeless wind turbines completely eliminate the need for mechanical elements, which can suffer wear and tear due to friction. Further, with the recent innovation of bladeless wind turbines, the risk of structural damage to the system can be reduced significantly. Moreover, the reduced weight of bladeless turbines is one of the primary drivers of the global bladeless wind turbine market.

While Vortex Bladeless is leading the effort in this space, with intensive ongoing research and product enhancements in the field, more companies are expected to enter the lucrative market of renewable energy utilisation. On the basis of region, the global bladeless wind turbine market can be categorised into six sections – Western Europe, Eastern Europe, Asia Pacific, Latin America, North America, and the Middle East and Africa. The adoption of bladeless wind turbines is expected to pick up speed in Western Europe owing to the presence of favourable environmental conditions and the availability of advanced technology. The Asia-Pacific market is estimated to flourish as well, due to an increasing number of government initiatives for promoting wind energy.

Advantages of bladeless turbines

  • There is no need for nacelles, support mechanisms and blades – costly components used in conventional wind generators.
  •  Bladeless turbines are very lightweight and have their gravity centres close to the ground. Thus, anchoring or foundation requirements are reduced significantly compared to regular turbines, easing installation.
  • The lower cost of manufacturing and maintenance of these turbines may contribute to an increase in their demand.
  • These turbines do not suffer large drops in power as their smaller swept area allows more turbines to be installed within the same surface area, compensating for the loss of power efficiency with space efficiency, in a cost-effective way.
  • Bladeless wind turbines contain few moving parts, which helps in eliminating the noise generated by bladed wind turbines.
  • Vortex turbines aim to be greener and noiseless alternatives in the wind power segment, as their simple design and light weight allow very efficient use of raw materials.
  •  Vortex Bladeless turbines are mainly a solution for distributed energy generation and are perfect for installation near houses or on roofs.
  • Bladeless turbines can work on-grid and off-grid, and can also be part of hybrid wind-solar installations.
  •  Vortex’s design allows the oscillatory movement in bladeless turbines to be tiny and thus less aggressive than traditional wind turbines. As a result, they do not disturb wildlife and allow birds and bats to avoid them easily while flying.

Outlook

In wind energy conversion, a wind turbine’s power generation is proportional to its swept area, and a Vortex turbine currently sweeps 30 per cent of the working area compared to a conventional three-blade turbine of identical height. As a result, generally speaking, a Vortex turbine’s wind power generation technique is less efficient than regular horizontal-axis wind turbines. Bladeless wind turbines are at a nascent stage and are thus less efficient in converting captured wind power into electrical energy, which is limiting their implementation on a large scale. But with future design and development using advanced technology and improved materials, bladeless wind turbines are likely to witness enhanced demand in the coming years.

 

By Dr S.S. Verma,
Department of Physics,
Sant Longowal Institute of Engineering & Technology

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