7 Outdated Wind Turbine Designs That Never Caught On

The Darrieus Turbine

The Darrieus turbine, named after French engineer Georges Darrieus who patented the design in 1931, was one of the first vertical axis wind turbines. This type of turbine has blades that are attached vertically on a rotating shaft. The curvature of the blades allows them to capture wind energy as they spin, regardless of wind direction.

While Darrieus turbines were touted for their omnidirectional operation, they had several drawbacks that prevented widespread adoption:

• Low starting torque made them unsuitable for pumping water or grinding grain. The blades needed an external power source to start spinning.

• The curved blades experienced large centripetal forces that put stress on the rotor and required a sturdy support structure.

• Efficiency was low compared to horizontal axis turbines.

• The height of the tower was limited by the need for guy wires to hold up the apparatus.

Despite enthusiasm in the 1970s, few Darrieus turbine installations were built. Interest waned as cheaper horizontal axis turbines dominated the market.

The Cycloturbine

In the 1920s, French inventor Georges Jeanne developed the cycloturbine, a novel vertical axis wind turbine. This design used curved airfoils that rotated around a central mast inside a fixed cylinder. The narrow gap between the airfoils and cylinder amplified wind speeds.

The cycloturbine offered several advantages:

• Its shape made it self-starting since the fins created an air funnel.

• The hollow center mast allowed access for maintenance.

• The compact shape reduced material costs.

However, major disadvantages prevented widespread adoption:

• Efficiency was less than 15%, much lower than propeller-type turbines.

• The enclosed cylinder was susceptible to damage from gusty winds.

• Keeping the rotor spinning smoothly required precise engineering.

While some experimental cycloturbines were installed in the 1930s, the design could not compete with more efficient three-bladed turbines. Interest faded by the 1950s.

The Savonius Rotor

In 1922, Finnish engineer Sigurd Savonius designed an S-shaped vertical axis wind turbine intended for low-power operations. The two half-cylinder blades operated based on the difference in drag force on the concave and convex sides.

The Savonius turbine had a simple design with several benefits:

• It self-started well due to the high starting torque.

• The rotor could accept wind from any direction.

• The shape was easy and inexpensive to build.

However, major drawbacks prevented widespread power generation use:

• Maximum efficiency was less than 30%. Better solutions existed.

• The pulsating torque caused excessive vibration.

• Being drag-driven, it could not turn faster than the wind speed.

While Savonius rotors found niche uses like ventilation and pumping, they were unsuitable for electricity generation. The high torque but low speed made them impractical.

The Giromill

In the 1930s, Georges Darrieus proposed an alternative to his original turbine design called the Giromill. It consisted of two or three straight blades attached to a vertical shaft. The linear vertical blades induced less bending stress than curved blades.

The Giromill offered a few benefits:

• The straight blades were simpler and cheaper to manufacture than airfoil blades.

• The design allowed the turbine to be built much taller than the Darrieus style.

• The lightweight blades put less strain on the structure.

However, significant disadvantages resulted in only prototype development:

• Efficiency was extremely poor, under 20% in real-world testing.

• The lightweight blades offered little inertia, causing unstable power output.

• Bearing and shaft fatigue made it high-maintenance.

• The pulsating torque caused noise and vibration issues.

While conceptually simple, the Giromill proved unviable for power generation. The low efficiency and high pulsating torque were insurmountable flaws.

The Vortexis Hydrokinetic Turbine

In the mid 2000s, a company called Vortex Hydro Energy developed a radical turbine design called the Vortexis. This vertical axis turbine used helical blades inspired by the geometry of DNA molecules and whirlpools.

The complex blade shape promised several hypothetical advantages:

• The helical form increased energy extraction from the fluid flow.

• It would supposedly work well in rivers with low current speeds.

• The design prevented debris buildup.

However, major problems became clear before commercialization:

• No full-scale prototype was ever built. Only small models were tested.

• Efficiency claims were wildly optimistic and unrealistic.

• The unconventional shape would have been expensive to manufacture.

• Structural integrity of the rotor was questionable.

Lacking funding and viable real-world data, the Vortexis concept stalled out and was abandoned around 2010. The radical turbine was only an unproven design.

The WindSphere

An unusual spherical wind turbine called the WindSphere was developed in Italy in the late 2000s. This hollow carbon fiber ball contained small vertical axis turbines around its equator.

Proposed benefits of this futuristic design included:

• Omnidirectional operation to capture wind from all directions.

• Capability to funnel wind toward the internal turbines.

• An efficient solidity ratio for the blade area.

• Resistance to storms due to the spherical shape.

However, problems arose that prevented commercialization:

• The complexity made it very expensive to manufacture.

• The small internal turbines could not generate significant power.

• Claims of high efficiency were theoretical - no prototype was built.

• The unconventional shape was difficult to service and maintain.

While visually striking, the WindSphere only made it to the concept phase. The high costs and unproven capabilities limited its prospects.

The Kite Turbine

In the 2000s, innovators proposed using large power kites to generate wind energy. This approach involved using a tethered wing floating at high altitude to drive a generator on the ground through a pulley system.

Potential upsides included:

• Accessing stronger and more consistent winds at higher altitudes.

• Low material cost compared to towers and blades.

• Ability to generate energy even during low wind conditions.

However, troubling disadvantages hampered development:

• Controlling the kite's flight path proved extremely difficult. Safety was a major concern.

• Sudden changes in wind speed could snap the tether.

• Lightning strikes posed a risk to the kite.

• Maintenance was challenging with ground-based equipment.

While an interesting idea, kite turbines failed to progress beyond small-scale prototypes. The difficulty of controlling airborne equipment at scale proved prohibitive.

Conclusion

In the history of wind energy, many novel turbine designs were proposed and tested but never became viable options. While creative in concept, these outdated wind turbines faced issues from low efficiency and high costs to unproven real-world performance. Although some offered advantages on paper, their drawbacks halted further development. Practical engineering challenges prevented these radical designs from displacing conventional three-bladed horizontal axis turbines. However, their innovation may inspire future advances in wind technology.