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Clean Power turbine

Published on January 14th, 2009 | by Ariel Schwartz

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Inventor Patents "Tree-Hugging" Hollow Wind Turbine For Urban Areas



turbine

Finding the space for wind turbines in urban areas is difficult—even for vertical turbines like Mariah Power’s Windspire. But a new design from Sridhar Condoor could drastically reduce the space requirements for wind turbines. Condoor’s turbine is hollow, cylindrical, and lacks a central hub. Its hollowness allows it to be placed around existing objects— so you could literally have a tree-hugging turbine.

The outside of Condoor’s turbine is fitted with inlets that catch the wind from all directions. The inlets are toothed on the inside to drive a gear that powers an internal generator.

An inner frame on the turbine lets the main cylinder rotate freely, and also provides the option for the turbine to be mounted around other objects either vertically or horizontally. In addition to minimizing space requirements, this feature could also help hide some of the turbine’s “uglier” features.

Condoor filed for a patent on December 9, 2008, so chances are that he has a long way to go before his turbine is ready for commercialization. Still, his design is something to keep an eye on.

Photo Credit: WIPO

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About the Author

was formerly the editor of CleanTechnica and is a senior editor at Co.Exist. She has contributed to SF Weekly, Popular Science, Inhabitat, Greenbiz, NBC Bay Area, GOOD Magazine, and more. A graduate of Vassar College, she has previously worked in publishing, organic farming, documentary film, and newspaper journalism. Her interests include permaculture, hiking, skiing, music, relocalization, and cob (the building material). She currently resides in San Francisco, CA.



  • Greg Gremminger

    Home Turbines, You need to understand autorotation principles – like gyroplane and helicopter rotors in autorotation – to understand really how these Darrieus rotors work. Drag on the advancing blade is not an issue. The working RPM is high enough to create forward aerodynamic lift forces on both the advancing and retreating blades – and even on the blades when they are traveling perpendicular to the wind.

    Darrieus rotors are a bit less efficient than “windmill” style turbines, but some advantages can make up for that less efficiency. One big issue is that wind from any direction applies energy to the vertical turbine – even if the wind is changing direction rapidly. A horizontal axis “windmill” style needs to be mechanically re-aligned with the wind direction to efficiently capture and process that wind energy – so it is less efficient in catching wind rapidly changing in direction.

    Another advantage is that the rotor can be lighter in weight, allowing it to speed up quickly to convert the energy from a strong wind gust. Horizontal axis “windmill” rotors need to be structurally stronger and heavier with less ability to accelerate in RPM to catch the “gust energy”. “Gust energy” is valuable because the energy in the wind is proportional to the cube of the wind speed. So, in an average wind of 12 mph, if the wind gusts to 20 mph for 10 seconds, that’s 4.5 times the energy for that 10 seconds.

    Darrieus rotors do not need to have the mechanical complexity of variable blade pitch angle. To capture the wind efficiently, and to self-start, “windmill” style rotors must mechanically pitch the blades to the angle of optimum attack for that windspeed. Darrieus rotor blades do not require that mechanical complexity.

    But, Darrieus rotors do normally need to be started spinning to start capturing wind energy with it’s “autorotation”. One way to do this is to run the generator as a motor initially when the wind gets to a speed that can provide enough energy to keep it spinning. At that point, the motor becomes a generator and starts feeding energy back into the grid.

    Another big advantage of vertical turbines is that the rotor and generator does not need to pivot to face into the wind. On horizontal axis turbines, the head and rotor need to be able to pivot – requiring mechanical complexity and at least flexible electrical conductors to connect from the generator to the ground grid.

    There are numbers of other advantages to a Darrieus vertical rotor – including simplicity, centrifugal strength, and generator mounting solidly at the base.

    My point – don’t dismiss the value of Darrieus rotors. They work and probably have a good niche for small, residential style applications. Modern inverter electronics can now make them essentialy plug & play into your house power.

    - gyrogreg

  • Greg Gremminger

    Home Turbines, You need to understand autorotation principles – like gyroplane and helicopter rotors in autorotation – to understand really how these Darrieus rotors work. Drag on the advancing blade is not an issue. The working RPM is high enough to create forward aerodynamic lift forces on both the advancing and retreating blades – and even on the blades when they are traveling perpendicular to the wind.

    Darrieus rotors are a bit less efficient than “windmill” style turbines, but some advantages can make up for that less efficiency. One big issue is that wind from any direction applies energy to the vertical turbine – even if the wind is changing direction rapidly. A horizontal axis “windmill” style needs to be mechanically re-aligned with the wind direction to efficiently capture and process that wind energy – so it is less efficient in catching wind rapidly changing in direction.

    Another advantage is that the rotor can be lighter in weight, allowing it to speed up quickly to convert the energy from a strong wind gust. Horizontal axis “windmill” rotors need to be structurally stronger and heavier with less ability to accelerate in RPM to catch the “gust energy”. “Gust energy” is valuable because the energy in the wind is proportional to the cube of the wind speed. So, in an average wind of 12 mph, if the wind gusts to 20 mph for 10 seconds, that’s 4.5 times the energy for that 10 seconds.

    Darrieus rotors do not need to have the mechanical complexity of variable blade pitch angle. To capture the wind efficiently, and to self-start, “windmill” style rotors must mechanically pitch the blades to the angle of optimum attack for that windspeed. Darrieus rotor blades do not require that mechanical complexity.

    But, Darrieus rotors do normally need to be started spinning to start capturing wind energy with it’s “autorotation”. One way to do this is to run the generator as a motor initially when the wind gets to a speed that can provide enough energy to keep it spinning. At that point, the motor becomes a generator and starts feeding energy back into the grid.

    Another big advantage of vertical turbines is that the rotor and generator does not need to pivot to face into the wind. On horizontal axis turbines, the head and rotor need to be able to pivot – requiring mechanical complexity and at least flexible electrical conductors to connect from the generator to the ground grid.

    There are numbers of other advantages to a Darrieus vertical rotor – including simplicity, centrifugal strength, and generator mounting solidly at the base.

    My point – don’t dismiss the value of Darrieus rotors. They work and probably have a good niche for small, residential style applications. Modern inverter electronics can now make them essentialy plug & play into your house power.

    - gyrogreg

  • Turbine fan

    Disregard Home Turbines comments.

    This does and will work.

    Great idea. Start manufacturing and you have a big winner

  • Turbine fan

    Disregard Home Turbines comments.

    This does and will work.

    Great idea. Start manufacturing and you have a big winner

  • http://windenergy7.com/turbines/ Home Turbines

    All of these ideas can work. But IMO they are a diversion from real progress. There’s no way this turbine can convert kinetic energy to electricity as efficiently as the three bladed horizontal axis turbines. As people keep being interested in all these very interesting designs, they are being diverted from going ahead with superior systems already in production. Example, the WindSpire referenced above has a cut in wind speed of 9mph. The reason is that it has serious drag. One side catches wind, the other resists wind. A three bladed turbine with a horizontal shaft, like home wind turbines developed by WindEnergy7 has very little drag in comparison. That’s why it has a cut in speed of less than 6mph. These odd looking vertical turbines like drawn here, and Windspire look cool, but simply cannot make energy as effectively, it takes so much more wind just to start them up. Like driving a car with the brakes on, it’s just not a good design in comparison, no matter how neat it may look. Sop, before you buy a “neat looking” vertical turbine, compare the cut in wind speed to a competing turbine like WindEnergy7.

    Like chrisp said above, right on buddy. With a small turbine and solar panel, put in an efficient LED light source, and you have a winner. But again, the most efficient models of this have a normal three bladed turbine, not an inefficient vertical drag turbine.

  • http://windenergy7.com/turbines/ Home Turbines

    All of these ideas can work. But IMO they are a diversion from real progress. There’s no way this turbine can convert kinetic energy to electricity as efficiently as the three bladed horizontal axis turbines. As people keep being interested in all these very interesting designs, they are being diverted from going ahead with superior systems already in production. Example, the WindSpire referenced above has a cut in wind speed of 9mph. The reason is that it has serious drag. One side catches wind, the other resists wind. A three bladed turbine with a horizontal shaft, like home wind turbines developed by WindEnergy7 has very little drag in comparison. That’s why it has a cut in speed of less than 6mph. These odd looking vertical turbines like drawn here, and Windspire look cool, but simply cannot make energy as effectively, it takes so much more wind just to start them up. Like driving a car with the brakes on, it’s just not a good design in comparison, no matter how neat it may look. Sop, before you buy a “neat looking” vertical turbine, compare the cut in wind speed to a competing turbine like WindEnergy7.

    Like chrisp said above, right on buddy. With a small turbine and solar panel, put in an efficient LED light source, and you have a winner. But again, the most efficient models of this have a normal three bladed turbine, not an inefficient vertical drag turbine.

  • chrisp

    Why hang it on a tree? How many trees are there in a concrete urban setting? Small ones at best I know, I know you are planting more…

    Instead hang them on a street lamp to power the light, like the new ones discussed in this article:

    http://www.inhabitat.com/2008/12/29/new-york-city-to-install-led-streetlamps/

    The lamp can be powered by solar and wind…

    Also you could hang them on telephone poles all across the country. Half of the infrusturcture is already in place. Just add the turbine and inverter.

  • chrisp

    Why hang it on a tree? How many trees are there in a concrete urban setting? Small ones at best I know, I know you are planting more…

    Instead hang them on a street lamp to power the light, like the new ones discussed in this article:

    http://www.inhabitat.com/2008/12/29/new-york-city-to-install-led-streetlamps/

    The lamp can be powered by solar and wind…

    Also you could hang them on telephone poles all across the country. Half of the infrusturcture is already in place. Just add the turbine and inverter.

  • Tim Bucci

    “so you could literally have a tree-hugging turbine” … or an expensive bird house.

  • Tim Bucci

    “so you could literally have a tree-hugging turbine” … or an expensive bird house.

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