Novel Wind Turbine Architecture

[JohnnyYesterday]

This is the most interesting wind energy concept that I have come across so far. It looks odd at first, but when you think about it, it makes perfect sense: the square-cube law makes many things less efficient, decreases their power to weight ratio, etc., as their volume increases; wind turbines are no different.

It also, brilliantly, allows the creation of solely tensile structures (much more efficient with materials) instead of towers under compressive and tensile loading. Imagine rope-like drive shafts reaching kilometers up into the sky . . .

http://youtu.be/P55HfnGR6kQ

http://www.selsam.com/

I should do a rewrite of my Turbine Plants. Flying whirligig vines filling the skies and "kelp" in water would be much more evocative.

[stevebowers]

Reminds me slightly of the 'wind-fences I put on Silenus, a particularly windy planet...


note that flying wind generators would create a hazard for aircraft, especially light aircraft...

[ai_vin]

Looks like an idea I once had for a generating tether, but that used a line of vertical axis wind turbines like the Darrieus wind turbine or Turby; http://en.wikipedia.org/wiki/Turby_wind_turbine

[JohnnyYesterday]

With radar, especially millimeter wave radar, it should be trivial to detect and avoid aerial wind turbines. If the density is too high, restriction of airspace is sensible. Fly over or around the zone.

Birds don't have radar, and they didn't evolve to have to deal with blades spinning through the air, or windows.

[JohnnyYesterday]

Looks like an idea I once had for a generating tether, but that used a line of vertical axis wind turbines like the Darrieus wind turbine or Turby; http://en.wikipedia.org/wiki/Turby_wind_turbine

I looked up Doug Selsam's patents, and some variations on his invention are a hybrid Superturbine/Darrieus.

https://www.google.com/patents/US6616402

https://www.google.com/patents/US6692230

https://www.google.com/patents/US8197179

[stevebowers]

Helium is becoming increasingly rare on this planet, and may be the first element to become scarce, especially if everyone want to use it for power generation and buoyancy; so until we can import it (the second most common element in the universe) we should think about reducing the buoyancy requirement for these turbine strings. Some kind of kytoon arrangement seems possible.


or a solar balloon (not so good at night)


This one has no buoyancy gas at all

[JohnnyYesterday]

I think he's using helium with his prototypes because of convenience. Kytoon arrangements are present in the patents.

The last one has several serious disadvantages in current RL, although with OA technology some of them could be minimized. The tether must be conductive, which right now means using relatively heavy electrically conductive materials like aluminum and copper, which limits the flying altitude as the tether gets longer and too heavy to fly. But carbon nanotubes are one of the best electrical conductors known. It's a UAV, with all the complexity (cost, and failure modes) of a flying machine.

[JohnnyYesterday]

While I did mention the square-cube law in the OP, I didn't explain just how much it affects something like a turbine. I'll let the first linked patent do it for me:

"The decision to use a single large rotor, rather than many small rotors, is based on a desire for simplicity, and economy of scale, but results in a whole new series of expenses: First, the circular area subtended by a spinning rotor is proportional to the diameter squared, while the rotor's actual volume (and hence its mass), is proportional to the diameter cubed. In other words, the larger the rotor, the less wind it can capture in relation to its mass. The significance of this cannot be overemphasized: The amount of wind available per unit rotor mass is inversely proportional to the rotor diameter. This means that a 10-meter rotor will capture 100 times as much wind as a 1-meter rotor, but will weigh 1000 times as much! So as its diameter has increased by an order of magnitude, its subtended wind collecting area per unit mass has decreased by an order of magnitude."

So if it doesn't matter how long a series of turbines is, the sensible thing to do is to make their diameters as small as possible.

[iancampbell]

Regarding buoyancy gas, one possible solution to the helium-shortage problem would be to use another less efficient but much more abundant gas; preferably, one easier to extract from air. Admittedly, almost any other buoyancy gas would be less efficient. A good candidate might be neon, with buoyancy approximately a third that of helium.

Alternatively, really big solar-heated aerostats might be used; these would have enough thermal inertia to stay up at night, at least at low latitudes.