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standing sail

electric generation from a standing sail
  [vote for,

Replacing a turbine, this sail or wing, permanently set on the roof of high rise buildings or in high-wind locations, catches wind energy and transfers it via a cable and gearbox to an electric generator.

For several hours the sail advances slowly by leaning forward but only 1 cm at most in 24 hours.

A cable transfers the power of movement

Once every few hours the sail is relaxed and pulled back to its original position.

Rather than "no moving parts" this is about "slow moving parts".

The benefits over a turbine would be: 1. You have more "wind catching space" so I would expect you can catch more energy in the same area. 2. Less parts and less moving parts. 3. Probably much cheaper to create, hoist up and maintain. 4. Less environmental objections. Could even be set up as a fence or roof shade.

One thing I don't understand is how much of the wind I have to let by, so that the strongest constant difference of pressure between the two sides of the sail is kept and what the best shape of the sail should be. Sailships use square sails when they want to advance with heavy cargo, but sailboats use triangular sails when they want to go faster than the wind, or in a direction that is not that of the wind.

When going in the same direction of the wind does that mean they are able to recieve more energy ?

pashute, May 21 2019

Sail generator proposal https://greendiary....urbine-designs.html
[2 fries shy of a happy meal, May 22 2019]

A bit of real physics https://en.wikipedia.org/wiki/Windbelt
One of those out of box inventions [wjt, May 23 2019]

Wikipedia: Betz's law https://en.wikipedi...g/wiki/Betz%27s_law
// One thing I don't understand is how much of the wind I have to let by // [notexactly, May 27 2019]

Electric_20Galleon [2 fries shy of a happy meal, May 27 2019]

About Catchwood's sail - actually a wind funnel https://www.wired.c.../11/kite-like-sail/
[pashute, May 27 2019]


       //the sail advances slowly by leaning forward but only 1 cm at most in 24 hours.// There's your problem. Energy=force x distance.   

       Suppose you have a wind turbine, where the blades travel a total distance of 100km in a day (that's very conservative), and the force acting on the blades is 1000kg or 10,000N (also conservative). That's 100,000 x 10,000 = 1e9 Joules of energy.   

       Now consider your system. Let's assume that the force acting on your almost-static sail is 100 times bigger than the wind turbine, or 100,000kg (100 tons), or 1e6N. The sail moves 0.01m in a day. Total energy= 10,000 Joules.
MaxwellBuchanan, May 21 2019

       So, adjust the figures. Have it swing forward a couple of meters, and then feather to swing back, every couple of seconds. Better, have a symmetrical section so it can generate force in both directions.
pocmloc, May 21 2019

       Or you could attach it to an axle ...   

       As [MB] points out, [-] Bad Physics.
8th of 7, May 21 2019

       //Better, have a symmetrical section so it can generate force in both directions.// Well, then you've essentially got a flapping structure. Not only do you waste lots of energy in accelerating/decelerating in each cycle, but the loads on the support structure will be huge.
MaxwellBuchanan, May 21 2019

       Put it on a trolly on rails so it can run 100km across the landscape every day, pulling a cable attached to a generator?   

       No it is a silly idea. Let us stop.
pocmloc, May 21 2019

       It can be made to work, after a fashion.   

       The mast and sail is on a trolley. The trolley runs on a track with a vane that keeps it pointing away from the wind direction.   

       From the trolley, a cable runs over a pulley and is attached to a bucket and a weight which are free to descend into a water well.   

       The wind pushes on the sail, which raises the bucket. When the bucket reaches the top, it is automatically tipped. This furls the sail. The weight pulls the bucket back down the well, and when the trolley hits the stop the sail is unfurled again; the cycle repeats.   

       More of an art installation than a practical pump.
8th of 7, May 21 2019

       Played with this basic idea for a while. Came up with the best incarnation of it.   

       Use it for decoration and build nuclear power plants.
doctorremulac3, May 21 2019

       There was a Venetian blind type generator that vibrated as wind traversed the belts or 'sails' if you like.
wjt, May 22 2019

       Used physics textbooks really aren't that expensive...
RayfordSteele, May 22 2019

Scroll down to #9.

       [2 fries...] As far as I can tell, that one uses the sail more as a "scoop" to channel more air into the turbine, rather than using the tension on the sail mounts directly.
neutrinos_shadow, May 22 2019

       Close though...   

wjt, May 23 2019

       ^ Interesting link. 2014 eh? I posted the idea to use wind power to vibrate cords stretched between magnetic cradles here in 2003. [link]   

       Nice, [2 fries], you may have inspired another bit of kit in the world. Just think how many words in this place have stimulated neurons, to alter actions and finally caused the manufacture something.
wjt, May 27 2019

       I knew Betz' law but never really understood it till going over it again now and finally having it rap around my mind. I think I get it, at least 59.3 %.   

       No need for a trolley or a bucket. The mast can be connected to the roof with a hinge so it swivels forward and backwards, and the cable catching the energy is tied to the top of the mast. A gearbox for a winch 10 cm wide, going at say 10 cm/minute means 1 rpm. (I'm being more realistic, instead of the 1 cm in 24 hours) Changing that to 3000 rpm is not impossible with a 1 to 3000 ratio gearbox.   

       As @MaxBu pointed out it is not uncommon to get 1 ton (10kN) of power, but contrary to what he wrote, I'm pulling a weight (or powering an electric generator) so the distance the sail moves is not the significant factor but rather the amount of energy passed from the wind to the generator.   

       I also re-learned the "faster than wind" sail, and realize now that the actual explanation is that the angle of the sail is alowing for a larger release of wind (and better Belz ratio) which means more power and more energy, hence the higher speed, which in the actual wind direction is still at the actual wind's speed, but using extra energy to move the boat additionally at an angle to the actual wind's direction.   

       A Like and laughing smily for doc @emulac3 (e mu - I understand from digital signal processing hense the audio equipment company name but what is lac3 referring to?)   

       Thanks to @Maxwel, @2friesShy, @wjt and @notExactly - you remarks are highly appreciated!   

       @pocmloc, @Rayford, perhaps you are right. But I'm not sure. This idea may still have some merit to it.   

       The "kite-sail" project from Chetwoods turns out to be a funnel for "catching the wind and directing it into a turbine". You guys have previously written about how and why that would be non productive in a former idea of mine a few years ago. [link]   

       The [+] Electric Galleon is, of course, an entirely different idea.
pashute, May 27 2019

       @Maxwell and pocmloc: using 10 instead of 9.8 and according to the book "Physics of Sailing":   

       If I have 100 kg mass at 1 m from the ground being pulled towards earth by gravity with a force of 1000 N and acceleration of 10N/kg, and I let it down by 10 cm, I lose those 10 cm worth of potential energy previously stored in the distance of the mass from the center of our planet. With the new position I can now send a railcar attached with a pulley at a lesser speed when reaching the ground, or I can now raise an equivalent weight of 100 kg to 90 cm only.   

       But If I put a sail of some size, which is stopping a constant wind that is exerting a force of the same 1000 N on it (not hard to achieve with a 15m2 sail in a 30km/hr fresh breeze) and the sail moves 10 cm, I do not lose any of the energy from the next wind coming up and still exerting 1000 N on the sail.   

       If this wind could raise 100 kg to 0.2 m (let's disregard the kinetic energy translated on the way, and avoid discussion of what stopped the movement when 1 m was reached) then the potential energy is 100 kg * 10 N/kg * 0.2m = 200j.   

       Theoretically I should be able to catch 50% of that energy, say by raising a mass of 100 kg to 10 cm, (within 1 minute) using rope and transmission. Is there a mistake in my calculations?
pashute, May 27 2019

       //Just think how many words in this place have stimulated neurons, to alter actions and finally caused the manufacture something.//   

       More than you would think.
One-liners on talk-shows, stunts, entire sit-com episodes, speed-bumps, theme park rides... etc...

       While I do a tiny little happy-dance every time I see something from here make it into reality I'm always disappointed that the origin is never mentioned.   


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