h a l f b a k e r y
OK, we're here. Now what?
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
Wind turbines are pretty cool, but it seems like they are pretty wasteful, since at any given time only a small surface area is capturing the air movement. I think it is possible to build a sort of gigantic sail to directly capture the maximum possible wind energy in a given surface area and translate
it directly to the spinning motion necessary to generate power from, say, a DC motor.
What is required is a sort of ratchet or something similar to the free wheel gearing on a bicycle. You have a large tarp (or perhaps a sheet of aluminum, for strength) facing the source of wind which is connected to a belt/chain or gear train so that a few feet of movement of the sail will cause the axle of a motor to spin at a high rate of speed. The sail is anchored by an array of bungee cords which stretch as the sail is pushed back by the wind, and when the wind dies down, the bungees freely pull the sail back in, preparing the device to accept the next big gust. If designed properly, it may be able to make use of all air movement from the slighted breeze to gale-force winds. A major limitation of conventional wind turbines is that they generally have to shut down if the wind is above a certain speed, in order to prevent damage to the device. This seems like an immense waste.
Efficiency of wind turbines
[kbecker, Oct 04 2004, last modified Oct 21 2004]
My own take on sails generating electricity.
Shameless self promo. [2 fries shy of a happy meal, Oct 04 2004]
It's the way of the future, I tells ya! [friendlyfire, Oct 04 2004, last modified Oct 21 2004]
||[DE] The problem is that the turbulence from one blade affects the next one. Making them bigger makes the problem worse.
A second limitation is that you have to leave some kinetic energy to the wind so it can move off behind the windmill. Otherwise a high pressure zone would develop behind the blade which obviously can't happen.
The best you can get is around 60% (link).
||I like it if I understand you correctly.
You don't want to make sails as the blades for a wind mill, but a huge sail, the tension of which would power a spinning wheel generator as it billows out.
I am probably wrong but I think you will need a way to release the trapped air as the sail captures the maximum it can hold or it will remain distended until the wind dies down. By releasing the air at intervals you will be able to renew the pull to your generator even if the wind doesnt let up.
||This is part baked, or something like it, I wish I could find the reference.
||There is a type of wind driven water pump (for wells etc) where a lever is weighted to rest pointing up into the air. There is a large flat sheet (or flap) at the top of the lever. As the wind blows the lever is pushed downwards lifing water from the well, when the lever gets down to about 45 degrees a mechanism trips and allows the flap to swing edge on to the wind. The lever raises and the cycle repeats.
||This not worth baking. It is worth
thinking about expanding the
range of usable wind but your
definition of efficiency is not well
thought out. To take your plan
directly: your bungies are
absorbing energy and are eating a
fair share before returning the
energy during the lulls. This is not
scavenging energy it is wasting it
by going through extra drive
chains and the like.
||And you mean alternator or
generator, not motor.
||Time to do some more research.
// A major limitation of
conventional wind turbines is that
they generally have to shut down if
the wind is above a certain speed,
in order to prevent damage to the
device. This seems like an
||your sense of proportion //major/
/ is off.
||This is a major waste Just like it is
a terrible waste to have golf clubs
you cannot use during the .05% of
every year when lightening is a
risk. Let's put a bunch on
engineers on fixing this one
||better to work on finding uses for
power that is unreliable but, over
all, plentiful. Uses that do not care
if things slow or speed up a bit:
||Charging hearing aid batteries.
pumping water to holding tanks.
operating cat doors, drilling deep
holes. grinding exotic grains. Just
non critical and ideally naturally
rotational tasks to reduce the
number of transmission losses.
||For instance Sail Convoys of "rust
free Texas Cars" to the upper
Mississippi river valley auto
restorers. Not time critical, the
cars are just getting more valuable
the longer they take!
||Seriously, you scheme here not
worth pursuing as it judges the
problem incorrectly and assumes
the possibility of freakishly
||DarkEnergy, I find your idea interesting, but not yet half-baked. There might be some use around my place where the wind is prevailing, but not FIXED. Your huge sail would have to have sophisticated gears that translate the lateral movement of the sail into unidirectional spin ... that is available, but takes a bit of energy.
||My pal, BrainSmith, built a tiny windmill by cutting nearly straight but exquisitely curved blades from a piece of PVC sewerpipe. He fastened these to a bicycle wheel (good bearings). The wheel turned two tiny generators (actually, motors from a cassette tape deck with the little 'inhibitor' removed) with those tiny rubberbands. It put out considerable energy. With this energy he runs LCD lights and his laptop computer. He lives in Montana in the deepwoods in a tamarack and plastic zuggurat that I can hardly find in the snowy woods ... and I live a (really long) stone's throw away.
||[DadManWalking] The wind in any one location is unreliable but its generally blowing somewhere. With lots of turbines in different locations supplying the grid you get a more constant supply.