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"It would work, if you can find alternatives to each of the steps involved in this process."
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[Edit] after realizing that currents are faster therefor
stronger close to the surface, at the end of this idea I
propose a new simplification.
Typical sea current energy recovery is done with heavy and
gigantic structures holding turbines. see link (to be posted).
Enter the halfSail system.
The halfSail base, suspended
directly beneath the boat/ship/platform, controls a folding
sail, opening and closing it in turn.
When open the sail pulls a cable which transfers the power
upwards via a pulley to the floating platform, pulling a
transmission system for generating electricity. (See details
below and illustration attached)
All electric generation is done at the surface above water,
with existing electric generator technology and well known
Thrown into the sea from any size ship, boat or floating
platform, it can be easily configured to work with any sail
and thus can be configured to produce any required quantity
of electricity available for recovery at the desired location.
There is no need for a permanent installation, and the
can be easily moved and redeployed at another location
the need arises. It is also extremely safe for marine life,
no fast moving parts in the water.
Here's how it works: (See illustration).
Two square half-sails overlap each other creating a
When the sail reaches the end of its rope, two "connecting
cables" are let to slide out from the sail connection,
the two halves to "fold out", and the sail to be easily pulled
Once reaching back to the base, the connecting cables are
pulled tight again and locked in place so that now the sail is
one large sail again, pulling on the current.
The ropes and the sail can be polycarbonates or plastics
(Kevlar ropes and carbon fiber sailcloth) making the system
cheap, foldable and lightweight.
That's all, folks! Stay tuned!
[Edit] simplification: The sail, floating with top on the water
surface pulls directly at a cable powering the generator on
typical marine current electricity generators
[pashute, Feb 23 2017]
halfsail closed -
pulled by sea current and generating electricity [pashute, Feb 23 2017]
easily pulled in to close and renew sail operation [pashute, Feb 23 2017]
look what i found!!!
[pashute, Aug 27 2019]
||No, it's not a bad idea...just sometimes good ideas fall between the cracks..
||It happens to me a lot. It's often when other ideas are
getting a lot of attention. Also, well all my ideas are
obviously crap <sob>.
||I see a problem. If this thing is going to be moveable, then it will not be anchored solidly to the sea floor (which is quite difficult to do anyway).
||If it is not firmly anchored, then you can only get a small amount of force from your sail, without dragging the whole thing off into the distance. And, if the force is small, you will only get lots of power by allowing the sails to travel quite fast over long distances. But now you have an underwater sail and lots of long cables, which will cause all kinds of problems.
||So, why is this any better than a turbine-style generator? A turbine can recover a good fraction of the energy in the moving water, operates continuously, and is much better at generating power from a limited amount of force (remember, we're talking about something that be //redeployed//). A turbine blade is just a sail that goes in a circle.
||Hmm. Surely by running with the wind, then tacking against the wind it's possible to collect enough energy to make some electricity? Given a flat enough piece of ground, model sailing boats on wheels could do this on land.
||A paddle steamer works in exactly the same way as your
design. Apart from the obvious direction of energy
transfer, you're extracting energy by slowing down
water, a paddle steamer expends energy to speed
water up. The paddle takes energy from the engine to
move water backwards before returning to its original
position in a less restrictive form, by moving through the
air not water. Your sails use moving water to turn an
engine before returning to the original position in a less
restrictive form, folded. It's the same. And for the same
reasons a propeller is better than paddles, a rotational
turbine has advantages over the sails. Mainly that they
eliminate the folded/out of water component so that
all the device is working all the time.
||And that they use lift instead of drag.
||An underwater sail or kite can push my ship at most at the
speed of the currents which are usually at most 5.6
meter/sec or 9km/h.
||But if I have a drag on my ship with traction to the sea floor,
or even an anchor, or by catching an undercurrent going in
the opposite or different direction, then I can pull a cable
extracting the kinetic energy from the water which is quite
a lot even at 5 meters per second. Say 10 square meter sail
during 2 seconds stopping all the water that comes to it by
converting it to energy (I'm being theoretical now): That
would be kinetic energy from 1000 cubic meters of water
weighing (1 ton x 5 meters/sec) =12.5 kJ or 3.5 KW*hours.
||The advantages from a turbine are several
1. Only the sail is submerged. No special underwater
electric generator. No underwater maintenance.
||2. Easily movable to more favorable location, and allows
location to revive if in any way altered.
||3. Extremely low cost for a 100 meter wide 10 meter deep
sail like this.
Compare to cost of 100 meter blade turbine costs.
||Those are some good advantages.