MOVED TO:
http://amasci.com/emotor/kelvin.html
OLD VERSION:
"Kelvin's Thunderstorm"
Lord Kelvin's water-drop electrostatic generator
Bill Beaty, 1995
NOTE: avoid using wood to support metal parts! See "debugging"
notes at end.
It is possible to build a very simple high voltage generator which has no
moving parts and is powered by the energy of falling water. By dribbling
water through some old soup cans, several thousand volts magically
appears. The magic lies in the fact that water (as well as everything
else!) is made of vast quantities of positive and negative electric charge
in perfect balance. It's not that hard to cause an imbalance. Water
normally has zero net electrical charge because it contains equal and
opposite charges. "Kelvin's Thunderstorm" is a gravity-powered charge
un-canceller.
||||||
|||||| Grounded
|||||| Water
|||||| Dripper
||||||
Negative charge ||||||
is 'induced' at \ /
tip of dripper - || -
- _ -
_ + + + + + + +
-o- + -------------- +
- + | | +
+ | positively | +
_ + | electrified | +
-o- + | object | +
- + | | +
+ | | +
Negatively + -------------- +
electrified _ + + + + + + +
droplets -o-
-
- -
- | | - Negative
| | Collector Can
- |--__----____---| -
| |
- | | -
| |
- |_______________| -
- - -
Fig 1. WATER DROPLETS BEING ELECTRIFIED BY "INDUCTION"
THE BASIC THEORY
Even though water has no net electric charge, it is full of movable
electric charges (ions). Half of the water's charges are positive and
half are negative. The positive object shown in the above diagram
attracts the water's negative ions and repels the positive. This draws an
excess of negative ions into the tip of the water dripper, while repelling
an equal amount of positive ions back into electrical ground. When the
water drop detaches from the tip of the dripper, an overall negative
electric charge is still trapped in the drop. The falling drop carries
away negative charge, leaving the earth slightly positive.
Negative water drops will be continuously created forever as long as the
water flows, yet this process does not exhaust the imbalanced charge on
the positive object. Sounds like perpetual motion? Actually no. The
electrical energy is all created by the work that gravity does in pulling
the negative droplet away from the grounded dripper, and away against the
attraction of the positive object. Electrical force from the positively-
charged object keeps the tip of the dripper charged negatively, but the
positively charged object does not supply energy. YOU supply the energy,
since you LIFT the water to a height to fill the dripper. It's like the
generator in a hydroelectric dam, but without the turbine or the spinning
coils and magnets. The water itself becomes the moving parts of the
electric generator.
(Note: the charge polarities can be reversed: if the "object" is negative,
the droplets would be positive.)
BUILDING A GENERATOR
If we already have a positively-charged object, we can make negative water
drops. But where can we get a positive object? If there was some way to
change the negative charge on the water into a positive charge, then we
could build a self-sustaining generator. There is a simple way to do
this: build a second water-drop device like that in figure 1! See? The
device in figure one uses a positive object to create negative water. It
uses positive to create negative. If we build a second device, it could
use the negative to create positive. We could hook the two devices in a
loop. The first one would create an imbalance of negative charge, which
could be fed to the second one which would create an imbalance of positive
charge, which would be fed back to the first one.
We will build two of the drippers in Fig. 1, set them side by side, then
collect the electrified water drops from one side and use them to
electrify the "charged object" on the other, and vice versa. We'll
cross-connect the lower and upper parts with wires. One side will have a
positive "object" and will make negative drops, while the other side will
have a negative "object" and will make positive drops. We'll then have a
self-sustaining electrical reaction.
__________________________
_ _____________________ \
\ \ \ \
\ \ \ \
\ \ \ \
|| || Drippers (need not be metal), ground
|| || the water supply with a wire to
|| || metal faucet, or to the screw on an
|| || electric outlet or wall switch
|| ||
|| ||
| | | | Bottomless metal coffee cans, or
| | | | wire rings, or bundt pans, or metal
| | Wires not shown, | | disks with holes (supported by
| | see next diagram | | insulating rods.) Called "Inducers."
| | (below) | |
| | | |
| | | |
| | | | Metal cans on insulators (styrofoam?
| | | | insulating rods?) The "Collectors"
|____| |____|
| | | | The inducers and collectors
| | | | should be separated from each
|__| |__| other by several inches
Fig. 2 TWO DROPLET-CHARGERS PLACED NEAR EACH OTHER (see below for wires)
Wires connect the two sides together. The negative droplets touching the
lower can of the first side will charge the negative upper ring of the
second side, and the positive droplets on the second side will touch the
second lower can and will charge the upper ring of the first side
positively. The grounded drippers are connected to each other and to
ground. This all is illustrated in Fig. 2. See Fig. 3 below to see how
the wires connect things together.
SELF-STARTING
In fact, if you build such a device, it will usually create voltage
spontaneously without being pre-charged. During dry conditions everything
ends up with a tiny electric charge just from being handled. If one of
the upper cans is slightly negative, it will cause the water to have
imbalanced positive, which will start up the other side of the generator,
which will make the negative side larger, etc., over and over. It's like
balancing a penny on edge: it's hard to start out with perfect balance,
and usually it falls one way or the other. Same with this generator. If
there's a tiny electrical imbalance at the start, the generator will
amplify it over and over. A high voltage will magically appear from
nowhere. (But nobody knows which side will start out positive and which
negative.)
CONSTRUCTION
The metal parts of the generator must be supported with insulating
materials. A vertical sheet of acrylic plastic works well. So does
styrofoam plastic. Don't use wood as the supports, it's too conductive.
Fasten the collectors and inducers to the sheet with screws or silicone
caulk, or make holes in the sheet and tie them to the sheet with string or
wire. Some people have used plastic rods or strips to support things.
The inducers and collectors must be spaced away from each other by several
inches horizontally and vertically. The lower collectors must be kept
away from the table surface.
Bare wires are used to cross-connect the four cans. The two diagonal
wires must be far from any other conductive object, and must not touch
together. Use bare wire, this will let you create sparks between the
wires, or to later flash a NE-2 neon bulb.
Connect the ends of the diagonal wires directly to the metal of the cans
and rings. If you use plastic-covered wire, strip off the plastic coating
from an inch of each end of the wire. You can use tape to hold the wire
against the metal, as long as the wire touches the bare metal directly
(not, for example against the painted part of a coffee can.) Alligator
clipleads (bought from Radio Shack stores) work well for this. Or poke a
hole in the metal near the edge of the can, stick the wire through the
hole, and bend it and tape it so it doesn't fall out.
__________________________
_ _____________________ \
\ \ \ \
\ \ \ \
\ \ \ \
|| ||
|| ||
|| ||
|| ||
| o | | o |
| | | |
| o |+ + - - | o |
+ | |----\ /---| | -
| o | + \ + - / - | o | (no connection between
+ \ / the crossed wires!)
o C/ o
- | | - / \ + | | +
- | o | - - / + \ + | o | +
| |_____/ \_____| |
- |----| - + |----| +
|____| |____|
| | | |
| | | |
|__| |__|
Fig. 3 LORD KELVIN'S THUNDERSTORM, W/WIRES SHOWN
The upper rings (or cans) must be near the place where the water droplets
break from the rest of the water. If the drops break away right at the
tip of the nozzle, then put the nozzles within the upper cans. If a solid
stream of water comes from the nozzle and breaks up further down, then
move the nozzels up so the water-break point is inside the cans.
OPERATION
Once you have the water dripping, you can expect high voltage to
immediately appear. After the device runs for a minute, touch one of the
coffee cans gently with a finger and listen for the tiny snap of a
"static" spark. If you don't hear a spark, the machine is running weakly
or not al all. See the "debugging" section near the end of this article.
If you can't hear any spark, you can try detecting sparks electronically
with an AM radio. Place a radio a foot away from your generator, tune it
between AM stations, and turn the volume up. Run your Kelvin machine.
Touch one of the cans with your finger and listen to the radio. You
should hear a "snap" noise as your finger touches the metal. Touch one
upper can, then the other, then the first. You should hear a "snap" each
time. Even when sparks are too small to hear or see, a radio will
sometimes still detect them.
FLASHING A NEON BULB
Once your machine is able to produce sparks, you can also make it flash a
small lightbulb. Normal flashlight bulbs won't work, you need a small
neon "pilot light" instead. Obtain a small "NE-2" neon light, the kind
which looks like a short glass tube with two parallel wires inside and two
bare wires sticking out of the glass. Hold the bulb by one wire, look at
the tube, then use the other wire to touch one of the cans of your Kelvin
device. You should see a dim orange flash inside the bulb. (It might
help to turn off the lights and work in a dimly lit room.) Hold one bulb
wire, then use the other wire to touch the positive can, then the negative
can, then the positive, and you should see a tiny orange flash each time.
CONTINUOUSLY FLASHING BULB
Don't connect the NE-2 bulb directly across the two generator wires. It
will short out the generator and prevent high voltage buildup. You can
make the generator automatically flash the neon bulb by making a "spark
gap". First twist one wire from the NE-2 around one of the generator's
diagonal wires, then bend the wires so other short wire from the NE-2 is
very close to the other generator wire ( but not touching). Small sparks
will occasionally jump across the small gap and flash the NE-2. The
smaller the gap, the faster (and dimmer) the flashing. Try a 1/16" gap at
first. If it works, increase the distance to get slow, bright flashes.
Bend the sharp tip of the wire over, this sometimes lets the voltage rise
higher before a spark jumps, which lets the bulb flash more brightly.
FLAPPING KLEENEX
To "see" the high voltage surrounding the cans, tape some strips of tissue
paper to the cans. Put tape only at the top of each strip of tissue so
the strip hangs down against the side of the can. When the can charges
up, the strips should lift slightly outwards. The higher the voltage, the
farther the strips move. When a spark jumps, the strips jerk because the
force suddenly becomes less.
SLOWING WATER
The energy that builds up between the cans comes from the falling of the
water, and as the stored energy grows, the water has to do more and more
work every time it adds a bit more imbalanced charge to the cans. The
electrified drops feel a repulsion force as they fall towards the
alike-charged cans. As the voltage increases, the drops will fall more
and more slowly. They may even start bending their paths, even
occasionally falling upwards!
EMPTYING THE LOWER CANS
If the device is run for very long, the lower cans fill up. How to get
the water out of the cans without discharging them? Here's my addition to
the classic Kelvin Waterdropper: use the "faraday ice pail" effect, where
a conductive hollow object always has no charge imbalance on its inside.
To do this, connect an exit tube inside each lower can as below, so the
water DRIPS out (if it falls in a solid stream, the cans will discharge
and the generator will stop working.)
|| ||
|| ||
|| ||
|| ||
||/\/\/\/\/\/\/\/\/||
|| || For best results, no sharp edges or
|| || burrs anywhere. Or, cover sharp edges
|| WATER || with thick bead of RTV silicone caulk
|| ||
|| __ __ ||
|| | | | | ||
|| | | | | ||
|| | U | ||
|| | O | ||
====== ======
O
Uncharged drops
O exit from bottom
Fig. 4 REMOVING THE WATER FROM THE LOWER CANS
Or, even simpler, install a cone-shaped piece of metal window screen
inside a bottomless can, so the water drops touch the screen and continue
through. Make sure the screen is centered vertically within the can, so
that the point of the cone doesn't extend past the lower lip of the can.
Don't let the water drip from the edge of the can, otherwise it will carry
charge away with each drop.
With a little catcher-tray and a fountain pump, you can make the system
recirculate. Or, you can stack all four parts of one Kelvin device in a
single row, for an in-line waterdropper generator. See my article on
"Inline Kelvin Thunderstorm Device" found on my site at
http://amasci.com/emotor/ikelv.txt. Note that the Inline
version is more tricky to make work. Build the above device first
before attempting the one below.
\ \
\ \
\ \
||
Grounded ||
Dripper ||
||
o
o
| |
Neg | |
can | o |
| |
Pos | |
can |...|
w/screen | | Connecting wires not shown, see ikelv.txt
| | article for more info
\ / Connect pos to pos, neg to neg
Grounded \ /
Funnel ||
o
| | Note that this is a more advanced project,
Pos | | and is more difficult to debug than
can | o | the side-by-side version.
| |
Neg | |
can |...|
w/screen | |
| |
o
Fig. 5 IN-LINE VERSION (wires not shown)
The water supply need not be a "dripper", it can be a high velocity spray,
as long as the jet divides into droplets, not a contiguous stream. And
multiple jets can be used, sort of like a shower head. The faster the
flow and the larger the number of separate streams, the higher the total
output current. (Higher current gives faster recharge rate after a spark,
and it lets the generator self-start more reliably.)
GIGANTIC VERSION
I've always wanted to build a gigantic version like the one below, with
hollow metal toroids. (Use halves of VandeGraff spheres, the halves with
the holes). Or maybe use metal 55-gal drums. But the drums have sharp
edges, and we can't get millions of volts if the edges are sharp. A
foil-covered truck innertube should support about a million volts before
corona leakage stops the voltage from rising any higher.
\\ \\
\\ \\
\\ \\
|| ||
|| || water
|| || spray
|| ||
___ ___ ___ ___
/ \ / \ / \ / \
| | | | | | | | Four torii
\___/ \___/ \___/ \___/ (shown cross-
sectional)
___ ___ ___ ___
/ \ / \ / \ / \
| |\ /| | | |\ /| |
\___/ \_/ \___/ \___/ \_/ \___/
conical screens in lower torii touch droplets and release,
discharging them. Entire screen assy must be deep within
the "hole" of each donut so the torus shields the departing
water drops from the field on the outside.
Fig. 6 GIANT KELVIN DEVICE BUILT FROM SPUN-METAL DONUTS (or tire
inner tubes covered with aluminum foil!)
High-velocity shower heads and cross-connecting conductors made from
large-diameter pipes will complete the scene above: a "VandeGraaff
Generator" version of Kelvin's Thunderstorm apparatus!
NEWS: I suspended a bundt-pan by fishlines, then sprayed water through
the center, so that the water did not touch the metal. I used a garden
hose with a "water breaker", a sort of shower head attachment. I
charged up the bundt pan with a power supply, and then measured the
electric current between a collector pot and ground. 2.5 microamps!
This doesn't sound like much, but it is as much as some VandeGraaff
generators put out.
I found that if I disconnected the power supply from the bundt pan,
the current did not vanish. The charge on the bundt pan stayed the
same as I watched for about 30sec. And this was in high humidity
conditions! Fishing line makes a VERY GOOD insulator. When I touched
the bundt pan with my finger, the electric current coming from the
collector can did go to zero.
RUNNING A MOTOR
The above generators can be used to run a motor, if the motor is my Pop
Bottle Electrostatic Motor at:
http://amasci.com/emotor/emotor.html
I find that these small Kelvin Waterdrop Generators are a little too
feeble to keep the motor going continuously. Instead it builds up a
charge imbalance, then the motor starts turning and rotates a few times.
This exhausts the imbalance, the motor stops, then it builds up again and
repeats. This happens a couple of times per minute. A bigger waterdrop
generator is needed if you want to run the motor continuously.
MULTIPLE DRIPPERS
I set up multiple nozzles on the waterdrop generator and this improved
things considerably. In a cluster of nozzles, the inner ones may be
electrically shielded by the outer ones. Therefor a circle of nozzles is
probably best. I drilled a circle of eight tiny holes in a plastic bowl
(using #64 drill bit), and this gave good results. Crude version of
multiple-dripper: use a soup can, and punch a bunch of holes in the bottom
by using a tiny nail. I've also seen a shower-head thing called a "water
breaker" in the garden supply section of hardware stores. If a circle of
tape was stuck to the center of one of these, it would plug up the middle
holes and form a ring of about 100 tiny water jets.
SPEEDING UP THE RECHARGE
Whenever you discharge the generator, you also discharge the inducer
rings. As a result, the generator takes quite a while to "ramp up" to
full voltage again. This is exponential growth, and it's quite slow at
first. There are two possible ways to solve this (I haven't tried them,
you be first!) One way to solve the problem is to insert very large
resistors in series with the wires to the inducers (large = thousands of
megohms). Then always discharge only the collectors. The resistors will
keep the inducers from instantly discharging, and the generator will
quickly recharge with a linear voltage increase curve rather than
exponential. High-value resistors are expensive, so perhaps use thin
strips of carbon paper, or use strips of paper with lines of india ink
(india ink is conductive carbon.)
Another possibility: insert high voltage diodes rather than resistors. For
example, use several 7,000-volt microwave oven diodes in series, available
from Allied Electronics. Orient the polarity of diodes to allow the
Inducers to charge but not to discharge. Diodes in one conductor should
point upwards, and in the other conductor should point downwards. This
way the collectors will charge the inducer rings, but when you discharge
the collectors, the diodes will turn off and the excess charge on the
inducer rings will remain high. Also, the generator polarity would always
be predictable, since the generator would not function if the polarity
became reversed.
WEIRDNESS: antigravity
If your generator really works well, you will see water droplets slow down
and their paths curve upwards! No, this is not antigravity, this is just
electrostatic repulsion. Alike charges repel.
WEIRDNESS: really really gigantic generators
In a private conversation someone told me that there were patents on a
wind generator based upon the Kelvin Generator. Build two big parallel
vertical metal screens the size of outdoor movie theater screens (or
larger). The upwind screen has coarse mesh, the downwind screen has fine
mesh to gather water drops. Suspend them on insulators which are good for
millions of volts. Charge the upwind screen with a power supply. Spray a
fine mist of water into the screens upwind, and let the wind push the
spray through the screens. The upwind screen will attract imbalanced
charges into the sprayer tips, and the water drops will have an imbalanced
charge of opposite polarity. The wind takes the place of gravity in the
classic Lord Kelvin device. Wind pushes charged water to the second,
fine-mesh screen. Water drops touch this screen and deliver their charge.
The wind is slowed by repulsion of the water mist, the upwind screen uses
no current, and the downwind screen puts out amperes at millions of volts
potential (megawatts). Simply step down the megavolts of DC and convert
it to AC. Ta da, a wind generator with no moving parts! An artificial
thunderstorm, harnessed as a commercial generator, powered by the wind.
DEBUGGING:
If your project will not work, it may be because the humidity is high and
your device is having trouble "deciding" which side should be positive and
which side negative. See my hints about humidity, found at
http://amasci.com/emotor/statelec.html. With Kevin generators
it takes voltage to make voltage. If your device starts totally at zero,
it may take a minute or two to build up to maximum. Therefor give it a
goose by holding an electrified object briefly near one of the cans while
the water is running (for example: a balloon, a 2liter pop bottle, or some
styrofoam, each rubbed on hair to electrify them.) This gives the
generator a "kick start."
AVOID WOOD
Kelvin Generators usually can tolerate fairly high humidity. Watch out
though. Materials with large internal surface area, such as wood, cloth,
masonite, etc., usually absorb moisture from the air and become slightly
conductive. Therefor, assume that these materials are the same as metal,
and avoid using them as supports or framework when you build this device.
Wood provides a leakage path and shorts out the high voltage. One
experimenter even found that problems were caused by supporting their cans
with insulating blocks glued to a wooden panel. The short lengths of
plastic must not have been sufficiently insulating, and there must have
been a leakage path across the plastic and through the wood. Switching to
all-plastic construction solved their problem.
If acrylic sheets such as plexiglas(tm) or perspex(tm) are not available,
large styrofoam blocks work well as supports. Avoid using solvent-based
glues with styrofoam, it makes it dissolve. Nylon fishing line makes a
good insulating support, especially during high humidity conditions. Long,
very thin supports such as fishing line have small surfaces and therefor
give less surface leakage than short, fat supports or flat panels. Don't
use twine or string as supports, of course, since these materials become
too conductive when the humidity is high.
If humidity is very high, even plastic can become slightly conductive.
This can be temporarily fixed by drying the plastic surfaces with a blow
dryer. Bathe the plastic in hot air for several minutes, taking care not
to heat it so much that it softens! Try testing your generator again, and
it may begin to work.
To detect the tiniest charge imbalance, build the RIDICOLOUSLY SENSITIVE
CHARGE DETECTOR shown elsewhere on my web pages.
(http://amasci.com/emotor/chargdet.html) This device will
detect a few hundred volts of electrostatic potential at a great distance
from the cans. It is extremely sensitive: the tiniest sparks won't begin
until the cans reach about 1,000v potential, yet the sensor responds to
about ten times less. A sparking Kelvin generator can make the Charge
Detector flash even if it is many feet away.
Don't neglect the balloon trick. If your device doesn't self-start, then
momentarily hold a charged balloon near one of the cans while the water is
running. (Verify that the balloon is really electrified, see if it raises
your arm-hair when rubbed. Sometimes humidity is so high that the balloon
will not aquire an imbalanced charge by rubbing on hair.)
A simple way to detect static charging: place a portable AM radio near the
device, tune it to a blank station, then touch one of the cans with a
finger. If your device is just barely working, there will be an
imperceptible spark. But this will make a loud click on the radio! If
you wear an AM Walkman headphone radio, it will extend your senses so that
you can hear the electromagnetic pulses given off by the tiniest spark.
Become a "Borg" from Star Trek, with the ability to hear electromagnetic
impulses via a biointerface to electronic circuitry (Walkman headphones).
:) Try spending the day wearing AM radio headphones tuned to an empty
station, and you will encounter all sorts of interesting electromagnetic
"sounds" in the environment. You'll hear the "crack" noises of distant
lightning even when the thunderstorms are too far away to hear the
thunder. Electric fences in countryside farms make a periodic click. The
overhead wires from electric city busses make all sorts of musical tones.
REFERENCES:
THE PHYSICS TEACHER (magazine), May 1988, pp304-306, The Ting-A-Ling
Machine, by Cliff Bettis (uses mixing bowls)
THE PHYSICS TEACHER (magazine), February 1972, pp100-101, Electrostatic
Lobby Display, by M. Fast (uses coffee cans)
Scientific American Magazine June 1960, THE AMATEUR SCIENTIST, by C. L.
Stong
Inline version of "Kelvin's Thunderstorm" electrostatic generator:
http://amasci.com/emotor/ikelv.txt
((((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
billbeskimo.com amasci.com
EE/programmer/sci-exhibits science projects, tesla, weird science
Seattle, WA 206-781-3320 freenrg-L taoshum-L vortex-L webhead-L