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Will this kind of electrical generator work?

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Posted by Antti Hyvari on November 14, 2004, 8:46 am
 
Here is a copy of the writing that I originally posted "Science
Hobbyist - General Science Forum" (www.amasci.com).

**********************************
Greetings from Finland to you all  :)

For some time now I've been thinking about building an experimental
generator that produces electric power. So far I haven't been able to
find from anywhere writings or thoughts of this kind of device. So
this might be unique idea or just my imagination running too wild. I
would hope that you could judge, from this writing that follows which
case it is.

Some time ago I was gazing the "How stuff works" website
(www.howstuffworks.com) and read about the Van de Graaff generator
(afterwards VG) which produces high amount of voltage. I started to
thinking about how this machine could be used to harness substantial
amount of electrical energy. The VG produces only a tiny amount of
current so at first it seemed that it would be useless to be used
anything but to rise peoples hair or to some other things that aren't
involved to produce electric power. Then I started to think about how
to increase this electrical current. I went on searching the web and
found this great "Science Hobbyist" site (www.amasci.com) and from
there I found answers to many of my questions along with huge amount
of information about electricity and other stuff.

One of the most interesting things that I found was this picture
(http://amasci.com/miscon/ele-map.html ) in which "static electricity
versus current electricity" was neatly illustrated. In the picture
there were of course these "tabletop" VGs in the right lower portion
of the picture. As we can see from this picture, the current involved
with VGs is measured in micro amps. What really caught my eye were
thermocouples. I already knew that these things exist, but before I
wasn't familiar at all to their characteristics. This picture shows
that thermocouple is quite an opposite to VG. It creates a high
current with only a minimal voltage. Here is address to another site
that describes functionality of a thermocouple
(http://www.allaboutcircuits.com/vol_1/chpt_9/5.html/thermocouple ).
Here are two interesting quotes from that site.

"The voltage produced by thermocouple junctions is strictly dependent
upon temperature. Any current in a thermocouple circuit is a function
of circuit resistance in opposition to this voltage (I=E/R). In other
words, the relationship between temperature and Seebeck voltage is
fixed, while the relationship between temperature and current is
variable, depending on the total resistance of the circuit. With heavy
enough thermocouple conductors, currents upwards of hundreds of amps
can be generated from a single pair of thermocouple junctions! (I've
actually seen this in a laboratory experiment, using heavy bars of
copper and copper/nickel alloy to form the junctions and the circuit
conductors.)"

"Thermocouples, however, can be built from heavy-gauge wire for low
resistance, and connected in such a way so as to generate very high
currents for purposes other than temperature measurement. One such
purpose is electric power generation. By connecting many thermocouples
in series, alternating hot/cold temperatures with each junction, a
device called a thermopile can be constructed to produce substantial
amounts of voltage and current:"

At first thermocouples or VGs alone aren't type of things which come
to a mind when thinking about producing electric power. But what if
the VG and the thermocouple can be somehow combined to produce a high
current with a high voltage? After thinking it for a while (month!),
the answer seems to be pretty simple. Just connect two wires made from
different metals together to make a thermocouple and connect the +
wire to the positive end (=sphere, if it's built to be positive) of
the VG and similarly connect the - wire to the negative end of the VG.
Don't ground the VG but instead connect the grounding wire or the
negative sphere to this - wire. To complete the electric circuit,
connect + and - ends from the VG to a electric load (e.g. light bulb).

Imagine a simple circuit of two conducting wires where thermocouple is
in the left side. This is the first junction point of the wires. The
VG is in the middle touching the upper and lower wires of the circuit
with it's + and - ends (=spheres, if it has two of them). The load is
in right side and this can be considered as the second junction point
of the wires.

There you have it. An electric circuit powered by combined generator
which produces direct high current, high voltage electric power to the
load. Key concept of my idea is that in the complete electric circuit,
which uses these combined energy sources, the VG doesn't short-circuit
the whole thing. Electromagnetic energy, harnessed from VG and
thermocouple, and carried along using conductive wires, will go to the
load and therefore can be used to operate normal electric applications
(electric motors, to produce hydrogen, light bulbs etc).

Let's assume for a while that this generator really works. Of course
the VG and the thermocouple need energy from somewhere to operate.
This is when things get interesting. The amount of voltage or current
these devices alone generate is very high. My current understanding is
that for purpose of generating electric power the size of the VG can
be very small. The whole operational circuit, powered with VG and
thermocouple, will be easy/cheap to build and it's capability to
harness the energy from heat (for the current) and motion (for the
voltage) is very high.

Small generator, in which the thermocouple would be heated using e.g.
a thermal solar energy and VG operated using a e.g. small windmill or
watermill (=renewable energy sources  :)  ), could be used to generate
extra electric power for your home. Another approach could be burning
biomass to produce heat for the thermocouple and motion (e.g. boiling
water) to operate the VG. At first I think it would probably easiest
to just use normal tabletop VG with small motor, a candle flame heated
thermocouple using thick, conducting metal wires to see quick results.
Of course for almost any electrical application, the high voltage
direct current produced must be run through transformers, regulators
and inverters, which all decrease the efficiency. If the power output
of this generator is still high enough (now I'm truly speculating  :)
), one could setup a power plant in which one (or more) very large
combined generator is operated and use this plant to provide
electricity to the power grid.

How much electric power could be produced with this type of generator
(if it works) is one question to which I can't find answer unless
actually trying it for real, although playing with the math (volts,
amps, watts, etc) can give you some impressive numbers. Simple way to
visualize this is to look again this electric map picture I mentioned
earlier and draw vertical and horizontal lines from thermocouples and
VGs to see where the connection point of these lines would be. As you
can see, the dot (this new generator) is placed relatively high in the
combined electromagnetic energy scale.
 
There are two reasons why I haven't yet tried to see if this works
myself or encouraged someone else to investigate it. First reason is
that if I'm correct, the amount of electromagnetic energy harnessed
can be very, very dangerous. I'm an amateur when considering
electricity or electric engineering, but curiosity keeps me wondering
about what kind of things one could do with this type of generator.
Another reason is that I would like to have (maybe more professional)
opinions from other people about this idea before proceeding. I want
to know if I'm totally misunderstood the concepts which I'm talking
about or if this is something worth of trying.
**********************************

Posted by Anthony Matonak on November 14, 2004, 11:13 am
 
Antti Hyvari wrote:
...

Clearly it can't work. The static generator's resistance is almost
complete and the thermocouples resistance is extremely low. Hooking
a low resistance wire across a static generator shorts it out and
you won't get much voltage. Hooking a huge resistance (nearly an
insulator) across the thermocouple will limit the current to almost
nothing. Low voltage, Low current, multiply them and you get low power.


Let's assume for a while that this generator doesn't really work.
What do you do now?

Anthony

Posted by Winston on November 14, 2004, 6:50 pm
 Antti Hyvari wrote:

(What if I connected a thermocouple in series with a Van de Graff?
  High current from the thermocouple times high voltage from the
  Van de Graff equals high power, right?)

Hi, Antti.

Thanks for the refreshing idea. It would work, but not the way you
intended.

*All* the current in a series circuit flows through *every* component
in that circuit.  So, you can have no more current flow than can be
passed through the 'highest impedance' component, in a series
circuit.

A VG is a very 'high impedance' component, so you could have a
battery (or thermocouple or other low impedance device) of infinite
current capability in series with it, but you would get no more
current flow through the VG than the VG produces without the battery.


*The Arithmetic*
Say you had a 1 watt 750 KV VG.  Ohm's law states that maximum
current flowing through the generator can be no more than about
1.333 microamperes.  The information you saw in the preceeding
paragraph shows that no matter what we do to this series circuit,
the total current flowing through it can be *no more* than
0.000,001,333 amperes.


Place a 0.01 V 0.1 A thermocouple in series and
you get a combined generator capable of 750,000.01 V at 0.000,001,3
Amperes. Our generating capability has jumped from 1.0 W all the way
to 1.000,000,013,33 W.  (About thirteen nanowatts increase.)

Yes, the power has increased.  Not by much, however.

The answer you seek is in placing high *current* devices in series.
Have a look at the thermopile:
http://www.allaboutcircuits.com/vol_1/chpt_9/5.html

Likewise, you can place high *voltage* devices in parallel to get
high power, too. Our electricity grid is made of high voltage
generators all connected in parallel to produce mind - boggling
amounts of power.

If you had several extremely high voltage rectifiers to isolate them
from each other, you could connect millions of VGs in parallel to get
huge levels of power.

Neither the VGs nor the thermocouples connected in any way will give
you an *efficient* power generator, however.

That is best done with a solar steam engine running an alternator.

Here is a site that you will find interesting:
http://www.homepower.com/

:)


All my best

--Winston


Posted by nospam.clare.nce on November 14, 2004, 9:35 pm
 wrote:


Won't work, as in a series circuit, current is limittted by the
highest resistance in the circuit - the VG. You can NOT cause a high
current to flow through a high resistance - even the VHV of a VG
generator cannot overcome the resistance of the circuit - if it could,
the current would go up, and the voltage down.


Posted by Winston on November 14, 2004, 10:08 pm
 nospam.clare.nce@sny.der.on.ca wrote:

Thanks for the clarification, Clarence.  I don't know what I was thinking
when I wrote:

  "*All* the current in a series circuit flows through *every* component
   in that circuit.  So, you can have no more current flow than can be
   passed through the 'highest impedance' component, in a series
   circuit."

Oops.  I should have read a little more closely, Antti-

You mentioned placing the thermocouple in *parallel* with the
Van de Graff.

"Imagine a simple circuit of two conducting wires where thermocouple is
  in the left side. This is the first junction point of the wires. The VG
  is in the middle touching the upper and lower wires of the circuit with
  it's + and - ends (=spheres, if it has two of them). The load is in right
  side and this can be considered as the second junction point of the wires."

As I implied in my earlier reply, the thermocouple is a very low
impedance component.  In parallel circuits, voltage across any component
will be the same as the voltage across all components.  The thermocouple
junction would short out the output of the Van de Graff generator.
Remember that the thermocouple is just two pieces of dissimilar wire
welded together.  The Van de Graff would be unable to generate any
more voltage than is already present across the thermocouple junction, as
a practical matter.  If you had a really gigantic Van de Graff, in theory
you could generate enough current to boost the voltage across the
thermocouple somewhat above the value that it would normally produce.

That would be amazingly wasteful and produce way less useful power
than just the Van de Graff by itself, however.


All my best

--Winston.


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