Some simple demonstrations to show
how wind turbines
designed for torque differ from high
speed turbines.
Try these experiments!
#1
Short out the power wires (touch them together) of your
high speed turbine and observe the results. The high speed turbines will
quickly come to a halt and stop producing power. If you try this with a
Hornet or other multi bladed turbine it will NOT stop turning and the copper
wires start to get HOT as the amperage is forced through the circuit. This
is the type of driving force that can ram high amperage into a bank of
dead batteries or force feed power into a grid feeding inverter at high
amperage levels.
#2
Place a small piece of tape on the blade of both a high
speed and Hornet turbine so the blades are bound to the mast and wait for
a windy day to see the results. The Hornet will break free from this sticky
situation at a very slow wind speeds as the big blade yields to the pressure
of the wind like a sail boat pushing forward.
However, the tiny piece of tape will hold the high speed
turbine in place, keeping it from turning even in wind speeds approaching
40 miles per hour plus!
What these experiments prove is that the driving force
in electrical current (Amperage) can be better served with hard turning
/ high torque wind turbine blades because high amperage loads can cause
alternators and turbine blades to drag severely.
Torque V. Speed or
think of it as Amperage V. Voltage
TORQUE! - OK. Here's the deal, in moderately plain
English.
Force, Work and Time
If you have a one pound weight bolted to the floor, and try to lift
it with one pound of force (or 10, or 50 pounds), you will have applied
force and exerted energy, but no work will have been done. If you unbolt
the weight, and apply a force sufficient to lift the weight one foot, then
one foot pound of work will have been done. If that event takes a minute
to accomplish, then you will be doing work at the rate of one foot pound
per minute. If it takes one second to accomplish the task, then work will
be done at the rate of 60 foot pounds per minute, and so on.
In order to apply these measurements to wind turbines and their
performance (whether you're speaking of torque, horsepower, newton meters,
watts, or any other terms), you need to address the three variables of
force, work and time.
Awhile back, a gentleman by the name of Watt (the same gent who
did all that neat stuff with steam engines) made some observations, and
concluded that the average horse of the time could lift a 550 pound weight
one foot in one second, thereby performing work at the rate of 550 foot
pounds per second, or 33,000 foot pounds per minute, for an eight hour
shift, more or less. He then published those observations, and stated that
33,000 foot pounds per minute of work was equivalent to the power of one
horse, or, one horsepower.
For purposes of this discussion, we need to measure units of force
from rotating objects such as wind turbine alternator shafts, so we'll
use terms which define a *twisting* force, such as foot pounds of torque.
A foot pound of torque is the twisting force necessary to support a one
pound weight on a weightless horizontal bar, one foot from the fulcrum
which is sometime a high speed turbine simply can't do.
Now, it's important to understand that nobody on the planet ever
actually measures horsepower from a running wind turbine. What we actually
measure (on a dynamometer) is torque, expressed in foot pounds (in the
U.S.), and then we *calculate* actual horsepower by converting the twisting
force of torque into the work units of horsepower and we can keep on going
to get to watts with enough other data.
Visualize that one pound weight we mentioned, one foot from the
fulcrum on its weightless bar. If we rotate that weight for one full revolution
against a one pound resistance, we have moved it a total of 6.2832 feet
(a two foot circle), and, incidentally, we have done 6.2832 foot pounds
of work.
OK. Remember Watt? He said that 33,000 foot pounds of work per minute
was equivalent to one horsepower. If we divide the 6.2832 foot pounds of
work we've done per revolution of that weight into 33,000 foot pounds,
we come up with the fact that one foot pound of torque at 5252 rpm is equal
to 33,000 foot pounds per minute of work, and is the equivalent of one
horsepower. If we only move that weight at the rate of 2626 rpm, it's the
equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on.
How does this all applies to wind turbines that have been designed
for high torque verse high speed??? We may all be arguing this point for
the next century but for the purposes of the Hornet we have settled on
a slower turning but torquey design that can quickly charge batteries,
power big grid inverters and even directly power an electric motor!
In short, when the amperage load is high you want
the Hornet wind turbine on your team!
Remember "FORCE, WORK and TIME??? The end result "ENERGY"
measured as "WATTS", "VOLTS" or "AMPS" output
by the wind turbine will be used for equal "WORK" by either the
fast turning or slow turning type designs BUT here are some distinct advantages
of the slow turning Hornet design to carefully consider.
The advantages of big, slow turning high angled blades:
* Extremely silent operation! (Does not
sound like a sword fight)
* High Torque! - High amperage loads
will not slow the turbine!
* Great low wind speed power output.
* Non-critical system. Blades do not
need to be balanced or have a perfect shape. Very forgiving.
* Able to operate other appliances like
pumps.
* Blade will not over-rev in stormy winds
(self slowing)
* Can be mounted very low to the ground!!!!
(Ground level wind turbulence does not
disturb multi-blade fans! -- While there is more wind power at higher elevations
most 2 and 3 blade turbine designs suffer greatly in low level mounts.
They can't find direction, whirl wildly in circles and loss momentum so
they have to start revving over and over again. The multi-bladed Stealth
turns with stability providing steady power even when wind is passing over
hills and through other objects.
For many people living in cities, high
level mounting is not allowed and wind is extremely turbulent due to the
presence of trees and structures, hence the silent running Stealth has
worked out for many people trying to find wind power in the city. While
looking like an over sized lawn toy it has also proved to be aesthetically
accepting to many would-be complaining neighbors. Many 12 foot high mounts
are now running in backyards across America making good power.
(Note; Over 85% of our population lives
in cities and suburbs so we need to work on turbines that can work in these
settings.)