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 stall 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 proved to be aesthetically acceptable 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.)