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Dene S. Matadeen
The Windmill Also Known As The Wind Turbine.
Windmills have always sparked my interest, may it be from growing up around
agricultural windmills or may it be from my mom buying me colorful, plastic versions of
windmills from our local market when I was a child. Historically, windmills served
originally to grind grain, though later applications included pumping water and, more
recently, generation of electricity. he more recent electricity generating windmills are
called wind turbines. !pon researching the way a windmill operates, a very plausible
"uestion arose. Is a windmill a heat engine or is it a perpetual machine#
Most engines convert heat energy into motion. he heat comes from burning a fuel
such as coal, gasoline, or hydrogen gas. he heat makes a gas such as air, e$pand
rapidly. %& heat engine is a device or machine that produces work from heat in a cyclic
process' ( Smith, ). M, H.*. +an ess, and M.M &bbott. Introduction to *hemical
-ngineering hermodynamics. th ed/(0igure I/. Wind is the result of convection currents
between hot and cold regions on the earth1s surface. he warm region on the earth1s
surface heats the air above it. his hot air begins to rise due to the buoyant force acting
on it. his creates a low pressure region near the hot surface. *ool air 2ows toward this
low pressure region. *an this hot and cold region be considered a source and sink for a
heat engine#
Initially, a windmill takes in air at atmospheric conditions. When it is run through
the system, the temperature of the air that comes out of the windmill is minutely
di3erent. here are no signi4cant changes in the air temperature at the outlet to call it a
sink. he heat that is involved in the process is very small, and there is also no burning of
fuel. -ven though it may appear that the windmill takes in wind, which is the result of
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convection currents between hot and cold regions of the earth5s surface, and it produces
heat, it is not considered to be a heat engine. Windmills %are not heat engines because
they do not rely of heat to produce
motion'(http677www.infoplease.com7dk7encyclopedia7engines. html/.
& perpetual machine is a device that does perpetual motion. %8erpetual motion or
perpetuum mobile, arose historically in connection with the "uest for a mechanism
which, once set in motion, would continue to do useful work without an e$ternal source of
energy or which would produce more energy than it absorbed in a cycle of
operation'(http677www.answers.com7topic7perpetual9motion/. his type of motion, which
is now called perpetual motion of the 4rst kind, involves only one of three distinct
concepts presently associated with the idea of perpetual motion.
he 4rst type of perpetual motion refers to a mechanism whose e:ciency e$ceeds
one hundred percent. his mechanism violates the 4rst law of thermodynamics, which is
conservation of energy. *onservation of energy states that energy can be transformed,
but it can neither be created nor destroyed. Sometimes the 4rst law of thermodynamics
states that a perpetuum mobile of the 4rst kind cannot e$ist.
he second kind of perpetual motion refers to a device that e$tracts heat from a
source and then converts this heat completely into other forms of energy. his process
satis4es the principle of conservation of energy. his type of perpetual motion e$plores
the idea of a limitless source of energy which violates the second law of thermodynamics.
he second law of thermodynamics states that heat can not be completely converted to
other forms of energy. herefore %by de4nition, perpetual motion machines of the second
kind, violates the second law to function' ( http677en.wikipedia.org7wiki7
Second;law;of;thermodynamics/.
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Dene S. Matadeen
he third kind of perpetual motion describes a device that can continue moving
forever. It could result in actual systems if all mechanisms by which energy is dissipated
could be eliminated. Since e$perience indicates that dissipative e3ects in mechanical
systems can be reduced, by lubrication in the case of friction, for e$ample, but not
eliminated, mechanical perpetual motion of the third kind can be appro$imated but never
achieved.
& windmill seems to have the attributes of a perpetual machine, but can not be a
perpetual machine because it cannot have a thermal e:ciency of one hundred percent.
In the study of thermodynamics, there is no device or machine that has one hundred
percent e:ciency. herefore from my conclusion, there are no real perpetual motion
machines, because it violates the laws of thermodynamics. he earliest references to
perpetual motion machines, was by an Indian mathematician9astronomer, <h=skara II,
date back to >>?@, where he described a wheel that he claimed would run forever. &
windmill can run forever, once there is air, but engineers believe that perpetual machines
are not possible. herefore I believe that a windmill is not a perpetual machine.
Seeing that a windmill is neither a heat engine nor a perpetual machine, I further
researched the possibilities of what type of device a windmill can be. & windmill also
called a wind turbine is a means of harnessing the kinetic energy of wind converting it
into electrical energy. his is accomplished by turning blades called aerofoils, which drive
a motor or turbine, and are connected to a generator.(0igure III/ -ven though a windmill
has some characteristics of both a heat engine and a perpetual machine, it is neither. &
windmill is a wind turbine.
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Bibliography
ASmith, ). M, H.*. +an ess, and M.M &bbott. Introduction to *hemical -ngineering
hermodynamics. th ed
A-ngines
http677www.infoplease.com7dk7encyclopedia7engines.html
A8erpetual Motion
http677www.answers.com7topic7perpetual9motion
ASecond Baw of hermodynamics
http677en.wikipedia.org7wiki7Second;law;of;thermodynamics
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Dene S. Matadeen
Figure I A !ea" #ngine $y%le
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Figure II #(amples )* Perpe"ual +a%hines.
The "Overbalanced Wheel". It was thought that the metal balls on the right side
would turn the wheel because of the longer lever arm, but since the left side had more balls than the
right side, the torque was balanced and the perpetual movement could not be achieved.
The "Float Belt". The ellow bloc!s indicate floaters. It was thought that the floaters
would rise through the liquid and turn the belt. owever pushing the floaters into the water at the
bottom would require more energ than the floating could generate.
The "#apillar Bowl". It was thought that the capillar action would !eep the water
flowing in the tube, but since the cohesion force that draws the liquid up the tube in first place holds the
droplet from releasing into the bowl, the flow is not perpetual.
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