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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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  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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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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Figure III Par"s o* A Windmill.

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