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JUSTIFICATION

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									                                  JUSTIFICATION



       In November 2007 Popular Mechanics published an article about the

windbelt generator which caught the attention of many physicists. I was made

aware of the article about a month later and was asked if I would be interested in

doing a research project attempting to recreate the results the article claimed. I

was very impressed by the video that was provided along with the online version

of the article, and I had felt for sometime that I wanted to do research which

included an in-depth look into electromagnetism.

       Although I had taken a course in electromagnetism (E&M), I had not

understood the subject as thoroughly as I wanted. Therefore, originally, I was

interested in using this project simply to gain a better understanding of that

subject matter. After taking a closer look at both the existing wind turbines and

the new windbelt generators, I realized that there is a great need for this type of

efficient, alternative energy source.

       Let me begin this section with a quick review of the most basic wind

generators. If the wind generator is used to provide mechanical power directly, it

is call a windmill. The windmill consists of several blades mounted on a shaft. At

the place where the blades meet the shaft there is usually some type of metal

bearing or lubricant to reduce the amount of friction generated between the

blades and the shaft. The shaft is usually mounted in such a way as to allow the

blades to constantly present their face to the wind.




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       If the wind generator is used to produce electrical power directly, it is

called a wind turbine. It operates under the same principle as the windmill, but is

usually far bigger. The disadvantages of both the windmill and the wind turbine

are that they are large, expensive, and require a high wind speed in order to

function properly.8

       The miniature wind turbine is an attempt to decrease the size of a normal

wind turbine in order to fill a growing need for cheap, small-scale energy. A

specific example of a miniature wind turbine is the Marine Air-X. This model

begins producing power with a wind speed of 3.6 meters per second (8 mph) and

peaks at around 400 Watts with an air speed of 14.7 meters per second (33

mph).9 Now the power which can be attained from any wind turbine is given by

the following equation.

                                          1
                                       P  r 2 v 3 .
                                          2

In this equation P is the power, α is a correction factor taking into account the

friction, ρ is the mass density of the air, r is the radius of the sail area, and v is

the velocity of the wind. As can be seen, the power output depends on the blade

area. If this area is reduced the turbine can no longer harness as much wind

energy as the normal, larger blades could. To balance the loss of sail area, the

fiction in the bearings must be reduced. To make the turbine blades turn in a low

wind situation, there must be as little friction as possible between the

components of the wind turbine. This requires that the bearings be machined

with as high a level of precision as possible. As is to be expected, this precision

greatly raises the cost of production. So, although the size has been reduced,


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and the ability to operate in a low speed wind has been gained, there is still the

disadvantage of the high cost.

      The basic premise that the windbelt generator operates under is to use a

ribbon under some tension and present it to a light wind in such a manner as to

produce aeroelastic flutter. When the wind angle is just right the ribbon will

vibrate with a surprising amount of energy. When magnets are attached to the

ribbon, they will oscillate with the same frequency as the ribbon and the user can

then harness that energy with the use of stationary coils of wire placed as near

as possible to the oscillating magnets. When the magnets are placed at a

particular spot on the ribbon the mode of vibration is very stable and has a large

amplitude. This is desirable since the EMF depends on the flux which in turn

depends on both the direction and amplitude through which the magnet is

moved.

      At first glance the windbelt generator appears to be incapable of providing

enough energy to perform simple tasks such as lighting a house or running a

clock. However, when adjusted properly a small windbelt can generate several

volts of EMF. The cost for producing the windbelt generator is very low compared

to the only other piece of technology, the miniature wind turbine, which uses low

wind speeds. In a video which was posted on Youtube.com, Shawn Frayne was

asked once to provide a specific example of the usefulness of the windbelt

generator. He gave the audience the example of the new smart buildings which

are being built in some major cities. These smart building have sensors placed in

the air ducts which monitor the air temperature and CO2 content. The sensors




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are currently powered by batteries which may cost as much as two thousand

dollars over the life span of the sensors. If windbelt generators were used in this

application, they could “sip” the energy from the air blowers to power the sensors

in a much more efficient manner.10

       Although the windbelt is inexpensive to make and only requires low wind

speed to function, it is a new development and still has many areas which can be

improved upon. Currently each ribbon/magnet pair must be adjusted individually

for the optimum performance. There is a need to make the process of

manufacturing more standardized. Also, there is a need to determine which

materials make the most durable ribbon, how much tension to place on the

ribbon and how to maximize the EMF. This research is an attempt to solve these

problems.   It   is also   an   attempt    to gain   a   better understanding of

electromagnetism, an understanding which may help create even cheaper and

more efficient generators in the future.




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