Alternative Energy Source: Windmills

Windmills as an alternative energy source must, to fulfill the current purpose of most windmills, generate electricity.  Historically, windmills were used for other purposes, and some might still be found performing other tasks.  They can be used to pump water from an aquifer, roll stones to grind grains, or any of a myriad of other mechanical purpose that requires a force to perform work.  But, our main interest in windmills today is to generate electricity.  And they can perform this duty quite well.

Basically, when an electric charge passes through a magnetic field, it experiences a force, depending or is magnitude, and the speed at which it moves perpendicular to the magnetic field lines.  This force is at right angles to both the movement of the charge across the magnetic field and to the magnetic field itself.  As an easy way to view this, if there is a magnetic field that is oriented north to south, and the movement of a charge is horizontal along the line from east to west, the force of the charge will be vertical, and thus change the path of the charge.  Well, the choice of directions here is arbitrary, but the force is perpendicular to both the field and the movement relative to the field.

A windmill turns a coil of wire through a magnetic field.  In any metal there are electrons that move from atom to atom freely, so they are free to be moved.  As the coil or wire spins, it goes through a magnetic field.  Opposite sides of the coil go through the field in opposite directions, so that causes the electrons to flow upward in one side of the coil, and downward in the other, or to move around the circle of the loop.  The electrons are constrained to the wire.  The moving current is taken off using conductive brushes, and can be made to flow in a circuit.

Notice that as the coil of wire spins it cuts the magnetic filed from parallel to the field, or no field lines crossed meaning no force, to perpendicular to the field, or a maximum force.  The result is alternating current in a sinusoidal shape. 

While our appliances require alternating current, it is unlikely a windmill will create the needed frequency, and if it does the time over which that frequency is created will be short.  We have devices to not only produce a desired frequency, but to match the output to the commercial power used.  In the United States that is sixty cycles per second.  Conversion is easier if we start with direct current, and we can also avoid having several windmills cancel electricity out.  So, a commutator can be used, a ring with two separations opposite each other.  Now, when the coil spins around it contacts different sides of the commutator, and if everything is synchronized this transition happens where the direction of current flow reverses.  So, the half waves always have the same sign in the circuit, meaning the current is direct current.

Other methods can be used, but each item placed in the circuit can result in loss energy.  The objective is not only to find alternative energy sources, but to use them as efficiently as possible.

Solar energy starts with direct current, so this allows windmills and solar power to be utilized, if properly connected, with each other, and multiple windmills be used at the same time.

A difficulty with solar power is that one cannot count on the sun coming up, for clouds exist.  And, solar energy is not a night time alternative.  But, the wind does not always blow, and when it does it may vary is both strength and direction. 

Solar panels work best when the sunlight is direct, but the angle of the sun constantly changes.  Following the sun is a difficult and expensive undertaking. 

Windmills work best when their blades face the wind for the most common type of windmill.  But, as the wind gusts and swirls there is a reaction time for the windmill to properly orient itself, and regain maximum efficiency.  On the other hand, wind does blow both day and night.

Aesthetics is also a concern, as is weight of anything being placed on a rooftop.

Windmills also cool the air, albeit slightly.  But this goes on over a prolonged period of time, and can add up.  Heat energy is defined as kinetic energy.  The heat in the atmosphere is the sum of all kinetic energy in the atmosphere.  Energy is conserved, so whatever energy is converted to electrical energy comes at the expense of the kinetic energy, or heat, of the atmosphere.  Of course solar power converts sunlight to electrical energy that might have partially been absorbed and converted to heat otherwise.

Both windmills and solar panels generate electricity without burning fossil fuel.  Many conventional power plants burn oil or gas.  Thus, windmills and solar energy do not leave a carbon footprint that is associated with global warming.  There are no greenhouse gases emitted.

Taller windmills can get past some of the swirling of the wind, and thus become more efficient.  But, the wind exerts a force on them, and if the support is too long that force can exert a torque that can shear bolts at its base and bring the windmill down.  It is the same principle as a lever, a force acting at a distance is magnified close to the pivot.

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