Download Electricity Electricity is the flow of charged particles along a given

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Electricity
Electricity is the flow of charged particles along a given path. A very familiar and natural
source, of electricity is lightning. Lightning is created from charged particles interacting and
making their way from the lower atmosphere. In order to transfer energy for personal use, we
rely on power plants and their generators. A generator uses mechanical movement to rotate
magnets in a coil of wire or a coil of wire in magnets. When magnetic fields from the magnets
interact with the coil of wire, an electric charge is excited in the wires and moves. This
movement produces an electric current. This principle is referred to as electromagnetism and is
used in electric motors.
Circuit: A path which an electrical charge flows along. When something is turned on, the circuit
is said to be closed because the path is complete for an electrical charge to flow. If something is
turned off, then the circuit is said to be open because there is a hole in the path, preventing the
electrical charge to flow completely through the circuit.
Charge (Q): An electric charge can be either positive (+) or negative (-). One proton (+) or
electron (-) is equal to +/- 1.602×10−19 C. When measuring charge, it is done so in coulombs.
Current (I): This is the rate at which a charge flows past a particular point in a circuit over a
period of time. If you think of it as a river flowing, the rate at which the water flows from one
point to the next would be considered the current. However, in electrical terms, the current is the
flow of electrons.
Resistance (R): You can think of resistance as an obstruction to the flow of electrical current or
something that slows the current. In the above images, the lighted bulb is applying resistance.
Voltage (V): Voltage can be thought of as the force behind the charge. In an EV, as the battery’s
capacity lowers due to use, so does its voltage. As the energy is used the power drops.
Power (P): The rate at which electric energy is transferred by an electric circuit. EVs require a
certain amount of electrical power to allow all the components to function properly. If for some
reason not enough power is making it through the circuit, then the components integrated will
function less efficiently or not at all.
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Activity 3: Measuring Current
A.
Knowing how to measure electrical measurements can greatly help when it comes to
designing products that use electricity. Why is it so important to have the correct measurements
of current?
B.
Find out as much as you can about the basics of current. How does this term fit in with
designing an electric vehicle? Make notes of what you think may happen if your battery does not
supply enough current to you vehicle.
C.
You will now learn how to measure current from your provided batteries to a motor using
the following steps.
1.) Hook up battery’s positive end to the positive (red) post of the multimeter then take the
negative (black) post and connect it to the DC motor. On the other connection of the DC
motor, connect it to the negative terminal of the battery holder. Your setup should look
similar to the one below.
2.) You will be testing for current and voltage.
-To measure current replace the red probe into the upper insert labeled 10A DC and set the
dial to 10A
3.) Apply testing for current
using the setup in step 1 and the
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settings from step 2 for your DC motor circuit. Record the current that you observe
running through the circuit. If your reading comes out negative, simply switch the
connections of the posts to test leads.
4.) Collect readings on the motor with no load and with a load. To apply a load simply slow
down the rotating shaft sticking out of the motor; this can be done by pinching it with
your fingers. What do you notice happening to your measurements of current?
5.) With the information, fill in the table below:
Current
DC Motor Circuit with no load
DC Motor Circuit with load
D.
What did you notice about your DC motor circuit and the amount of current? Think of
what may happen if there is too much load on a motor and how it acts with how much power is
available from batteries.
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Solar Energy
Over the years, developments in sustainable technology have enabled more advances in solar
energy or energy from the sun. Solar energy refers to the sun as a whole and does not strictly mean
light energy, but also thermal energy which is bombarding Earth. Cities are implementing more uses
of solar energy by using photovoltaic (PV) panels to capture the sun’s energy and utilize it for
addressing a growing number of needs. Businesses and homes are beginning to use PV panels to
capture energy for lighting inside and outside as well as other uses. In order to properly use solar
energy, it helps to understand how it works. What is taking place is explained in the name itself:
Photo = light and Voltaic = Electricity.
PV panels consist of a semiconductor (a material made of an insulator and conductor) which
holds electrons. When photons hit the panel, they are absorbed by the semiconductor which results in
electrons being knocked out of the way. The semiconductor has two types of silicon, an N-type and
P-type. The P-type (P=positive) silicon is free of electrons or just empty and the N-type (N-Negative)
silicon is full of electrons looking for someplace to go. Panels have at least one electric field to direct
the flow of these free electrons when movement is to occur. Once light is absorbed through the
silicon and excites the electrons in the N-type silicon, the electrons are attracted to the empty P-type
silicon. This results in electrons moving around in the semiconductor and a flow to be directed by the
electric field. A flow of electrons ends up creating a current that can be attached to metal contacts
and used for electricity.
A = Cover Glass * B = Antireflective Coating * C = Contact Grid * D = N-Type Silicon * E = P-Type Silicon * F = Back Contact
PV panels are used to generate energy during the day to provide power to a residence. Energy
may be stored in batteries for future use or sold back to the grid. PV panels can be connected to
batteries which store the collected energy and use the energy at night, during power outages, or other
times when power is needed. When batteries are not used, the power may be sold back to the grid
through net metering. Many homes can use PV panels to charge batteries for external lighting at
night, if power goes out, or just to save money on energy costs. Not only is lighting a result of
photovoltaic energy, but also cameras and emergency phones. Even electric vehicle batteries can be
charged using photovoltaic technology.
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Solar Irradiance
Everyday an energy source bombards Earth which, at ideal conditions, can provide up to
1000 watts of power per square meter. The factors that can limit being able to reach the full
amount of power available range from water vapor to carbon dioxide in the atmosphere. It is
important to remember that the sun setting and rising causes variations in how much light is
available at different times of the day. Peak sun hours are considered the times during the day
when the most sunlight is available. These times can differ during the year when the tilt of Earth
in relation to the sun changes.
Below is an image of the different positions of the sun at different times of the day for Northern Latitude locations
Various
locations on Earth
receive different amounts of light at distinctive times because of the way the planet tilts. An area
in the northern hemisphere will experience summer when another area in the southern
hemisphere experiences winter. In this scenario, the location in the northern hemisphere will
receive more sunlight than the location in the southern hemisphere. This is not true all year
though as we can see through seasonal changes.
Another factor to consider is a location’s orientation to north and south. Depending on
your location on Earth, you will gather the most sunlight when oriented to true north or south.
Interestingly, true north and south differ to some degrees from the Magnetic North and South
Poles. This means that when a compass is pointing north, it is actually a few degrees off from
what the actual north point of Earth is. As a result of this, maps have been created where you can
see how many degrees to add to your location so that when you install PV panels you can orient
them to true north.
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To use the map below, pinpoint your location, find out its orientation to magnetic south
and add the number of degrees the map shows near your location. Since the map is of the United
States, which is in the northern hemisphere, we want orientation to the south where we will gain
the most sunlight.
Your location on Earth and its orientation to the sun are not the only angles to think about
when putting up PV panels. The angle of the panels themselves must be considered. A panel that
is angled too steep or too shallow will not gather the amount of sunlight truly available in that
area. To achieve the best tilt angle, it is a good idea to simply use the latitude of the location.
This is because a location’s latitude determines how high the sun appears above the horizon at
solar noon during the year.
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Activity 4: Graphing Solar Energy
A)
At different times during the day, a photovoltaic (PV) panel produces varying amounts of
power from the sun. What variables do you think affect the power output of a PV panel?
B.)
Research possible factors that play a role in how much power a PV panel produces. Take
note of certain angles and directions of exposure in varying areas of the world. To best measure
the energy output of your PV panel, create a circuit using the panel and the multimeter.
However, instead of using a battery pack, use your PV panel as the source of energy. Be aware
that if you get a negative reading on your multimeter, then simply switch the connection points.
It may also help to label the positive point of the panel.
Set you multimeter by placing the probes in VΩmA and
set the dial to DCV 20
Measuring voltage from a PV panel: To measure voltage above 20V set dial to 200 DCV,
connect the multimeter to the PV panel as in the photo above.
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C)
Power produced by the PV panel depends on how much sunlight is hitting the surface. On
cloudy days, one will notice that a panel produces less energy because less sunlight is making its
way to the surface. Take your PV panel and attach it to a multimeter to measure the voltage that
is produced. Do things such as holding the panel at different angels or covering up certain parts
of the panel and note their results on the voltage produced.
Affect on Panel:
Held at angle 0◦
Held at angle 45◦
Held at angle 90◦
Held at angle 135◦
Cover up a third of the panel held at 45◦
Cover up half of the panel held at 45◦
Voltage:
D) Construct a chart of energy output versus angle of panel to present to individuals a visual for
how angles play a role in determining power output. For examples of solar charts, visit
www.gridc.net.
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Wind Energy, Wind Power and Wind Turbines
When you step outside and feel the wind blowing, what you are feeling is wind energy.
Wind is produced due to the unequal heating on Earth that causes pressure differences. These
differences in air pressures cause masses of air to move from one point to another. It is this
movement of air that is called wind.
Image: National Energy
Education Development
Project (Public Domain)
Humans have been using wind energy for centuries. Even before wind energy was used
to produce electricity it was used to help produce food. Windmills use wind energy to push the
blades, which in turn rotate a shaft. When the shaft rotates, it also rotates a grinding stone; which
is used to mill grain. Wind turbines use the same basic idea of windmills to produce wind power.
Wind energy and wind power terms are used interchangeably, even though there are differences
for each.
Wind Energy – The kinetic energy of moving wind caused by the different air pressures on
Earth creating moving air masses called wind
Wind Power – Power produced by a wind turbine using wind energy.
Wind turbines use wind energy to produce electricity much like how a windmill uses
wind energy to mill grain. As wind energy pushes along the blades of the rotor, this rotates a
shaft inside the turbine. The shaft is attached to gears. The gears inside the wind turbine attach to
a generator. Electric power is produced by the generator when the shaft rotates. From this
rotation we get wind power produced using wind energy.
Image by Paul Anderson
from geograph.org.uk
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Numerous factors affect how much power is produced using surround wind energy. First
off, wind is required for wind power to be produced. Wind speed plays an important role because
the wind has to be moving fast enough for a wind turbine to begin moving. Some turbines
require the wind to be blowing at 11 miles per hour before their rotor begins to move. Some
turbines may require less wind speed, while others may require more wind speed. Many wind
turbines are even equipped with brakes in case the wind speed gets too high. If wind speed is too
high and a wind turbine doesn’t stop rotating, it can exceed the turbine’s centrifugal force and
break itself apart due to the high stress of fast moving parts. This breaking apart causes great
damage to a wind turbine.
While wind speed is vital in helping to produce wind power, it also helps to actually have
some wind. Earth is a very large place and there are areas that have a lot of strong wind, while
other areas may have no wind at all. The location of a wind turbine determines how much wind it
will encounter. A turbine located in a low lying area with many obstacles (trees, hills, buildings,
etc…) that block wind will not produce an efficient amount of power. However, when a wind
turbine is located in areas such as high in the air, on top of a mountain, along a coast, or any area
free of wind blocking obstacles then they will most likely have a sufficient amount of wind to
produce power. Below you will see a map that details the best areas for wind resources with blue
labeling the superb locations and orange showing fair locations. For a clearer version of the map
visit the National Renewable Energy Laboratory site at
http://www.nrel.gov/gis/pdfs/windsmodel4pub1-1-9base200904enh.pdf.
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The design of a wind turbine also determines how much power it can produce. There are
plenty of different designs of wind turbines and more are being researched. On all wind turbines
there are some form of blades that are used to capture the wind and rotate the rotor. The blades
can be of different designs which include what material they made out of, how they are shaped,
and the angle they are attached. Wind turbines need light blades so that not as much wind is
required to move the rotor. However, the blades also need to be strong in order to prevent
damage which could hinder how much power is produced. Materials the blades are made out of
include aluminum and composite materials.
How a blade is designed can affect how much noise is produced by the wind turbine
when it is functioning as well as how strong of winds the turbine can handle. In addition to the
blade design, it is also important how many blades are on a turbine. The number of blades on a
wind turbine can improve efficiency by catching more wind, but blade count also affects the
design of the turbine. The more blades a turbine has, the more weight is added; so it is important
to research how much wind the turbine will encounter to determine if it is necessary to have
more blades. Typically, wind turbines have 3 blades, but different design may have different
number of blades.
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Since wind turbines are being used and researched more and more, there have been
numerous designs that have been made. Two basic categories of wind turbine designs are vertical
and horizontal. Each design has their pros and cons, so it is important to look at each one
carefully when deciding what design to use. Horizontal wind turbines are the traditional form
and can be very efficient for catching wind and producing power at taller heights and in good
wind areas. However, some vertical wind turbine designs are better for catching low level winds,
produce less noise and may be efficient enough for certain areas.
Horizontal Wind Turbine
Vertical Wind Turbine
Wind turbines are being used to put power into the grid and to help areas use more
renewable energy sources. All around the world, wind farms are being built and used. A wind
farm is a collection of wind turbines in a sufficient wind area. Wind turbine technology is also
getting to a point where people can purchase them from a home improvement store or other
vendors to use for personal use at home. A person can install a wind turbine at their home to sell
energy back to power companies (which can leverage how much they pay for energy) or to store
energy to use it when necessary. It is possible to use a wind turbine to charge a battery and then
use that stored energy whenever needed (like during a storm when the power goes out).
As the smart grid comes into play, there are plans to incorporate more renewable energy
technologies including wind turbines. This use of renewable energy technologies to produce and
store energy for the grid is intended to help energy consumers and producers by reducing
demands on power companies during hours of peak energy use. Research projects are in place to
study how efficient wind turbines can be in certain locations (mountains, coast, and plains).
Through these types of research projects, people are getting a better idea of how wind energy can
be used to produce wind power in order to help with the rising energy consumption worldwide.
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