The links below provide an outline of the material for this lesson. Be sure to carefully read through the entire lesson before returning to Canvas to submit your assignments.
It looks like we are ready to go for lesson 1: Energy and Society. This lesson is going to teach us about energy! What is energy, and with which units do we measure energy? We will learn about the commonly used units we use to measure energy. There are different forms of energy that we use; for example, we use electrical energy or mechanical energy, like moving a car, etc., and we need to know the units in which we measure these different forms of energy. So we will also learn about forms of energy. We will learn about the units in which we measure these forms of energy, and also we will get into a very, very important distinction between energy and power. To be clear, that is the key concept in this lesson that I want you to concentrate on – power and energy. And once we know the difference, we know that using power, we can calculate energy, or if we know the energy and time, we can calculate power.
We will also look at some of those calculations. Once we know the power, we can calculate the energy. For example, a computer consumes some power, the rate at which energy is drawn, and if we use the computer for so many hours, what is the energy consumption by this computer? We can do the same thing for a refrigerator, or we can do it for any other appliance that you use at home. These are common appliances that we are using every day in our lives. When we add up the energy consumed by a computer, by a toaster, by an oven, by a refrigerator, by lighting, etc., at your place then you get energy consumption of all your equipment for a day. So we are going to do that and calculate energy consumption for a day, and then for a month, and we can calculate also the electric bill for one whole month -- that would be our objective in this lesson.
Be careful, again, because the distinction between energy and power is a very important concept. Forms of energy and the units in which we measure energy are the concepts that we will be looking at in this wonderful lesson. All Right! Why Wait? Let’s go and start our lesson.
Good Luck!
When thinking about energy the following questions may come to mind:
Energy is the lifeblood of any modern society. Energy is used in every walk of life. Without it, modern life would almost come to a standstill. From the moment of waking up in the morning with an alarm clock, we use energy for almost everything we do.
Energy is a property of matter that can be converted to work, heat, or radiation. It can move things or do work, produce heat even if it does not move anything, and be converted to light (or more accurately, radiation).
Upon completing this lesson, you should be able to:
Step | Activity | Access / Directions |
---|---|---|
1 | Read the online lesson | Lesson 1 - Energy Supply and Demand |
2 | Review | Lesson 1 - Review & Extra Resources (supplemental materials that are optional...but informative!) |
3 | Take | Lesson 1 - Quiz (graded) The quiz is available in Canvas. |
Please refer to the Calendar in Canvas for specific timeframes and due dates.
If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!
Energy exists in a number of different forms, all of which measure the ability of an object or system to do work on another object or system. There are six different basic forms in which we use energy in our day-to-day life:
A book sitting on a shelf in the library is said to have potential energy because if it is nudged off the shelf, gravity will accelerate the book, giving the book kinetic energy. Because the Earth's gravity is necessary to create this kinetic energy, and because this gravity depends on the Earth being present, we say that the Earth-book system is what really possesses this potential energy, and that this energy is converted into kinetic energy as the book falls.
The glucose (blood sugar) in your body is said to have "chemical energy" because the glucose releases energy when chemically reacted (combusted) with oxygen. Your muscles use this energy to generate mechanical force (work) and also heat.
A hot cup of coffee is said to possess "thermal energy," or "heat energy," because it has a combination of kinetic energy (its molecules are moving and vibrating) and potential energy (the molecules have a mutual attraction for one another) - much the same way that the book on the bookshelf and the Earth have potential energy because they attract each other.
All matter is made up of atoms, and atoms are made up of smaller particles called protons (which have positive charge), neutrons (which have neutral charge), and electrons (which are negatively charged).
In both fusion and fission, some of the matter making up the nuclei is converted into energy, represented by the famous equation:
Even things that we encounter in our every day life contain some radioactive material, either natural or man-made. Smoke detectors, compact fluorescent bulbs, some watches and granite countertops can emit some nuclear radiation. Even plane travel at high altitudes cause exposure from cosmic rays.
Photons are created when electrons jump to lower energy levels in atoms, and are absorbed when electrons jump to higher levels. Photons are also created when a charged particle, such as an electron or proton, is accelerated. An example of this phenomenon is a radio transmitter antenna that generates radio waves.
Please watch the following 5:00 video about the electromagnetic spectrum:
As depicted in the image above, the lower the energy, the longer the wavelength and lower the frequency, and vice versa.
The reason that sunlight can hurt your skin or your eyes is because it contains "ultraviolet light," which consists of high energy photons. These photons have short wavelength and high frequency, and pack enough energy in each photon to cause physical damage to your skin if they get past the outer layer of skin or the lens in your eye.
Radio waves, and the radiant heat you feel at a distance from a campfire, for example, are also forms of electromagnetic radiation, or light, except that they consist of low energy photons (long wavelength and high frequencies - in the infrared band and lower) that your eyes can't perceive. This was a great discovery of the nineteenth century - that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.
About 20% of the electricity used in the US is used to produce visible light for lighting purposes.
Can you identify the different forms of energy in the picture below? Enter your answer in the table below and click the "Check Answers" button to check your work.
These things, listed below, represent the six fundamental forms of energy: Mechanical, Chemical, Thermal/Heat, Electrical, Nuclear and Radiation. Your task is to determine what form of energy is represented by each item.
Now spend some time trying to identify the different forms of energy that are at work in the above items. Once you have thought through this and have some answers, read on to see if you are correct.
AnswersLight bulb in a lamp post - Electrical Energy
Cups of water. One is sitting on a table and the other is in a woman's hand. - Thermal or Heat Energy
An X-ray - Nuclear Energy
A Frisbee flying through the air - Mechanical (kinetic) Energy
The sun - Radiation
A golf club getting ready to hit a ball - Mechanical (Potential)
The ice cream in an ice cream cone - Chemical
Energy can be converted from one form to another.
Examples:
Most of the day-to-day devices that we use are energy conversion devices. In this activity, you will identify the fundamental form of energy that is put in to each device and the output form of energy that is a result.
Your task is to look at six devices and decide what form of energy is the input and which is the output form of energy. Think about your answers carefully before reading ahead to the answers.
Device | Input form of Energy | Output form of energy | |
---|---|---|---|
1 | Lawn Mower | Chemical | Mechanical or kinetic |
2 | Computer | Electrical | Light and Sound |
3 | Sun | Nuclear | Radiant |
4 | Tree | Radiant | Chemical |
5 | Gas Furnace | Chemical | Thermal or Heat |
6 | Hair Dryer | Electrical | Heat or Electric |
How is energy measured? It is measured in various units by various industries or countries, in much the same way as the value of goods is expressed in Dollars in the U.S. and Yen in Japan and Pounds in Britain.
The table below identifies different units for measuring energy. A lot of it also has some historical context. Our early studies of energy involved heating things up, so we name units based on how hard it was to heat things. Makes sense, right? Now we pass electrical energy to operate many devices, so now we use units that "better" capture this process.
Unit | Definition | Used In | Equivalent to |
---|---|---|---|
British Thermal Unit BTU | A unit of energy equal to the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. Equivalent to energy found in the tip of a match stick. | Heating and Cooling industries | 1 BTU = 1,055 Joules (J) |
calorie or small calorie (cal) | The amount of energy needed to raise the temperature of one gram of water by one degree Celsius. | Science and Engineering | 1 calorie = 0.003969 BTUs |
Food Calorie, Kilocalorie or large calorie (Cal, kcal, Calorie) | The amount of energy needed to raise the temperature of one kilogram of water one degree Celsius. The food calorie is often used when measuring the energy content of food. | Nutrition | 1 Cal = 1,000 cal, 4,187 J or 3.969 BTUs |
Joule (J) | It is a smaller quantity of energy than calorie and much smaller than a BTU. | Science and Engineering | 1 Joule = 0.2388 calories and 0.0009481 BTUs |
Kilowatt Hour (kWh) | An amount of energy from the steady production or consumption of one kilowatt of power for a period of one hour. | Electrical fields | 1 kWh = 3,413 BTUs or 3,600,000 J |
Therm | A unit describing the energy contained in natural gas. | Home heating appliances | 1 therm = 100,000 BTUs |
When writing BTUs, one uses a base of “10” raised to a particular exponent.
For example:
More specific notation involves the following:
To express measurements greater than those with a base of 10, you would do the following:
Prof. Bruce Logan [1] of Penn State published a fascinating way to view your energy and climate impact. Using what you learned in this section, you can start to piece together just how much energy each of us uses to maintain our busy lifestyles.
The premise of this approach is to define (another!) unit of energy, but one with a bit more meaning. The daily energy unit, D. We are all supposed to eat about 2000 food Calories a day to survive. So, let’s set this amount of energy to equal 1 D. Now, how many Ds does the typical U.S. home each day (normally in KWh) or operate a car (normally joules or BTUs )? This method of comparing energy consumption allows us to better understand the scale of our energy habits (which might be shocking!) and tell you how many big mac-powered humans it would take to do what your car does…
Here are a few examples he shows to give you an idea.
Once we tally up all the energy it takes to fuel our lifestyle (professional + personal uses), each person consumed about 101 D of energy! (remember this is daily) For comparison, a Swiss citizen consumes about 54 D. Check out his website for more comparisons [1]. Watch this video (5 min 46 sec)
Energy is stored and is available in different forms and sources. The ~24,000 times more solar energy that is available than we need is not in a readily usable form. It needs to be concentrated.
For example, when oil (a concentrated fuel) is burned with air, the resulting gases can reach high temperatures. Solar energy, as it is, is not concentrated and cannot reach those high temperatures. Therefore, we use more concentrated energy sources. These sources are divided into two groups—renewable and nonrenewable.
They're called fossil fuels because they were formed over millions and millions of years by the action of heat from the Earth's core and pressure from rock and soil on the remains (or 'fossils') of dead plants and animals.
Fossil fuels, non-renewable energy sources formed over a million years, are not distributed uniformly over the earth’s surface. Depending on the climate conditions millions of years ago, certain parts of the land masses were favorable for organic matter to grow and thrive.
Over geological ages, these land masses moved, and certain regions are richer in fossil fuels than others. Review the information on the map below, and then answer the questions below the map based on your observations.
The most abundant resources for various global regions are as follows:
The activity below is a drag and drop. Select the items listed in the center of the image and drag them to the corresponding or matching energy type listed on the side.
Click the "play" button below and observe what happens. (Note: The video has no audio.)
Both cyclists did the same amount of work (they both pedaled 10 miles), and used the same amount of energy (218 calories). The blue cyclist, however, demonstrated the most power, because he did the equivalent amount of work as the red cyclist, but in a faster time.
Power is the rate at which we do work.
Energy is the capacity to do work.
Work is the amount done.
Units of Power are not the same as units of energy (i.e., Btus, calories). Units of power are measured in terms of units of energy used per some unit of time.
Examples of Units of Power include:
Power can be determined by the following formula:
On a winter day, a home needs 1 x 106 or 1,000,000 BTUs of fuel energy every 24 hours to maintain the interior at 65° F. At what rate is the energy being consumed in Watts?
If 1 J/s = 1 Watt, and 1,000 Watt = 1kW, then 12,200 J/s = 12,200 Watts = 12.2 kW
To solve this problem, you must realize the following: You know the Power (1,000,000 BTUs/24 hours) and the time (24 hours), so you need to solve for Energy. The measurements must be consistent, so the BTUs should be converted to a consistent measure, such as Joules:
If using Joules per second instead of watts, you must convert 24 hours into seconds or divide it by the number of seconds in an hour (3,600).
Image Credit: © Penn State University, is licensed under CC BY-NX-SA 4.0 [4]
We can also use a version of the Power formula to determine Cost of Energy:
If a 100 W light bulb is accidentally left on overnight (8 hours), how much energy does it consume?
How much energy does this cost, if electricity costs 10 cents per Kilowatt?
How is energy use of Home Appliances calculated?
You just learned in a previous discussion on power that:
or
By modifying this formula slightly, we can determine Energy Consumption per Day:
Where:
Since we want to measure Energy Consumption in Kilowatt hours, we must change the way Power Consumption is measured from Watts to Kilowatts (kWh). We know that 1 kilowatt hour (kWh) = 1,000 Watts hours, so we can adjust the formula above to:
If you use a ceiling fan (200 watts) for four hours per day, and for 120 days per year, what would be the annual energy consumption?
Use this formula:
Energy Consumption / Day (kWh) = Power Consumption ( Watts / 1000) × Hours Used / Day
Energy Consumption per Day (kWh) = (200 / 1000) × 4 (hours used per day)
Energy Consumption per Day (kWh) = (1/5) × 4
Energy Consumption per Day (kWh) =4/5 or 0.8
So the Energy Consumption per Day is 0.8 kWh To find out energy for 120 days, do simple multiplication: 0.8 x 120 = 96 kWh
If the price per kWh for electricity is $0.0845, what is the annual cost to operate the ceiling fan?
If you use a personal computer (120 Watts) and monitor (150 Watts) for four hours per day, and for 365 days per year, what would be the annual energy consumption?
So the Energy Consumption per Day is 1.08 kWh. To find out energy for 365 days, do simple multiplication:
The annual cost if electricity is $0.0845 per kWh would be:
What is the energy consumption of a refrigerator with a wattage rating of 700 Watts when it is operated for 24 hours a day?
To solve, use the following formula:
Where:Energy Consumption = Watt Hours (Wh) or KiloWatt Hours (kWh)
Power Consumption = Watts (W) or kW (KiloWatts)
Number of Hours Operated = Hours (h) For the example above:
Energy Consumption = 700 W x 24 h
Energy Consumption = 16800 W h
To convert from Wh to kWh, remember that 1kWh = 1000 Wh
To solve, set up as a ratio and use linear algebra to solve for ?.
Use the following link to generate a random practice problem [5].
You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.
A refrigerator, although turned "on" all the time, actually cycles on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals.
To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.
The table below shows wattage of some typical household appliances.
Appliance | Wattage (range) |
---|---|
Clock Radio | 10 |
Coffee Maker | 900 - 1200 |
Clothes Washer | 350 - 500 |
Clothes Dryer | 1800-5000 |
Dishwasher | 1200-2400 |
Hair Dryer | 1200-1875 |
Microwave Oven | 750-1100 |
Laptop | 50 |
Refrigerator | 725 |
36" Television | 133 |
Toaster | 800-1400 |
Water Heater | 4500-5500 |
Appliance | Wattage |
---|---|
Aquarium | 50 - 1210 |
Clock Radio | 10 |
Coffee Maker | 900 - 1200 |
Clothes Washer | 350 - 500 |
Clothes Dryer | 1800-5000 |
Dishwasher | 1200 -2400 (using the drying feature greatly increases energy consumption) |
Dehumidifier | 785 |
Electric Blanket - Single/Double | 60 / 100 |
Fan - ceiling | 65 - 175 |
Fan - window | 55 - 250 |
Fan - furnace | 750 |
Fan - whole house | 240 - 750 |
Hair Dryer | 1200 - 1875 |
Heater (portable) | 750 - 1500 |
Clothes Iron | 1000 - 1800 |
Microwave Oven | 750 - 1100 |
Personal Computer - CPU - awake / asleep | 120 / 30 or less |
Personal Computer - Monitor - awake / asleep | 150 / 30 or less |
Laptop | 50 |
Radio (stereo) | 70 - 400 |
Refrigerator (frost free, 16 cubic feet) | 725 |
19" Television | 65 - 110 |
27" Television | 113 |
36" Television | 133 |
53" - 61" Projection TV | 170 |
Flat Screen TV | 120 |
Toaster | 800-1400 |
Toaster Oven | 1225 |
VCR / DVD | 17 - 21 / 20 - 25 |
Vacuum Cleaner | 1000 - 1440 |
Water heater (40 gallon) | 4500 - 5500 |
Water pump (deep well) | 250 - 1100 |
Water bed (w/heater, no cover) | 120 - 380 |
If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance.
Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage.
If not, find an ammeter to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment.
Take a reading while the device is running; this is the actual amount of current being used at that instant.
Also note that many appliances continue to draw a small amount of power when they are switched "off."
These "phantom loads" occur in most appliances that use electricity, such as VCR, televisions, stereos, computers, and kitchen appliances.
Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance.
Watch this 3 minute 41 second video review Lesson 1
For more information on topics discussed in Lesson 1, see these selected references:
You must complete a short quiz that covers the reading material in lesson 1. The Lesson 1 Quiz can be found in the Lesson 1: Energy and Society module in Canvas. Please refer to the Calendar in Canvas for specific time frames and due dates.
Links
[1] https://sites.psu.edu/energyunitd/unit-d/
[2] http://creativecommons.org/licenses/by-sa/3.0/
[3] https://commons.wikimedia.org/wiki/File:BlankMap-World-v2.png
[4] https://creativecommons.org/licenses/by-nc-sa/4.0/
[5] https://courseware.e-education.psu.edu/courses/egee102/L01Instruction/activity/check012701.html
[6] https://www.flickr.com/photos/90494562@N05/8222743554/
[7] https://www.flickr.com/
[8] https://creativecommons.org/licenses/by/2.0/
[9] http://www.eia.doe.gov/kids/energyfacts/index.html
[10] http://www.eere.energy.gov/consumer/